Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: Given an accelerator-based neutrino experiment with the beam energy E \lesssim 1 GeV, we expand the probabilities of \nu_\mu \to \nu_e and \overline {\nu}_\mu \to \overline {\nu}_e oscillations in matter in terms of two small quantities \Delta_{21}/\Delta_{31} and A/\Delta_{31}, where \Delta_{21} \equiv m^2_2 - m^2_1 and \Delta_{31} \equiv m^2_3 - m^2_1 are the neutrino mass-squared differences, and A measures the strength of terrestrial matter effects. Our analytical approximations are numerically more accurate than those made by Freund in this energy region, and thus they are particularly applicable for the study of leptonic CP violation in the low-energy MOMENT, ESS\nuSM and T2K oscillation experiments. As a by-product, the new analytical approximations help us to easily understand why the matter-corrected Jarlskog parameter \widetilde{\cal J} peaks at the resonance energy E_* \simeq 0.14 GeV (or 0.12 GeV) for the normal (or inverted) neutrino mass hierarchy, and how the three Dirac unitarity triangles are deformed due to the terrestrial matter contamination. We also affirm that a medium-baseline neutrino oscillation experiment with the beam energy E lying in the E_* \lesssim E \lesssim 2 E_* range is capable of exploring leptonic CP violation with little matter-induced suppression.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: The ability of background discrimination using pulse shape discrimination (PSD) in broad-energy germanium (BEGe) detectors makes them as competitive candidates for neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) experiments. The measurements of key parameters for detector modeling in a commercial p-type BEGe detector are presented in this paper. Point-like sources were used to investigate the energy resolution and linearity of the detector. A cylindrical volume source was used for the efficiency calibration. With an assembled device for source positioning, a collimated 133Ba point-like source was used to scan the detector and investigate the active volume. A point-like source of 241Am was used to measure the dead layer thicknesses, which are approximately 0.17 mm on the front and 1.18 mm on the side. The described characterization method will play an important role in the 0{\nu}\b{eta}\b{eta} experiments with BEGe detectors at China JinPing underground Laboratory (CJPL) in the future.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: We study the strong decay channels P+c(4380)→J/ψp and P+c(4450)→J/ψp under ΣcD¯∗ molecular state ansatz. With various spin-parity assignments, the partial decay widths of J/ψp final state are calculated. Our results show that all the P wave ΣcD¯∗ assignments are excluded, while S wave ΣcD¯∗ pictures for Pc(4380) and Pc(4450) are both allowed by present experimental data. The JP=3/2− Σ∗cD¯ and Σ∗cD¯∗ molecules are also discussed in the heavy quark limit, and find that the Σ∗cD¯ system for Pc(4380) is possible. More experimental information on spin-parities and partial decay widths and theoretical investigations on other decay modes are needed to clarify the nature of the two Pc states.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: A new hybrid experiment has been constructed to measure the chemical composition of cosmic rays around the "knee" in the wide energy range by the Tibet ASγ collaboration at Tibet, China, since 2014. They consist of a high-energy air-shower-core array (YAC-II), a high-density air-shower array (Tibet-III) and a large underground water-Cherenkov muon-detector array (MD). In order to obtain the primary proton, helium and iron spectra and their "knee" positions in the energy range lower than 1016 eV, each of PMTs equipped to the MD cell is required to measure the number of photons capable of covering a wide dynamic range of 100 - 106 photoelectrons (PEs) according to Monte Carlo simulations. In this paper, we firstly compare the characteristic features between R5912-PMT made by Japan Hamamatsu and CR365-PMT made by Beijing Hamamatsu. This is the first comparison between R5912-PMT and CR365-PMT. If there exists no serious difference, we will then add two 8-inch-in-diameter PMTs to meet our requirements in each MD cell, which are responsible for the range of 100 - 10000 PEs and 2000 - 1000000 PEs, respectively. That is, MD cell is expected to be able to measure the number of muons over 6 orders of magnitude.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: In this article we study spontaneous chiral symmetry breaking for quark matter in the background of static and homogeneous parallel electric field $\bm E$ and magnetic field $\bm B$. We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at finite temperature for a wide range of E and B. We study the effect of this background on inverse catalysis of chiral symmetry breaking for E and B of the same order of magnitude. We then focus on the effect of equilibration of chiral density, n5, produced dynamically by axial anomaly on the critical temperature. The equilibration of n5, a consequence of chirality flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential, μ5, which is computed self-consistently as a function of temperature and field strength by coupling the number equation to the gap equation, and solving the two within an expansion in E/T2, B/T2 and μ25/T2. We find that even if chirality is produced and equilibrates within a relaxation time τM, it does not change drastically the thermodynamics, with particular reference to the inverse catalysis induced by the external fields, as long as the average μ5 at equilibrium is not too large.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: A new air-shower core-detector array (YAC : Yangbajing Air-shower Core-detector array) has been developed to measure the primary cosmic-ray composition at the "knee" energies in Tibet, China, focusing mainly on the light components. The prototype experiment (YAC-I) consisting of 16 detectors has been constructed and operated at Yangbajing (4300 m a.s.l.) in Tibet since May 2009. YAC-I is installed in the Tibet-III AS array and operates together. In this paper, we performed a Monte Carlo simulation to check the sensitivity of YAC-I+Tibet-III array to the cosmic-ray light component of cosmic rays around the knee energies, taking account of the observation conditions of actual YAC-I+Tibet-III array. The selection of light component from others was made by use of an artificial neural network (ANN). The simulation shows that the light-component spectrum estimated by our methods can well reproduce the input ones within 10\% error, and there will be about 30\% systematic errors mostly induced by the primary and interaction models used. It is found that the full-scale YAC and the Tibet-III array is powerful to study the cosmic-ray composition, in particular, to obtain the energy spectra of protons and helium nuclei around the knee energies.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: We propose a novel framework for asymmetric scalar dark matter (ADM), which has interesting collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local燯(1)d爏ymmetry which is broken at a low scale and provides a light gauge boson燲. The dark gauge coupling is strong and then ADM can annihilate away into燲-pair effectively. Therefore, the ADM can form bound state due to its large self-interaction via燲爉ediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with燽b� Of particular interest, our setup nicely explains the recent di-photon anomaly at 750 GeV via the events from�{\rm ADMonium}\ra 2X(\ra e^+e^-)$, where the electrons are identified as (un)converted photons. The remarkable prediction of an ADM near 375 GeV can be tested at the direct detection experiments in the near future.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: The optimization of resistive anode for two dimensional imaging detectors which consists of a series of high resistive square pads surrounding by low resistive strips has been studied by both numerical simulations and experimental tests. It has been found that to obtain good detector performance, the resistance ratio of the pad to the strip should be larger than 5, the nonuniformity of the pad surface resistivity had better be less than 20%, a smaller pad width leads to a smaller spatial resolution and when the pad width is 6mm, the spatial resolution (σ) can reach about 105μm. Based on the study results, a 2-D GEM detector prototype with the optimized resistive anode is constructed and a good imaging performance is achieved.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: We compute the s−s¯ asymmetry in the proton in chiral effective theory, using phenomenological constraints based upon existing data. Unlike previous meson cloud model calculations, which accounted for kaon loop contributions with on-shell intermediate states alone, this work includes off-shell terms and contact interactions, which impact the shape of the s−s¯ difference. Using a regularization procedure that preserves chiral symmetry and Lorentz invariance, we find that existing data limit the integrated value of the first moment of the asymmetry to the range −0.07×10−3≤⟨x(s−s¯)⟩≤1.12×10−3 at a scale of Q2=1GeV2. In contrast to some suggestions in the literature, the magnitude of this correction is too small to account for the NuTeV anomaly.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: Careful observation of the experimental spectra of heavy-light mesons tells us that heavy-light mesons with the same angular momentum L are almost degenerate. The estimate is given how much this degeneracy is broken in our relativistic potential model, and it is analytically shown that expectation values of a commutator between the lowest order Hamiltonian and L⃗ 2 are of the order of 1/mQ with a heavy quark mass mQ. It turns out that nonrelativistic approximation of heavy quark system has a rotational symmetry and hence degeneracy among states with the same L. This feature can be tested by measuring higher orbitally and radially excited heavy-light meson spectra for D/Ds/B/Bs in LHCb and forthcoming BelleII.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: The quality of PMT signal is one of the key items for a large and high precision neutrino experiment, like Daya Bay, JUNO, while most of the experiments are affected by the PMT signal overshoot from its positive HV-single cable scheme. For JUNO prototype detector, we have a detailed study on the PMT overshoot and successfully reduced the ratio of overshoot amplitude to signal to ~1% from previous typical ~10%, with no affection to PMT other parameters. Furthermore, we calculated that the overshoot is a result of discharging of capacitors in the HV-signal splitter and the PMT voltage divider. The study result is extremely important for JUNO and other similar experiments.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: We classify the different phases by the "pole-zero mechanism" for a holographic fermionic system which contains a dipole coupling with strength爌爋n a Q-lattice background. A complete phase structure in爌space can be depicted in terms of Fermi liquid, non-Fermi liquid, Mott phase and pseudo-gap phase. In particular, we find that in general the region of the pseudo-gap phase in爌爏pace is suppressed when the Q-lattice background is dual to a deep insulating phase, while for an anisotropic background, we have an anisotropic region for the pseudo-gap phase in爌爏pace as well. In addition, we find that the duality between zeros and poles always exists regardless of whether or not the model is isotropic.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: In this article we study restoration of chiral symmetry at finite temperature for quark matter with a chiral chemical potential, μ5, by means of a nonlocal Nambu-Jona-Lasinio model. This model allows to introduce in the simplest way possible a Euclidean momentum, pE, dependent quark mass function which decays (neglecting logarithms) as 1/p2E for large pE, in agreement with asymptotic behaviour expected in QCD in presence of a nonperturbative quark condensate. We focus on the critical temperature for chiral symmetry restoration in the chiral limit, Tc, versus μ5, as well as on the order of the phase transition. We find that Tc increases with μ5, and that the transition remains of the second order for the whole range of μ5 considered.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: In recent decades, inorganic crystals have been widely used in dark matter direct search experiments. To contribute to the understanding of the capabilities of CsI(Na) and CaF2(Eu) crystals, a mono-energetic neutron beam is utilized to study the properties of nuclear recoils, which are expected to be similar to signals of dark matter direct detection. The quenching factor of nuclear recoils in CsI(Na) and CaF2(Eu), as well as an improved discrimination factor between nuclear recoils and γ backgrounds in CsI(Na), are reported.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-31
Abstract: We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved - cosmology, astrophysics, nuclear, and particle physics - in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.
Peer Review Status:Awaiting Review
Subjects: Mathematics >> Control and Optimization. submitted time 2016-08-30
Abstract:In this paper necessary conditions and sufficient conditions are given for a linear operator to be a positive operators of an Extended Lorentz cone. Similarities and differences with the positive operators of Lorentz cones are investigated.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-30
Abstract: We report the neutrino mass hierarchy (MH) sensitivity of medium baseline reactor neutrino experiments with multiple detectors. Sensitivity of determining the MH can be significantly improved by adding a near detector and combining both the near and far detectors. The size of the sensitivity improvement is related to accuracy of the individual mass-splitting measurements and requires strict control on the relative energy scale uncertainty of the near and far detectors. We study the impact of both baseline and target mass of the near detector on the combined sensitivity. A figure-of-merit is defined to optimize the baseline and target mass of the near detector and the optimal selections are ∼13~km and ∼4~kton respectively for a far detector with the 20~kton target mass and 52.5~km baseline. As typical examples of future medium baseline reactor neutrino experiments, the optimal location and target mass of the near detector are selected for JUNO and RENO-50. Finally, we discuss distinct effects of the neutrino spectrum uncertainty for setups of a single detector and double detectors, which indicate that the spectrum uncertainty can be well constrained in the presence of the near detector.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-30
Abstract: In this article we study restoration of chiral symmetry at finite temperature for quark matter with a chiral chemical potential, μ5, by means of a quark-meson model with vacuum fluctuations included. Vacuum fluctuations give a divergent contribution to the vacuum energy, so the latter has to be renormalized before computing physical quantities. The vacuum term is important for restoration of chiral symmetry at finite temperature and μ5≠0, therefore we present several plausible renormalization schemes for the ultraviolet divergences at μ5≠0. Then we compute the critical temperature as a function of μ5. The main result of our study is that the choice of a renormalization scheme affects the critical temperature; among the three renormalization schemes we investigate, there exists one in which the critical temperature increases with μ5, a result which has not been found before by chiral model studies and which is in qualitative agreement with recent lattice data as well as with studies based on Schwinger-Dyson equations and universality arguments.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-30
Abstract: A new tuner control system of spoke superconducting radio frequency (SRF) cavity has been developed and applied to cryomodule I (CM1) of C-ADS injector I at IHEP. We have successfully implemented the tuner controllerfor the first time and achieved a cavity tuning phase error of 0.7degrees (about 4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper will present the preliminary experimental results based on the new tuner controller under proton beam commissioning.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-08-30
Abstract: A conservative constraint on the Einstein Equivalence Principle (EEP) can be obtained under the assumption that the observed time delay between correlated particles from astronomical sources is dominated by the gravitational fields through which they move. Current limits on the EEP are mainly based on the observed time delays of photons with different energies, and it is highly desirable to develop more accurate tests involving different types of particles. The detection by the advanced LIGO/VIRGO systems of gravitational waves (GWs) will provide attractive candidates for constraining the EEP, which would further extend the tested particle species to the gravitons, with potentially higher accuracy. Considering the capabilities of the advanced LIGO/VIRGO network and the source direction uncertainty, we show that the joint detection of GWs and electromagnetic signals can potentially probe the EEP to an accuracy of 10−11, which is several orders of magnitude tighter than previous limits.
Peer Review Status:Awaiting Review