Showing papers by "Deqing Fang published in 2015"

Low-mass dark matter search results from full exposure of the PandaX-I experiment

Abstract: We report the results of a weakly interacting massive particle (WIMP) dark matter search using the full 80.1 live-day exposure of the first stage of the PandaX experiment (PandaX-I) located in the China Jin-Ping Underground Laboratory. The PandaX-I detector has been optimized for detecting low-mass WIMPs, achieving a photon detection efficiency of 9.6%. With a fiducial liquid xenon target mass of 54.0 kg, no significant excess events were found above the expected background. A profile likelihood ratio analysis confirms our earlier finding that the PandaX-I data disfavor all positive low-mass WIMP signals reported in the literature under standard assumptions. A stringent bound on a low-mass WIMP is set at a WIMP mass below 10 GeV=c(2), demonstrating that liquid xenon detectors can be competitive for low-mass WIMP searches.

A detection system for charged-particle decay studies with a continuous-implantation method

Abstract: A new detection system with high detection efficiency and low detection threshold has been developed for charged-particle decay studies, including beta-delayed proton, alpha decay or direct proton emission from proton-rich nuclei. The performance was evaluated by using the beta-delayed proton emitter Si-24 produced by projectile fragmentation at the First Radioactive Ion Beam Line in Lanzhou. Under a continuous-beam mode, the isotopes of interest were implanted into two double-sided silicon strip detectors, where the subsequent decays were measured and correlated to the preceding implantations by using position and time information. The system allows us to measure protons with energies down to about 200 keV without obvious 13 background in the proton spectrum. Further application of the detection system can be extended to the measurements of beta-delayed proton decay and the direct proton emission of more exotic proton-rich nuclei. (C) 2015 Elsevier B.V. All rights reserved.

Azimuthal Asymmetry of Pion-Meson Emission around the Projectile and Target Sides in Au+Au Collision at 1AGeV*

Abstract: The ratio of the number of emitted pions from the target side to that from the projectile side at target rapidity within the reaction plane is investigated for the study of the pion dynamics with an isospin-dependent quantum molecular dynamic model. The results show that high-energy pions are emitted preferentially towards the target side and, therefore, they are freezed out at the early stage of the collision. By contrast, low-energy pions are emitted predominantly in the opposite direction, which means that they are emitted in a later stage. This argument is based on the shadowing effect caused by the interaction of pions with the spectator matter in peripheral collisions at target or projectile rapidities. This phenomenon disappears in the central collision or at midrapidity due to the weaker shadowing effect. The calculated ratios are also compared with the experimental data.

The CUORE and CUORE-0 experiments at Gran Sasso

Abstract: The Cryogenic Underground Observatory for Rare Events (CUORE) is an experiment to search for neutrinoless double beta decay (0 nu beta beta) in Te-130 and other rare processes. CUORE is a cryogenic detector composed of 988 TeO2 bolometers for a total mass of about 741 kg. The detector is being constructed at the Laboratori Nazionali del Gran Sasso, Italy, where it will start taking data in 2015. If the target background of 0.01 counts/(keV.kg.y) will be reached, in five years of data taking CUORE will have an half life sensitivity around 1 x 10(26) y at 90% C.L. As a first step towards CUORE a smaller experiment CUORE-0, constructed to test and demonstrate the performances expected for CUORE, has been assembled and is running. The detector is a single tower of 52 CUORE-like bolometers that started taking data in spring 2013. The status and perspectives of CUORE will be discussed, and the first CUORE-0 data will be presented.