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]
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