30971943
New limit on neutrinoless double beta decay in 136Xe with a time projection chamber.
A xenon time projection chamber with an active volume of 207 L has been built to study neutrinoless double β decay in ^(136)Xe. Data were taken in the Gotthard Underground Laboratory, with 5 atm of xenon enriched to 62.5% in ^(136)Xe. From 3380 h of data, no evidence has been found for the 0ν 0^(+)→0^(+) transition. Half-life limits of T_(1/2)^(0ν)>2.5(4.9)×10^(23) yr in the mass-mechanism mode and T_(1/2)^(0ν)>1.7(3.2)×10^(23) yr in the right-handed-current mode, at the 90(68)% C.L., were derived. An upper limit for the Majorana neutrino mass parameter was deduced.
199684513
DARK MATTER SEARCH WITH SUB-keV GERMANIUM DETECTORS AT THE CHINA JINPING UNDERGROUND LABORATORY
Germanium detectors with sub-keV sensitivities open a window to search for low-mass WIMP dark matter. The CDEX-TEXONO Collaboration is conducting the first research program at the new China Jinping Underground Laboratory with this approach. The status and plans of the laboratory and the experiment are discussed.
123495553
Limits on Low-Mass WIMP Dark Matter with an Ultra-Low-Energy Germanium Detector at 220 eV Threshold
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[1]. This provides a unique probe to WIMP dark matter with mass below 10 GeV. With low background data taken at the Kuo-Sheng Laboratory, constraints on WIMPs in the galactic halo were derived. Both spin-independent WIMP-nucleon and spin-dependent WIMP-neutron bounds improve over previous results for WIMP mass between 3 6 GeV. These results, together with those on spin-dependent couplings, will be presented. Sensitivities for full-scale experiments were projected. This detector technique makes the unexplored sub-keV energy window accessible for new neutrino and dark matter experiments. 1. MOTIVATIONS Weakly Interacting Massive Particles (WIMP, denoted by �) are the leading candidates for Cold Dark Matter (CDM)[2]. There are intense experimental efforts to look for WIMPs through direct detection of nuclear recoils
121441164
Measurement of neutrino-electron scattering cross section and the EW parameters at the Kuo-Sheng reactor neutrino laboratory
The e−e− elastic scattering cross-section was measured at the Kuo-Sheng Nuclear Power Station with a CsI(Tl) scintillating crystal detector array with a total mass of 187 kg. The detector was exposed to a reactor e flux of 6.4 × 1012 cm−2s−1 originated from a core with 2.9 GW thermal power. A cross-section ratio of Rexpt = [1.08 ± 0.21 (stat) ± 0.16 (sys)] × RSM was measured. Constraints on the electroweak parameters (gv,gA) were placed, corresponding to a weak mixing angle measurement of sin2θw = 0.251 ± 0.031 (stat) ± 0.024 (sys). The destructive interference in the SM e-e processes was verified with the value of RINTexpt = [0.92 ± 0.30 (stat) ± 0.24 (sys)] × RINTSM. Bounds on neutrino anomalous electromagnetic properties were placed: neutrino magnetic moment at μe = [0.61 ± 1.30 (stat) ± 1.01 (sys)] × 10−32 cm2.
121604922
LOW ENERGY NEUTRINO AND DARK MATTER PHYSICS WITH SUB-keV GERMANIUM DETECTORS
The theme of the TEXONO-CDEX research program is on the studies of low energy neutrino and dark matter physics at Kuo-Sheng Reactor Neutrino Laboratory and China Jin-Ping Underground Laboratory. The current goal is to open the "sub-keV" detector window with germanium detectors. The three main scientific subjects are neutrino magnetic moments, neutrino-nucleus coherent scattering, and dark matter searches. We highlight the status, results and plans in this article.
14989310
RESEARCH PROGRAM OF THE TEXONO COLLABORATION: STATUS AND HIGHLIGHTS
This article reviews the research program and efforts for the TEXONO Collaboration among scientists from Taiwan and China. These include reactor-based neutrino physics at the Kuo-Sheng Power Plant in Taiwan as well as various R&D efforts related to the various experimental techniques in neutrino and astro-particle physics.
7343393
Asymmetric left-right model for generating radiative quark and lepton masses.
The conventional SU(2){sub {ital L}}{times}SU(2){sub {ital R}}{times}U(1) electroweak gauge model is extended to include two heavy singlet quarks and one heavy singlet lepton. The scalar sector consists of two (2,1,1/2) doublets, two (1,2,1/2) doublets, one (2,1,3/2) doublet, one (1,2,3/2) doublet, as well as one (1,3,1) triplet. Realistic radiative masses for all light quarks and leptons are obtained. A {ital Z}{sub 2} discrete symmetry serves to distinguish the electron (or muon) and its neutrino from the other leptons.
39329664
One-loop-induced fermion masses and exotic interactions in a standard-model context.
The standard SU(2)\ifmmode\times\else\texttimes\fi{}U(1) electroweak gauge model is extended to include a fourth generation of quarks and leptons as well as four extra Higgs-boson doublets. With the implementation of a ${Z}_{4}$ discrete symmetry, which is softly broken down to ${Z}_{2}$, realistic radiative quark and lepton masses for the first two generations can be obtained. Assuming that the third and fourth lepton generations are odd under the unbroken ${Z}_{2}$, we discuss a number of interesting phenomenological consequences such as a longer $\ensuremath{\tau}$ lifetime and some possible anomalous $\ensuremath{\tau}$ interactions. We also single out some processes involving fourth-generation quarks and leptons which cannot be confused experimentally with those of the standard model.
40901564
Dichotomy of leptons: Radiative masses and rare decays.
A model is presented where the electron and muon masses are radiative and depend, respectively, on the masses of {tau} and a fourth charged lepton {ital E}. A discrete {ital Z}{sub 4} symmetry is softly broken down to {ital Z}{sub 2} which distinguishes ({mu},{tau}) from ({ital e},{ital E}). All three known neutrinos acquire radiative Majorana masses.