R. Partridge

Search for low-mass weakly interacting massive particles with SuperCDMS.

We report a first search for weakly interacting massive particles (WIMPs) using the background rejection capabilities of SuperCDMS. An exposure of 577 kg-days was analyzed for WIMPs with mass < 30 GeV/c2, with the signal region blinded. Eleven events were observed after unblinding. We set an upper limit on the spin-independent WIMP-nucleon cross section of 1.2e-42 cm2 at 8 GeV/c2. This result is in tension with WIMP interpretations of recent experiments and probes new parameter space for WIMP-nucleon scattering for WIMP masses < 6 GeV/c2.

New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment

R. Agnese, A.J. Anderson, T. Aramaki, M. Asai, W. Baker, D. Balakishiyeva, D. Barker, R. Basu Thakur, 23 D.A. Bauer, J. Billard, A. Borgland, M.A. Bowles, P.L. Brink, R. Bunker, B. Cabrera, D.O. Caldwell, R. Calkins, D.G. Cerdeno, H. Chagani, Y. Chen, J. Cooley, B. Cornell, P. Cushman, M. Daal, P.C.F. Di Stefano, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, M. Ghaith, G.L. Godfrey, S.R. Golwala, J. Hall, H.R. Harris, T. Hofer, D. Holmgren, L. Hsu, M.E. Huber, D. Jardin, A. Jastram, O. Kamaev, B. Kara, M.H. Kelsey, A. Kennedy, A. Leder, B. Loer, E. Lopez Asamar, P. Lukens, R. Mahapatra, V. Mandic, N. Mast, N. Mirabolfathi, R.A. Moffatt, J.D. Morales Mendoza, S.M. Oser, K. Page, W.A. Page, R. Partridge, M. Pepin, ∗ A. Phipps, K. Prasad, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, Y. Ricci, A. Roberts, H.E. Rogers, T. Saab, B. Sadoulet, 4 J. Sander, K. Schneck, R.W. Schnee, S. Scorza, B. Serfass, B. Shank, D. Speller, D. Toback, R. Underwood, S. Upadhyayula, A.N. Villano, B. Welliver, J.S. Wilson, D.H. Wright, S. Yellin, J.J. Yen, B.A. Young, and J. Zhang

Search for a New Gauge Boson in Electron-Nucleus Fixed-Target Scattering by the APEX Experiment

S. Abrahamyan,1 Z. Ahmed,2 K. Allada,3 D. Anez,4 T. Averett,5 A. Barbieri,6 K. Bartlett,7 J. Beacham,8 J. Bono,9 J.R. Boyce,10 P. Brindza,10 A. Camsonne,10 K. Cranmer,8 M.M. Dalton,6 C.W. de Jager,10, 6 J. Donaghy,7 R. Essig,11, ∗ C. Field,11 E. Folts,10 A. Gasparian,12 N. Goeckner-Wald,13 J. Gomez,10 M. Graham,11 J.-O. Hansen,10 D.W. Higinbotham,10 T. Holmstrom,14 J. Huang,15 S. Iqbal,16 J. Jaros,11 E. Jensen,5 A. Kelleher,15 M. Khandaker,17, 10 J.J. LeRose,10 R. Lindgren,6 N. Liyanage,6 E. Long,18 J. Mammei,19 P. Markowitz,9 T. Maruyama,11 V. Maxwell,9 S. Mayilyan,1 J. McDonald,11 R. Michaels,10 K. Moffeit,11 V. Nelyubin,6 A. Odian,11 M. Oriunno,11 R. Partridge,11 M. Paolone,20 E. Piasetzky,21 I. Pomerantz,21 Y. Qiang,10 S. Riordan,19 Y. Roblin,10 B. Sawatzky,10 P. Schuster,11, 22, † J. Segal,10 L. Selvy,18 A. Shahinyan,1 R. Subedi,23 V. Sulkosky,15 S. Stepanyan,10 N. Toro,24, 22, ‡ D. Walz,11 B. Wojtsekhowski,10, § and J. Zhang10 Yerevan Physics Institute, Yerevan 375036, Armenia Syracuse University, Syracuse, New York 13244 University of Kentucky, Lexington, Kentucky 40506 Saint Mary’s University, Halifax, NS B3H 3C3, Canada College of William and Mary, Williamsburg, Virginia 23187 University of Virginia, Charlottesville, Virginia 22903 University of New Hampshire, Durham, New Hampshire 03824 New York University, New York, New York 10012 Florida International University, Miami, Florida 33199 Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 SLAC National Accelerator Laboratory, Menlo Park, California 94025 North Carolina Agricultural and Technical State University, Greensboro, North Carolina 27411 Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 Longwood University, Farmville, Virginia 23909 Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 California State University at Los Angeles, Los Angeles, California 90032 Norfolk State University, Norfolk, Virginia 23504 Kent State University, Kent, Ohio 44242 University of Massachusetts, Amherst, Massachusetts 01003 University of South Carolina, Columbia, South Carolina 29225 Tel Aviv University, Tel Aviv, 69978 Israel Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5, Canada George Washington University, Washington DC 20052 Stanford University, Menlo Park, California 94025 (Dated: February 1, 2013)

Search for Low-Mass WIMPs with SuperCDMS

We report a first search for weakly interacting massive particles (WIMPs) using the background rejection capabilities of SuperCDMS. An exposure of 577 kg-days was analyzed for WIMPs with mass < 30 GeV/c2, with the signal region blinded. Eleven events were observed after unblinding. We set an upper limit on the spin-independent WIMP-nucleon cross section of 1.2e-42 cm2 at 8 GeV/c2. This result is in tension with WIMP interpretations of recent experiments and probes new parameter space for WIMP-nucleon scattering for WIMP masses < 6 GeV/c2.

Silicon detector results from the first five-tower run of CDMS II

We report results of a search for weakly interacting massive particles (WIMPs) with the Si detectors of the CDMS II experiment. This report describes a blind analysis of the first data taken with CDMS II’s full complement of detectors in 2006–2007; results from this exposure using the Ge detectors have already been presented. We observed no candidate WIMP-scattering events in an exposure of 55.9 kg-days before analysis cuts, with an expected background of ∼1.1 events. The exposure of this analysis is equivalent to 10.3 kg-days over a recoil energy range of 7–100 keV for an ideal Si detector and a WIMP mass of 10  GeV/c^2. These data set an upper limit of 1.7×10^(-41)  cm^2 on the WIMP-nucleon spin-independent cross section of a 10  GeV/c^2 WIMP. These data exclude parameter space for spin-independent WIMP-nucleon elastic scattering that is relevant to recent searches for low-mass WIMPs.

Projected sensitivity of the SuperCDMS SNOLAB experiment

SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤ 10 GeV/c^2) that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ∼ 1×10^(−43) cm^2 for a dark matter particle mass of 1 GeV/c^2, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced ^3H and naturally occurring ^(32)Si will be present in the detectors at some level. Even if these backgrounds are 10 times higher than expected, the science reach of the HV detectors would be over 3 orders of magnitude beyond current results for a dark matter mass of 1 GeV/c^2. The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particles with masses ≳ 5 GeV/c^2. The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the “neutrino floor,” where coherent scatters of solar neutrinos become a limiting background.

Measurement of the Branching Fractions for D0 ---> pi- e+ electron-neutrino and D0 ---> K- e+ electron-neutrino and Determination of (V (c d) / V (c s))**2

Measurements of the exclusive branching fractions B(D^0→π^-e^+ν_e) and B(D^0→K^-e^+ν_e), using data collected at the ψ(3770) with the Mark III detector at the SLAC e^+e^- storage ring SPEAR, are used to determine the ratio of the Kobayashi-Maskawa matrix elements │V_(cd)/V_(cs)│^2 =0.057_(-0.015)^(+0.038)±0.005.

Resonant substructure in Kππ decays of charmed D mesons

Abstract Dalitz plot analyses of four Kππ decays of the D 0 and D + mesons are presented. The relative amounts of K ∗ π, Kϱ and non-resonant Kππ in each decay mode are determined, and isospin amplitudes and phases are derived. These results are compared with predictions from QCD. The K − π + π + mode has a non-uniform, non-resonant contribution; attempts to fit this distribution are described.

Improved WIMP-search reach of the CDMS II germanium data

CDMS II data from the five-tower runs at the Soudan Underground Laboratory were reprocessed with an improved charge-pulse fitting algorithm. Two new analysis techniques to reject surface-event backgrounds were applied to the 612 kg days germanium-detector weakly interacting massive particle (WIMP)-search exposure. An extended analysis was also completed by decreasing the 10 keV analysis threshold to ∼5  keV, to increase sensitivity near a WIMP mass of 8  GeV/c^2. After unblinding, there were zero candidate events above a deposited energy of 10 keV and six events in the lower-threshold analysis. This yielded minimum WIMP-nucleon spin-independent scattering cross-section limits of 1.8×10^(−44) and 1.18×10^(−41) at 90% confidence for 60 and 8.6  GeV/c^2 WIMPs, respectively. This improves the previous CDMS II result by a factor of 2.4 (2.7) for 60 (8.6)  GeV/c^2 WIMPs.

Demonstration of surface electron rejection with interleaved germanium detectors for dark matter searches

The SuperCDMS experiment in the Soudan Underground Laboratory searches for dark matter with a 9-kg array of cryogenic germanium detectors. Symmetric sensors on opposite sides measure both charge and phonons from each particle interaction, providing excellent discrimination between electron and nuclear recoils, and between surface and interior events. Surface event rejection capabilities were tested with two ^(210)Pb sources producing ∼130 beta decays/hr. In ∼800 live hours, no events leaked into the 8–115 keV signal region, giving upper limit leakage fraction 1.7 × 10^(−5) at 90% C.L., corresponding to < 0.6 surface event background in the future 200-kg SuperCDMS SNOLAB experiment.