119629879
Study of a prototype water Cherenkov detector for the Daya Bay neutrino experiment
The Daya Bay reactor neutrino experiment is designed to precisely measure the neutrino mixing angle theta(13). The anti-neutrino detectors are shielded by highly purified water against radioactivity and spallation neutrons from surrounding rocks. The water also serves as a Cherenkov detector to tag cosmic-ray muons, which induce main backgrounds. In order to study water purification and details of the detector response, a prototype water Cherenkov detector is constructed at the Institute of High Energy Physics (IHEP), Beijing. The detector is divided by Tyvek into two sections and viewed by two 8 in. photomultipliers. Cosmic-ray muons are used for detector response studies and a Monte Carlo simulation based on the Geant4 package shows good agreement with the experimental data. (C) 2012 Elsevier B.V. All rights reserved.
124732180
Correction of PMT position effect for a lead-scintillating fiber electromagnetic calorimeter
The position effect of the photoelectron multiplier tube (PMT) of the electromagnetic calorimeter (ECAL) of Alpha Magnetic Spectrometer-02 (AMS-02) has been studied with beam-test data. The reconstructed deposited energy in a layer versus incidence position in the cell can be described by Gaussian distribution, maximum and minimum value can be obtained when the particle passes across the center and the edge of a cell respectively. The distribution can be used to correct the effect of incidence position on energy reconstruction. Much better energy resolution was acquired be got with the correction, for 100 GeV electrons, energy resolution improved from 3% to 2%.
119265345
Bound to bounce: a coupled scalar-tachyon model for a smooth bouncing/cyclic universe
We introduce a string-inspired model for a bouncing/cyclic universe, utilizing the scalar-tachyon coupling as well as contribution from curvature in a closed universe. The universe undergoes the locked inflation, tachyon matter dominated rolling expansion, turnaround and contraction, as well as the subsequent deflation and "bounce" in each cycle of the cosmological evolution. We perform extensive analytic and numerical studies of the above evolution process. The minimum size of the universe is nonzero for generic initial values. The smooth bounce are made possible because of the negative contribution to effective energy density by the curvature term. No ghosts are ever generated at any point in the entire evolution of the universe, with the Null, Weak, and Dominant Energy Conditions preserved even at the bounce points, contrary to many bounce models previously proposed. And the Strong Energy Condition is satisfied in periods with tachyon matter domination.
119251292
Leakage tests of the stainless steel vessels of the antineutrino detectors in the Daya Bay reactor neutrino experiment
The antineutrino detectors for the Daya Bay reactor neutrino experiment are liquid scintillator detectors designed to detect electron anti-neutrino via inverse beta interactions with high efficiency and low backgrounds. Since the antineutrino detector will be installed and immerged in water Cherenkov detector and will run for 3 to 5 years, water tightness is critical to the successful operation of the antineutrino detectors. A special seal technique was used for this purpose. Three leak checking methods have been employed to ensure the seal quality. This paper describes the sealing method and leakage testing results.
123724946
Expression of interest to the Superconducting Super Collider Laboratory by the L* Collaboration
118438822
Dark matter and Higgs phenomenology predicted by left-right twin Higgs model in light of CDMS II results
The left-right twin Higgs model predicts a light stable scalar Ŝ, which is a candidate for WIMP dark matter. We study its scattering on nucleon and find that the cross section is below the CDMS II upper bound but can reach the SuperCDMS sensitivity. Then we study the Higgs phenomenology by paying special attention to the decay h → ŜŜ which is strongly correlated with the dark matter scattering on nucleon. We find that such an invisible decay can be sizable, which can severely suppress the conventional decay modes like h → VV (V = W, Z) and $ h \to b\bar b $. On the other hand, compared to the SM prediction, the rates of Higgs boson productions at the LHC via gluon-gluon fusion, weak boson fusion or in association with top quark pairs are all reduced significantly, e.g., the gluon-gluon fusion channel can be suppressed by about 30%.
119955860
Improved calculation of the energy release in neutron-induced fission
Fission energy is one of the basic parameters needed in the calculation of antineutrino ux from nuclear reactors. Improving the precision of ssion energy calculations is useful for current and future reactor neutrino experiments, which are aimed at more precise determinations of neutrino oscillation parameters. In this article, we give new values for ssion energies of some common thermal reactor fuel isotopes, with improvements on three aspects. One is more recent input data acquired from updated nuclear databases. The second improvement is a consideration of the production yields of ssion fragments from both thermal and fast incident neutrons for each of the four main fuel isotopes. The third improvement is a more careful calculation of the average energy taken away by antineutrinos in thermal ssion involving a comparison of antineutrino spectra from dierent models. The change in calculated antineutrino ux due to the new values of ssion energy is about 0.32%, and the uncertainties of the new values are about 50% smaller.