Limits on Light Weakly Interacting Massive Particles from the First 102.8 kg×day Data of the CDEX-10 Experiment

Abstract

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36} cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5 GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2 GeV/c^{2}.

Coherent elastic neutrino-nucleus scattering at the European Spallation Source

“…D. Low-threshold, multi-kg p-type point contact germanium detectors P-type point contact germanium detectors (PPCs, [108]) provide a unique combination of detector mass, ultra-low energy threshold, and background rejection capabilities. As such they have found multiple applications in neutrino (Majorana [109], GERDA [110], TEXONO [111], CONUS [112]) and dark matter searches (CoGeNT [113], CDEX [114]). A continuous improvement in PPC mass and energy threshold [115] has resulted in large devices approaching 0.1 keV ee sensitivity.…”

Annual modulation in direct dark matter searches

“…At the China Jinping Underground Laboratory, in Sichuan, the China Dark Matter Experiment (CDEX [155]) has undertaken several increasingly large target mass runs. Protected by a rock overburden of 2400m, the germanium detectors of CDEX-1 are enclosed in NaI(Tl) cylinders [107] enabling competitive background suppression to very low energy thresholds (0.32 keV ee ) for the Phase 1 run, the threshold reached was halved in the upgrade to CDEX-10 [109] and will ultimately be 100 eV ee for CDEX-1T [155].…”

“…The Migdal effect was incorporated to further decrease the mass window by an order of magnitude [158], setting spin-independent mass limits of 3 × 10 −32 − −9 × 10 −38 cm 2 for masses between 75MeV/c 2 -3GeV/c 2 using the annual modulation null detection. Following the success of CDEX-1, an order of magnitude greater detector mass was constructed to form CDEX-10 [109] with the 10 kg of pPCGedetectors now distributed in three triple-element 'strings' immersed in liquid nitrogen. This LN 2 provides super shielding and better control of backgrounds than the previous reliance on high-atomic number materials [109].…”

“…This LN 2 provides super shielding and better control of backgrounds than the previous reliance on high-atomic number materials [109]. Unfortunately, due to one string being upgraded, and others suffering faulty cabling and high backgrounds only one of the nine detectors overall were reported in the latest CDEX-10 run [109]. However in the low energy range the detector reported corrected bulk background counts of 2.47 (2.15) [kg keV day] −1 in the energy range 0.16 -0.26 (1.96 -2.06) keV ee , in an exposure of 102.8 [kg d] of fiducial mass 0.939 kg over an energy range 160 eV ee to 12 keV ee [109].…”

Prototype of pulse digitizer and readout electronics for CDEX-10 in CJPL

“…V1724 (8-channel 14-Bit 100 MSPS digitizer) [4], N93B (dual timer) [5], and N840 (8-channel leading edge discriminator) [6], etc. The new stage of CDEX has increased HPGe detectors to 9 modules (with a total detector mass of ~10 kg) and will scale up to ~100 kg in the future [7] [8]. Due to the slight difference of rise-time between bulk and very bulk events, it is insufficient for pulse shape discrimination by the previous DAQ with limited sampling speed (100 MSPS).…”