Improved limits on solar axions and bosonic dark matter from the CDEX-1B experiment using the profile likelihood ratio method

Wang, Y.; Yue, Qian; Liu, S. K.; Kang, K.; Li, Y. J.; An, Haipeng; Cheng, Jianping; Chen, J. H.; Chen, Y. H.; Cheng, J.; Dai, Wenhan; Deng, Zhi; Geng, X. P.; Gong, H.; Gu, Ping; Guo, Xuyuan; He, H. T.; He, Longzhuang; He, S.; Hu, Juan; Huang, Hanxiong; Huang, Tuchen; Jia, Liping; Li, H. B.; Li, H.; Li, M. X.; Li, J. M.; Li, J.; Li, X.; Li, X. Q.; Li, Y. L.; Liao, Bin; Lin, F. K.; Lin, Shou-De; Liu, Y. D.; Liu, Y. Y.; Liu, Z. Z.; Ma, H.; Nie, Q. Y.; Ning, Jinhua; Pan, H.; Qi, Ningchun; Qiao, Chen-Kai; Ren, Jie; Ruan, Xichao; Sharma, V.; She, Z.; Singh, L.; Singh, M. K.; Sun, Tao; Tang, C. J.; Tang, W. Y.; Tian, Yang; Wang, G. F.; Wang, L.; Wang, Q.; Wang, Z.; Wong, H. T.; Wu, Shiyong; Wu, Y. C.; Xing, Haoyang; Yin, Xuefeng; Xue, Tao; Yan, Yupeng; Yang, L. T.; Nan, Yi; Yu, C. X.; Yu, Hao; Yue, Jianfeng; Zeng, X. H.; Zeng, Ming; Zeng, Zhi; Zhang, B. T.; Zhang, F. S.; Zhang, L.; Zhang, Z. Y.; Zhao, M. G.; Zhou, J. F.; Zhou, Z. Y.; Zhu, J. J.

doi:10.1103/physrevd.101.052003

“…The China dark matter experiment (CDEX), aiming at direct dark matter detection and the study of neutrinoless double beta decay of 76 Ge, operates p-type point-contact germanium detectors (PPCGe) at the China Jinping Underground Laboratory (CJPL) [7,[13][14][15][16]. The copper used in the PPCGe detectors of the CDEX experiment leads to a crucial background contribution, which requires assessment due to cosmogenic activation in copper to establish the background model for the CDEX experiment.…”

Section: Introductionmentioning

confidence: 99%

Study of cosmogenic activation in copper for rare event search experiments

She

¹

,

Zeng

²

,

Ma

³

et al. 2021

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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.

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“…are shown in black with the expected 1 (2) σ sensitivities in green (yellow). Limits from other detectors or astrophysical constraints are also shown for both the pseudoscalar and vector cases [157,151,32,3,46,27,27,9,94,18,7,4]. background-only datasets, searched over our pre-selected masses, and saved the largest local significance, the distribution of which is used for reporting the global significance.…”

Section: Bosonic Dark Matter Resultsmentioning

confidence: 99%

“…are shown in black with the expected 1 (2) σ sensitivities in green (yellow). Limits from other detectors or astrophysical constraints are also shown for both the pseudoscalar and vector cases[157,151,32,3,46,27,27,9,94,18,7,4].…”

mentioning

confidence: 94%

Study of Excess Electronic Recoil Events in XENON1T

Shockley¹

2021

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“…are shown in black with the expected 1 (2) σ sensitivities in green (yellow). Limits from other detectors or astrophysical constraints are also shown for both the pseudoscalar and vector cases[53,84,85,[121][122][123][124][125][126][126][127][128].FIG. 11.…”

mentioning

confidence: 98%

Excess electronic recoil events in XENON1T

Aprile¹,

Aalbers²,

Agostini³

et al. 2020

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We report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 0.65 tonne-years and an unprecedentedly low background rate of 76 AE 2 stat events=ðtonne × year × keVÞ between 1 and 30 keV, the data enable one of the most sensitive searches for solar axions, an enhanced neutrino magnetic moment using solar neutrinos, and bosonic dark matter. An excess over known backgrounds is observed at low energies and most prominent between 2 and 3 keV. The solar axion model has a 3.4σ significance, and a three-dimensional 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by g ae < 3.8 × 10 −12 , g ae g eff an < 4.8 × 10 −18 , and g ae g aγ < 7.7 × 10 −22 GeV −1 , and excludes either g ae ¼ 0 or g ae g aγ ¼ g ae g eff an ¼ 0. The neutrino magnetic moment signal is similarly favored over background at 3.2σ, and a confidence interval of μ ν ∈ ð1.4; 2.9Þ × 10 −11 μ B (90% C.L.) is reported. Both results are in strong tension with stellar constraints. The excess can also be explained by β decays of tritium at 3.2σ significance with a corresponding tritium concentration in xenon of ð6.2 AE 2.0Þ × 10 −25 mol=mol. Such a trace amount can neither be confirmed nor excluded with current knowledge of its production and reduction mechanisms. The significances of the solar axion and neutrino magnetic moment hypotheses are decreased to 2.0σ and 0.9σ, respectively, if an unconstrained tritium component is included in the fitting. With respect to bosonic dark matter, the excess favors a monoenergetic peak at ð2.3 AE 0.2Þ keV (68% C.L.) with a 3.0σ global (4.0σ local) significance over background. This analysis sets the most restrictive direct constraints to date on pseudoscalar and vector bosonic dark matter for most masses between 1 and 210 keV=c 2. We also consider the possibility that 37 Ar may be present in the detector, yielding a 2.82 keV peak from electron capture. Contrary to tritium, the 37 Ar concentration can be tightly constrained and is found to be negligible.

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Improved limits on solar axions and bosonic dark matter from the CDEX-1B experiment using the profile likelihood ratio method

Cited by 33 publications

References 51 publications

Study of cosmogenic activation in copper for rare event search experiments

Study of cosmogenic activation in copper for rare event search experiments

Study of Excess Electronic Recoil Events in XENON1T

Excess electronic recoil events in XENON1T

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