Probing dark matter particles from evaporating primordial black holes via electron scattering in the CDEX-10 experiment

Dark matter(DM)is a major constituent of the Universe.However,no definite evidence of DM particles(denoted as“χ”)has been found in DM direct detection(DD)experiments to date.There is a novel concept of detectingχfrom evaporating primordial black holes(PBHs).We search forχemitted from PBHs by investigating their interaction with target electrons.The examined PBH masses range from 1×10^(15)to 7×10^(16)g under the current limits of PBH abundance fPBH.Using 205.4 kg·day data obtained from the CDEX-10 experiment conducted in the China Jinping Underground Laboratory,we exclude theχ-electron(χ-e)elastic-scattering cross sectionσ_(χe)~5×10^(-29)cm^(2)forχwith a mass■keV from our results.With the higher radiation background but lower energy threshold(160 eV),CDEX-10 fills a part of the gap in the previous work.If(m_(χ),σ_(χe))can be determined in the future,DD experiments are expected to impose strong constraints on fPBHfor large MPBHs.

First experimental constraints on WIMP couplings in the effective field theory framework from CDEX

We present weakly interacting massive particles(WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment(CDEX), based on the data from both CDEX-1B and CDEX-10 stages. In the nonrelativistic effective field theory approach, both time-integrated and annual modulation analyses were used to set new limits for the coupling of WIMP-nucleon effective operators at 90% confidence level(C.L.) and improve over the current bounds in the low mχregion. In the chiral effective field theory approach, data from CDEX-10 were used to set an upper limit on WIMP-pion coupling at 90% C.L. We for the first time extended the limit to the m_(χ)<6 GeV/c^(2) region.

First results on ^(76)Ge neutrinoless double beta decay from CDEX-1 experiment

We report the first results on 76Ge neutrinoless double beta decay from stage one of the China dark-matter experiment （CDEX）. A p-type point-contact high-purity germanium detector with a mass of 994g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304kgd has been analyzed over a wide spectral band from 500keV to 3MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039MeV energy range. The half-life of76Ge neutrinoless double beta decay derived based on this result is 70v2〉6.4× 1022 yr （90%C.L.）. An upper limit on the effective Majorana-neutrino mass of 5.0eV has been achieved.

Performances of a prototype point-contact germanium detector immersed in liquid nitrogen for light dark matter search

The CDEX-10 experiment searches for light weakly interacting massive particles, a form of dark matter, at the China Jinping Underground Laboratory, where approximately 10 kg of germanium detectors are arranged in an array and immersed in liquid nitrogen. Herein, we report on the experimental apparatus, detector characterization, and spectrum analysis of one prototype detector. Owing to the higher rise-time resolution of the CDEX-10 prototype detector as compared with CDEX-1 B, we identified the origin of an observed category of extremely fast events. For data analysis of the CDEX-10 prototype detector, we introduced and applied an improved bulk/surface event discrimination method. The results of the new method were compared to those of the CDEX-1 B spectrum. Both sets of results showed good consistency in the 0-12 ke Vee energy range, except for the 8.0 keV K-shell X-ray peak from the external copper.