Search

We report constraints on the dark photon effective kinetic mixing parameter (${\kappa}$) 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 ${\kappa}$ 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 ${\rm{\kappa=1.3 \times 10^{-15}}}$ at ${\rm{m_V=200\ eV/c^2}}$., Comment: 5 pages, 6 figures

We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses ($m_{\chi}$) 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$\cdot$day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg$\cdot$day exposure and 250 eVee threshold for AM analysis. The sensitive windows in $m_{\chi}$ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on $\sigma_{\chi N}^{\rm SI}$ at 90\% confidence level are derived as $2\times$10$^{-32}\sim7\times$10$^{-35}$ $\rm cm^2$ for TI analysis at $m_{\chi}\sim$ 50$-$180 MeV/$c^2$, and $3\times$10$^{-32}\sim9\times$10$^{-38}$ $\rm cm^2$ for AM analysis at $m_{\chi}\sim$75 MeV/$c^2-$3.0 GeV/$c^2$., Comment: 5 pages, 4 figures

The electromagnetic properties of neutrinos, which are either trivial or negligible in the context of the Standard Model, can probe new physics and have significant implications in astrophysics and cosmology. The current best direct limits on the neutrino millicharges and magnetic moments are both derived from data taken with germanium detectors with low thresholds at keV levels. In this paper, we discuss in detail a robust, ab initio method: the multiconfiguration relativistic random-phase approximation, that enables us to reliably understand the germanium detector response at the sub-keV level, where atomic many-body physics matters. By using existing data with sub-keV thresholds, limits on the reactor antineutrino's millicharge, magnetic moment, and charge radius squared are derived. The projected sensitivities for next-generation experiments are also given and discussed.

The p-type point-contact germanium detectors are novel techniques offering kg-scale radiation sensors with sub-keV sensitivities. They have been used for light Dark Matter WIMPs searches and may have potential applications in neutrino physics. There are, however, anomalous surface behaviour which needs to be characterized and understood. We describe the methods and results of a research program whose goals are to identify the bulk and surface events via software pulse shape analysis techniques, and to devise calibration schemes to evaluate the selection efficiency factors. Efficiencies-corrected background spectra from the low-background facility at Kuo-Sheng Neutrino Laboratory are derived., 9 pages, 10 figures, 2 tables; Published Version as V2

Weakly Interacting Massive Particles (WIMPs) are the candidates of dark matter in our universe. Up to now any direct interaction of WIMP with nuclei has not been observed yet. The exclusion limits of the spin-independent cross section of WIMP-nucleon which have been experimentally obtained is about 10^{-7}pb at high mass region and only 10^{-5}pb} at low mass region. China Jin-Ping underground laboratory CJPL is the deepest underground lab in the world and provides a very promising environment for direct observation of dark matter. The China Dark Matter Experiment (CDEX) experiment is going to directly detect the WIMP flux with high sensitivity in the low mass region. Both CJPL and CDEX have achieved a remarkable progress in recent two years. The CDEX employs a point-contact germanium semi-conductor detector PCGe whose detection threshold is less than 300 eV. We report the measurement results of Muon flux, monitoring of radioactivity and Radon concentration carried out in CJPL, as well describe the structure and performance of the 1 kg PCGe detector CDEX-1 and 10kg detector array CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of the CDEX-1, CDEX-10 and the future CDEX-1T detectors., 36pages,39 figures

An energy threshold of (220+-10) eV was achieved at an efficiency of 50% with a four-channel ultra-low-energy germanium detector each with an active mass of 5 g. This provides a unique probe to WIMP dark matter with mass below 10 GeV. With a data acquisition live time of 0.338 kg-day at the Kuo-Sheng Laboratory, constraints on WIMPs in the galactic halo were derived. The limits improve over previous results on both the spin-independent WIMP-nucleon and the spin-dependent WIMP-neutron cross-sections for WIMP mass between 3-6 GeV. Sensitivities for full-scale experiments are projected. This detector technique makes the unexplored sub-keV energy window accessible for new neutrino and dark matter experiments. Two appendices are included after Version-3 to address questions raised on trigger and selection efficiencies as well as other issues., Main Text: 5 pages, 1 table, 6 figures ; V1 -- spin-independent bounds ; V2 -- include spin-dependent bounds ; V3 -- Two appendices added to address questions raised ; V4 -- fixed technical errors

This article reports the first study of possible emissions of axions from power reactors using Primakoff and Compton conversions as the detection mechanisms. The expected experimental signatures are mono-energetic lines produced by their Primakoff or Compton conversions at a high-purity germanium (HPGe) detector. No evidence of axion emissions were observed and constraints on axion couplings versus axion mass within the framework of invisible axion models were placed. This experimental approach provides a unique probe for axion mass at the keV-MeV range not accessible to the other techniques.

A search of axions produced in nuclear transitions was performed at the Kuo-Sheng Nuclear Power Station with a high-purity germanium detector of mass 1.06 kg at a distance of 28 m from the 2.9 GW reactor core. The expected experimental signatures were monoenergetic lines produced by their Primakoff or Compton conversions at the detector. Based on 459.0/96.3 days of reactor ON/OFF data, no evidence of axion emissions were observed and constraints on the couplings g{sub a{gamma}}{sub {gamma}} and g{sub aee} versus axion mass m{sub a} within the framework of invisible axion models were placed. The KSVZ and DFSZ models can be excluded for 10{sup 4} eV < or approx. m{sub a} < or approx. 10{sup 6} eV. Model-independent constraints on g{sub a{gamma}}{sub {gamma}}{center_dot}g{sub aNN}{sup 1}

The low energy part of the reactor neutrino spectra has not been experimentally measured. Its uncertainties limit the sensitivities in certain reactor neutrino experiments. The origin of these uncertainties are discussed, and the effects on measurements of neutrino interactions with electrons and nuclei are studied. Comparisons are made with existing results. In particular, the discrepancies between previous measurements with Standard Model expectations can be explained by an under-estimation of the low energy reactor neutrino spectra. To optimize the experimental sensitivities, measurements for $\nuebar$-e cross-sections should focus on events with large ($>$1.5 MeV) recoil energy while those for neutrino magnetic moment searches should be based on events $, Comment: 25 pages, 9 figures