We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (m χ) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in m χ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σ SI χN at 90% confidence level are derived as 2 × 10 −32 ∼ 7 × 10 −35 cm 2 for TI analysis at m χ ∼ 50-180 MeV=c 2 , and 3 × 10 −32 ∼ 9 × 10 −38 cm 2 for AM analysis at m χ ∼ 75 MeV=c 2-3.0 GeV=c 2 .

We present results on light weakly interacting massive particle (WIMP) searches with annual modulation (AM) analysis on data from a 1-kg mass p-type point-contact germanium detector of the CDEX-1B experiment at the China Jinping Underground Laboratory. Datasets with a total live time of 3.2 yr within a 4.2 yr span are analyzed with analysis threshold of 250 eVee. Limits on WIMP-nucleus (χ-N ) spin-independent cross sections as function of WIMP mass (mχ) at 90% confidence level (C.L.) are derived using the dark matter halo model. Within the context of the standard halo model, 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 sensitivity at mχ<6 GeV/c 2 among WIMP AM measurements to date. PACS numbers: 95.35.+d, 98.70.Vc Compelling cosmological evidence indicates that about one-quarter of the energy density of the Universe manifests as dark matter [1], a favored candidate of which is the weakly interacting massive particle (WIMP, denoted as χ). In direct laboratory searches of WIMPs conducted with WIMP-nucleus (χ-N ) elastic scattering, positive evidence of WIMPs can only be established by assuming detailed knowledge of the background. The annual modulation (AM) analysis, on the other hand, only requires the background at the relevant energy range is stable with time. It can provide smoking-gun signatures for WIMPs independent of background modeling. Within the astrophysical dark matter halo model [2], the expected χ-N rates have distinctive AM features with maximum intensity in June and a period of 1 yr due to the Earth's motion relative to the galaxy dark matter distribution.Positive results were concluded at significance of 12.9 σ and 2.2 σ from AM-based analysis of DAMA/LIBRA [3][4][5] and CoGeNT [6-8] experiments, respectively. However, these interpretations are challenged by integrated rate experiments with liquid xenon [9-11], cryogenic bolometer [12][13][14] and ionization germanium [15][16][17][18][19] detectors, when the data were analyzed in certain scenarios where the dark matter particle properties and distributions in the Milky Way's halo are precisely defined. Comparison of AM data with differnet targets is also model dependent. The AM-allowed regions of DAMA/LIBRA and CoGeNT have been probed and excluded by AM analysis from the XMASS-1 experiment [20,21], which is limited by the diminishing sensitivities of the liquid xenon techniques at light WIMP masses (m χ ) below 6 GeV/c 2 . The and COSINE-100 [23] experiments aim to resolve this tension by a model-independent test of DAMA/LIBRA's obser-arXiv:1904.12889v2 [hep-ex]

Rare event search experiments using germanium detectors are performed in underground laboratories to minimize the background induced by cosmic rays. However, the cosmogenic activation of cupreous detector components on the ground generates long half-life radioisotopes and contributes to the background level. We measured cosmogenic activation with 142.50 kg of copper bricks after 504 days of exposure at an altitude of 2469.4 m outside the China Jinping Underground Laboratory (CJPL). The specific activities of the cosmogenic nuclides produced in the copper bricks were measured using a low-background germanium gamma-ray spectrometer at CJPL. The production rates at sea level, in units of nuclei/kg/day, were $${18.6 \pm 2.0}$$ 18.6 ± 2.0 for $${^{54}}$$ 54 Mn, $${9.9 \pm 1.3}$$ 9.9 ± 1.3 for $${^{56}}$$ 56 Co, $${48.3 \pm 5.5}$$ 48.3 ± 5.5 for $${^{57}}$$ 57 Co, $${51.8 \pm 2.5}$$ 51.8 ± 2.5 for $${^{58}}$$ 58 Co, and $${39.7 \pm 5.7}$$ 39.7 ± 5.7 for $${^{60}}$$ 60 Co. The measurement will help to constrain cosmogenic background estimation for rare event searches using copper as a detector structure and shielding material. Based on the measured production rates, the impact of the cosmogenic background in cupreous components of germanium detectors on the next generation CDEX-100 experiment was assessed with the expected exposure history above ground.

We report constraints on the dark photon effective kinetic mixing parameter (κ) with data taken from two p-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on κ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (m V) from 10 to 300 eV=c 2 in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with m V from 0.1 to 4.0 keV=c 2 are set from 449.6 kg-day data, with a minimum of κ ¼ 1.3 × 10 −15 at m V ¼ 200 eV=c 2 .

We present improved constraints on couplings of solar axions and more generic bosonic dark matter particles using 737.1 kg-days of data from the CDEX-1B experiment. The CDEX-1B experiment, located at the China Jinping Underground Laboratory, primarily aims at the direct detection of WIMPs using a p-type point-contact germanium detector. We develop the profile likelihood ratio method for analysis of data in the presence of backgrounds. The background modeling is compatible with the data and no excess signals are observed. An energy threshold of 160 eV was achieved. This significantly improve the sensitivity for the bosonic dark matter below 0.8 keV. Limits are also placed on the coupling gAe < 2.26 × 10 −11 from Compton, bremsstrahlung, atomic-recombination and deexcitation channels and g ef f AN × gAe < 4.14 × 10 −17 from a 57 Fe M1 transition at 90% confidence level. All the constrains improve over our previous results.