CDEX
Z. H. Zhang, L. T. Yang, Q. Yue et al.
Search for boosted keV-MeV light dark matter particles from evaporating\\ primordial black holes at the CDEX-10 experiment
Phys. Rev. D 108, 052006 (2023)
We present novel constraints on boosted light dark matter particles (denoted as ``$\chi$'') from evaporating primordial black holes (PBHs) using 205.4 kg$\cdot$day data from the China Jinping Underground Laboratory's CDEX-10 p-type point contact germanium detector with a 160 eVee analysis threshold. $\chi$ from PBHs with masses ranging from 1$\times$10$^{15}$ g to 7$\times$10$^{16}$ g are searched in this work. In the presence of PBH abundance compatible with present bounds, our result excludes the $\chi$-nucleon elastic-scattering cross section region from 3.4$\times$10$^{-32}$ cm$^{2}$ to 2.3$\times$10$^{-29}$ cm$^{2}$ for $\chi$ of 1 keV to 24 MeV from PBHs with masses of 5$\times$10$^{15}$ g, as well as from 1.1$\times$10$^{-28}$ cm$^{2}$ to 7.6$\times$10$^{-28}$ cm$^{2}$ for $\chi$ of 1 keV to 0.6 MeV from PBHs with masses of 7$\times$10$^{16}$ g. If the $\chi$-nucleon elastic-scattering cross section can be determined in the future, the abundance of PBHs may be severely constrained by $\chi$ evaporation. With the lower threshold (160 eVee) of the CDEX-10 experiment compared to the previously used experiments, this work allows for a better reach at soft spectra produced by heavier PBHs, which demonstrates the vast potential of such a technical route to pursue $\chi$ from larger PBHs with a low threshold.
X. P. Geng, L. T. Yang, Q. Yue et al.
Search for exotic interactions of solar neutrinos in the CDEX-10 experiment
Phys. Rev. D 107, 112002 (2023)
We investigate exotic neutrino interactions using the 205.4 kg$\cdot$day dataset from the CDEX-10 experiment at the China Jinping Underground Laboratory. New constraints on the mass and couplings of new gauge bosons are presented. Two nonstandard neutrino interactions are considered: a $U(1)_{B-L}$ gauge-boson-induced interaction between an active neutrino and electron/nucleus, and a dark-photon-induced interaction between a sterile neutrino and electron/nucleus via kinetic mixing with a photon. This work probes an unexplored parameter space involving sterile neutrino coupling with a dark photon. New laboratory limits are derived on dark photon masses below $1~{\rm eV}/c^{2}$ at some benchmark values of $\Delta m_{41}^{2}$ and $g^{\prime2}{\rm{sin}}^{2}2\theta_{14}$.
W. H. Dai, L. P. Jia, H. Ma et al.
Exotic Dark Matter Search with CDEX-10 Experiment at China Jinping Underground Laboratory
Phys. Rev. Lett. 129, 221802 (2022)
A search for exotic dark matter (DM) in the sub-GeV mass range has been conducted using 205 kg$\cdot$day data taken from a p-type point contact germanium detector of CDEX-10 experiment at China Jinping underground laboratory. New low-mass dark matter searching channels, neutral current fermionic DM absorption ($\chi+A\rightarrow \nu+A$) and DM-nucleus 3$\rightarrow$2 scattering ($\chi+\chi+A\rightarrow \phi+A$), have been analyzed with an energy threshold of 160 eVee. No significant signal was found, thus new limits on the DM-nucleon interaction cross section are set for both models at sub-GeV DM mass region. A cross section limit for the fermionic DM absorption is set to be $\rm 2.5\times 10^{-46} cm^2$(90\% C.L.) at DM mass of 10 MeV/c$^2$. For the DM-nucleus 3$\rightarrow$2 scattering scenario, limits are extended to DM mass of 5 MeV/c$^2$ and 14 MeV/c$^2$ for the massless dark photon and bound DM final state, respectively.
Z. Y. Zhang, L. T. Yang, Q. Yue et al.
Constraints on Sub-GeV Dark Matter-Electron Scattering from the CDEX-10 Experiment
Phys. Rev. Lett. 129, 221301 (2022)
We present improved germanium-based constraints on sub-GeV dark matter via dark matter--electron ($\chi$-$e$) scattering using the 205.4 kg$\cdot$day dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted $\chi$-$e$ scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for $m_{\chi}$ larger than 80 MeV/c$^2$ compared to previous germanium-based $\chi$-$e$ results. We also present the most stringent $\chi$-$e$ cross-section limit to date among experiments using solid-state detectors for $m_{\chi}$ larger than 90 MeV/c$^2$ with heavy mediators and $m_{\chi}$ larger than 100 MeV/c$^2$ with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new $\chi$-$e$ detection method with high-purity germanium detectors in ultralow radioactive background.
R. Xu, L. T. Yang, Q. Yue et al.
Constraints on sub-GeV dark matter boosted by cosmic Rays from the CDEX-10 experiment at the China Jinping Underground Laboratory
Phys. Rev. D 106, 052008 (2022)
We report new constraints on light dark matter boosted by cosmic rays (CRDM) using the 205.4 kg day data of the CDEX-10 experiment conducted at the China Jinping Underground Laboratory. The Monte Carlo simulation package CJPL_ESS was employed to evaluate the Earth shielding effect. Several key factors have been introduced and discussed in our CRDM analysis, including the contributions from heavier CR nuclei than proton and helium, the inhomogeneity of CR distribution, and the impact of the form factor in the Earth attenuation calculation. Our result excludes dark matter-nucleon elastic scattering cross section region from 3 × 10-30 cm2 to 10-26 cm2 for dark matter of 10 keV/c2 to 1 GeV/c2.
W. H. Dai, H. Ma, Q. Yue et al.
Search for neutrinoless double-beta decay of 76Ge with a natural broad energy germanium detector
Phys. Rev. D 106, 032012 (2022)
A natural broad energy germanium (BEGe) detector is operated in the China Jinping Underground Laboratory (CJPL) for a feasibility study of building the next generation experiment of the neutrinoless double-beta (0\textup{$\nu\beta\beta$}) decay of $^{76}$Ge. The setup of the prototype facility, characteristics of the BEGe detector, background reduction methods and data analysis are described in this paper. A background index of 6.4$\times$10$^{-3}$ counts/(keV$\cdot$kg$\cdot$day) is achieved and 1.86 times lower than our previous result of the CDEX-1 detector. No signal is observed with an exposure of 186.4 kg$\cdot$day, thus a limit on the half life of $^{76}$Ge 0\textup{$\nu\beta\beta$} decay is set at T$_{1/2}^{0\nu}$ $>$ 5.62×10$^{22}$ yr at 90\% C.L.. The limit corresponds to an effective Majorana neutrino mass in the range of 4.6 $\sim$ 10.3 eV, dependent on the nuclear matrix elements.
Z. Z. Liu, L. T. Yang, Q. Yue et al.
Studies of the Earth shielding effect to direct dark matter searches at the China Jinping Underground Laboratory
Phys. Rev. D 105, 052005 (2022)
Dark matter direct detection experiments mostly operate at deep underground laboratories. It is necessary to consider shielding effect of the Earth, especially for dark matter particles interacting with a large cross section. We analyzed and simulated the Earth shielding effect for dark matter at the China Jinping Underground Laboratory (CJPL) with a simulation package, CJPL Earth Shielding Simulation code (CJPL_ESS), which is applicable to other underground locations. The further constraints on the χ-N cross section exclusion regions are derived based on the studies with CDEX experiment data.
Y. Wang, Z. Zeng, Q. Yue et al.
First experimental constraints on WIMP couplings in the effective field theory framework from CDEX
Sci. China-Phys. Mech. Astron. 64, 281011 (2021)
We present weakly interacting massive particles (WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment (CDEX), based on the data from both CDEX-1B and CDEX-10 stages. In the nonrelativistic effective field theory approach, both time-integrated and annual modulation analyses were used to set new limits for the coupling of WIMP-nucleon effective operators at 90% confidence level (C.L.) and improve over the current bounds in the low mχ region. In the chiral effective field theory approach, data from CDEX-10 were used to set an upper limit on WIMP-pion coupling at 90% C.L. We for the first time extended the limit to the mχ<6 GeV/c2 region.
Z. She, L. P. Jia, Q. Yue et al.
Direct Detection Constraints on Dark Photons with the CDEX-10 Experiment at the China Jinping Underground Laboratory
Phys. Rev. Lett. 124, 111301 (2020)
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 (mV) from 10 to 300 eV/c2 in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with mV from 0.1 to 4.0 keV/c2 are set from 449.6 kg-day data, with a minimum of κ = 1.3 × 10−15 at mV = 200 eV/c2.
Y. Wang, Q. Yue, S. K. Liu et al.
Improved limits on solar axions and bosonic dark matter from the CDEX-1B experiment using the profile likelihood ratio method
Phys. Rev. D 101, 052003 (2020)
We present the 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 weakly interacting massive particles using a p-type point-contact germanium detector. We adopt the profile likelihood ratio method for analysis of data in the presence of backgrounds. An energy threshold of 160 eV was achieved, much better than the 475 eVof CDEX-1A with an exposure of 335.6 kg days. This significantly improves the sensitivity for the bosonic dark matter below 0.8 keV among germanium detectors. Limits are also placed on the coupling gAe < 2.48 × 10−11 from Compton, bremsstrahlung, atomic-recombination, and deexcitation channels and geff AN × gAe < 4.14 × 10−17 from a 57Fe M1 transition at 90% confidence level.
L. T. Yang, H. B. Li, Q. Yue et al.
Search for Light Weakly-Interacting-Massive-Particle Dark Matter by Annual Modulation Analysis with a Point-Contact Germanium Detector at the China Jinping Underground Laboratory
Phys. Rev. Lett. 123, 221301 (2019)
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) spinindependent 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/c2 among WIMP AM measurements to date.
Z. Z. Liu, Q. Yue, L. T. Yang et al.
Constraints on Spin-Independent Nucleus Scattering with sub-GeV Weakly Interacting Massive Particle Dark Matter from the CDEX-1B Experiment at the China Jinping Underground Laboratory
Phys. Rev. Lett. 123, 161301 (2019)
We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (mχ ) 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 mχ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σSIχN at 90% confidence level are derived as 2 × 10−32 ∼ 7 × 10−35 cm2 for TI analysis at mχ ∼ 50–180 MeV/c2, and 3 × 10−32 ∼ 9 × 10−38 cm2 for AM analysis at mχ ∼ 75 MeV/c2–3.0 GeV/c2.
H. Jiang, L.P. Jia, Q. Yue et al.
Limits on Light Weakly Interacting Massive Particles from the First 102.8 kg×day Data of the CDEX-10 Experiment
L. T. Yang, H. B. Li, Q. Yue et al.
Limits on light WIMPs with a 1 kg-scale germanium detector at 160 eVee physics threshold at the China Jinping Underground Laboratory
Chin. Phys. C 42, 023002 (2018)
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.
L. Wang, Q. Yue, K. J. Kang et al.
First results on 76Ge neutrinoless double beta decay from CDEX-1 experiment
Sci. China-Phys. Mech. Astron. 60, 071011 (2017).
We report the first results on 76Ge neutrinoless double beta decay from stage one of the China dark-matter experiment (CDEX). A p-type point-contact high-purity germanium detector with a mass of 994 g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg d has been analyzed over a wide spectral band from 500 keV to 3 MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039 MeV energy range. The half-life of 76Ge neutrinoless double beta decay derived based on this result is T0ν1/2 >6.4×1022yr(90%C.L.) upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved.
S. K. Liu, Q. Yue, K. J. Kang et al.
Constraints on axion couplings from the CDEX-1 experiment at the China Jinping Underground Laboratory
Phys. Rev. D 95, 052006 (2017)
We report the results of searches for solar axions and galactic dark matter axions or axionlike particles with the CDEX-1 experiment at the China Jinping Underground Laboratory, using 335.6 kg days of data from a p-type point-contact germanium detector. The data are compatible with the background model, and no excess signals are observed. Limits of solar axions on the model-independent coupling gAe < 2.5 × 10−11 from Compton, bremsstrahlung, atomic-recombination, and deexcitation channels and geffAN × gAe < 6.4 × 10−17 from a 57Fe M1 transition at 90% confidence level are derived. Within the framework of the Dine-Fischler-Srednicki-Zhitnitskiy and Kim-Shifman-Vainshtein-Zakharov models, our results exclude the axion mass heavier than 0.9 and 177 eV/c2, respectively. The derived constraints for dark matter axions below 1 keV improve over the previous results.
W. Zhao, Q. Yue, K. J. Kang et al.
Search of low-mass WIMPs with a p-type point contact germanium detector in the CDEX-1 experiment
Phys. Rev. D 93, 092003 (2016)
The CDEX-1 experiment conducted a search of low-mass (<10 GeV/c2) weakly interacting massive particles dark matter at the China Jinping Underground Laboratory using a p-type point-contact germanium detector with a fiducial mass of 915 g at a physics analysis threshold of 475 eVee. We report the hardware setup, detector characterization, data acquisition, and analysis procedures of this experiment. No excess of unidentified events is observed after the subtraction of the known background. Using 335.6 kg-days of data, exclusion constraints on the weakly interacting massive particle-nucleon spin-independent and spin-dependent couplings are derived.
Q. Yue, W. Zhao, K. J. Kang et al.
Limits on light weakly interacting massive particles from the CDEX-1 experiment with a p-type point-contact germanium detector at the China Jinping Underground Laboratory
Phys. Rev. D 90, 091701 (2014)
We report results of a search for light dark matter weakly interacting massive particles (WIMPs) with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a p-type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6–20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by dark matter, since identical detector techniques are used in both experiments.
S. K. Liu, Q. Yue, K. J. Kang et al.
Limits on light WIMPs with a germanium detector at 177 eVee threshold at the China Jinping Underground Laboratory
Phys. Rev. D 90, 032003 (2014)
The China Dark Matter Experiment reports results on light WIMP dark matter searches at the China Jinping Underground Laboratory with a germanium detector array with a total mass of 20 g. The physics threshold achieved is 177 eVee (“ee” represents electron equivalent energy) at 50% signal efficiency. With 0.784 kg-days of data, exclusion region on spin-independent coupling with the nucleon is derived, improving over our earlier bounds at WIMP mass less than 4.6 GeV.
W. Zhao, Q. Yue, K. J. Kang et al.
First results on low-mass WIMPs from the CDEX-1 experiment at the China Jinping underground laboratory
Phys. Rev. D 88, 052004 (2013)
The China Dark Matter Experiment Collaboration reports the first experimental limit on weakly interacting massive particles (WIMPs) dark matter from 14.6 kg-days of data taken with a 994 g p-type point-contact germanium detector at the China Jinping underground laboratory where the rock overburden is more than 2400 m. The energy threshold achieved was 400 eVee. According to the 14.6 kg-day live data, we placed the limit of σxN =1.75×10-40m2 at a 90% confidence level on the spin-independent cross section at a WIMP mass of 7 GeV before differentiating bulk signals from the surface backgrounds.
J. L. Ma, Q. Yue, Q. Wang et al.
Appl. Radiat. Isot. 127, 130 (2017)
The characteristics of the surface inactive layer of a 1-kg-mass p-type point-contact germanium detector were studied. The thickness of the inactive layer and its uniformity on the top and lateral surfaces were measured. A charge collection efficiency function was developed according to the Monte Carlo simulation to describe the charge collection capacity along the depth within this inactive layer. In the energy range below 18 keV, the surface, bulk, and total spectra of 57Co, 133Ba, 137Cs, and 60Co from simulations based on the charge collection efficiency function were well consistent with those from experiments.
H. Jiang, L. T. Yang, Q. Yue et al.
Sci. China Phys. Mech. Astron. (2019) 62: 031012.
The CDEX-10 experiment searches for light weakly interacting massive particles, a form of dark matter, at the China Jinping Underground Laboratory, where approximately 10 kg of germanium detectors are arranged in an array and immersed in liquid nitrogen. Herein, we report on the experimental apparatus, detector characterization, and spectrum analysis of one prototype detector. Owing to the higher rise-time resolution of the CDEX-10 prototype detector as compared with CDEX-1B, we identified the origin of an observed category of extremely fast events. For data analysis of the CDEX-10 prototype detector, we introduced and applied an improved bulk/surface event discrimination method. The results of the new method were compared to those of the CDEX-1B spectrum. Both sets of results showed good consistency in the 0–12 keVee energy range, except for the 8.0 keV K-shell X-ray peak from the external copper.
H. Jiang, Q. Yue, Y. L. Li et al.
Measurement of the dead layer thickness in a p-type point contact germanium detector
Chin. Phys. C, 40 096001 (2016)
A 994 g mass p-type PCGe detector has been deployed during the first phase of the China Dark matter EXperiment, aiming at direct searches for light weakly interacting massive particles. Measuring the thickness of the dead layer of a p-type germanium detector is an issue of major importance since it determines the fiducial mass of the detector. This work reports a method using an uncollimated Ba-133 source to determine the dead layer thickness. The experimental design, data analysis and Monte Carlo simulation processes, as well as the statistical and systematic uncertainties are described. A dead layer thickness of 1.02 mm was obtained based on a comparison between the experimental data and the simulated results.
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