24 research outputs found
Effective-field theory with the differential operator technique for a kinetic Blume-Capel model with random diluted single-ion anisotropy
No full textWe 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
Static quadrupolar susceptibility for a Blume-Emery-Griffiths model based on the mean-field approximation
No full textThe expressions for the dipolar and quadrupolar susceptibilities are obtained within the mean-held approximation in the Blume-Emery-Griffiths model. Temperature as well as crystal held dependences of the susceptibilities are investigated for two different phase diagram topologies which take place for K/J=3 and K/J=5.0.Their behavior near the second and first order transition points as well as multi-critical points such as tricritical, triple and critical endpoint is presented It is found that in addition to the jumps connected with the phase transitions there are broad peaks in the quadrupolar susceptibility. It is indicated that these broad peaks lie on a prolongation of the first-order line from a triple point to a critical point ending the line of first-order transitions between two distinct paramagnetic phases It is argued that the broad peaks are a reminiscence of very strong quaclrupolar fluctuations at the critical point. The results reveal the fact that near ferromagnetic-paramagnetic phase transitions the quaclrupolar susceptibility generally shows a jump whereas near the phase transition between two distinct paramagnetic phases it is an edge-like. (C) 2015 Elsevier BM. All rights reserved
The Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND)
No full textThe observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neu-trinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 1028 years, using existing resources as appropriate to expedite physics results
Constraints on nonstandard intermediate boson exchange models from neutrino-electron scattering
No full textConstraints on couplings of several beyond-Standard-Model-physics scenarios, mediated by massive intermediate particles including ( 1) an extra Z-prime, ( 2) a new light spin-1 boson, and ( 3) a charged Higgs boson, are placed via the neutrino-electron scattering channel to test the Standard Model at a low energy-momentum transfer regime. Data on (nu) over bar (e) - e and nu(e) - e scattering from the TEXONO and LSND, respectively, are used. Upper bounds to coupling constants of the flavor-conserving and flavor-violating new light spin-1 boson and the 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
Studies of quantum-mechanical coherency effects in neutrino-nucleus elastic scattering
No full textNeutrino-nucleus elastic scattering (nu 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 a 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 x 10(3) MeV2 and p = 0.016 at q(2) = 2.3 x 10(3) MeV2, respectively, verifying that both QM superpositions and nuclear many-body effects contribute to.Ael interactions
Constraints on Spin-Independent Nucleus Scattering with sub-GeV Weakly Interacting Massive Particle Dark Matter from the CDEX-1B Experiment at the China Jinping Underground Laboratory
No full textWe 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 day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg 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(SI)(chi N) at 90% confidence level are derived as 2 x 10(-32) similar to 7 x 10 (-35) cm(2) for TI analysis at m(chi) similar to 50-180 MeV/c(2), and 3 x 10(-32) similar to 9 x 10 (-38) cm(2) for AM analysis at m(chi) similar to 75 MeV/c(2)-3.0 GeV/c(2)
Limits on Light Weakly Interacting Massive Particles from the First <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>102.8</mml:mn><mml:mtext> </mml:mtext><mml:mtext>kg</mml:mtext><mml:mo>×</mml:mo><mml:mtext>day</mml:mtext></mml:mrow></mml:math> Data of the CDEX-10 Experiment
No full textWe 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 x 10(-42) and 3 x 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(chi)) of 5 GeV/c(2) are achieved. The lower reach of m(chi) is extended to 2 GeV/c(2)
Search for Light Weakly-Interacting-Massive-Particle Dark Matter by Annual Modulation Analysis with a Point-Contact Germanium Detector at the China Jinping Underground Laboratory
No full textWe present results on light weakly interacting massive particle (WIMP) searches with annual modulation (AM) analysis on data from a 1-kg mass p-type point-contact germanium detector of the CDEX-1B experiment at the China Jinping Underground Laboratory. Datasets with a total live time of 3.2 yr within a 4.2-yr span are analyzed with analysis threshold of 250 eVee. Limits on WIMP-nucleus (chi-N) spin-independent cross sections as function of WIMP mass (m(chi)) at 90% confidence level (C.L.) are derived using the dark matter halo model. Within the context of the standard halo model, the 90% C.L. allowed regions implied by the DAMA/LIBRA and CoGeNT AM-based analysis are excluded at >99.99% and 98% C.L., respectively. These results correspond to the best sensitivity at m(chi) < 6 GeV/c(2) among WIMP AM measurements to date
The large enriched germanium experiment for neutrinoless double beta decay (LEGEND)
No full textThe observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neu-trinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 1028 years, using existing resources as appropriate to expedite physics results
Constraints on millicharged particles with low-threshold germanium detectors at Kuo-Sheng Reactor Neutrino Laboratory
No full textRelativistic millicharged particles (χ[subscript q]) have been proposed in various extensions to the standard model of particle physics. We consider the scenarios where they are produced at nuclear reactor core and via interactions of cosmic rays with the Earth’s atmosphere. Millicharged particles could also be candidates for dark matter and become relativistic through acceleration by supernova explosion shock waves. The atomic ionization cross section of χ[subscript q] with matter are derived with the equivalent photon approximation. Smoking-gun signatures with significant enhancement in the differential cross section are identified. New limits on the mass and charge of χ[subscript q] are derived, using data taken with a point-contact germanium detector with 500 g mass functioning at an energy threshold of 300 eV at the Kuo-Sheng Reactor Neutrino Laboratory
