Light WIMPs Search by Annual Modulation Analysis with a Point-Contact Germanium Detector at the China Jinping Underground Laboratory

Hau-Bin Li^1*, Henry Tsz-King Wong¹

¹Institute of Physics, Academia Sinica, Taipei City,, Taiwan

* Presenter:Hau-Bin Li, email:lihb@gate.sinica.edu.tw

We present results on light weakly interacting massive particles (WIMPs) searches with annual modulation (AM) analysis on data obtained from a 1-kg mass p-type point-contact germanium detector (pGe) of the CDEX-1B experiment at the China Jinping Underground Laboratory. A total of 3.0 years of live-time data within a span of 3.7 years were recorded and analyzed with a physics threshold of 250 eVee. The unmodulated background levels are treated as free parameters without assumptions on the background spectral. Limits at 90% confidence level on WIMP-nucleon spin-independent cross-sections as function of WIMP mass are derived using the Halo Dark Matter model. The data is consistent with No-AM null hypothesis with p-value>0.32 independent of modulation phases, for WIMP mass in the range 3.5-25 GeV/c². The 90% C.L. allowed regions implied by the DAMA/LIBRA and CoGeNT AM-based analysis are excluded at >99.99% and >98% C.L., respectively. These results correspond to the best sensitivities at WIMP mass < 8 GeV/c² among WIMP AM measurements.

Keywords: Dark Matter, WIMP, Germanium Detector, Underground Laboratory