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 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 $m_{\chi}$ 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 $m_{\chi}, Comment: version accepted by Science China-PMA, 8 pages, 8 figures

Neutrino-nucleus elastic scattering ($\nu {\rm A}_{el}$) provides a unique laboratory to study the quantum-mechanical (QM) coherency effects in electroweak interactions. The deviations of the cross-sections from those of completely coherent systems can be quantitatively characterized through a coherency parameter $\alpha ( q^2 )$. The relations between $\alpha$ and the underlying nuclear physics in terms of nuclear form factors are derived. The dependence of cross-section on $\alpha ( q^2 )$ for the various neutrino sources is presented. The $\alpha ( q^2 )$-values are evaluated from the measured data of the COHERENT CsI and Ar experiments. Complete coherency and decoherency conditions are excluded by the CsI data with $p {=} 0.004$ at $q^2 {=} 3.1 {\times} 10^{3} ~ {\rm MeV^2}$ and with $p {=} 0.016$ at $q^2 {=} 2.3 {\times} 10^{3} ~ {\rm MeV^2}$, respectively, verifying that both QM superpositions and nuclear many-body effects contribute to $\nu {\rm A}_{el}$ interactions., Comment: V2 Published Version, 10 pages, 10 figures

The p-type point-contact germanium detectors have been adopted for light dark matter WIMP searches and the studies of low energy neutrino physics. These detectors exhibit anomalous behavior to events located at the surface layer. The previous spectral shape method to identify these surface events from the bulk signals relies on spectral shape assumptions and the use of external calibration sources. We report an improved method in separating them by taking the ratios among different categories of in situ event samples as calibration sources. Data from CDEX-1 and TEXONO experiments are re-examined using the ratio method. Results are shown to be consistent with the spectral shape method., Comment: 29 pages, 16 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

We report in situ neutron background measurements at the Kuo-Sheng Reactor Neutrino Laboratory (KSNL) by a hybrid neutron detector (HND) with a data size of 33.8 days under identical shielding configurations as during the neutrino physics data taking. The HND consists of BC-501A liquid and BC-702 phosphor powder scintillation neutron detectors, which is sensitive to both fast and thermal neutrons, respectively. Neutron-induced events for the two channels are identified and differentiated by pulse shape analysis, such that background of both are simultaneously measured. The fast neutron fluxes are derived by an iterative unfolding algorithm. Neutron induced background in the germanium detector under the same fluxes, both due to cosmic-rays and ambient radioactivity, are derived and compared with the measurements. The results are valuable to background understanding of the neutrino data at the KSNL. In particular, neutron-induced background events due to ambient radioactivity as well as from reactor operation are negligible compared to intrinsic cosmogenic activity and ambient $\gamma$-activity. The detector concept and analysis procedures are applicable to neutron background characterization in similar rare-event experiments., Comment: 12 pages, 29 figures

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36} cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5 GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2 GeV/c^{2}.

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10−42 and 3×10−36 cm2 at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (mχ) of 5 GeV/c2 are achieved. The lower reach of mχ is extended to 2 GeV/c2.

We report results from searches of pseudoscalar and vector bosonic super-weakly interacting massive particles (super-WIMP) in the TEXONO experiment at the Kuo-Sheng Nuclear Power Station, using 314.15 kg days of data from $n$-type Point-Contact Germanium detector. The super-WIMPs are absorbed and deposit total energy in the detector, such that the experimental signatures are spectral peaks corresponding to the super-WIMP mass. Measured data are compatible with the background model, and no significant excess of super-WIMP signals are observed. We derived new upper limits on couplings of electrons with the pseudoscalar and vector bosonic super-WIMPs in the sub-keV mass region, assuming they are the dominant contributions to the dark matter density of our galaxy., Comment: 23 pages, 17 figures

The static and dynamic linear response functions for the spin-1 mean-field Blume-Capel model with a random diluted single-ion anisotropy are derived using the thermodynamics of linear irreversible processes. Thermal dependence of the static susceptibility is studied in detail. In addition, by utilizing the stationary solution of the kinetic equation in existence of sinusoidal external magnetic field, the low frequency thermal behavior of the magnetic absorption and dispersion factors are investigated. Particularly, we have analyzed the behaviors of these quantities near both first-and second-order transition temperatures and multicritical points such as tricritical point, critical endpoint and double critical endpoint. The static and dynamical mean field critical exponents in hydrodynamic limit are also calculated in order to formulate the critical and multicritical behaviors of the magnetic susceptibility. Finally, a comparison of the findings of this study with previous theoretical and experimental studies is presented and it is shown that a good agreement is found with our results. (C) 2017 Elsevier B.V. All rights reserved.

We report the performance and characterization of a custom-built hybrid detector consisting of BC501A liquid scintillator for fast neutrons and BC702 scintillator for thermal neutrons. The calibration and the resolution of the BC501A liquid scintillator detector are performed. The event identification via Pulse Shape Discrimination (PSD) technique is developed in order to distinguish gamma, fast and thermal neutrons. Monte Carlo simulation packages are developed in GEANT4 to obtain actual neutron energy spectrum from the measured recoil spectrum. The developed methods are tested by reconstruction of 241AmBe(\alpha, n) neutron spectrum., Comment: 12 pages, 32 figures

Constraints on couplings of several Beyond Standard Model Physics scenarios, mediated by massive intermediate particles including (1) Extra Z-prime, (2) New Light Spin-1 Boson, and (3) Charged Higgs Boson, are placed via neutrino-electron scattering channel to test Standard Model at low energy-momentum transfer regime. Data on $\bar{\nu}_{e}-e$ and $\nu_{e}-e$ scattering from the TEXONO and LSND Experiments, respectively, are used. Upper bounds to coupling constants of Flavor Conserving and Flavor Violating New Light Spin-1 Boson and Charged Higgs Boson with respect to different mediator masses are determined. The relevant parameter spaces are extended by allowing light mediators. New lower mass limits for extra Z-prime gauge boson models are also placed., Comment: 14 pages, 29 figures

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

Germanium ionization detectors with sensitivities as low as 100 eVee (electron-equivalent energy) open new windows for studies on neutrino and dark matter physics. The relevant physics subjects are summarized. The detectors have to measure physics signals whose amplitude is comparable to that of pedestal electronic noise. To fully exploit this new detector technique, various experimental issues including quenching factors, energy reconstruction and calibration, signal triggering and selection as well as evaluation of their associated efficiencies have to be attended. The efforts and results of a research program to address these challenges are presented., Comment: 18 pages, 18 figures, 3 table; v3 -- Published Version

We present the dynamical phase diagrams of the kinetic Blume-Capel model with random diluted single-ion anisotropy in a square lattice under the presence of a time-varying (oscillating) external magnetic field calculated by an analytical method, the effective-field theory (EFT). The kinetics is modeled with the formalism of a master equation. The time-averaged magnetization (M) acts as the order parameter and divides the temperature-field plane into three regions: ferromagnetic, paramagnetic, and coexistence of ferromagnetic and paramagnetic phases. In addition, the hysteresis loop area and the dynamic correlation function are calculated. It is observed that the inclusion of spin-spin correlations suppress the first-order transition lines and dynamical tricritical points for all values of the crystal-field concentration. (c) 2012 Elsevier B.V. All rights reserved.