Direct dark matter search by annual modulation with 2.7 years of XMASS-I data

Abstract

An annual modulation signal due to the Earth orbiting around the Sun would be one of the strongest indications of the direct detection of dark matter. In 2016, we reported a search for dark matter by looking for this annual modulation with our single-phase liquid xenon XMASS-I detector. That analysis resulted in a slightly negative modulation amplitude at low energy. In this work, we included more than one year of additional data, which more than doubles the exposure to 800 live days with the same 832 kg target mass. When we assume weakly interacting massive particle (WIMP) dark matter elastically scattering on the xenon target, the exclusion upper limit for the WIMP-nucleon cross section was improved by a factor of 2 to 1.9×10 −41 cm 2 at 8 GeV/c 2 at 90% confidence level with our newly implemented data selection through a likelihood method. For the model-independent case, without assuming any specific dark matter model, we obtained more consistency with the null hypothesis than before with a p-value of 0.11 in the 1−20 keV energy region. This search probed this region with an exposure that was larger than that of DAMA/LIBRA. We also did not find any significant amplitude in the data for periodicity with periods between 50 and 600 days in the energy region between 1 to 6 keV.

Monte Carlo simulation of the SABRE PoP background

“…Recently, the DAMA collaboration has released the first results from their Phase-2 experiment [7], confirming the evidence of a signal that meets all the requirements of a modelindependent dark matter annual modulation signature at 12.9 σ significance. When interpreted in the standard WIMP framework, the results from DAMA are in conflict with other results from experiments using different target materials [8,9,10,11]. However such comparison is based on several assumptions of the astrophysical and nuclear models, and on the nature of dark matter particles and their interaction.…”

Search for a Dark Matter-Induced Annual Modulation Signal in NaI(Tl) with the COSINE-100 Experiment

“…One experiment, DAMA/LIBRA, observes annual modulations in the detected event rate with a significance exceeding 12 σ, which they attribute to the presence of dark matter [10][11][12]. DAMA/LIBRAs observation is inconsistent with other experiments under most well-motivated WIMP dark matter models [13][14][15][16][17][18][19][20][21]; however, none of these other experiments have used the same target material as DAMA, thallium-doped sodium iodide [NaI(Tl)] scintillating crystals. Thus, these comparisons are necessarily dependent on the particular model of WIMPnucleus scattering and the assumed WIMP halo structure.…”

Shielding of a direct detection experiment and implications for the DAMA annual modulation signal

“…There may even be some dependence on the atmospheric temperature variations of the ordinary matter. Of course, it is unclear if such effects can account for the intriguing results obtained at other locations, including the hint of a small annual modulation, with amplitude of opposite sign to DAMA observed in the Kamioka Observatory (XMASS) [35] and in the Homestake mine (LUX) [36], but it might well be possible.…”