Proceedings of The Magnificent CE ν NS Workshop 2018
D. Aristizabal Sierra, A.B. Balantekin, D. Caratelli, B. Cogswell, J.I. Collar, C.E. Dahl, J. Dent, B. Dutta, J. Engel, J. Estrada, J. Formaggio, S. Gariazzo, R. Han, S. Hedges, P. Huber, A. Konovalov, R.F. Lang, S. Liao, M. Lindner, P. Machado, R. Mahapatra, D. Marfatia, I. Martinez-Soler, O. Miranda, D. Misiak, D.V. Naumov, J. Newby, J. Newstead, D. Papoulias, K. Patton, S. Pereverzev, M. Pospelov, K. Scholberg, G. Sinev, R. Strauss, L. Strigari, R. Tayloe, J. Tiffenberg, M. Vidal, M. Vignati, V. Wagner, J. Walker, T.-T. Yu, J. Zettlemoyer, G.C. Rich
PProceedings of
The Magnificent CE ν NS Workshop 2018
A workshop held at the University of ChicagoNovember 2 & 3, 2018
EditorsG.C. Rich, L. Strigari a r X i v : . [ h e p - e x ] O c t ith contributions from D. Aristizabal Sierra , A.B. Balantekin , D. Caratelli , B. Cogswell , J.I. Collar , C.E. Dahl , J. Dent ,B. Dutta , J. Engel , J. Estrada , J. Formaggio , S. Gariazzo , R. Han , S. Hedges , P. Huber ,A. Konovalov , R.F. Lang , S. Liao , M. Lindner , P. Machado , R. Mahapatra , D. Marfatia , I.Martinez-Soler , O. Miranda , D. Misiak , D.V. Naumov , J. Newby , J. Newstead , D. Papoulias ,K. Patton , S. Pereverzev , M. Pospelov , K. Scholberg , G. Sinev , R. Strauss , L. Strigari , R.Tayloe , J. Tiffenberg , M. Vidal , M. Vignati , V. Wagner , J. Walker , T.-T. Yu , and J.Zettlemoyer Universidad T´ecnica Federico Santa Mar´ıa-Departamento de F´ısica Casilla 110-V, Avda. Espa˜na 1680,Valpara´ıso, Chile IFPA, D´epartment AGO, Universit´e de Li`ege, Bˆat B5, Sart Tilman B-4000 Li`ege 1, Belgium Department of Physics, University of Wisconsin, Madison, WI 53706, USA Fermi National Accelerator Laboratory, Batavia, IL 60510, USA The University of Manchester, Manchester, M13 9PL, UK Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL60637, USA Department of Physics, University of Chicago, Chicago, IL 60637, USA Northwestern University, Evanston, IL 60208, USA Department of Physics, Sam Houston State University, Huntsville, TX 77341, USA Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy,Texas A&M University, College Station, TX 77845, USA Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC27599, USA Massachusetts Institute of Technology, Cambridge, MA 02139, USA Instituto de F´ısica Corpuscular (CSIC-Universitat de Val`encia), Paterna (Valencia), Spain Beijing Institute of Spacecraft Environment Engineering, Beijing 100094, China Duke University, Durham, NC 27708, USA Triangle Universities Nuclear Laboratory, Durham, NC 27708, USA Center for Neutrino Physics, Virginia Tech, Blacksburg, VA 24061, USA Institute for Theoretical and Experimental Physics named by A.I. Alikhanov of National ResearchCentre “Kurchatov Institute”, Moscow, 117218, Russian Federation National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409,Russian Federation Purdue University, West Lafayette, IN 47907, USA Max-Planck-Institut f¨ur Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA Departamento de F´ısica, Centro de Investigaci´on y de Estudios Avanzados del IPN, Apdo. Postal 14-740,07000 Ciudad de M´exico, M´exico Univ Lyon, Universit´e Lyon 1, CNRS/IN2P3, IPNL-Lyon, F-69622 Villeurbanne, France Joint Institute for Nuclear Research, Dubna, Russian Federation Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Department of Physics, Arizona State University, Tempe, AZ 85287, USA Institute for Nuclear Theory, University of Washington, Seattle, WA 98195, USA Lawrence Livermore National Laboratory, Livermore, CA 94550, USA Perimeter Institute for Theoretical Physics, Waterloo, ON, N2J 2W9, Canada Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada Technical University of Munich, D-85748 Garching, Germany Indiana University, Bloomington, IN 47405, USA Department of Physics, Engineering Physics & Astronomy, Queen’s University, Kingston, Ontario K7L3N6, Canada INFN, Sezione di Roma, P.le Aldo Moro 2, 00185 Roma, Italy IRFU, CEA, Universit´e Paris Saclay, F-91191 Gif-sur-Yvette, France University of Oregon, Eugene, OR 97403, USA orewordOrigins and spirit of the meeting
From its initial description, the process of coherent elastic neutrino-nucleus scattering (CE ν NS) has beenof interest to the nuclear, particle, and astrophysics communities, appealing to those working either ontheory or experiment. Seizing on some of the momentum generated by the first observation of CE ν NSby COHERENT in 2017, the Magnificent CE ν NS workshop was held on November 2 & 3, 2018 on thecampus of the University of Chicago, organized by G.C. Rich, L. Strigari, and J.I. Collar with financialand administrative support generously contributed by the
Enrico Fermi Institute (EFI) and the
KavliInstitute for Cosmological Physics (KICP) , both at the University of Chicago. Recognition of theinterest for such a meeting grew out of conversations at various conferences and workshops in 2018, including:Neutrino 2018 in Heidelberg, Germany; NDM 2018 in Daejeon, South Korea; and ICHEP 2018 in Seoul,South Korea. We are grateful to the organizers of the aforementioned meetings for having assembled excellentcommunities to foster productive discussions, and we would like to especially acknowledge discussions with,and encouragement from, Raimund Strauss.The goal of this workshop was to develop and strengthen connections between experimentalistsand theorists/phenomenologists working in this nascent and exciting field. By forming strong lines ofcommunications between the many groups working on or around the process, it was hoped that effortsranging from short- to long-term time scales could be positively impacted, maximizing the realizable scientificoutput of the community: experimentalists could share with each other lessons learned, helping advance theongoing experimental efforts; the experimental community could share with theorists/phenomenologists theneeded information to most meaningfully incorporate the experimental projects in theoretical calculations;and the theory/pheno community could provide input for next-generation experiments, making sure theytarget the most exciting physics questions. Complementing the direct scientific impacts, by encouragingconstructive discourse and interaction, we hope to foster an overall positive and inclusive atmosphere in theCE ν NS community.This collection of brief summaries , and the accompanying presentations, are meant to serve as a snapshotof the CE ν NS field as of late 2018. It is hoped that the Zenodo community for the workshop , collectingthis document and the presentations, provides a convenient resource for those interested in the process andseeking either high-level or low-level details on the progress of the myriad efforts. Citing these proceedings
In general, the most appropriate way to cite the scientific content of any specific contribution in theseproceedings is to reference the Zenodo posting of the contribution in question and to use itsparticular DOI . If making reference to specific scientific content of any contribution, this collection ofsummaries can be cited in addition to contribution-specific Zenodo post but this decision is left to thediscretion of researchers making the reference.In addition to potentially supplementing a reference to specific contributions, there may be instanceswhere reference to this document by itself are appropriate. In any case, after replacing xxxxx with the Credit for the title-page image goes to Connor Awe of Duke University. The organizers of Neutrino 2018 set an excellent example for how “proceedings” of conferences or workshopscould be defined moving forward, making use of the tremendous resource that is Zenodo; see their community at https://zenodo.org/communities/neutrino2018 . iiippropriate arXiv identifier, we recommend citing this document asD. Aristizabal Sierra et al. (2019). Proceedings of The Magnificent CE ν NS Workshop 2018.Zenodo. DOI: 10.5281/zenodo.3489190. arXiv: . Magnificent CE ν NS 2019 (and beyond)
With the success of this meeting, a second workshop on the same subject will be held
November 9 – 11,2019 in Chapel Hill, NC . More information can be found at the website magnificentcevns.org/2019 .The goal is to make this workshop a regular venue for community building and collaboration betweenresearchers involved, either directly or indirectly, with this exciting and rapidly developing field.Looking forward, we hope this meeting is able to continue to help direct global CE ν NS efforts towardsthe richest scientific program possible and to play a role in facilitating the extraction of exciting new insightsfrom the vibrant palette of experimental results that are expected soon. Meetings such as this, and strongcommunities such as that working on CE ν NS, present opportunities to enhance synergistic activities andalign disparate efforts from networks of researchers around the world. We hope the spirit of collaborationcontinues to thrive within the CE ν NS community and involved researchers work to establish best practices/ principals to further enhance communication and the sharing of both theoretical and experimental results,along with effective analysis practices honed by the diverse experiences of the community.CE ν NS was unobserved for more than 40 years after its description, and efforts to observe the processwere originally characterized as “act[s] of hubris” [1]. These experiments remain extremely challenging, andeven the act of sharing experimental results must be given thoughtful effort for maximal efficacy [2], but thepotential in this field to reach for new physics, or to approach questions from different angles and will differentprobes, is thrilling. We are optimistic and excited about the science that we expect to be produced by theCE ν NS community and similarly optimistic that the community dynamic will continue to be welcoming andcollaborative, hopefully in even more concrete ways.The Magnificent CE ν NS (2018) iv ontents ν NS cross section 1
Alexey Konovalov ν NS 2
Jayden Newstead A Quenching” 3
Jon Engel
Dmitry V. Naumov
Gleb Sinev
Diego Aristizabal Sierra ν NS etc 7
Danny Marfatia
Bhaskar Dutta
Louis Strigari
10 Coherent scattering of “light objects” on nuclei 10
Maxim Pospelov
11 Sub-GeV Dark Matter Theory 12
Tien-Tien Yu vONTENTS
12 CE ν NS in dark matter experiments 13
Pedro Machado
13 CE ν NS in the 2020s With Liquid Xenon 14
Rafael F. Lang
14 Resolving CP degeneracy using atmospheric neutrino at dark matter detector 15
Shu Liao
15 Bremsstrahlung and the Migdal Effect for Coherent Elastic Neutrino-Nucleus Scattering(CE ν NS) 16
James Dent
16 A Precision Neutrino Laboratory at the Spallation Neutron Source 18
Jason Newby
17 The COHERENT NaI[Tl] Detector 19
Sam Hedges
18 The CONUS Coherent Reactor Neutrino Scattering Experiment 20
Manfred Lindner
19 CONNIE 21
Juan Estrada
20 MINER – A Reactor Coherent Neutrino Scattering Experiment to Search for SterileNeutrinos and Non-Standard Interactions 22
Rupak Mahapatra
21 Precision measurement of CE ν NS (Ge PPCs @ COHERENT) 24
Juan I. Collar
22 New Constraints on the matter potential from global analysis of oscillation data 25
Ivan Martinez-Soler
23 Light sterile neutrinos: the 2018 status 26
Stefano Gariazzo
24 Complementarity Short-Baseline Neutrino Oscillation Searches with CE ν NS 27
Joel Walker
25 Reactor fluxes for CE ν NS 28
The Magnificent CE νν
The Magnificent CE νν NS (2018) viONTENTS
Patrick Huber
26 Exploring New Roles for CE ν NS and Neutrinos 29
Bernadette Cogswell
27 NU-CLEUS: Exploring CE ν NS at low energies with cryogenic calorimeters 30
Raimund Strauss
28 The Very Near Site at Chooz - a New Exerimental Hall to Study CE ν NS 32
Victoria Wagner
29 The Ricochet Experiment 33
J.A. Formaggio
30 The Cryocube Detector Array for Ricochet 35
Dimitri Misiak
31 BULLKID - Bulky and low-threshold kinetic inductance detectors 36
Marco Vignati
32 Towards 10-kg Skipper CCD detectors 38
Javier Tiffenberg
33 The CE ν NS Glow of a Supernova 39
Kate Scholberg
34 CE ν NS as a Probe of Nuclear Neutron Form Factors 41
Kelly Patton
35 Future sensitivity of CE ν NS to a weak mixing angle 42
Omar Miranda
36 Neutrino constraints on conventional and exotic CE ν NS interactions 43
D.K. Papoulias
37 Aspects of Elastic Scattering of Neutrinos 45
A.B. Balantekin
38 Measurement of CE ν NS with LAr 46
Rex Tayloe
The Magnificent CE ν NS (2018) viiONTENTS
39 A Search for CE ν NS with the CENNS-10 Liquid Argon Detector for COHERENT 47
Jacob Zettlemoyer
40 Spherical proportional counters and their application for CEnNS detection 48
Marie Vidal
41 Progress on liquid-noble bubble chambers for CE ν NS 50
C. Eric Dahl
42 LArCADe: lowering thresholds in LArTPC detectors 52
David Caratelli
43 Dark side of the exciton: self-organized criticality and low energy threshold detectors 53
Sergey Pereverzev
44 The development of low threshold dual phase argon detector in China for CE ν NSmeasurement 54
Ran Han
REFERENCES 56
The Magnificent CE ν NS (2018) viii iscrepancies in the published expressions for the CE ν NS crosssection
Alexey Konovalov
Institute for Theoretical and Experimental Physics named by A.I. Alikhanov of National Research Centre “KurchatovInstitute”, Moscow, 117218, Russian FederationNational Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409, RussianFederation
Presentation and citeable DOI:
Following the first observations the investigation of CE ν NS is to enter the era of precision measurements.A wide spectrum of scientific goals including detailed study of the nuclear neutron form-factor, non-standard interactions of neutrino with quarks and the electroweak mixing angle value at the energy scale oftens of MeV requires percent and sub-percent precision from both experimental results and the Standardmodel prediction. The published SM CE ν NS cross section predictions including the recent ones lack thecomprehensive expression taking into account effects of the weak axial current and the spin of a nucleus.It is of particular interest if the transitions with a change of the nuclear spin projection should contributeto a coherent or an inelastic channel. A comprehensive expression for the SM CE ν NS cross section andcorresponding calculation apparatus are highly desirable in order to encourage the experimental effort andimprove understanding of various apects of CE ν NS. 1 evisiting the axial contribution to CE ν NS Jayden Newstead
Department of Physics, Arizona State University, Tempe, AZ 85287, USA
Presentation and citeable DOI:
A precise calculation of the Standard Model CE ν NS rate is required before any discovery of ‘new physics’ canbe claimed. With the increasing number of experimental groups entering the CE ν NS community, bringingdiverse detector targets and neutrino sources, it is desirable to have a consistent formalism for predictingexperimental rates. As pointed out in A. Konovalov’s talk, there are discrepancies among CE ν NS crosssections in the literature. Additionally, there are few examples in the literature which account for the axialcurrents. The appropriate formalism for these calculations in semi-leptonic electroweak theory was originallydeveloped in [3] and [4]. In this formalism the hadronic currents are spherically decomposed and expanded inmultipoles to obtain irreducible tensor operators which act on single nucleon states, which can be expressedin a harmonic oscillator basis [5]. Given the low momentum transfer of the CE ν NS process, the one-bodycalculation provides a reasonable starting point (and can be efficiently calculated using available tools). Asan example I have calculated the rate expected by the COHERENT collaboration, finding that the axialcontribution is negligible. Previous calculations overestimate the axial contribution for two reasons, firstthey do not properly handle the projection of the neutrino’s spin onto the nuclear spin, and second, the spinheld by the nucleons is overestimated. 2 eutrino Scattering to Understand “g A Quenching”
Jon Engel
Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
Presentation and citeable DOI:
Calculations within nuclear models overestimate the matrix elements that occur in beta decay, two-neutrinodouble-beta decay, and related processes. The overestimate is often remedied by using an artificially reduced(“quenched”) value for the axial-vector coupling constant g A , which multiplies the matrix elements. Thephysics responsible for the quenching is not fully understood, but must be a combination of correlations thatescape models and many-body weak currents. The momentum dependence of the quenching, which we needto know to accurately calculate the matrix elements that govern neutrinoless double-beta decay, will dependon the relative size of these two contributions.Neutrinos from stopped pions can transfer significant amounts of momentum. Measuring the crosssections for inelastic neutrino-nucleus scattering thus has the potential to tell us about the momentumdependence of g A quenching. In charge-current scattering, one can obtain detailed information on inelasticevents by measuring the energies of outgoing electrons. If the energies of any photons can be measured aswell, then one can reconstruct cross sections to specific excited states and compare them with the predictionsof models and/or ab-initio calculations. The data would be of immense help to theorists struggling to reducethe currently large uncertainty in double-beta matrix elements.3 oherency and incoherency in neutrino-nucleus elastic and inelasticscattering Dmitry V. Naumov
Joint Institute for Nuclear Research, Dubna, Russian Federation
Co-author(s):
Vadim A. Bednyakov
Presentation and citeable DOI:
Neutrino-nucleus scattering νA → νA , in which the nucleus conserves its integrity, is considered. Ourconsideration follows a microscopic description of the nucleus as a bound state of its constituent nucleonsdescribed by a multi-particle wave-function of a general form.We show that elastic interactions keeping the nucleus in the same quantum state lead to a quadraticenhancement of the corresponding cross-section in terms of the number of nucleons. Meanwhile, the cross-section of inelastic processes in which the quantum state of the nucleus is changed, essentially has a lineardependence on the number of nucleons. These two classes of processes are referred to as coherent andincoherent, respectively.Accounting for all possible initial and final internal states of the nucleus leads to a general conclusionindependent of the nuclear model. The coherent and incoherent cross-sections are driven by factors | F p/n | and (1 − | F p/n | ), where | F p/n | is a proton/neutron form-factor of the nucleus, averaged over its initialstates. Therefore, our assessment suggests a smooth transition between regimes of coherent and incoherentneutrino-nucleus scattering. In general, both regimes contribute to experimental observables.The coherent cross-section formula used in the literature is revised and corrections depending onkinematics are estimated. Consideration of only those matrix elements which correspond to the same initialand final spin states of the nucleus and accounting for a non-zero momentum of the target nucleon are twomain sources of the corrections.As an illustration of the importance of the incoherent channel we considered three experimental setupswith different nuclei. As an example, for Cs and neutrino energies of 30 −
50 MeV the incoherent cross-section is about 10-20% of the coherent contribution if experimental detection threshold is accounted for.Experiments attempting to measure coherent neutrino scattering by solely detecting the recoiling nucleus,as is typical, might be including an incoherent background that is indistinguishable from the signal if theexcitation gamma eludes its detection. However, as is shown here, the incoherent component can be measureddirectly by searching for photons released by the excited nuclei inherent to the incoherent channel. For abeam experiment these gammas should be correlated in time with the beam, and their higher energiesmake the corresponding signal easily detectable at a rate governed by the ratio of incoherent to coherentcross-sections. The detection of signals due to the nuclear recoil and excitation γ s provides a more sensitiveinstrument in studies of nuclear structure and possible signs of new physics.4 onstraining NSI with Multiple Targets Gleb Sinev
Duke University, Durham, NC 27708, USA
Presentation and citeable DOI:
Non-standard interactions (NSI) mediated by heavy particles can suppress or enhance the rate of coherentelastic neutrino-nucleus scattering (CE ν NS) by introducing additional couplings between neutrinos andquarks [6]. The values of these couplings can be constrained by CE ν NS measurements; however, usinga single target nucleus for this purpose results in ambiguities, because different combinations of couplingvalues can produce the same detected rate of nuclear recoils. Therefore, CE ν NS detection on multipletargets is required to make an unambiguous measurement of the NSI couplings, with a combination of lightand heavy nuclei providing the best result. This contribution shows, as an example, NSI coupling valuesproducing Standard Model CE ν NS rates in six targets: CsI, Ar, NaI, Ge, Ne, and Xe (see figure 1). TheCOHERENT experiment has been taking CE ν NS data with CsI and Ar detectors and has plans to installNaI and Ge detectors in the near future [7], a combined analysis of which can result in a significant decreaseof the allowed parameter space for the NSI couplings.Figure 1: Values of two NSI couplings (with the rest of the couplings set to 0) that do not change theStandard Model CE ν NS rate for each of the considered target materials.5 onstraints on neutrino generalized interactions from COHERENTdata
Diego Aristizabal Sierra
Universidad T´ecnica Federico Santa Mar´ıa-Departamento de F´ısica Casilla 110-V, Avda. Espa˜na 1680, Valpara´ıso,ChileIFPA, D´epartment AGO, Universit´e de Li`ege, Bˆat B5, Sart Tilman B-4000 Li`ege 1, Belgium
Co-author(s):
V. De Romeri, N. Rojas
Presentation and citeable DOI:
Neutrino Generalized Interactions (NGI) are dimension-six effective neutrino-quark interactions which coverall possible Lorentz invariant structures. From the effective point of view NGI determine the most generalway of accessing new interactions effects in CE ν NS experiments. They include the well-studied neutrinonon-standard interactions (NSI), but span a larger set which includes — among others — scalar and tensorfour-point couplings. NGI are constrained by data from laboratory experiments which include neutrino deepinelastic scattering (CHARM and NuTeV) and monojets searches at the LHC. Constraints from the formerare readily evaded if the NGI are generated by mediators with masses below 1 GeV or so, while limits fromthe latter are relevant if the mediator can be integrated out at LHC energies, O ( E ) ∼ TeV. Thus if onerelies only on these laboratories probes the mediator mass range [1 , ] MeV is barely unconstrained. Fromthat perspective, COHERENT data plays a crucial role. Bounds on NGI derived from the observation ofthe CE ν NS process place sensitive bounds on the otherwise poorly constrained parameter space. The limits,although substantial, still enable for rather large NGI parameters, this mainly due to the relatively largeexperimental uncertainties. Future COHERENT measurements (or any other CE ν NS measurement, withuncertainties below those currently involved) can either observe effects of these new interactions or improveon NGI limits. Near-future experimental setups such as COHERENT phase-II and phase-III, CONUS andmulti-tonne scale dark matter detectors (e.g. DARWIN or DarkSide-20k) will be able to test whether tracesof NGI are present in CE ν NS. [Editor’s note: the work summarized here and reflected in the associated presentation is published asRef. [8].] SI @ CE ν NS etc
Danny Marfatia
Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA
Presentation and citeable DOI:
Coherent elastic neutrino-nucleus scattering consistent with the standard model has been observed by theCOHERENT experiment. For nonstandard neutrino interactions (NSI) generated by a vector mediatorlighter than 50 MeV, only couplings of the mediator are constrained by the detected spectrum, and largeNSI are still viable. For a heavier mediator, in spite of degeneracies between the NSI parameters, currentCOHERENT data place meaningful constraints on the effective NSI parameters in Earth matter.7 odel building and connections to charged current experiments
Bhaskar Dutta
Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&MUniversity, College Station, TX 77845, USA
Presentation and citeable DOI:
The recent detection of CE ν NS events by the COHERENT experiment using 14.6-kg CsI[Na] scintillatordetectors at 6.7- σ level has opened up a new window into the neutrino interactions in the low energy regime,and along with it provides a new probe into beyond the SM physics. Since CE ν NS is well predicted in theSM and therefore a measured deviation from it can provide a test of new physics.In this section we highlightand discuss three well-motivated scenarios for new physics which have particles in the MeV-GeV range: (i)kinetic mixing, (ii) hidden sectors, and (iii) scenarios with a L µ - L τ symmetry. We highlight the role ofCE ν NS and low energy neutrino experiments in probing these models. In addition, CE ν NS experiments canalso probe the parameter space of a fourth neutrino with mass Delta m ∼ , which has been hintedat by several neutrino experiments but whose existence is still inconclusive. The inclusion of both timingand energy data provide the best constraint for all these models compared to most of the experimentalconstraints. In addition CE ν NS experiments can probe light dark matter models with a choice of optimizedcuts ( E rec >
14 keV and t < . µs ) which would remove the SM background. The ongoing COHERENTconstraint on the dark matter parameter space also is better than most of the existing constraints on lightdark matter models. 8 strophysical Applications of Coherent Neutrino Scattering Louis Strigari
Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&MUniversity, College Station, TX 77845, USA
Presentation and citeable DOI:
With the recent discovery of coherent elastic neutrino-nucleus scattering, we are now in the exciting positionof looking forward to understand the physics that can be extracted from the CE ν NS signal. The CE ν NSprocess is unique, because it is intertwined with three major areas of physics: nuclear, high-energy, andastrophysics. From a nuclear physics perspective, CE ν NS will shed light on the neutron form factor andthe weak charge distribution in the nucleus. From a high-energy physics perspective, because it is able toprobe non-standard neutrino interactions (NSI) separately for up and down quarks, CE ν NS will probe NSIin a regime that is not accessible to standard neutrino oscillation experiments. In astrophysics, CE ν NS willprovide a new window into the interior of supernovae, the Sun, and the atmosphere. In addition to thesetheoretical applications, it will be possible to search for sterile neutrinos, and shed light on the reactor andgallium anomalies, which both remain unexplained.There are now several experimental probes of CE ν NS that aim to measure this cross section across awide range of energy scales. These include terrestrial experiments that utilize nuclear reactor and stoppedpion sources, as well as astroparticle experiments that search for dark matter. A CE ν NS detection througheach of these methods will ultimately be important to understand the energy dependance of the signal, aswell as how the signal depends on the target used for detection. Thus there is a natural three-pronged,complementary experimental approach that may be utilized in order to extract maximal information fromthe signal.In the particular field of Solar neutrinos, with a CE ν NS detection dark matter experiments will be ableto probe the properties of neutrinos and the Sun that has not been possible with current experiments.For example, future liquid noble gas and cryogenic dark matter experiments will be able to make the firstneutral current measurement of the B components of the solar neutrino flux. This will provide the firstdetected neutral current energy spectrum of B neutrinos, and be able to shed light on the long-standingSolar metallicity issue. This detection will also help in a search for sterile neutrinos. With low threshold darkmatter detectors, lower energy components of the Solar neutrino flux may also be studied. These can be thefirst pure neutral current measurements of the low-energy Be and pep solar neutrino fluxes. Low-thresholdton-scale detectors may also be able to establish the first measurement of neutrinos from the CNO cycle.This is a long sought-after component of the solar neutrino spectrum that generates ∼
1% of solar energy.9 oherent scattering of “light objects” on nuclei
Maxim Pospelov
Perimeter Institute for Theoretical Physics, Waterloo, ON, N2J 2W9, CanadaDepartment of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada
Presentation and citeable DOI:
This talk is based on two recent papers, Refs. [9, 10] , and the unifying theme for both is the “coherentscattering of light obejcts” on nuclei. In a broad sense, it fits the theme of this meeting, dedicated to theneutrino coherent scattering.The first paper [9] considers the case of interacting “dark radiation” (DR). Usually dark radiation ismentioned in the framwork of modified cosmology, when it contributes to the energy density of the Universe,and modifies the Hubble expansion rate. In our approach, we have considered a hypothetical case of darkradiation which constitutes a subdominant fraction of Universe’s energy balance, and is not numerous, butrather energetic compared to the CMB: ω DR n DR < ρ tot ; ω DR (cid:29) ω CMB ; n DR (cid:29) n CMB . (1)A concrete realization of such situation occur when massive DM particles decay to dark radiation. Thecentral question studied in our paper is about prospects of searching for such dark radiation component,using its coherent scattering on nuclei. It is easy to see that for the DM mass in tens of MeV, and the lifetimeagainst decaying to DR somewhat longer than the age of the Universe, the resulting flux of DR particlescan be significant and indeed comparable to the B neutrino flux, O (10 cm − s − ). If there is an interactionbetween DR and nuclei, and DR and electrons, then there is a chance of detecting DR prior to detecting darkmatter (DM) particles. Our paper considers two types of interaction, via a new light particle called darkphoton, and via an analogous vector boson that couples only to baryons. Conclusions : coherent scatteringof DR on nuclei, specifically in the underground “direct detection” experiments, provide a very competitivesensitivity reach to DR, and limit its interaction strength with nuclei to be comparable or smaller than theweak interaction strength, G F . Figure 2 summarizes the constraints on the parameter space of the model incase of the baryonic force mediator.Second work presented in this talk [10] , is a recent study of light and relatively strongly interacting darkmatter. In this case, the signal from dark matter elastic scattering falls below the experimental thresholdfor detection. Our paper derives novel limits, employing a two-step process. First, the cosmic rays collidewith dark matter particles, and accelerate them to significant velocities/momenta. These “cosmic ray darkmatter” (CRDM) states then scatter inside the detectors creating observable signals, as they are safely abovethe background. When the stopping inside the Earth is not an issue, the signal scales as ∝ σ χ . For sizeable σ χ and small DM masses m χ , we derive novel limits, that reach down to cross sections 10 − cm and applyto all masses, including a very small m χ . Again, elastic scattering of CRDM on nuclei is the main mechanismdriving these limits, that for the case of the spin-independent scattering are shown in Figure 3. Editor’s note: the citation for [10] was updated, subsequent to the submission of these proceedings, to represent the publishedwork; the original citation referred to the (first) arXiv submission alone. Editor’s note: see previous. − − − LUXXENON1T m X (MeV) τ X / t .DR = χ Borexino G B = 10 G F m χ = 10 MeV − − − Figure 2: Constraint on the parameter space of decaying dark matter particles X . Its products of decay,dark radiation particles χ , scatter on nuceli via a baryonic force of strength G B producing a recoil. - - - - - - - - - - - - - - m χ [ GeV ] σ S I [ c m ] Xenon 1t ( this work ) MiniBooNE ( this work ) CMB gas cloudcooling X e1 t ( p r ev . ) CR ESS T II CR ESS T XQC
Figure 3: Constraint on the spin-independent scattering cross section derived from the two step-collision:cosmic rays colliding with DM, and accelerating it to relativstic velocities, with subsequent scattering ofenergetic particles within neutrino and DM detectors.The Magnificent CE νν
Figure 3: Constraint on the spin-independent scattering cross section derived from the two step-collision:cosmic rays colliding with DM, and accelerating it to relativstic velocities, with subsequent scattering ofenergetic particles within neutrino and DM detectors.The Magnificent CE νν NS (2018) 11 ub-GeV Dark Matter Theory
Tien-Tien Yu
University of Oregon, Eugene, OR 97403, USA
Presentation and citeable DOI:
In recent years, there has been incredible interest in the search for sub-GeV candidates of particle darkmatter (see e.g. [11] for summary). One of the proposed avenues is new techniques for the direct detection ofdark matter. Traditional direct detection experiments which have been in operation for the last few decadesare optimized for the detection of weakly-interacting massive particles (WIMPs) that scatter off of the nucleiin the various target materials. These dark matter candidates are typically O (100 GeV) in mass and resultin energy transfers of O (10 keV), which is well within the realm of detectability. However, once the DMmass drops below a few GeV, the energy transfer drops to below ∼ eV and these nuclear recoil experimentscompletely lose sensitivity. Instead, for these sub-GeV candidates, one can consider DM-electron scattering,which results in energy transfers of O (10 eV). The energy transfer manifests itself as ionized electrons orphotons, depending on the experimental setup. Thus, successful experimental setups need to have energythresholds to detect electrons and photons with energies of around an eV.Coherent neutrino-nucleus scattering(CE ν NS) is an inevitable background to any dark matter directdetection experiment as it closely mimic the signature of dark matter. For DM-nuclear scatteringexperiments, the signature of the neutrino-scattering vs. DM-scattering is the same: a recoiling nucleus.However, CE ν NS also manifests itself in DM-electron scattering experiments. The nuclear recoil that resultsfrom CE ν NS will produce secondary electrons, a process whose efficiency can be calculated through variousmodels such as the Lindhard model [12]. For sub-GeV DM experiments, the dominant source of neutrinosare solar neutrinos and the impact of solar neutrinos on sub-GeV DM searches was investigated in [13]. Theexposures for detecting at least one neutrino event range from 0.05 to 9.7 kg-years for silicon, germanium,and xenon, with xenon at the low-end of the range and germanium and silicon at the high-end. The exactvalue also depends on the ionization efficiency. For example, the exposures in silicon can range from 0.2-9.7kg-years, 0.3-2 kg-years for germanium, and 0.05-0.16 kg-years for xenon. Thus, the sensitivity to a sub-GeVDM search will be limited by neutrinos once the exposures are larger than those listed above. However, thereis no absolute neutrino “floor” beyond which there is no improvement possible.12 E ν NS in dark matter experiments
Pedro Machado
Fermi National Accelerator Laboratory, Batavia, IL 60510, USA
Presentation and citeable DOI:
In this talk, I have presented how new physics models could contribute to the coherent elastic neutrino-nucleus scattering cross section. New physics could enhance the irreducible solar neutrino background, a.k.a.the neutrino floor, in dark matter experiments. By examining the experimentally allowed parameter spacein three realistic models, we have estimated the maximum enhancement the neutrino floor could receive.The non-standard neutrino floor could easily be a factor of two larger than the standard model case, or evengreater depending on the robustness of certain astrophysical constraints.13 E ν NS in the 2020s With Liquid Xenon
Rafael F. Lang
Purdue University, West Lafayette, IN 47907, USA
Presentation and citeable DOI:
As searches for WIMP Dark Matter require low ( ∼ keV) energy thresholds, direct Dark Matter detectionexperiments can also be sensitive to CE ν NS. Liquid xenon time projection chambers are a particularlysuccessful and promising technology to fully probe the accessible WIMP Dark Matter parameter space.These experiments search for nuclear recoils from simple elastic scatters. Since the relevant kinematicsis degenerate in momentum transferred, these detectors can in principle not distinguish the nuclear recoilspectrum induced by non-relativistic (10 − c) heavy ( > GeV /c ) WIMPs from the spectrum of correspondinglight, relativistic neutrinos through CE ν NS [14]. Thus, CE ν NS from astrophysical neutrino sources is nowoften shown in the usual WIMP explusion plots. In particular the CE ν NS signal from atmospheric neutrinoshas become known as the neutrino floor of direct detection, although the name is rather misleading for avariety of reasons. The currently-running XENON1T experiment [15] is already sensitive to any Galacticsupernova through this channel [16]. 2019 will see the commissioning of XENONnT and LZ, which canbe expected to measure solar boron-8 neutrinos through CE ν NS in a few years [17]. Given a low-enoughthreshold in the usual scintillation-plus-ionization channel, or else a low-enough background in the ionization-only channel as pursued by the LBECA collaboration, these experiments might improve our knowledge of thesolar metallicity through this channel [18]. However, truly probing the neutrino floor requires a measurementof CE ν NS from atmospheric neutrinos. To properly achieve this such a measurement requires an exposureof order 1 kilotonne × year in xenon, only achievable by a generation-3 Dark Matter experiment [19]. In allcases, measuring CE ν NS in those experiment has unique sensitivity to a variety of new interactions [20].Taken together, such liquid xenon experiments will feature a rich science case with signals from various DarkMatter candidates as well as from a variety of astrophysical neutrino sources.14 esolving CP degeneracy using atmospheric neutrino at darkmatter detector
Shu Liao
Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&MUniversity, College Station, TX 77845, USA
Co-author(s):
B. Dutta, L. Strigari
Presentation and citeable DOI:
Direct dark matter search detectors provide a source to examine the non-standard aspect of neutrinointeractions via solar and atmospheric neutrinos. The low threshold of such detectors will probe the someNSI parameter space at 2 σ significance through solar neutrino with a tonne-year scale exposure. It will alsoallow the observation of the influence of NSI parameters on neutrino oscillation. Through the oscillationat different zenith angles of atmospheric neutrino, the future observation of atmospheric neutrino at directdark matter search detector can help to resolve the degeneracies between CP phase and NSI parameters,which is otherwise impossible to solve at fixed length neutrino oscillation experiment.15 remsstrahlung and the Migdal Effect for Coherent ElasticNeutrino-Nucleus Scattering (CE ν NS)
James Dent
Department of Physics, Sam Houston State University, Huntsville, TX 77341, USA
Co-author(s):
N. Bell, J. Newstead, S. Sabharwal, T. Weiler
Presentation and citeable DOI:
It has recently been shown that including the effects of photon bremsstrahlung in the dark matter-nucleusscattering process [21], or examining ionization and electronic excitation of a target atom due to the Migdaleffect (where the electron cloud’s motion is not modeled as instantaneously following the recoiling nucleus[22–26] ), can extend the reach of direct detection experiments to lower dark matter masses. It is alsowell known that, as experiments searching for dark matter through direct detection continue to achievelower thresholds and larger exposures, they can become sensitive to a solar and atmospheric neutrinobackground interacting with the detector’s target nuclei via the CE ν NS process. It is therefore of interestto determine whether bremsstrahlung or the Migdal effect accompanying the CE ν NS process can provideadditional experimental signals. In Fig. 4 we show the effects for the bremsstrahlung process and the Migdaleffect in both liquid argon and liquid xenon targets for astrophysical neutrinos (this includes both solar andatmospheric neutrinos), as well as for reactor neutrinos and neutrinos from the stopped pion source at theSNS. We see that the bremsstrahlung process is sub-dominant to both the Migdal effect and the standardnuclear recoil except at energies above O (10 keVee) for reactor and stopped-pion sourced neutrinos, thoughthe rate at those energies is suppressed by many orders of magnitude compared to the peak for nuclear recoils.For astrophysical neutrinos, the Migdal effect has competitive rates with the standard nuclear recoil rateat the point where the CE ν NS process from atmospheric neutrinos becomes dominant as the B neutrinoflux rapidly diminishes. This could pose an interesting opportunity for future multi-ton direct detectionexperiments. Editor’s note: following submission of these proceedings, the reference to [26] was updated to represent the published versionof the article; the original citation referred only to the arXiv version, which was last revised prior to the Magnificent CE ν NSworkshop and, based on revision notes, should match the published work. Editor’s note: similarly, Ref. [24] has been updated to reflect the published work; the reference should be to the initial arXivversion. In this case, it is not clear if there are substantive changes between the initial preprint and the published work. N denotes the contribution from electronsin the N th energy level), and bremsstrahlung for liquid argon (left) and liquid xenon (right) detectors. Theprocesses addressed are: astrophysical neutrinos (top) with ν − e scattering also shown, stopped pion sourcedneutrinos such as those at the SNS (middle), and reactor neutrinos (bottom) normalized to that of a detectora distance of 1 m from a 1 MW reactor.The Magnificent CE νν
It has recently been shown that including the effects of photon bremsstrahlung in the dark matter-nucleusscattering process [21], or examining ionization and electronic excitation of a target atom due to the Migdaleffect (where the electron cloud’s motion is not modeled as instantaneously following the recoiling nucleus[22–26] ), can extend the reach of direct detection experiments to lower dark matter masses. It is alsowell known that, as experiments searching for dark matter through direct detection continue to achievelower thresholds and larger exposures, they can become sensitive to a solar and atmospheric neutrinobackground interacting with the detector’s target nuclei via the CE ν NS process. It is therefore of interestto determine whether bremsstrahlung or the Migdal effect accompanying the CE ν NS process can provideadditional experimental signals. In Fig. 4 we show the effects for the bremsstrahlung process and the Migdaleffect in both liquid argon and liquid xenon targets for astrophysical neutrinos (this includes both solar andatmospheric neutrinos), as well as for reactor neutrinos and neutrinos from the stopped pion source at theSNS. We see that the bremsstrahlung process is sub-dominant to both the Migdal effect and the standardnuclear recoil except at energies above O (10 keVee) for reactor and stopped-pion sourced neutrinos, thoughthe rate at those energies is suppressed by many orders of magnitude compared to the peak for nuclear recoils.For astrophysical neutrinos, the Migdal effect has competitive rates with the standard nuclear recoil rateat the point where the CE ν NS process from atmospheric neutrinos becomes dominant as the B neutrinoflux rapidly diminishes. This could pose an interesting opportunity for future multi-ton direct detectionexperiments. Editor’s note: following submission of these proceedings, the reference to [26] was updated to represent the published versionof the article; the original citation referred only to the arXiv version, which was last revised prior to the Magnificent CE ν NSworkshop and, based on revision notes, should match the published work. Editor’s note: similarly, Ref. [24] has been updated to reflect the published work; the reference should be to the initial arXivversion. In this case, it is not clear if there are substantive changes between the initial preprint and the published work. N denotes the contribution from electronsin the N th energy level), and bremsstrahlung for liquid argon (left) and liquid xenon (right) detectors. Theprocesses addressed are: astrophysical neutrinos (top) with ν − e scattering also shown, stopped pion sourcedneutrinos such as those at the SNS (middle), and reactor neutrinos (bottom) normalized to that of a detectora distance of 1 m from a 1 MW reactor.The Magnificent CE νν NS (2018) 17
Precision Neutrino Laboratory at the Spallation Neutron Source
Jason Newby
Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
Presentation and citeable DOI:
The first observation of coherent elastic neutrino nucleus scattering (CE ν NS) by the COHERENTcollaboration at the Spallation Neutron Source demonstrated the capability of the facility in experimentalneutrino physics. COHERENT is now measuring the target scaling of the interaction with multiple small-scale, first-light detectors. These measurements are already setting new limits on nonstandard lepton-quarkinteractions. The potential of the neutrino source is fully realized with a suite of high precision neutrinomeasurements with ton-scale instruments. The neutrino flux is known within 10% and will present a floor inthe uncertainty for detectors now being considered for a precision program. The collaboration plans to deploya heavy water detector to directly measure the neutrino flux at the SNS using the well-known ν e -deuteroncharged current cross-section. This interaction, known to a few percent, is detected via Cherenkov light fromthe produced electron. A sufficient number of interactions will be recorded to achieve this statistical precisionwithin two year in a ton-scale detector with an optimized design to suppress backgrounds. This precisionmeasurement will ensure that the greatest impact is achieved from the planned suite of more massive CE ν NStargets including argon, germanium, and sodium. 18 he COHERENT NaI[Tl] Detector
Sam Hedges
Duke University, Durham, NC 27708, USATriangle Universities Nuclear Laboratory, Durham, NC 27708, USA
For the COHERENT collaboration
Presentation and citeable DOI:
COHERENT is deploying a NaI[Tl] detector to the SNS for measuring CE ν NS recoils off Na nuclei. Themeasurement of the CE ν NS cross section on a light nuclei will help verify its N scaling with neutronnumber and provide further tests of the standard model. A 185-kg prototype detector has been deployed tothe SNS and acquiring data since 2016. This prototype is providing an in situ measurement of low-energybackgrounds as well as for studying the electron neutrino charged-current interaction on I. The currentdesign parameters (subject to change) of the detector are listed below: • Mass: between 2079 kg and 3388 kg. Detector designed to be modular, with final mass determined bydigitization costs and space constraints. Additional mass available for future deployment. • Shielding: 7” of water on all sides surrounding detector, followed by 2” of lead outside the water. • Distance from target to center of array: ∼
21 m. • Threshold: 3 keVee. • Steady-state backgrounds: 200-500 counts/keV/kg/day in the energy ROI, before backgroundreduction from beam timing. • Energy resolution: FWHM /E = (cid:112) αE + βE + γ , with α = 0 . β = 1 . γ = 1 . × − , and E in keVee. • Quenching factor assumption: flat, 19.65% ± he CONUS Coherent Reactor Neutrino Scattering Experiment Manfred Lindner
Max-Planck-Institut f¨ur Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany
Presentation and citeable DOI:
Coherent elastic neutrino nucleus scattering (CE ν NS) has been predicted since 1973 and was first observedin 2017 with neutrinos from pion decay at rest. CONUS aims at detecting CE ν NS with low energy reactoranti-neutrinos. It uses novel Germanium detector technology and a virtual depth shield for operation atshallow depth only 17 meters away from the core of a multi GW power reactor. The talk will describe theexperiment, the latest results and the potential of future detectors of this kind.20
ONNIE
Juan Estrada
Fermi National Accelerator Laboratory, Batavia, IL 60510, USA
Presentation and citeable DOI: INER – A Reactor Coherent Neutrino Scattering Experiment toSearch for Sterile Neutrinos and Non-Standard Interactions
Rupak Mahapatra
Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&MUniversity, College Station, TX 77845, USA
Presentation and citeable DOI:
The Mitchell Institute Neutrino Experiment at Reactor (MINER) is a reactor based experiment at TexasA&M university that combines well-demonstrated low-threshold cryogenic detectors developed for theSuperCDMS dark matter search with a unique megawatt research reactor that has a movable core providingmeter-scale proximity to the core. The low-threshold detectors ( ≈
100 eV recoil energy) will allow detectionof coherent scattering of low energy neutrinos that is yet to be detected in any reactor experiment. Thesehigh resolution detectors, combined with a movable core, provide the ideal setup to search for short-baselinesterile neutrino oscillation by removing the most common systematic in current experiments, the reactorflux uncertainty. Very short baseline oscillation will be explored as a ratio of rates at various distances,with expected SM rates and known scaling of background. Hence MINER will be largely insensitive toabsolute reactor flux. Additionally, low variation in a MW research reactor power combined with meter-scale proximity to the core provides much better systematics compared to a GW power reactor, where thetypical detector to core distance is of the order of 30 meters or higher resulting in similar neutrino fluxincident on a detector. Utilizing multiple targets (Ge/Si) allows for detailed understanding of the signal andbackgrounds in the experiment. Precise understanding of the background is important for searches of NonStandard Interactions (NSI) through a small additional signal.Phase-1 of the MINER experiment is already operational as a demonstration experiment with a 2-kg (4-kgmaximum capacity) payload at a distance of approximately 4.5 m from the reactor core, that would provide asignal rate approaching 1000 events per year and a target background of 100-1000 counts/keV/kg/day (DRU).Phase-2 of the MINER experiment experiment will have a 20 kg payload (inside a 30-kg infrastructure),using a recently purchased cryogen-free refrigerator. The operational 2-kg demonstration phase provides anexcellent opportunity to design the full MINER experiment with 10x larger payload, 10x higher flux due toproximity to core and 10x lower background due to hermetic passive and active shielding. The sensitivity toCE ν NS will improve by at least two orders of magnitude, allowing for precisions tests of eV-scale sterile- ν ,Non-Standard Interactions and neutrino magnetic moment.The MINER experiment aims to become the first experiment to measure CE ν NS at a reactor and mayopen windows to much exciting new physics of immediate interest:
Precision CE ν NS with high statistical ( ∼ ≈ Search for sterile neutrinos as a possible deficit in predicted Standard Model rates using a preciselymovable core. MINER’s very short baseline (1–10 m) search provides important complementarity tothe PROSPECT non-coherent (IBD process) search.22 earch for light and heavy Z (cid:48) and NSI. For light Z (cid:48) down to a mass scale of 1 MeV, the sensitivitycan improve upon that of fixed target and atomic parity violation experiments. For heavy Z (cid:48) up to amass scale of 4 TeV, the sensitivity is competitive with and complementary to LHC searches. Due todifferent flavor composition, the sensitivity to light and heavy Z (cid:48) and NSI will be complementary tothat of the COHERENT experiment.The Magnificent CE νν
Precision CE ν NS with high statistical ( ∼ ≈ Search for sterile neutrinos as a possible deficit in predicted Standard Model rates using a preciselymovable core. MINER’s very short baseline (1–10 m) search provides important complementarity tothe PROSPECT non-coherent (IBD process) search.22 earch for light and heavy Z (cid:48) and NSI. For light Z (cid:48) down to a mass scale of 1 MeV, the sensitivitycan improve upon that of fixed target and atomic parity violation experiments. For heavy Z (cid:48) up to amass scale of 4 TeV, the sensitivity is competitive with and complementary to LHC searches. Due todifferent flavor composition, the sensitivity to light and heavy Z (cid:48) and NSI will be complementary tothat of the COHERENT experiment.The Magnificent CE νν NS (2018) 23 recision measurement of CE ν NS (Ge PPCs @ COHERENT)
Juan I. Collar
Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USADepartment of Physics, University of Chicago, Chicago, IL 60637, USA
Presentation and citeable DOI:
The state-of-the-art in p-type point contact (PPC) germanium detectors has reached a level of maturitysufficient to envision their use for CE ν NS measurements at both spallation and reactor sources. Crystalsin the 3–4 kg mass range are presently under development with noise characteristics sufficient to provide a150 eV ionization ( ∼
600 eV recoil) energy threshold, with high ( > ew Constraints on the matter potential from global analysis ofoscillation data Ivan Martinez-Soler
Fermi National Accelerator Laboratory, Batavia, IL 60510, USANorthwestern University, Evanston, IL 60208, USA
Presentation and citeable DOI:
The neutrino evolution is a long-standing problem in particle physics since many decades ago. In the lightof the latest global oscillation analysis, we are entering into the precision era [27] . The description of theneutrino evolution in matter is crucial for the determination of most of the remaining uncertainties in theneutrino evolution: • The measurement of the mass ordering driven by Super-Kamiokande [28] depends on the measurementof the 1-3 mixing resonance in atmospheric neutrinos crossing the Earth’s mantle with E ν ∼ • the phase that violates the CP symmetry in the lepton sector is measured by Super-Kamiokande [28]in the interference region between the 1-2 ( E ν ∼ . • the two issues that contribute to the tension in the determination of the solar mass parameter [27]are the matter effects introduced by the Earth over the solar neutrinos, and the turn up of the solarspectrum in the low energy region where the solar matter effect dominates.In the presence of non-standard interactions (NSI) of the neutrino with the matter, their evolution andtherefore the determination of the oscillation parameter will be altered. In this talk, we are going to discussour knowledge of the size and flavor structure of NSI by a global fit of oscillation data [29], considering ageneral neutral current neutrino interaction with quarks. We assume that the lepton-flavor structure of thenew interactions is independent of the quark type. The results have been obtained using all the availabledata from oscillation experiments alone and in combination with the results on coherent neutrino-nucleusscattering from the COHERENT [30] experiment. In our analysis, we study the robustness of the threeneutrino mixing scenario in the presence of NSI, and the LMA-D solution. As a result, we also derive newbounds of the non-standard couplings to up and down quarks. The results obtained are robust under thebroad spectrum of up-to-down strengths found in the neutrino propagation along the Sun and the Earth. Editor’s note: this reference has been updated to reflect the published version of the work originally cited only as a preprint. ight sterile neutrinos: the 2018 status Stefano Gariazzo
Instituto de F´ısica Corpuscular (CSIC-Universitat de Val`encia), Paterna (Valencia), Spain
Co-author(s):
C. Giunti, M. Laveder, Y.F. Li
Presentation and citeable DOI:
In the recent years, sterile neutrinos with a mass around 1 eV have been studied as a possible solutionfor the Short-BaseLine (SBL) neutrino oscillation anomalies, which include results from LSND [31] andMiniBooNE [32], from GALLEX and SAGE [33] and from a number of reactor antineutrino experiments[34]. These experimental measurements cannot be explained in the context of the standard three neutrinooscillations. The current status of the search of such light sterile neutrino has been reviewed using all theavailable appearance and disappearance data in SBL experiments. Muon (anti)neutrino disappearance asconstrained mainly by the IceCube and MINOS/MINOS+ experiments is substantially in tension with theobservation of electron (anti)neutrinos appearance in a flux of muon (anti)neutrinos, as observed by LSNDand MiniBooNE, when also the electron (anti)neutrino disappearance results are taken into account [35].From this latter channel, however, we have the first model-independent indications [36] in favor of active-sterile neutrino oscillations, thanks to the observations from the NEOS [37] and DANSS [38] experiments.The two collaborations aim at measuring the reactor antineutrino flux at different distances (between 10and 25 m) in order to distinguish the effect related to a global normalization, which does not depend on thedistance at which the measurement is performed, from the one due to neutrino oscillations, which insteadvaries with the baseline. In the incoming years, these and other currently running experiments will usestandard techniques to test the current best-fit parameters and probe the signal observed by LSND andMiniBooNE, to definitely confirm or rule out the existence of a light sterile neutrino. Meanwhile, the firstCE ν NS experimental results have also been employed to derive bounds on the active-sterile neutrino. Whileat the moment these probes are not competitive with the above mentioned constrains [39], CE ν NS will playa role in this game in the future [40]: studies show that experiments based on coherent scattering will beextremely useful to test neutrino oscillations at reactors, at very small distances (possibly down to 1-3 m):these experiments, therefore, will be perfect probes for active-sterile neutrino oscillations.26 omplementarity Short-Baseline Neutrino Oscillation Searcheswith CE ν NS Joel Walker
Department of Physics, Sam Houston State University, Huntsville, TX 77341, USA
Co-author(s):
B. Dutta, J. Dent
Presentation and citeable DOI:
Anomalies in the expected magnitude and spectrum of neutrino flux have been pointed out for severalyears in reactor (¯ ν e deficit) and Gallium ( ν e deficit) data. Newer reactor (Daya Bay, DANSS, NEOS)analyses take ratios of observations at different baselines in order to remove dependence upon the fluxnormalization and intrinsic spectral shape; inclusion of a sterile then improves the goodness of fit at around3 σ preference. Recently, the accelerator-based MiniBoone experiment has presented results ( ν e appearancewithin a ν µ beam) consistent with anomalies observed previously by LSND. Detection is flavor-sensitive,with E ν (cid:39)
500 MeV and L (cid:39) L = 6–12 m. IBD is flavor sensitive and fully reconstructs the neutrino energy, allowing for“coherency” of an oscillation signal over may cycles in L/E . A relative preference (∆ χ ) for oscillation isreported at the level of 3 σ . The various anomalies are generally consistent within “types” (when multipleexperiments exist), although it is difficult to reconcile them across types with simple models.Various CEvNS experiments are well-positioned to probe possible connections of a short-baseline neutrinooscillation effect to existing anomalies. New physics will be most visible to CEvNS when it impacts theexpected event distribution shape (e.g. for light mediators, magnetic moment, and steriles), rather thanonly the rate (e.g. for heavy Z (cid:48) ). Large statistics associated with the CEvNS coherency enhancement canallow for precision discrimination. Considerable complementarity in the flavor and mass space is possible bya combination of experimental efforts. The CEvNS neutral current touches all flavors. Prompt/delayedsignal discrimination for COHERENT at the SNS, together with reactor data, and application of theunitarity constraint provides enough information to independently constrain this multi-flavor system at thematrix element level. The SNS uses stopped pions to produce an isotropic prompt monochromatic ν µ with E (cid:39)
30 MeV, and secondary isotropic delayed ¯ ν µ and ν e with calculable energy spectra. This high energyenhances the cross section (as a square) and allows for comparatively simple detectors (threshold requirementsare also quadratic) that scale well to high mass. Background control is good, enhanced by timing information.However, the neutrino flux is lower than typical reactor facilities by around 5 magnitude orders. At reactors,neutrino flux is extraordinarily high (10 − cm − s − ). But, backgrounds are challenging and detectors(e.g. high-voltage Ge/Si with transition-edge phonon sensors) must be carefully designed for sensitivityto soft recoil. Additionally, the reactor spectrum is widely spread across energies in the few MeV range(although the shape is reasonably well known), which leads to dispersion of an oscillation signal beyond 1-2cycles. Binning in the recoil, and the extraction of independent bins at ultra-low recoil, can help greatly.An advantage is that this spread in energies is effectively equivalent to scanning multiple length baselinessimultaneously. Simplifications include lack of flavor ambiguity and ability to neglect the nuclear form factor(coherency is fully maintained). In the future, directional detection could resolve the event-by-event neutrinoenergy ambiguity. Additional important experimental complementarities include diversity in the range of L/E deployments and nuclear target materials. 27 eactor fluxes for CE ν NS Patrick Huber
Center for Neutrino Physics, Virginia Tech, Blacksburg, VA 24061, USA
Presentation and citeable DOI:
Reactor neutrinos have played a central role in neutrino physics since their first detection by Reines andCowan [41]; since then every experiment needed to have some understanding of emitted antineutrino flux andenergy distribution stemming from a reactor. Much work has been done for the antineutrino yield above theinverse beta decay (IBD) threshold [42, 43], but little work for lower energies. CE ν NS being a threshold-lessreaction therefore puts up new challenges, but of course for now we await experimental progress towardsthe detection of reactor antineutrinos using CE ν NS and it will be a while before antineutrinos below IBDthreshold will be detected, since these correspond to recoil energies of ∼
100 eV or less. Standard lore isthat neutron captures play a negligible or at best percent-level role for antineutrino yields [44] above IBDthreshold. This is different at low energy, with the most abundant reaction being
U + n → U, whichthen leads to two beta decays with neutrino energies of up to 1.2 MeV. The antineutrino yield from thisreaction exceeds the one of all fission fragments by an order of magnitude at 1 MeV. Other reactions havebeen pointed out where neutrons capture on structural materials in the reactor core [45]. A detailed surveyof nuclear data bases certainly will reveal more relevant isotopes and then the question of how well knownthe neutron capture cross sections actually are will arise. Another interesting wrinkle, are the potentialcontributions from β + decays which would yield neutrinos instead of antineutrinos. Neutron captures do notrepresent a fundamental issue, but care needs to be taken to understand the specific reaction rates in a specificcore with its specific core inventory; at low energies reactors start to become individual neutrino sourceswhose details matter. Also, at low energy the half-lives of antineutrino emitters increase significantly andthus many isotopes will be not in equilibrium, as a consequence the operational history of a reactor becomesimportant as well and instantaneous thermal power no longer is a direct predictor for the antineutrino flux.Increased collaboration with and input from nuclear engineers and reactor operators will be needed to addressthese issues.This work was supported by the U.S. Department of Energy under award number DE-SC0018327.28 xploring New Roles for CE ν NS and Neutrinos
Bernadette Cogswell
The University of Manchester, Manchester, M13 9PL, UK
Presentation and citeable DOI: U-CLEUS: Exploring CE ν NS at low energies with cryogeniccalorimeters
Raimund Strauss
Technical University of Munich, D-85748 Garching, Germany
For the NU-CLEUS collaboration
Presentation and citeable DOI:
The NU-CLEUS experiment is a new experiment [46] to explore coherent-neutrino nucleus scattering(CE ν NS) [1, 47] at a nuclear power reactor. Recent results from a prototype gram-scale cryogenic calorimeters(gramCC) [48] operated at the Max-Planck-Institute for Physics (MPP), opened a new window to neutrinophysics at unprecedentedly low energies. An energy threshold for nuclear recoils of (19 . ± .
9) eV wasreached, which is one order of magnitude lower than previous results of macroscopic cryogenic detectors [49]and a factor of 50 – 100 lower than the state-of-the-art germanium detector technology based on ionizationtechnology. This breakthrough enables a rich physics program to study the fundamental properties andinteractions of neutrinos, to perform precision tests of the electroweak theory as well as nuclear and reactorphysics. NU-CLEUS aims for the exploration of CE ν NS at the low-energy frontier which opens the door fornew physics beyond the Standard Model of Particle Physics.The gramCCs will be operated within a fiducial-volume cryogenic detector, a promising new conceptFigure 5: Left: Technical drawing of the NU-CLEUS prototype detector. 1) target, 2) inner veto, 3) outerveto. Right: MC simulation of the expected energy deposit in case of a background similar to the remainingone in the Dortmund Low Background facility. Black: Without any veto, Blue: in case of a passive outerveto, red: in case of an active outer veto with a threshold of 1 keV. Figure adopted from [46] and referencestherein.developed for NU-CLEUS, that is suited for an above ground operation at significantly suppressed30ackground levels. It consists of three subsets of cryogenic calorimeters – the outer and the inner veto anda neutrino target – all operated at mK temperatures (see Fig. 5 left). Located at a nuclear power reactorthis detector has the potential to achieve a signal to background ratio of up to 10 , a unique situation inneutrino physics [46] (see Fig. 5 right). This will enable a rapid observation of CE ν NS within 1 – 2 weekswith a total detector mass of 10 g. After a measuring time of only 10 weeks we will exceed the precision oftoday’s results of COHERENT [30] and overcome its systematic uncertainties.The Magnificent CE νν
9) eV wasreached, which is one order of magnitude lower than previous results of macroscopic cryogenic detectors [49]and a factor of 50 – 100 lower than the state-of-the-art germanium detector technology based on ionizationtechnology. This breakthrough enables a rich physics program to study the fundamental properties andinteractions of neutrinos, to perform precision tests of the electroweak theory as well as nuclear and reactorphysics. NU-CLEUS aims for the exploration of CE ν NS at the low-energy frontier which opens the door fornew physics beyond the Standard Model of Particle Physics.The gramCCs will be operated within a fiducial-volume cryogenic detector, a promising new conceptFigure 5: Left: Technical drawing of the NU-CLEUS prototype detector. 1) target, 2) inner veto, 3) outerveto. Right: MC simulation of the expected energy deposit in case of a background similar to the remainingone in the Dortmund Low Background facility. Black: Without any veto, Blue: in case of a passive outerveto, red: in case of an active outer veto with a threshold of 1 keV. Figure adopted from [46] and referencestherein.developed for NU-CLEUS, that is suited for an above ground operation at significantly suppressed30ackground levels. It consists of three subsets of cryogenic calorimeters – the outer and the inner veto anda neutrino target – all operated at mK temperatures (see Fig. 5 left). Located at a nuclear power reactorthis detector has the potential to achieve a signal to background ratio of up to 10 , a unique situation inneutrino physics [46] (see Fig. 5 right). This will enable a rapid observation of CE ν NS within 1 – 2 weekswith a total detector mass of 10 g. After a measuring time of only 10 weeks we will exceed the precision oftoday’s results of COHERENT [30] and overcome its systematic uncertainties.The Magnificent CE νν NS (2018) 31 he Very Near Site at Chooz - a New Exerimental Hall to StudyCE ν NS Victoria Wagner
IRFU, CEA, Universit´e Paris Saclay, F-91191 Gif-sur-Yvette, France
Co-author(s):
T. Lasserre, A. Langenk¨amper, C. Nones, J. Rothe, R. Strauss, M. Vivier, A.Zolotarova
Presentation and citeable DOI:
The Very-Near-Site (VNS) is a very promising new experimental site for future experiments to study coherentelastic neutrino nucleus scattering (CE ν NS). With a baseline of 72 m and 102 m, respectively, the VNS islocated in the close proximity of the two reactor cores of the Chooz nuclear power plant in France, eachrunning at a nominal thermal power of 4.25 GW th . The expected anti-neutrino flux at the VNS is of the orderof 10 cm − · s − . Any experimental setup at the VNS is restricted both in weight and volume. First muonattenuation measurements indicate a shallow overburden of 3 m.w.e.: CE ν NS experiments located at theVNS face a high cosmic muon rate of the order of 100 m − · s − and a potentially challenging muon-inducedneutron background.The NU-CLEUS detector concept [46] provides a suitable technology for a next generation CE ν NSexperiment at the VNS. Thanks to the unprecedented low energy threshold of ≤
20 eV nr [48], a strongCE ν NS signal is expected even for gram-scale target masses. To reduce muon-induced backgrounds, theexperimental volume containing the NU-CLEUS detectors will be surrounded by a passive shielding whichwill be complemented with an active muon-veto. With the fast rise-time of the NU-CLEUS detectors, themuon-induced dead-time will stay below a few percent, even for large surfaces of the active muon-vetooperated at shallow overburden. Additional and complementary ways to fight the backgrounds are beinginvestigated. As such, the BASKET [50] R&D program seeks to develop detectors which could achieve anin-situ neutron background characterization. In a first phase, a 10-g version of the NU-CLEUS detector isplanned to be installed and commissioned at the VNS in 2020.32 he Ricochet Experiment
J.A. Formaggio
Massachusetts Institute of Technology, Cambridge, MA 02139, USA
For the Ricochet collaboration
Presentation and citeable DOI:
Ricochet is a bolometer-based CENNS experiment aimed at measuring neutrinos created from the fissionprocess deep within the reactor core. In the first phase of its deployment, Ricochet aims to deploy a 1kilogram load to measure the nuclear neutrino flux. Ricochet leverages two cryogenic technologies as part ofits measurement program:1.
Germanium Semi-conductors : In semiconductor bolometers, the rejection between backgrounds andCENNS-signal events will be achieved thanks to the double measurement of the heat and ionizationenergies, which ratio depends on the nature of the interacting particle: gamma- or beta-inducedelectronic recoils (electromagnetic interactions), CENNS- or neutron-induced nuclear recoils (latticeinteractions). The goal is to reach ∼
10 eV (RMS) energy resolution in heat and ∼
20 eV (RMS)resolution in ionization to provide a rejection power of 10 down to the energy threshold. To reachsuch outstanding background rejection to all sorts of electromagnetic backgrounds, two key featureshave to be met: i) low-capacitance ( ∼
10 pF) Fully Inter-Digited (FID) electrodes, as first introducedby the EDELWEISS collaboration [51], thanks to which events happening near the surface (within 100 µ m) can be tagged as such and be rejected while providing excellent charge collection for bulk events;ii) ∼
20 eV eVee ionization energy resolution (RMS) per electrode, which is five times better than thebest resolution achieved so far in such massive cryogenic bolometers [52].2.
Metallic Zinc-Superconductors : In Zn-detectors, due to the vanishing quasiparticle-phonon couplingin superconducting metals below ∼
100 mK and the difference in thermalization processes betweenelectronic recoil backgrounds and CENNS-induced nuclear recoils, we expect vastly different heatpulse shapes between these two populations of events. From preliminary simulations, assuming aquasiparticle recombination rate 5 times longer than the phonon thermalization rate, we expect abackground rejection power of 10 down to the energy threshold. Indications that such behaviormay indeed exist in such target medium has been documented by the MARE collaboration in theirmeasurements using superconducting rhenium and alpha particles ( ∼ has beenderived [25]. Nowadays, the main R&D focus is dedicated to demonstrating the rejection capabilities of theelectromagnetic backgrounds down to the energy threshold. To that end, a first version of a HEMT-basedpreamplifer developed by the IPNL group is being tested, and new electrode designs are being developed inparallel. An intermediate goal of a 30-g scale Ge bolometer combining a 20 eV heat energy resolution (RMS)together with a 50 eV ionization energy resolution (RMS) is planned for the end of 2019.33he Ricochet ExperimentAt the end of 2019, the two technologies will be scaled to multiple targets for a total target mass of 1 kg.The two detector types, CryoCube and
Q-Array are briefly described below. • The CryoCube: it consists of an array of 3 × × × × radio-pure infrared-tight copper box suspended below the mixing chamber with its dedicated cryogenicsuspension system [55], and its cold front end electronics in close proximity of the detectors. Eachsingle crystal is designed to reach a O (10) eV energy threshold and a 10 electromagnetic backgroundrejection power down to the energy threshold. This detector array is fully funded by the CENNS -ERC starting grant. • The Q-Array: it consists of an array of 8 or 16 superconducting 40-gram zinc cubes. Each unit willbe read out by a transition-edge sensor and the signal feed into a microwave resonant SQUID array(uMUX), allowing the signals from multiple detectors to be read out by a single feed line. The uMUXarray operates at frequencies near 7 GHz, with each channel specifically tuned to a correspondingresonant frequency set by the capacitance of the transmission line. A prototype SQUID array has beendesigned and produced by Lincoln Laboratories at MIT and is currently undergoing testing. Initialresults show excellent quality factors ( Q (cid:39) , νν
Q-Array are briefly described below. • The CryoCube: it consists of an array of 3 × × × × radio-pure infrared-tight copper box suspended below the mixing chamber with its dedicated cryogenicsuspension system [55], and its cold front end electronics in close proximity of the detectors. Eachsingle crystal is designed to reach a O (10) eV energy threshold and a 10 electromagnetic backgroundrejection power down to the energy threshold. This detector array is fully funded by the CENNS -ERC starting grant. • The Q-Array: it consists of an array of 8 or 16 superconducting 40-gram zinc cubes. Each unit willbe read out by a transition-edge sensor and the signal feed into a microwave resonant SQUID array(uMUX), allowing the signals from multiple detectors to be read out by a single feed line. The uMUXarray operates at frequencies near 7 GHz, with each channel specifically tuned to a correspondingresonant frequency set by the capacitance of the transmission line. A prototype SQUID array has beendesigned and produced by Lincoln Laboratories at MIT and is currently undergoing testing. Initialresults show excellent quality factors ( Q (cid:39) , νν NS (2018) 34 he Cryocube Detector Array for Ricochet
Dimitri Misiak
Univ Lyon, Universit´e Lyon 1, CNRS/IN2P3, IPNL-Lyon, F-69622 Villeurbanne, France
For the Ricochet collaboration
Presentation and citeable DOI:
The Cryocube project, being part of the Ricochet experiment, aims for a percentage-level precisionmeasurement of the CENNS process to probe various exotic physics scenarios. It consists in a cubic compactarray of cryogenic detectors with the following specifications: • a very low energy threshold of O (10)eV on the phonon heat signal, • an electromagnetic background rejection of at least 10 , • a total target mass of 1kg divided between 27 crystals of 32g, • two complementary target elements: germanium and zinc.Investigation on the thermal sensor technology (NTD Germanium, NbSi TES) and detector thermalmodelization is ongoing with a first prototype that achieved a 55eV of energy threshold, within theEDELWEISS R&D program. The event discrimination is realized in semiconductor germanium crystalswith HEMT-based ionization readout to reach O (10)eV in ionization resolution, and in superconductingzinc crystals with heat pulse shape discrimination. An accurate low-energy measurement of the Quenchingfactor will be conducted using an in-situ neutron calibration based on the multiple detector coincidence.The installation of the Cryocube in a dry cryostat with shielding and already proven vibration-decouplingstrategy is planned within three years near an optimal nuclear reactor. After an exposure of 1 kg · year, apercentage-level precision measurement of the CENNS process will be delivered by 2024.35 ULLKID - Bulky and low-threshold kinetic inductance detectors
Marco Vignati
INFN, Sezione di Roma, P.le Aldo Moro 2, 00185 Roma, Italy
For the BULLKID proto- collaboration
Presentation and citeable DOI:
BULLKID is an R&D for new experiments on sub-GeV dark matter and coherent neutrino-nucleus scatteringwhich leverages the sensitivity and high multiplexing capability of superconducting Microwave KineticInductance Detectors (MKIDs [56]) to reach low energy thresholds ( <
100 eVnr) and high target masses( ∼ or 5x5 cm , 300 µ m thick, silicon substrates as photon absorbers, the DarkMatter or neutrino target of BULLKID will consist in a 5x5x5 mm silicon voxel. To exploit the MKIDmultiplexing several voxels will be carved from a single 5 mm thick silicon wafer with a diameter of 3”: oneside of the wafer will host the lithography, with a single feedline running through all the MKIDs (Fig 6,left); the opposite side will be cut into a square grid of 5 mm pitch with a 4.5 mm dice depth, so as toobtain almost cubic voxels, and leave the surface hosting the MKIDs intact (Fig 6, right). In this way thephonons produced in a voxel will be isolated, and absorbed by a single MKID to improve the signal to noiseratio. This geometry also ensures an efficient background reduction, as multiple-voxel events can only begenerated by cosmic rays or natural radioactivity and not by neutrinos or dark matter particles. Around100 voxels of 0.3 g each can be obtained from a 3” wafer, for a total active detector mass of 30 g. In a futureexperiment with higher target mass several wafers could be stacked and read independently to reach highertarget masses. 36igure 6: The proposed BULLKID layout. Left: around 100 MKID sensors are deposited on a 5 mm thick,3” diameter silicon wafer and coupled to a single feedline for multiplexing. Right: the wafer is diced fromthe bottom to obtain independent 5x5x5 mm voxels acting as particle absorbers.The Magnificent CE νν
100 eVnr) and high target masses( ∼ or 5x5 cm , 300 µ m thick, silicon substrates as photon absorbers, the DarkMatter or neutrino target of BULLKID will consist in a 5x5x5 mm silicon voxel. To exploit the MKIDmultiplexing several voxels will be carved from a single 5 mm thick silicon wafer with a diameter of 3”: oneside of the wafer will host the lithography, with a single feedline running through all the MKIDs (Fig 6,left); the opposite side will be cut into a square grid of 5 mm pitch with a 4.5 mm dice depth, so as toobtain almost cubic voxels, and leave the surface hosting the MKIDs intact (Fig 6, right). In this way thephonons produced in a voxel will be isolated, and absorbed by a single MKID to improve the signal to noiseratio. This geometry also ensures an efficient background reduction, as multiple-voxel events can only begenerated by cosmic rays or natural radioactivity and not by neutrinos or dark matter particles. Around100 voxels of 0.3 g each can be obtained from a 3” wafer, for a total active detector mass of 30 g. In a futureexperiment with higher target mass several wafers could be stacked and read independently to reach highertarget masses. 36igure 6: The proposed BULLKID layout. Left: around 100 MKID sensors are deposited on a 5 mm thick,3” diameter silicon wafer and coupled to a single feedline for multiplexing. Right: the wafer is diced fromthe bottom to obtain independent 5x5x5 mm voxels acting as particle absorbers.The Magnificent CE νν NS (2018) 37 owards 10-kg Skipper CCD detectors
Javier Tiffenberg
Fermi National Accelerator Laboratory, Batavia, IL 60510, USA
Presentation and citeable DOI:
The newly developed Skipper-CCD sensor has a natural and immediate application for the detection of lowenergy neutrino interactions through the recently observed Coherent Elastic Neutrino-Nucleus Scattering(CE ν NS) process. The first working instrument using Skipper-CCD sensors was produced in 2016 at Fermilabin collaboration with the LBNL MicroSystems Lab. This system was able to unambiguously detect singleionized electrons and reach a groundbreaking 1.1 eV energy threshold, the theoretical limit of ionizationdetectors based on silicon (given by its band gap). This technological breakthrough opens a new path forminiaturized neutrino detectors by providing the capability to observe reactor neutrinos at the 1 MeV scalethrough the CE ν NS process with an unprecedented low energy threshold. Technical advances are requiredto scale up in mass and build multi-kilogram neutrino detectors. Also, to fully profit from a mass increase,a direct measurement of the ionization efficiency of Silicon nuclei at low recoil energies is planned. Thismeasurement is essential to establish the sensitivity of a silicon sensor to low energy neutrinos and hasimplications for other silicon based detectors such as SuperCDMS-SNOLAB and DAMIC-M. There is afunded R&D path for the next 5 yrs to enable a new generation of compact detectors with unprecedentedsensitivity to low energy neutrinos that will allow the exploration of their fundamental nature in the lowenergy regime, that is particularly interesting for new physics searches.38 he CE ν NS Glow of a Supernova
Kate Scholberg
Duke University, Durham, NC 27708, USA
Co-author(s):
A. Smith, G. Sinev
Presentation and citeable DOI:
The collapse of the core of a massive star at the end of its life will produce a compact remnant such asa neutron star or black hole, in many cases a violent explosion in electromagnetic radiation and kineticenergy, and likely in all cases a brilliant burst of neutrinos over a few tens of seconds. These supernova-burstneutrinos come in all flavors. Most are emitted quasi-thermally with energies of a few tens of MeV [60].The flavor, energy and time structure of the neutrino burst carries information about the astrophysics ofthe collapse, the remnant and the subsequent explosion. It also carries information about the properties ofneutrinos themselves, including information about mass hierarchy and flavor transitions within the star.The burst of supernova neutrinos can be detected in large neutrino detectors worldwide for collapseswithin a few hundred kiloparsecs [61]. Neutrino interactions with matter in the few tens of MeV rangedepend on flavor, energy and detector material. Because supernova neutrino energies are less than 100MeV, neutrinos can interact via charged-current channels only for ν e and ¯ ν e flavor. Because charged-currentthreshold for muon neutrinos is greater than 100 MeV, the muon and tau flavor components of the supernovaburst are accessible only via neutral-current interactions.The main existing large detector types for current and future detectors are water Cherenkov (Super-Kand Hyper-K, as well as IceCube, KM3NET), liquid scintillator (LVD, Borexino, KamLAND, JUNO) andliquid argon (DUNE). The water and scintillator detectors’ primary sensitivity is the ¯ ν e , via inverse betadecay (IBD) on free protons, ¯ ν e + p → e + + n . Argon detectors are primarily sensitive to CC interactionsof ν e on Ar. Some neutral-current interactions are visible via scattering on protons in liquid scintillator,the deexcitation of nuclei excited via neutral-current scattering, and a component of elastic scattering onelectrons, but these are subdominant channels. Detection and tagging of neutral-current interactions areespecially valuable in the supernova-neutrino detection game, due to the neutral current’s sensitivity to the total supernova neutrino flux. Neutral-current detection is important not only for understanding the totalenergy release of the supernova, but also because it enables understanding of flavor transitions within thesupernova.CE ν NS is a neutral-current interaction channel which may be used to measure the total neutrino fluxfrom a supernova. The cross section is large compared to other interactions used for supernova detection,but the produced signal is in the form of recoiling nuclei with energies of tens of keV or less, which is wellbelow the threshold of most supernova-sensitive neutrino detectors. The exception is WIMP dark matterdetectors, which are now reaching tonne scale, and which will be able to observe a handful of events pertonne for a core collapse at a standard distance of 10 kpc (e.g., [16].)A new idea presented in this talk is to exploit kilotonne-scale underground detectors for CE ν NS detection,to determine the total neutrino flux over the supernova burst. The few-keV CE ν NS recoils are invisible inwater Cherenkov detectors; however in scintillator and argon detectors, there could in principle be “IceCubestyle” detection of CE ν NS interactions. IceCube, which has very sparse photomultiplier arrays, does notdetect individual IBD interactions; rather, it collects single photons from the diffuse glow of supernova-39he CE ν NS Glow of a Supernovaneutrino-induced Cherenkov photons in the ice [62]. Similarly, single photons from the diffuse glow of CE ν NSinteractions from scintillation in liquid hydrocarbon or argon could be collected over the time scale of theburst. The back-of-the-envelope calculation is as follows: there are about two orders of magnitude moreCE ν NS than CC interactions in a given target, but about three orders of magnitude less energy depositionper interaction. Furthermore, there is typically a quenching factor of at least a few in photon productionfor recoils of heavy particles (nuclei) with respect to light ones (electrons or positrons). On the other hand,there is a factor of six for CE ν NS with respect to CC, given that the neutrino flux is approximately equallydivided among flavors. Overall this results in few to ten percent of CE ν NS-induced photons with respect toCC-induced photons. However the CE ν NS glow photons should be diffused over the burst rather than inshort, inelastic-interaction-associated spikes.The primary issue for detection of CE ν NS glow is background. Preliminary calculations show thatcosmogenic Ar β decays, which have a rate of about a Bq/kg in natural argon, may completely swamp thesignal in argon. Underground argon, depleted in this isotope, could mitigate this. Large liquid scintillatordetectors are likely quieter. One will also know the time frame of the burst given inelastic event detection.The distribution of photon numbers as a function of time may be a handle for extracting signal frombackground. This idea is ambitious and it is not yet clear it is feasible, but we are continuing to study it.Figure 7: Distributions of numbers of photons arriving at a detection surface as a function of time, for thesupernova neutrino production model of Ref. [63], from a preliminary analytic calculation by A. Smith. Topplots: argon scintillation. Bottom plots: liquid hydrocarbon scintillation. The left plots show photons fromCE ν NS; center plots are photons from the primary charged- and neutral-current channels in the respectivematerial, and right plots show photons due to backgrounds. Note that there can also be “CE ν NS buzz” from ionization collected in liquid argon TPCs.
The Magnificent CE νν
The Magnificent CE νν NS (2018) 40 E ν NS as a Probe of Nuclear Neutron Form Factors
Kelly Patton
Institute for Nuclear Theory, University of Washington, Seattle, WA 98195, USA
Co-author(s):
G. McLaughlin, K. Scholberg, J. Engel, N. Schunck
Presentation and citeable DOI:
The size of a nucleus is one of its most fundamental properties. While the distribution of protons has beenwell measured through the use of charged probes, the neutron distribution has remained difficult to probe.Previous measurements have used hadronic scattering and report uncertainties on the root-mean-square(RMS) radius of ∼
1% [64, 65], but require assumptions about the underlying nuclear structure to obtainresults. The PREX experiment used parity violating electron scattering to measure the neutron skin andRMS radius of
Pb, reporting an uncertainty of 2 .
5% on the RMS radius [66]. CE ν NS provides a newmethod for measuring the RMS radius for a range of nuclei.All nuclear structure information in the CE ν NS cross section is included in the form factor F ( Q ), whichis defined as F ( Q ) = 1 Q W (cid:90) ( ρ n ( r ) − (1 − θ W ) ρ p ( r )) sin( Qr ) Qr r dr. (2)Here, Q W is the weak charge of the nucleus, and ρ n,p are the neutron and proton densities. Since this processis very low energy, we can Taylor expand the form factor and write it in terms of moments of the distribution[67]. So, for example, the neutron terms can be written as F n ( Q ) ≈ N (cid:18) − Q (cid:104) R n (cid:105) + Q (cid:104) R n (cid:105) + · · · (cid:19) , (3)where (cid:104) R kn (cid:105) is the k th moment of the distribution. Changes in the values of these moments has an effect onthe number of events as a function of energy, which can be measured in a CE ν NS experiment. For a detectorplaced 20 m from the source at the SNS, corresponding to the location of Neutrino Alley, we find that theRMS radius can be measured with an uncertainty of ∼
5% for Ar, Ge, and Xe, using detectors of 3.5 tonnes,1.5 tonnes, and 300 kg, respectively. These calculations assumed an detector threshold of 5 keV. It is alsopossible to get the first experimental measurement of the fourth moment of the neutron distribution, withuncertainties on the order of ∼ −
20% [67]. These measurements also depend on detector uncertainties,in particular the spectral shape uncertainty which describes the difference in efficiency between energy bins.We have found that this specific uncertainty must be known to the level of ∼
1% to measure the RMS radiusto 5% at the 90% confidence level for Ar, Ge, and Xe [68]. These results show that CE ν NS is a promisingnew method of probing neutron distributions in nuclei.41 uture sensitivity of CE ν NS to a weak mixing angle
Omar Miranda
Departamento de F´ısica, Centro de Investigaci´on y de Estudios Avanzados del IPN, Apdo. Postal 14-740, 07000Ciudad de M´exico, M´exico
Presentation and citeable DOI:
Precise measurements of CE ν NS will allow to measure the weak mixing angle with precision. There is roomof improvement for this important parameter of the standar model in the low energy regime [69], whereCE ν NS measurements are performed. We have studied the potential of future CE ν NS detectors locatedclose to reactor antineutrino fluxes [70]. For this kind of measurements, the ratio of protons to neutrons isvery relevant since the dependence on the weak mixing angle is present only in the proton coupling constants.Besides, for large statistic experiments, the reactor antineutrino flux uncertainties will also be an importantissue to solve, since current uncertainties translate into a systematic error around one percent for the weakmixing angle measurement. 42 eutrino constraints on conventional and exotic CE ν NS interac-tions
D.K. Papoulias
Instituto de F´ısica Corpuscular (CSIC-Universitat de Val`encia), Paterna (Valencia), Spain
Co-author(s):
T.S. Kosmas
Presentation and citeable DOI:
Assuming one non-zero parameter at a time, the current extracted 90% C.L. limits on the weak mixingangle, NSI and electromagnetic properties (neutrino magnetic moment and charge radius) are summarizedin Table 2 [39]. The next phase of the COHERENT program, on the basis of a multi-target strategywith ton-scale detectors, will lead to significant improvements on the current determination of the weakmixing angle as well as to improvements on NSI, sterile neutrino and new mediator (vector Z (cid:48) and scalar Φ)constraints by one order of magnitude (see e.g. [71, 72]). Next generation advances of CE ν NS experimentswith ultra low-threshold technologies are expected to provide severe constraints on neutrino electromagneticproperties that will compete with current neutrino-electron scattering data [73, 74]. The latter will alsoenable validation of the neutrino-floor and detector-response models relevant to Dark Matter searches [75].43eutrino constraints on conventional and exotic CE ν NS interactionsParameter Limit (90% C.L.)sin θ W (cid:15) uVee -0.08 – 0.47 (cid:15) dVee -0.07 – 0.42 (cid:15) uVµµ -0.09 – 0.48 (cid:15) dVµµ -0.08 – 0.43 (cid:15) uTee -0.013 – 0.013 (cid:15) dTee -0.011 – 0.011 (cid:15) uTµµ -0.013 – 0.013 (cid:15) dTµµ -0.011 – 0.011 µ ν × − µ B µ ν e × − µ B µ ν µ × − µ B (cid:104) r ν (cid:105) -31.4 – -23.1 and -4.9 – 3.4 (cid:104) r ν e (cid:105) -38.0 – -26.6 and -1.4 – 10.1 (cid:104) r ν µ (cid:105) -39.6 – -27.4 and -0.6 – 11.7Table 2: Constraints on SM and exotic parameters from the first observation of CE ν NS at the COHERENTexperiment. For the case of the neutrino charge radius the results are given in units of 10 − cm [39].The Magnificent CE νν
Assuming one non-zero parameter at a time, the current extracted 90% C.L. limits on the weak mixingangle, NSI and electromagnetic properties (neutrino magnetic moment and charge radius) are summarizedin Table 2 [39]. The next phase of the COHERENT program, on the basis of a multi-target strategywith ton-scale detectors, will lead to significant improvements on the current determination of the weakmixing angle as well as to improvements on NSI, sterile neutrino and new mediator (vector Z (cid:48) and scalar Φ)constraints by one order of magnitude (see e.g. [71, 72]). Next generation advances of CE ν NS experimentswith ultra low-threshold technologies are expected to provide severe constraints on neutrino electromagneticproperties that will compete with current neutrino-electron scattering data [73, 74]. The latter will alsoenable validation of the neutrino-floor and detector-response models relevant to Dark Matter searches [75].43eutrino constraints on conventional and exotic CE ν NS interactionsParameter Limit (90% C.L.)sin θ W (cid:15) uVee -0.08 – 0.47 (cid:15) dVee -0.07 – 0.42 (cid:15) uVµµ -0.09 – 0.48 (cid:15) dVµµ -0.08 – 0.43 (cid:15) uTee -0.013 – 0.013 (cid:15) dTee -0.011 – 0.011 (cid:15) uTµµ -0.013 – 0.013 (cid:15) dTµµ -0.011 – 0.011 µ ν × − µ B µ ν e × − µ B µ ν µ × − µ B (cid:104) r ν (cid:105) -31.4 – -23.1 and -4.9 – 3.4 (cid:104) r ν e (cid:105) -38.0 – -26.6 and -1.4 – 10.1 (cid:104) r ν µ (cid:105) -39.6 – -27.4 and -0.6 – 11.7Table 2: Constraints on SM and exotic parameters from the first observation of CE ν NS at the COHERENTexperiment. For the case of the neutrino charge radius the results are given in units of 10 − cm [39].The Magnificent CE νν NS (2018) 44 spects of Elastic Scattering of Neutrinos
A.B. Balantekin
Department of Physics, University of Wisconsin, Madison, WI 53706, USA
Presentation and citeable DOI:
Coherent elastic scattering of neutrinos off nuclei was experimentally observed for the first time only recently[30]. The associated cross section is sensitive to the neutron distribution in the target nuclei. Even a singleextra neutron appreciably increases the coherent scattering cross section as illustrated in Ref. [76] for Cversus C.Elastic scattering of neutrinos off nuclei is primarily governed by weak neutral current scattering. Sinceneutrinos have mass we know that neutrino magnetic moments are non-zero, but we do not know just howlarge they are [77, 78]. Neutrino elastic scattering can also have a small electromagnetic component due toneutrino magnetic moments. The differential scattering cross section is then sum of the two components: dσdT = G F π Q W M (cid:34) − (cid:18) TT max (cid:19) + (cid:18) TE (cid:19) (cid:35) (cid:2) F Z ( Q ) (cid:3) + πα m e Z µ (cid:20) T − E (cid:21) (cid:2) F γ ( Q ) (cid:3) where E is the neutrino energy, T and M are the recoil energy and the mass of the nucleus, respectively,and Q W = [ N − (1 − θ W )]. The effective neutrino magnetic moment is given by µ = (cid:88) i (cid:12)(cid:12)(cid:12)(cid:12)(cid:12)(cid:12)(cid:88) j U (e or µ ) j e − iE j L µ ji (cid:12)(cid:12)(cid:12)(cid:12)(cid:12)(cid:12) where L is the distance traveled by the neutrino before it scatters, E j is the energy of the j -th mass eigenstate,and µ ij are the elements of the neutrino magnetic moment matrix in the mass basis. Note that not onlythe second term in the above cross section is smaller than the first term, but two form factors F Z ( Q ) and F γ ( Q ) represent represent two rather different aspects of the nuclear structure, i.e. primarily neutron versusproton distributions in the nuclei. 45 easurement of CE ν NS with LAr
Rex Tayloe
Indiana University, Bloomington, IN 47405, USA
Presentation and citeable DOI:
The ORNL Spallation Neutron Source provides the world’s most intense pulsed neutron beams. The 1.4 MW,1.0 GeV pulsed proton beam also provides a world-class pion decay-at-rest neutrino source with a 600 nswidth, 60 Hz repetition rate for a duty-factor of 10 − . This beam, combined with a low-energy-threshold LArdetector, will allow for low-background, precision studies of the coherent elastic neutrino nucleus scattering(CE ν NS) process. An initial run with the CENNS-10 22 kg fiducial volume detector has demonstrated thata low energy threshold and small backgrounds can be obtained in a large volume. Design parameters for thenext-generation COHERENT LAr detector are: • detector mass (total/fiducial): 750(612) kg • integrated beam power (protons-on-target): 7000 MWhr/yr (1.6E23POT/yr) • pion decays-at-rest/protons-on-target: 0.9 • pion production target - detector distance: 27.5 mag • light yield: 5 ± • argon quenching factor: 0 . ± • energy threshold: 20 keVnr • estimated detected CE ν NS event sample: 3000 events/year • signal/background ratio with atmospheric (underground [79]) argon: 1:10 (1:1)46 Search for CE ν NS with the CENNS-10 Liquid Argon Detectorfor COHERENT
Jacob Zettlemoyer
Indiana University, Bloomington, IN 47405, USA
Presentation and citeable DOI:
The COHERENT Collaboration deploys the CENNS-10 detector, a 22-kg liquid argon detector, at theSpallation Neutron Source at Oak Ridge National Laboratory for a measurement of CE ν NS on a lightnucleus to complement other planned measurements within COHERENT. The detector began operation inDecember 2016 and was upgraded for improved light collection in July 2017 and has been running sincethe upgrade. The initial run will be used to measure the flux of neutrons that occur in time with theSNS beam pulse at the CENNS-10 location and confirm previous measurements. With the full shieldingstructure, simulations show the main component of the steady-state background is the internal component Ar. Using the timing of the SNS beam and the pulse shape discrimination capabilities of liquid argon,these backgrounds can be reduced to levels necessary for a CE ν NS measurement. The analysis of the physicsdata is ongoing. The current parameters are: • Detector mass: 22 kg, fiducial. • Shielding: 20 cm cylindrical water tank, 1.27 cm copper on all sides outside water tank, and 10.16 cmlead on all sides outside of the copper. • Light Yield: 4.2 ± • Threshold: 20 keVnr. • Steady state backgrounds: measured 1.7 Hz in energy ROI (0 – 35 keVee), includes SNS timing. • Energy Resolution: 9.1% at 41 keVee. • Quenching factor: QF = aE + b with a = 0 .
251 and b = 7 . × − with E in keVnr from 0-120keVnr. 47 pherical proportional counters and their application for CEnNSdetection Marie Vidal
Department of Physics, Engineering Physics & Astronomy, Queen’s University, Kingston, Ontario K7L 3N6, Canada
For the NEWS-G collaboration
Presentation and citeable DOI:
The NEWS-G collaboration uses spherical proportional counters to search for low mass Dark Matter. Theimportant features and results of the experiment are listed below: • Flexibility in gas choice: noble gases and operating pressure • Detector sensitivity to single electron: low energy threshold • Constraints in the Spin-Independent WIMP-nucleon cross section vs WIMP mass: 0.6 GeV. For LSMdata (2017): 9.6 kg.days with a mixture of Neon + 0.7% CH : [80] • Preliminary projection for next experiment (2019): below 0.1 GeV. For a Neon + 10% CH andsensitivity down to ∼ − cm .Here are some preliminary calculation for CEnNS detection using reactor neutrino, considering: • •
10m from core • Neutrino flux: VogelDetector conditions: • Low threshold 100 eV ee or below achieved • Moderate size sphere: 80 cm of diameter • ∼ • Mean energy to create e − /ion pair: 36 eV in Neon: [81, 82] • quenching factor: Lindhard parametrization • Poisson distribution • single electron response: [83]Event rate: 48 Total event rate: 112 events/kg/day • Event rate above 50 eV ee : 28 events/kg/day • Event rate above 100 eV ee : 15 events/kg/dayThe Magnificent CE νν
10m from core • Neutrino flux: VogelDetector conditions: • Low threshold 100 eV ee or below achieved • Moderate size sphere: 80 cm of diameter • ∼ • Mean energy to create e − /ion pair: 36 eV in Neon: [81, 82] • quenching factor: Lindhard parametrization • Poisson distribution • single electron response: [83]Event rate: 48 Total event rate: 112 events/kg/day • Event rate above 50 eV ee : 28 events/kg/day • Event rate above 100 eV ee : 15 events/kg/dayThe Magnificent CE νν NS (2018) 49 rogress on liquid-noble bubble chambers for CE ν NS C. Eric Dahl
Northwestern University, Evanston, IL 60208, USA
For the SBC collaboration
Presentation and citeable DOI:
Detector Concept
Scintillating argon bubble chamber
Nuclear recoils (NRs) from CE ν NS in a superheated liquid argon target can both produce scintillationlight and nucleate a single bubble in the superheated fluid. Electron-recoil (ER) backgrounds (beta-decays,gammas) produce scintillation light only. This does-it-make-a-bubble discrimination is effective at muchlower thresholds than pulse-shape discrimination in the scintillation signal — we expect 10 − ER sensitivityat sub-keV NR bubble nucleation thresholds.
Scin%lla%ng Bubble Chambers for WIMPs and Reactor CEvNS
Eric Dahl Northwestern University Fermilab Novel Instrumenta%on for Fundamental Physics, Nov 2018 –65 to –50 °C superheated –105 °C normal Mirrors To hydraulic controller PMT Camera LXe I R ill u m i n a @ o n Vacuum Cryostat Piezo Scin@lla@on & Bubble Muon paddle –65 to –50 °C superheated –105 °C normal Mirrors To hydraulic controller PMT Camera LXe I R ill u m i n a @ o n Vacuum Cryostat Piezo Scin@lla@on & Bubble Muon paddle
Piezo IR LED VUV SiPM
Ar + 10ppm Xe CF -0.5 0 0.5 1 1.5 Time from acoustic onset [ms] -50 0 50 100 150 200
Time from PMT trigger [ns] c m Figure 8:
Left:
Sample nuclear recoil event from the prototype xenon bubble chamber [84]. Top: Stereoimage of a single xenon vapor bubble. Middle: Acoustic record (blue) of bubble formation, giving the time ofnucleation to ± µ s. In this case nucleation is coincident with a scintillation trigger (red). The lag betweenthe scintillation pulse and acoustic onset matches the sound speed in liquid xenon. Bottom: PMT waveformsshowing xenon scintillation. The bubble-coincident pulse is shown in red. ER’s generate scintillation pulseswithout coincident bubble nucleation (gray traces). Left:
Schematic and model of the 10-kg argon bubblechamber, showing the pressure and temperature control, bubble imaging, and scintillation detection schemefor the chamber. The solid model and rendering were done by the FNAL PPD/Mech Eng Dept.50 ey Performance Specifications: Goals for the Fermilab Scintillat-ing Bubble Chamber
Target Material/Mass — 10-kg superheated argon @ 25 psia, 130 K
Bubble threshold — Effecient NR bubble nucleation @ 0.1 keV— 10 − ER sensitivity
Scintillation threshold — 1 photon detected / 2 keV (NR)— Bubble-nucleating events with 0 photons detectedare included in the CE ν NS signal region
Energy Resolution — Event-by-event energy resolution from scintilla-tion: 2 keV— Spectral resolution from bubble nucleation thresh-old scan: 0.1 keV
Spatial resolution — 1-mm absolute resolution, from stereo imaging ofbubble— 0.1-mm resolution for indentifying multi-scatterevents, from acoustic signal strength
Timing resolution — 10 ns for events with coincident scintillation signal— 25 µ s for events without coincident scintillation( (cid:46) Backgrounds — Negligible ER backgrounds, including Ar, due tobubble discrimination— No high-Z shielding required, reducing neutrino-induced-neutron backgrounds— Signifcant dead time ( ∼
30 seconds) after everybubble-nucleating event limits the background NRrate to < νν
30 seconds) after everybubble-nucleating event limits the background NRrate to < νν NS (2018) 51
ArCADe: lowering thresholds in LArTPC detectors
David Caratelli
Fermi National Accelerator Laboratory, Batavia, IL 60510, USA
Co-author(s):
A. Fava
Presentation and citeable DOI:
The recent detection of CE ν NS by the COHERENT collaboration, and the rich physics program thatCEvNS can deliver, motivate the optimization of existing detectors and development of new technologiesfor the purpose of improving the sensitivity to the experimental signature of coherent neutrino scatteringprocesses. The LArCADe project aims to investigate the feasibility of reducing detection thresholds forionization electrons in single-phase Liquid Argon Time Projection Chamber (LArTPC) detectors by enoughto enable the detection of nuclear recoils. The program aims to allow for the amplification of drifting electronsignals directly in the liquid phase by modifying the geometry of the charge-collecting anode sensors. Sucha technological achievement could merge into one the advantages of kiloton-scale liquid argon detectors andthose of low-threshold double-phase dark-matter TPCs.Nuclear recoils in liquid argon lead to small ionization signals, further reduced by the significant quenchingcaused by ion recombination and dissipation of energy into atomic excitations. Nuclear recoils of 1 – 10sof keV, originating from O (10 MeV) CE ν NS interactions, are expected to yield 1 – 100 free electrons, withsignificant variation in the tails of such distributions depending on the assumed quenching model [85–87].These values are a factor of 100 smaller than current state of the art detection thresholds in LArTPCs[88]. In order to amplify ionization charge directly in the liquid phase, strong fields of > V/cm arenecessary. The LArCADe program is exploring the possibility of obtaining stable charge amplification ofdrifting electrons by shaping the electric field over micron-scale distances in the proximity of the charge-collecting anode-planes. The first phase of this R&D effort is employing tungsten tips of micron radii, andhas demonstrated preliminary controlled amplification in gaseous argon using a few-cm drift chamber whichrecords ionization charge produced by a pulsed LED source impinging on a photocathode. A second phase,currently underway, aims to use O (100 nm) tips to obtain amplification in liquid, characterizing stabilityand potential complications which may arise, such as the formation of argon gas bubbles which can disruptsignal detection. A successful demonstration of this program can lead in the future to the construction ofsmall-scale detectors sensitive to CE ν NS interactions in the proximity of intense neutrino beams.52 ark side of the exciton: self-organized criticality and low energythreshold detectors
Sergey Pereverzev
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Co-author(s):
A. Bernstein, J. Xu
Presentation and citeable DOI:
With interest to detect coherent scattering of low energy solar and reactor neutrinos on nuclei of the detectormaterials, we analyses low energy response of different detectors. It is common for ionization and scintillationdetectors to demonstrate increase of low-energy background at energies of the order of excitations in thedetector material- i.e., at the level of few electrons or photons. Practically in all solid materials, includingrare gases solid, slow irradiation by muons and residual radioactivity leads to accumulation of energy in formof trapped charges (pairs of ions, trapped electrons and holes)- which lead to effects as thermally-stimulatedluminescence, thermally stimulated exaelectron emission (electron emission from the surface of dielectricsor dielectric films on metal surfaces), thermally stimulated conductivity (in semiconductors and dielectrics).Defects / impurities clustering is another common effect in solids. Thus, one can expect to see Self-OrganizedCriticality type of dynamics- slow accumulation of excitations and events of their annihilation in form ofsmall avalanches. In dual-phase Ar and Xe detectors solid phase is present in a form of solid physiosorbedfilms on all internal surfaces. Native positive ions Xe + (Ar + ) , and negatively charged complexes formedout Xe (Ar) and O, F, H atoms (these can be due to small residual amount of oxygen, water, and fluoridecompounds coming from TEFLON) can be produced due to ionization events and due to exposure of solidfilms on surfaces to UV light (gas electroluminescence light- S2 pulses). Accumulation of those species onelectrodes and their avalanche-like annihilation can lead to “few electrons events” which mimic real low energyparticles detection events. By application of strong AC electric field in between grid wires ion recombinationon the cathode grid can be reinforced and ions accumulation suppressed. Decrease of parasitic backgroundin this case can be experimentally verified.Our analysis illustrates that searches for rare and low energy particles interactions require carefulexamination of the detector physics and advanced studies of condensed matter effects.This work was performed under the auspices of the U.S. Department of Energy by Lawrence LivermoreNational Laboratory under Contract DE-AC52-07NA27344.53 he development of low threshold dual phase argon detector inChina for CE ν NS measurement
Ran Han
Beijing Institute of Spacecraft Environment Engineering, Beijing 100094, China
Co-author(s):
W. Yang
Presentation and citeable DOI:
The dual-phase liquid argon time projection chamber (TPC) is designed for the coherent elastic neutrino-nucleus scattering [1, 89] research. The detector are planned to settled near the core of Taishan reactor(located in Guangdong province) at the distance of 31 m. The power of the Taishan reactor is 4.6 GWwhich provides a reactor flux around 4 . × / (cid:0) cm · s (cid:1) in total. The TPC is designed as a cylinderwhile the dimensions of TPC are: the diameter d = 56 cm, the height h = 58 cm and the mass of liquidargon is about 200 kg, see Fig. 9. Three electrodes are used to generate the drift field, extraction field andcollection field, respectively. Gas pocket is generated by the vaporization of the liquid argon which thicknessis 10 mm. The grid is placed below the gas-liquid interface 5 mm. Drift field is design as 400 V/cm aftersimulation. The inner container is made of acrylic material to reduce the radio activities background. SiPMsare used to collect S1 and S2 signals instead of photomultiplier tubes (PMTs). Properties of SiPM andacquisition systems at low temperature are under study. To obtain the low threshold results, only S2 signalsare collected.To detect the low recoil energy in the dual-phase liquid argon TPC, quenching factor have to be precisedetermined. Quenching factor defined as the ratio of the light yields of the nuclear recoils with respect to theones of the electron recoils at the same energy. Generally, the electron recoils are taken as no quenching effectand set to be unit. In order to determine the quenching factor, nuclear recoil energies should be measured.Nuclear recoil energies or deposit energies can be measured according to the following equation [90] E r ≈ E n M n M Ar ( M n + M Ar ) (1 − cos θ ) , where E r , E n are the nuclear recoil energy and the neutron beam energy, respectively. M n is the mass ofa neutron and M Ar is the mass of the argon nucleus. θ is the scattering angle of the outgoing neutron. Toreduce the background and the systematic errors, the TPC have to be the smaller the better. The diameterof the sensitive region is designed as 7.6 cm while the sensitive mass is about 0.5 kg. Neutron detectors areplaced at relatively large distance from the TPC for the small scattering angle neutron detection. Neutrondetectors arrays are also used to increase the statistics at different angles, respectively. Shield can be usedto separate two kinds of neutron beams, coming directly from the neutron source beam and the scatteringneutron beam, for small scattering angle detections. For the measurement of quenching factor at sub-keVscale, sub-MeV neutron source have to be used and the TPC also have to be exposed for a few mouths toobtain enough data. 54igure 9: The design drawing of the LAr detector.The Magnificent CE νν
The dual-phase liquid argon time projection chamber (TPC) is designed for the coherent elastic neutrino-nucleus scattering [1, 89] research. The detector are planned to settled near the core of Taishan reactor(located in Guangdong province) at the distance of 31 m. The power of the Taishan reactor is 4.6 GWwhich provides a reactor flux around 4 . × / (cid:0) cm · s (cid:1) in total. The TPC is designed as a cylinderwhile the dimensions of TPC are: the diameter d = 56 cm, the height h = 58 cm and the mass of liquidargon is about 200 kg, see Fig. 9. Three electrodes are used to generate the drift field, extraction field andcollection field, respectively. Gas pocket is generated by the vaporization of the liquid argon which thicknessis 10 mm. The grid is placed below the gas-liquid interface 5 mm. Drift field is design as 400 V/cm aftersimulation. The inner container is made of acrylic material to reduce the radio activities background. SiPMsare used to collect S1 and S2 signals instead of photomultiplier tubes (PMTs). Properties of SiPM andacquisition systems at low temperature are under study. To obtain the low threshold results, only S2 signalsare collected.To detect the low recoil energy in the dual-phase liquid argon TPC, quenching factor have to be precisedetermined. Quenching factor defined as the ratio of the light yields of the nuclear recoils with respect to theones of the electron recoils at the same energy. Generally, the electron recoils are taken as no quenching effectand set to be unit. In order to determine the quenching factor, nuclear recoil energies should be measured.Nuclear recoil energies or deposit energies can be measured according to the following equation [90] E r ≈ E n M n M Ar ( M n + M Ar ) (1 − cos θ ) , where E r , E n are the nuclear recoil energy and the neutron beam energy, respectively. M n is the mass ofa neutron and M Ar is the mass of the argon nucleus. θ is the scattering angle of the outgoing neutron. Toreduce the background and the systematic errors, the TPC have to be the smaller the better. The diameterof the sensitive region is designed as 7.6 cm while the sensitive mass is about 0.5 kg. Neutron detectors areplaced at relatively large distance from the TPC for the small scattering angle neutron detection. Neutrondetectors arrays are also used to increase the statistics at different angles, respectively. Shield can be usedto separate two kinds of neutron beams, coming directly from the neutron source beam and the scatteringneutron beam, for small scattering angle detections. For the measurement of quenching factor at sub-keVscale, sub-MeV neutron source have to be used and the TPC also have to be exposed for a few mouths toobtain enough data. 54igure 9: The design drawing of the LAr detector.The Magnificent CE νν NS (2018) 55
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