Ji-Haeng Huh

Generalized halo independent comparison of direct dark matter detection data

We extend the halo-independent method to compare direct dark matter detection data, so far used only for spin-independent WIMP-nucleon interactions, to any type of interaction. As an example we apply the method to magnetic moment interactions.

Update on light WIMP limits: LUX, lite and light

We reexamine the current direct dark matter data including the recent CDMSlite and LUX data, assuming that the dark matter consists of light WIMPs, with mass close to 10 GeV/c2 with spin-independent and isospin-conserving or isospin-violating interactions. We compare the data with a standard model for the dark halo of our galaxy and also in a halo-independent manner. In our standard-halo analysis, we find that for isospin-conserving couplings, CDMSlite and LUX together exclude the DAMA, CoGeNT, CDMS-II-Si, and CRESST-II possible WIMP signal regions. For isospin-violating couplings instead, we find that a substantial portion of the CDMS-II-Si region is compatible with all exclusion limits. In our halo-independent analysis, we find that for isospin-conserving couplings, the situation is of strong tension between the positive and negative results, as it was before the LUX and CDMSlite bounds, which turn out to exclude the same possible WIMP signals as previous limits. For isospin-violating couplings, we find that LUX and CDMS-II-Si bounds together exclude or severely constrain the DAMA, CoGeNT and CRESST-II possible WIMP signals.

Very light right-handed sneutrino dark matter in the NMSSM

Very light right-handed (RH) sneutrinos in the Next-to-Minimal Supersymmetric Standard Model can be viable candidates for cold dark matter. We investigate the prospects for their direct detection, addressing their compatibility with the recent signal observed by the CoGeNT detector, and study the implications for Higgs phenomenology. We find that in order to reproduce the correct relic abundance very light RH sneutrinos can annihilate into either a fermion-antifermion pair, very light pseudoscalar Higgses or RH neutrinos. If the main annihilation channel is into fermions, we point out that RH sneutrinos could naturally account for the CoGeNT signal. Furthermore, the lightest Higgs has a very large invisible decay width, and in some cases the second-lightest Higgs too. On the other hand, if the RH sneutrino annihilates mostly into pseudoscalars or RH neutrinos the predictions for direct detection are below the current experimental sensitivities and satisfy the constraints set by CDMS and XENON. We also calculate the gamma ray flux from RH sneutrino annihilation in the Galactic centre, including as an interesting new possibility RH neutrinos in the final state. These are produced through a resonance with the Higgs and the resulting flux can exhibit a significant Breit-Wigner enhancement.

Reevaluation of spin-dependent WIMP-proton interactions as an explanation of the DAMA data

We reexamine the interpretation of the annual modulation signal observed by the DAMA experiment as due to WIMPs with a spin-dependent coupling mostly to protons. We consider both axial-vector and pseudo-scalar couplings, and elastic as well as endothermic and exothermic inelastic scattering. We conclude that the DAMA signal is in strong tension with null results of other direct detection experiments, particularly PICASSO and KIMS.

Direct detection of light “Ge-phobic” exothermic dark matter

We present comparisons of direct dark matter (DM) detection data for light WIMPs with exothermic scattering with nuclei (exoDM), both assuming the Standard Halo Model (SHM) and in a halo model — independent manner. Exothermic interactions favor light targets, thus reducing the importance of upper limits derived from xenon targets, the most restrictive of which is at present the LUX limit. In our SHM analysis the CDMS-II-Si and CoGeNT regions become allowed by these bounds, however the recent SuperCDMS limit rejects both regions for exoDM with isospin-conserving couplings. An isospin-violating coupling of the exoDM, in particular one with a neutron to proton coupling ratio of −0.8 (which we call “Ge-phobic”), maximally reduces the DM coupling to germanium and allows the CDMS-II-Si region to become compatible with all bounds. This is also clearly shown in our halo-independent analysis.

Nuclear uncertainties in the spin-dependent structure functions for direct dark matter detection

D. G. C. is supported by the Ramo´n y Cajal program of the Spanish MICINN. M. F. is supported by a Leverhulme Trust grant. J.-H. H. is supported by a MultiDark Fellowship. M. P. is supported by a MultiDark Scholarship. This work was supported by the Consolider-Ingenio 2010 Programme under MultiDark Grant No. CSD2009-00064. We also thank the support of the Spanish MICINN under Grants No. FPA2009-08958 and FPA2012-34694, the Spanish MINECO ‘‘Centro de excelencia Severo Ochoa Program’’ under Grant No. SEV-2012-0249, the Community of Madrid under Grant No. HEPHACOS S2009/ESP-1473, and the European Union under the Marie Curie-ITN Program No. PITN-GA-2009-237920

Asymmetric dark matter annihilation as a test of non-standard cosmologies

We show that the relic abundance of the minority component of asymmetric dark matter can be very sensitive to the expansion rate of the Universe and the temperature of transition between a non-standard pre-Big Bang Nucleosynthesis cosmological phase and the standard radiation dominated phase, if chemical decoupling happens before this transition. In particular, because the annihilation cross section of asymmetric dark matter is typically larger than that of symmetric dark matter in the standard cosmology, the decrease in relic density of the minority component in non-standard cosmologies with respect to the majority component may be compensated by the increase in annihilation cross section, so that the annihilation rate at present of asymmetric dark matter, contrary to general belief, could be larger than that of symmetric dark matter in the standard cosmology. Thus, if the annihilation cross section of the asymmetric dark matter candidate is known, the annihilation rate at present, if detectable, could be used to test the Universe before Big Bang Nucleosynthesis, an epoch from which we do not yet have any data.

Extended maximum likelihood halo-independent analysis of dark matter direct detection data

We extend and correct a recently proposed maximum-likelihood halo-independent method to analyze unbinned direct dark matter detection data. Instead of the recoil energy as independent variable we use the minimum speed a dark matter particle must have to impart a given recoil energy to a nucleus. This has the advantage of allowing us to apply the method to any type of target composition and interaction, e.g. with general momentum and velocity dependence, and with elastic or inelastic scattering. We prove the method and provide a rigorous statistical interpretation of the results. As rst applications, we nd that for dark matter particles with elastic spin-independent interactions and neutron to proton coupling ratio fn=fp = 0:7, the WIMP interpretation of the signal observed by CDMS- II-Si is compatible with the constraints imposed by all other experiments with null results. We also nd a similar compatibility for exothermic inelastic spin-independent interactions with fn=fp = 0:8.

Complementarity of dark matter direct detection: the role of bolometric targets

We study how the combined observation of dark matter in various direct detection experiments can be used to determine the phenomenological properties of WIMP dark matter: mass, spin-dependent (SD) and spin-independent (SI) scattering cross section off nucleons. A convenient choice of target materials, including nuclei that couple to dark matter particles through a significantly different ratio of SD vs SI interactions, could break the degeneracies in the determination of those parameters that a single experiment cannot discriminate. In this work we investigate different targets that can be used as scintillating bolometers and could provide complementary information to germanium and xenon detectors. We observe that Al2O3 and LiF bolometers could allow a good reconstruction of the DM properties over regions of the parameter space with a SD scattering cross section as small as 10−5 pb and a SI cross section as small as 5 × 10−10 pb for a 50 GeV WIMP. In the case of a CaWO4 bolometer the area in which full complementarity is obtained is smaller but we show that it can be used to determine the WIMP mass and its SI cross section. For each target we study the required exposure and background.

U(1)

Abstract We propose a U ( 1 ) ′ mediated supersymmetry (SUSY) breaking, in which U ( 1 ) ′ is identified with U ( 1 ) B 1 + B 2 − 2 L 1 . The U ( 1 ) B 1 + B 2 − 2 L 1 gauge symmetry, which is anomaly-free with the field contents of the minimal supersymmetric standard model, assigns ± 1 / 3 charges to the first and second generations of the quarks, and ∓2 to the first generation of the leptons. As a result, the first two generations of squarks acquire masses of about 7 TeV, and the first generation of the sleptons do those of 40 TeV, respectively, in the presence of one or three pairs of extra vector-like matter { 5 , 5 ¯ } . Non-observation on extra colored particles below 1 TeV at the large hadron collider, and also the flavor violations such as μ − → e − γ are explained. By virtue of such a gauge symmetry, proton stability can be protected. The other squarks and sleptons as well as the gauginos can obtain masses of order 10 2 − 3 GeV through the conventional gravity or gauge mediated SUSY breaking mechanism. The relative light smuon/sneutrino and the neutralino/chargino could be responsible for the ( g − 2 ) μ deviated from the standard model prediction. The stop mass of ∼ 500 GeV relieves the fine-tuning problem in the Higgs sector. Two-loop effects by the relatively heavy sfermions can protect the smallness of the stop mass from the radiative correction by the heavy gluino ( ≳ 1 TeV ). Extra vector-like matter can enhance the radiative corrections to the Higgs mass up to 126 GeV, and induce the desired mixing among the chiral fermions after U ( 1 ) B 1 + B 2 − 2 L 1 breaking.