Search

A search for dark matter was conducted by looking for an annual modulation signal due to the Earth's rotation around the Sun using XMASS, a single phase liquid xenon detector. The data used for this analysis was 359.2 live days times 832 kg of exposure accumulated between November 2013 and March 2015. When we assume Weakly Interacting Massive Particle (WIMP) dark matter elastically scattering on the target nuclei, the exclusion upper limit of the WIMP–nucleon cross section 4.3×10−41 cm2 at 8 GeV/c$^{2}$ was obtained and we exclude almost all the DAMA/LIBRA allowed region in the 6 to 16 GeV/c$^{2}$ range at ∼10$^{−40}$ cm$^{2}$. The result of a simple modulation analysis, without assuming any specific dark matter model but including electron/γ events, showed a slight negative amplitude. The p-values obtained with two independent analyses are 0.014 and 0.068 for null hypothesis, respectively. We obtained 90% C.L. upper bounds that can be used to test various models. This is the first extensive annual modulation search probing this region with an exposure comparable to DAMA/LIBRA.

Dark matter detectors built primarily to probe elastic scattering of WIMPs on nuclei are also precise probes of light, weakly coupled particles that may be absorbed by the detector material. In this paper, we derive constraints on the minimal model of dark matter comprised of long-lived vector states V (dark photons) in the 0.01-100 keV mass range. The absence of an ionization signal in direct detection experiments such as XENON10 and XENON100 places a very strong constraint on the dark photon mixing angle, down to $O(10^{-15})$, assuming that dark photons comprise the dominant fraction of dark matter. This sensitivity to dark photon dark matter exceeds the indirect bounds derived from stellar energy loss considerations over a significant fraction of the available mass range. We also revisit indirect constraints from $V\to 3\gamma$ decay and show that limits from modifications to the cosmological ionization history are comparable to the updated limits from the diffuse gamma-ray flux., Comment: 10 pages, 4 figures; numerical bug in J-factor corrected; main results unchanged

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4+-0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (1422+-67) kg d exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1x10^-44 cm^2 for a WIMP mass of 100 GeV/c^2., 26 pages, 7 figures; updated figures and references, notably Fig. 7 has updated CDMSII curve; fixed typos; clarified some language and figures; updated references

Searches for dark matter scattering off nuclei are typically compared assuming that the dark matter's spin-independent couplings are identical for protons and neutrons. This assumption is neither innocuous nor well motivated. We consider isospin-violating dark matter (IVDM) with one extra parameter, the ratio of neutron to proton couplings, and include the isotope distribution for each detector. For a single choice of the coupling ratio, the DAMA and CoGeNT signals are consistent with each other and with current XENON constraints, and they unambiguously predict near future signals at XENON and CRESST. We provide a quark-level realization of IVDM as WIMPless dark matter that is consistent with all collider and low-energy bounds., Comment: 5 pages; v2: added references and fixed figures for Mac users; v3: published version; v4: fixed erroneous Ar values in table I

We compute the primordial mirror helium He′ mass fraction emerging from Big Bang nucleosynthesis in the mirror sector of particles in the presence of kinetic mixing between photons and mirror photons. We explore the kinetic mixing parameter ( e ) values relevant for cosmology and which are also currently probed by the dark matter direct detection experiments. In particular, we find that for e ∼ 10 − 9 , as suggested by the DAMA/Libra and other experiments, a large HeO mass fraction ( Y He ′ ≈ 90 % ) is produced. Such a large value of the primordial He′ mass fraction will have important implications for the mirror dark matter interpretation of the direct detection experiments, as well as for the study of mirror star formation and evolution.

Gamma-rays induced by annihilation or decay of dark matter can be its smoking gun signature. In particular, gamma-rays generated by internal bremsstrahlung of Majorana and real scalar dark matter is promising since it can be a leading emission of sharp gamma-rays. However in the case of Majorana dark matter, its cross section for internal bremsstrahlung cannot be large enough to be observed by future gamma-ray experiments if the observed relic density is assumed to be thermally produced. In this paper, we introduce some degenerate particles with Majorana dark matter, and show they lead enhancement of the cross section. As a result, increase of about one order of magnitude for the cross section is possible without conflict with the observed relic density, and it would be tested by the future gamma-ray experiments such as GAMMA-400 and Cherenkov Telescope Array (CTA). In addition, the constraints of perturbativity, positron observation by the AMS experiment and direct search for dark matter are discussed., 13 pages, 4 figures, version to appear in Physics Letters B

The results achieved with a statistics of 14962 kg . day, collected with the large mass highly radiopure DAMA NaI(TI) set-up, are described and investigated in terms of WIMP annual modulation signature. A maximum likelihood analysis of these data, combined with the statistics of 4549 kg day previously published (total statistics of 19511 kg . day), favours the hypothesis of presence of an annual modulation at 99.6% C.L. (C) 1999 Elsevier Science B.V. All rights reserved.

A new search of non-paulian nuclear processes, i.e. processes normally forbidden by the Pauli exclusion principle, was carried out by determining an improved upper limit for the spontaneous emission rate of protons in 23 Na and 127 I. A large set-up of highly radiopure NaI(Tl) crystals was employed; it was placed deeply underground at the Gran Sasso National Laboratory of I.N.F.N. The upper limit on the unit time probability of non-paulian emission of protons with energy E p ⩾ 10 MeV is λ ⩽ 4.6 · 10 −33 s −1 . The corresponding limit on the relative strength ( δ 2 ) for the searched non-paulian transitions has been estimated to be δ 2 ≲ 1.0 · 10 −54 .

Improved limits on WIMP search have been obtained by the pulse shape analysis of the data collected with a large-mass low-radioactivity NaI(Tl) set-up at Gran Sasso National Laboratory.

Peaking consistently in June for nearly eleven years, the annual modulation signal reported by DAMA/NaI and DAMA/LIBRA offers strong evidence for the identity of dark matter. DAMA's signal strongly suggest that dark matter inelastically scatters into an excited state split by O(100 keV). We propose that DAMA is observing hyperfine transitions of a composite dark matter particle. As an example, we consider a meson of a QCD-like sector, built out of constituent fermions whose spin-spin interactions break the degeneracy of the ground state. An axially coupled U(1) gauge boson that mixes kinetically with hypercharge induces inelastic hyperfine transitions of the meson dark matter that can explain the DAMA signal., 5 pages (two-column), 1 figure, revised version, references added

We consider the prospects for studying spin-independent isospin-violating dark matter-nucleon interactions with neutrinos from dark matter annihilation in the Sun, with a focus on IceCube/DeepCore (IC/DC). If dark matter-nucleon interactions are isospin violating, IC/DC's reach in the spin-independent cross section may be competitive with current direct detection experiments for a wide range of dark matter masses. We also compare IC/DC's sensitivity to that of next generation argon, germanium, neon and xenon based detectors., 14 pages, 3 figures, PDFLaTeX, journal version