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. PACS numbers: 95.35.+d, 29.40.-n * Participating as a member of TEXONO Collaboration

Finite neutrino magnetic moments are consequences of nonzero neutrino masses. The particle physics aspects of the neutrino electromagnetic interactions are reviewed. The astrophysical bounds and the results from recent direct experiments are reviewed, with emphasis on the reactor neutrino experiments. Future projects and prospects are surveyed.

With the advent of detectors with sub-keV sensitivities, atomic ionization has been identified as a promising avenue to probe possible neutrino electromagnetic properties. The interaction crosssections induced by millicharged neutrinos are evaluated with the ab-initio multi-configuration relativistic random-phase approximation. There is significant enhancement at atomic binding energies compared to that when the electrons are taken as free particles. Positive signals would distinctly manifest as peaks at specific energies with known intensity ratios. Selected reactor neutrino data with germanium detectors at analysis threshold as low as 300 eV are studied. No such signatures are observed, and a combined limit on the neutrino charge fraction of |δQ| < 1.0 × 10 −12 at 90% confidence level is derived.PACS numbers: 14.60. Lm, 13.15.+g, 13.40.Gp The physical origin and experimental consequences of finite neutrino masses and mixings [1] are not fully understood. Investigations on anomalous neutrino properties and interactions [2] are crucial to address these fundamental questions and may provide hints or constraints to new physics beyond the Standard Model (SM). An avenue is on the studies of possible neutrino electromagnetic interactions [2-4] which, in addition, offer the potentials to differentiate between Majorana and Dirac neutrinos. The neutrino electromagnetic form factors in C, P and T-conserving theories can be formulated as:, and (2)γ µ and σ µν are the standard QED matrices, e 0 and m e are the electron charge and mass, respectively, q = (q 0 , q) is the four-momentum transfer, while the neutrino properties are parametrized by the neutrino fractional charge relative to the electron (δ Q − commonly referred to as "neutrino millicharge" in the literature), the neutrino charge radius ( r 2 ν ), and the anomalous neutrino magnetic moment (µ ν ) [3,4] in units of the Bohr magneton µ B . The F 1 and F 2 terms characterize neutrino interactions without and with a change of the helicity states, respectively. The studies of δ Q and r 2 ν should in general * Corresponding Author: lakhwinder@phys.sinica.edu.tw † Corresponding Author: htwong@phys.sinica.edu.tw ‡ Corresponding Author: b97b02002@ntu.edu.tw be coupled to those due to SM-electroweak interactions to account for the possible interference effects among them. For completeness, we note that two additional form factors are possible [4]: the electric dipole moments in theories violating both P-and T-symmetries, and the anapole moments in P-violating theories.The theme of this article is to report a new direct laboratory limit on |δ Q |. The searches are based onν e emitted from the nuclear power reactor via atomic ionization [5], an interaction channel considered for the first time in this process. The cross-section is derived using the Multi-Configuration Relativistic Random-Phase Approximation (MCRRPA) theory [6,7]. As will be demonstrated in Figure 1b, the bounds on event rates from δ Qinduced atomic interactions [ν e -A(δ Q )]:to be probed in this work (...

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.

A new detection channel on atomic ionization for possible neutrino electromagnetic interactions is identified and studied. Significant sensitivity enhancement is demonstrated when the energy transfer to the target is of the atomic-transition scale. The interaction cross section induced by neutrino magnetic moments () is evaluated with the equivalent photon method. A new limit of ð " e Þ < 1:3 Â 10 À11 B at 90% confidence level is derived by using current reactor neutrino data. Potential reaches for future experiments are explored. Experiments with sub-keV sensitivities can probe to 10 À13 B. Positive observations of in this range would imply that neutrinos are Majorana particles.