arXiv subjects

J. P. Cheng

Publications and source records attributed to J. P. Cheng.

At least 19 recordsLinked to original sources

arXiv2026

Search for Cosmic Ray Electron Boosted Dark Matter with the CDEX-10 Experiment

We present new constraints on the cosmic ray electron boosted light dark matter (CReDM) using the 205.4 kg$\cdot$day data of the CDEX-10 experiment located at the China Jinping Underground Laboratory. The cosmic ray electron spectrum and distribution in the Galaxy are generated by the $\tt GALPROP$ code package. In the calculation process of DM-electron scattering process in the Galaxy, we consider the energy-dependency of the DM-electron scattering cross section. The constraints on CReDM are set for both heavy and light mediator scenarios using the CDEX-10 dataset. The result exceeds previous Standard Halo Model (SHM) limits for DM mass lower than 0.6 MeV in heavy mediator case and corresponds to the best sensitivity among all direct detection experiments from 1 keV to 0.5 MeV in the light mediator scenario.

hep-ex↗

arXiv2025

Constraints on ultraheavy dark matter from the CDEX-10 experiment at the China Jinping Underground Laboratory

We report a search for ultraheavy dark matter (UHDM) with the CDEX-10 experiment at the China Jinping Underground Laboratory. Using a Monte Carlo framework that incorporates Earth shielding effects, we simulated UHDM propagation and energy deposition in p-type point-contact germanium detectors. Analysis of 205.4 kg$\cdot$day exposure in the 0.16--4.16 keVee range showed no excess above background. Our results exclude the spin-independent UHDM-nucleon scattering with two cross section scales, with the UHDM mass from $10^6$ to $10^{11}$ GeV, and provide the most stringent constraints with solid-state detectors below $10^8$ GeV.

hep-ex↗

arXiv2025

Constraints on inelastic dark matter from the CDEX-1B experiment

We present limits on spin-independent inelastic weakly interacting massive particles (WIMP)-nucleus scattering using the 737.1 kg$\cdot$day dataset from the CDEX-1B experiment. Expected nuclear recoil spectra for various inelastic WIMP masses $m_\chi$ and mass splittings $\delta$ are calculated under the standard halo model. An accurate background model of CDEX-1B is constructed by simulating all major background sources. The model parameters are then determined through maximum likelihood estimation and Markov chain Monte Carlo fitting. The resulting 90\% confidence level upper limits on the WIMP-nucleon cross section $\sigma_{\mathrm{n}}$ exclude certain DAMA/LIBRA allowed regions: the $\chi^2 < 4$ regions for $\delta < 30$ keV at $m_\chi = 250$ GeV and the $\chi^2 < 9$ region for $\delta < 50$ keV at $m_\chi = 500$ GeV. The method is applicable to other inelastic dark matter scenarios, and the upcoming CDEX-50 experiment is expected to improve sensitivity by four orders of magnitude.

hep-ex↗

arXiv2025

Constraints on dark matter boosted by supernova shock within the effective field theory framework from the CDEX-10 experiment

Supernova shocks can boost dark matter (DM) particles to high, yet nonrelativistic, velocities, providing a suitable mechanism for analysis within the framework of the nonrelativistic effective field theory (NREFT). These accelerated DM sources extend the experimental ability to scan the parameter space of light DM into the sub-GeV region. In this study, we specifically analyze DM accelerated by the Monogem Ring supernova remnant, whose age ($\sim 68000$ yr) and distance to Earth ($\sim 300$ parsec) are strategically matched to enable detection with current terrestrial detectors. Utilizing the 205.4 kg$\cdot$day data obtained from the CDEX-10 experiment at the China Jinping Underground Laboratory, we derive new constraints on boosted DM within the NREFT framework. The NREFT coupling constant exclusion regions now penetrate the sub-GeV mass range, with optimal sensitivity achieved for operators $\mathcal{O}_{3}$, $\mathcal{O}_{6}$, $\mathcal{O}_{15}$ in the 0.4--0.6 GeV mass range.

hep-ph↗

arXiv2024

Evaluation of cosmogenic Ge-68 background in a high purity germanium detector via a time series fitting method

Ge-68 is a cosmogenic isotope in germanium with a half-life of 270.9 days.Ge-68 and its decay daughter Ga-68 contribute considerable background with energy up to 3 MeV to low background $\gamma$ spectrometers using high purity germanium (HPGe) detectors. In this paper, we evaluated the background of Ge-68 and Ga-68 in a $p$-type coaxial HPGe detector operated at China Jinping underground laboratory (CJPL) via a time series fitting method. Under the assumption that Ge-68 and Ga-68 are in radioactive equilibrium and airborne radon daughters are uniformly distributed in the measurement chamber of the spectrometer, we fit the time series of count rate in 1-3 MeV to calculate the Ge-68 activity, radon daughter concentrations, and the time-invariant background component. A total of 90-day measurement data were used in the analysis, a hypothesis test confirmed a significant Ge-68 signal at 99.64% confidence level. The initial activity of Ge-68 is fitted to be 477.0$\pm$112.4 $\mu$Bq/kg, corresponding to an integral count rate of 55.9 count/day in the 1-3 MeV range. During the measurement, Ge-68 activity decreased by about 30%, contributing about 62% of the total background in the 1-3 MeV range. Our method also provides an estimation of the variation of airborne radon daughter concentrations in the measurement chamber, which could be used to monitor the performance of radon reduction measures.

physics.ins-det↗

arXiv2024

Probing Dark Matter Particles from Evaporating Primordial Black Holes via Electron Scattering in the CDEX-10 Experiment

Dark matter (DM) is a major constituent of the Universe. However, no definite evidence of DM particles (denoted as ``$χ$") has been found in DM direct detection (DD) experiments to date. There is a novel concept of detecting $χ$ from evaporating primordial black holes (PBHs). We search for $χ$ emitted from PBHs by investigating their interaction with target electrons. The examined PBH masses range from 1$\times$10$^{15}$ to 7$\times$10$^{16}$ g under the current limits of PBH abundance $f_{PBH}$. Using 205.4 kg$\cdot$day data obtained from the CDEX-10 experiment conducted in the China Jinping Underground Laboratory, we exclude the $χ$--electron ($χ$--$e$) elastic-scattering cross section $σ_{χe} \sim 5\times10^{-29}$ cm$^2$ for $χ$ with a mass $m_χ\lesssim$ 0.1 keV from our results. With the higher radiation background but lower energy threshold (160 eV), CDEX-10 fill a part of the gap in the previous work. If ($m_χ$, $σ_{χe}$) can be determined in the future, DD experiments are expected to impose strong constraints on $f_{PBH}$ for large $M_{PBH}$s.

hep-ex↗

arXiv2024

Searching for $^{76}$Ge neutrinoless double beta decay with the CDEX-1B experiment

We operated a p-type point contact high purity germanium (PPCGe) detector (CDEX-1B, 1.008 kg) in the China Jinping Underground Laboratory (CJPL) for 500.3 days to search for neutrinoless double beta ($0νββ$) decay of $^{76}$Ge. A total of 504.3 kg$\cdot$day effective exposure data was accumulated. The anti-coincidence and the multi/single-site event (MSE/SSE) discrimination methods were used to suppress the background in the energy region of interest (ROI, 1989$-$2089 keV for this work) with a factor of 23. A background level of 0.33 counts/(keV$\cdot$kg$\cdot$yr) was realized. The lower limit on the half life of $^{76}$Ge $0νββ$ decay was constrained as $T_{1/2}^{0ν}\ > \ {1.0}\times 10^{23}\ \rm yr\ (90\% \ C.L.)$, corresponding to the upper limits on the effective Majorana neutrino mass: $\langle m_{ββ}\rangle < $3.2$-$7.5$\ \mathrm{eV}$.

nucl-ex↗

arXiv2024

Projected WIMP sensitivity of the CDEX-50 dark matter experiment

CDEX-50 is a next-generation project of the China Dark Matter Experiment (CDEX) that aims to search for dark matter using a 50-kg germanium detector array. This paper comprises a thorough summary of the CDEX-50 dark matter experiment, including an investigation of potential background sources and the development of a background model. Based on the baseline model, the projected sensitivity of weakly interacting massive particle (WIMP) is also presented. The expected background level within the energy region of interest, set to 2--2.5 keVee, is $\sim$0.01 counts keVee$^{-1}$ kg$^{-1}$ day$^{-1}$. At 90\% confidence level, the expected sensitivity to spin-independent WIMP-nucleon couplings is estimated to reach a cross-section of 5.1 $\times$ 10$^{-45}$ cm$^{2}$ for a WIMP mass of 5 GeV/c$^{2}$ with an exposure objective of 150 kg$\cdot$year and an analysis threshold of 160 eVee. This science goal will correspond to the most sensitive results for WIMPs with a mass of 2.2--8 GeV/c$^{2}$.

hep-ex↗

arXiv2024

Search for solar axions by Primakoff effect with the full dataset of the CDEX-1B Experiment

We present the first limit on $g_{Aγ}$ coupling constant using the Bragg-Primakoff conversion based on an exposure of 1107.5 kg days of data from the CDEX-1B experiment at the China Jinping Underground Laboratory. The data are consistent with the null signal hypothesis, and no excess signals are observed. Limits of the coupling $g_{Aγ}<2.08\times10^{-9}$ GeV$^{-1}$ (95\% C.L.) are derived for axions with mass up to 100 eV/$c^2$. Within the hadronic model of KSVZ, our results exclude axion mass $>5.3~\rm{eV}/c^2$ at 95\% C.L.

hep-ex↗

arXiv2024

Experimental Limits on Solar Reflected Dark Matter with a New Approach on Accelerated-Dark-Matter-Electron Analysis in Semiconductors

Recently a dark matter-electron (DM-electron) paradigm has drawn much attention. Models beyond the standard halo model describing DM accelerated by high energy celestial bodies are under intense examination as well. In this Letter, a velocity components analysis (VCA) method dedicated to swift analysis of accelerated DM-electron interactions via semiconductor detectors is proposed and the first HPGe detector-based accelerated DM-electron analysis is realized. Utilizing the method, the first germanium based constraint on sub-GeV solar reflected DM-electron interaction is presented with the 205.4 kg$\cdot$day dataset from the CDEX-10 experiment. In the heavy mediator scenario, our result excels in the mass range of 5$-$15 keV/$c^2$, achieving a 3 orders of magnitude improvement comparing with previous semiconductor experiments. In the light mediator scenario, the strongest laboratory constraint for DM lighter than 0.1 MeV/$c^2$ is presented. The result proves the feasibility and demonstrates the vast potential of the VCA technique in future accelerated DM-electron analyses with semiconductor detectors.

hep-ex↗

arXiv2024

First search for light fermionic dark matter absorption on electrons using germanium detector in CDEX-10 experiment

We present the first results of the search for sub-MeV fermionic dark matter absorbed by electron targets of germanium using the 205.4~kg$\cdot$day data collected by the CDEX-10 experiment, with the analysis threshold of 160~eVee. No significant dark matter (DM) signals over the background are observed. Results are presented as limits on the cross section of DM--electron interaction. We present new constraints of cross section in the DM range of 0.1--10 keV/$c^2$ for vector and axial-vector interaction. The upper limit on the cross section is set to be $\rm 6.8\times10^{-46}~cm^2$ for vector interaction, and $\rm 2.3\times10^{-46}~cm^2$ for axial-vector interaction at DM mass of 5 keV/$c^2$.

hep-ex↗

arXiv2024

Constraints on the Blazar-Boosted Dark Matter from the CDEX-10 Experiment

We report new constraints on light dark matter (DM) boosted by blazars using the 205.4 kg day data from the CDEX-10 experiment located at the China Jinping Underground Laboratory. Two representative blazars, TXS 0506+56 and BL Lacertae are studied. The results derived from TXS 0506+56 exclude DM-nucleon elastic scattering cross sections from $4.6\times 10^{-33}\ \rm cm^2$ to $1\times10^{-26}\ \rm cm^2$ for DM masses between 10 keV and 1 GeV, and the results derived from BL Lacertae exclude DM-nucleon elastic scattering cross sections from $2.4\times 10^{-34}\ \rm cm^2$ to $1\times10^{-26}\ \rm cm^2$ for the same range of DM masses. The constraints correspond to the best sensitivities among solid-state detector experiments in the sub-MeV mass range.

hep-ex↗

arXiv2023

Search for boosted keV-MeV light dark matter particles from evaporating primordial black holes at the CDEX-10 experiment

We present novel constraints on boosted light dark matter particles (denoted as ``$χ$'') 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. $χ$ 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 $χ$-nucleon elastic-scattering cross section region from 3.4$\times$10$^{-32}$ cm$^{2}$ to 2.3$\times$10$^{-29}$ cm$^{2}$ for $χ$ 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 $χ$ of 1 keV to 0.6 MeV from PBHs with masses of 7$\times$10$^{16}$ g. If the $χ$-nucleon elastic-scattering cross section can be determined in the future, the abundance of PBHs may be severely constrained by $χ$ 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 $χ$ from larger PBHs with a low threshold.

hep-ex↗

arXiv2023

Virtual segmentation of a small contact HPGe detector: inference of hit positions of single-site events via pulse shape analysis

Exploring hit positions of recorded events can help to understand and suppress backgrounds in rare event searching experiments. In this study, we virtually segment a small contact P-type high purity germanium detector (HPGe) into two layers. Single-site events (SSEs) in each layer are selected by an algorithm based on two pulse shape parameters: the charge pulse drift time ($T_{Q}$) and current pulse rise time ($T_{I}$). To determine the shapes and volumes of the two layers, a Th-228 source is placed at top and side positions to irradiate the detector. The double escape peak events from 2614.5 keV $γ$-ray are selected as typical SSEs, their numbers in the two layers are used to calculate the volumes and shapes of those layers. Considering the statistical and systematic uncertainties, the inner layer volume is evaluated to be 47.2\%$\pm$0.26(stat.)\%$\pm$0.22(sys.)\% of the total sensitive volume. We extend our analysis for SSEs in 1400-2100 keV, the spectra of inner layer events acquired from experimental data using the selection algorithm are in good agreement with those from the simulation. For sources outside the HPGe detector, the outer layer can act as a shielding for the inner layer. Selecting the inner layer as the analysis volume can reduce the externalbackground in the signal region of Ge-76 neutrinoless double beta (0$νββ$) decay. We use the Th-228 source to evaluate the background suppression power of the virtual segmentation. After performing the single and multi-site event discrimination, the event rate in the 0$νββ$ signal region can be further suppressed by 12\% by selecting the inner layer as the analysis volume. The virtual segmentation could be used to efficiently suppress surface background like electrons from Ar-42/K-42 decay in 0$νββ$ experiments using germanium detector immersed in liquid argon.

physics.ins-det↗

arXiv2023

Search for exotic interactions of solar neutrinos in the CDEX-10 experiment

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 $Δm_{41}^{2}$ and $g^{\prime2}{\rm{sin}}^{2}2θ_{14}$.

hep-ex↗

arXiv2022

Modeling the Charge Collection Efficiency in the Li-diffused Inactive Layer of a P-type Point-Contact Germanium Detector

A model of the Li-diffused inactive layer in P-type high purity germanium detectors is built to describe the transportation of charge carriers and calculate the charge collection efficiency therein. The model is applied to calculate charge collection efficiency of a P-type point-contact germanium detector used in rare event physics experiments and validated in another P-type semi-planar germanium detector. The calculated charge collection efficiency curves are well consistent with measurements for both detectors. Effects of the Li doping processes on the charge collection efficiency are discussed based on the model. This model can be easily extended to other P-type germanium detectors, for instance, the P-type broad-energy Ge detector, and the P-type inverted-coaxial point-contact detector.

physics.ins-det↗

arXiv2022

Exotic Dark Matter Search with CDEX-10 Experiment at China's Jinping Underground Laboratory

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 ($χ+A\rightarrow ν+A$) and DM-nucleus 3$\rightarrow$2 scattering ($χ+χ+A\rightarrow ϕ+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.

hep-ex↗

arXiv2022

Constraints on Sub-GeV Dark Matter--Electron Scattering from the CDEX-10 Experiment

We present improved germanium-based constraints on sub-GeV dark matter via dark matter--electron ($χ$-$e$) scattering using the 205.4 kg$\cdot$day dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted $χ$-$e$ scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for $m_χ$ larger than 80 MeV/c$^2$ compared to previous germanium-based $χ$-$e$ results. We also present the most stringent $χ$-$e$ cross-section limit to date among experiments using solid-state detectors for $m_χ$ larger than 90 MeV/c$^2$ with heavy mediators and $m_χ$ larger than 100 MeV/c$^2$ with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new $χ$-$e$ detection method with high-purity germanium detectors in ultralow radioactive background.

hep-ex↗