Abstract
We report results of a search for light weakly interacting massive particle (WIMP) dark matter from the CDEX-1 experiment at the China Jinping Underground Laboratory (CJPL). Constraints on WIMP-nucleon spin-independent (SI) and spin-dependent (SD) couplings are derived with a physics threshold of 160 eVee, from an exposure of 737.1 kg-days. The SI and SD limits extend the lower reach of light WIMPs to 2 GeV and improve over our earlier bounds at WIMP mass less than 6 GeV.
Highlights
Compelling evidence from astroparticle physics and cosmology indicates that dark matter constitutes about 27% of the energy density of our Universe [1]
Details of the CDEX-1B experimental setup, data analysis, and the constraints on weakly interacting massive particle (WIMP)-nucleon elastic scattering based on an exposure of 737.1 kg-days at China Jinping Underground Laboratory (CJPL) are discussed in the subsequent sections
The germanium (Ge) cryostat and NaI(Tl) anti-Compton detectors are inside an oxygen-free high conductivity (OFHC) copper shielding with a thickness of 20 cm, enclosed by an acrylic box, which was purged by nitrogen gas evaporated from the liquid nitrogen dewar
Summary
Compelling evidence from astroparticle physics and cosmology indicates that dark matter constitutes about 27% of the energy density of our Universe [1]. WIMPs are the leading candidate for cold dark matter [2], which is one kind of dark matter component. With excellent energy resolution and low threshold, a kind of p-type point contact germanium detector (pPCGe) [3, 5] has been used and further developed to search for light WIMPs in recent years. Earlier measurements of the phase-I experiment of the CDEX collaboration (CDEX-1) [5–7] have provided results on lowmass WIMP searches with a pPCGe detector of target mass 994 g, and the physics threshold reached 475 eVee (“eVee” represents electron equivalent energy). For CDEX, lower energy threshold and lower background level are two main directions to pursue to get more sensitive results on low mass dark matter searches. Details of the CDEX-1B experimental setup, data analysis, and the constraints on WIMP-nucleon elastic scattering based on an exposure of 737.1 kg-days at CJPL are discussed in the subsequent sections
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