Secondary electron time detector for mass measurements at CSRe

The Isochronous Mass Spectrometry is a high accurate mass spectrometer. A secondary electrons time detector has been developed and used for mass measurements. Secondary electrons from a thin carbon foil are accelerated by an electric field and deflected 180°by a magnetic field onto a micro-channel plate. The time detector has been tested with alpha particles and a time resolution of 197 ps （FWHM） was obtained in the laboratory. A mass resolution around 8×10^-6 for Am/m was achieved by using this time detector in a pilot mass measurement experiment.     

Characterization of deep acceptor level in as-grown ZnO thin film by molecular beam epitaxy

We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy(MBE). The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current–voltage(I–V)measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49±0.03 eV and capture cross-section of 8.57×10-18cm2. Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy(SIMS) of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen–zinc vacancy complex in ZnO.     

HIAF-SRing的等时性模式光学设计

高精度环形谱仪SRing作为HIAF装置的核心之一,是获取高品质放射性次级束,并将束流用于加速器技术研究、原子物理及核物理实验的关键设备。SRing有三种运行模式:等时性模式、正常模式与内靶模式。等时性模式下,SRing运行在特殊线性光学设置下,可以精确测量寿命低至几十微秒的原子核的质量。介绍SRing等时性模式的线性光学及高阶项校正的设计方案。在使用程序GICOSY进行等时性高阶项校正数值计算后,将得到的光学传输矩阵输入到程序MOCADI进行粒子跟踪模拟。以γ_t=1.43的等时性模式为例,SRing的动量接收度为±0.20%,粒子跟踪结果显示,在仅满足一阶等时性条件时SRing的质量分辨能力R=1.6×104。在保证动量接收度不变的前提下,考虑了等时性高阶项校正后SRing的质量分辨能力提高到R=1.2×106,达到设计要求。The Spectrometer Ring, as the most important experiment terminal of the High Intensity heavy-ion Accelerator Facility (HIAF) project, is a key device to obtain high-quality radioactive ion beams (RIBs) for atomic physics, nuclear physics experiments and accelerator technology researches. Three operation modes including the isochronous mode, the normal mode and the internal target mode, have been designed for the SRing. In the isochronous mode, the SRing operates under a special ion optics and could be used for precision mass measurement of short-lived nuclei with half-life shorter than several tens of microseconds. This study aims to design the ion optics for the isochronous mode and improve the mass resolving power of the SRing with higher-order ion-optical correction scheme for isochronism while preserve a large momentum acceptance of SRing. The ion optics and the higher-order correction for the isochronous mode are calculated with the code MAD-X and GICOSY respectively. Three ion optics with γ_t=1.43, 1.67, 1.83 settings have been calculated. The code MCOADI which utilizes the matrixes generated by the code GICOSY is used for particles tracking to verify the correction results. For the ion-optical setting of γ_t=1.43 with a momentum acceptance of ±0.20%, the mass resolving power of the SRing could be improved from R=1.6×104 to R=1.2×106, after isochronous higher-order corrections.     

熔合反应中入射道质量不对成度效应

The symmetric and asymmetric fusion reaction systems forming the same compound nuclei ^26Al, ^30Si, ^38Ar and ^170Hf are investigated with the frame of improved isospin dependent quantum molecular dynamics model. The entrance channel mass asymmetry dependence of compound nucleus formation is found by analyzing the shell correction energies, the Coulomb barriers and the fusion cross sections. The calculated fusion cross sections agree quantitatively with the experimental data. The results indicate that compound nucleus formation is favorable for the systems with larger mass asymmetry because of the smaller Coulomb contribution to the fusion barrier.     

Unquenched Effects and Quark Mass Dependence of Lattice Gluon Propagator in Infrared Region

In this paper, the gluon propagator in Landau gauge has been studied on a lattice, including the quenched and the unquenched one. The small geometry size of lattice we use is 16^3 × 32, and the big one is 20^3 × 64. For the quenched approximation, we fit the numerical results and give a little different fitting values. We also obtain unquenched effects by comparing the gluon propagator resulting from the quenched and unquenched configurations, for both the two-flavor and three-flavor cases. For the unquenched configurations, an obvious quark mass dependence has not been found in the small quark mass case, but is found in the three-flavor case when the quark mass is big.     

Technical Improvements in the Experiment of Isochronous Mass Measurement of 58Ni Projectile Fragments

 The combination of in-flight fragment separator and the isochronous mass spectrometry(IMS) in storage rings have been proven to be a powerful tool for the precision mass measurements of shortlived exotic nuclei. In IMS, the mass-over-charge ratio is only related to the revolution period of stored ions, and the relative mass resolution can reach up to the order of 10−6. However, the instability of the magnetic field of storage ring deteriorates the resolution of revolution period, making it very difficult to distinguish the ions with very close mass-over-charge ratio via their revolution periods. To improve the resolution of revolution periods, a new method of weighted shift correction (WSC) has been developed to accurately correct the influence of the magnetic field instabilities in the isochronous mass measurements of 58Ni projectile fragments. By using the new method, the influence of unstable magnetic fields can be greatly reduced, and the mass resolution can be improved by a factor up to 1.7. Moreover, for the ions that still cannot be distinguished after correcting the magnetic field instabilities, we developed a new method of pulse height analysis for particle identification. By analyzing the mean pulse amplitude of each ion from the timing detector, the stored ions with close mass-over-charge ratios but different charge states such as 34Ar and 51Co can be identified, and thus the mass of 51Co can be determined. The charge-resolved IMS may be helpful in the future experiments of isochronous mass measurement even for N =Z nuclei.     

Observation and analysis of halo current in EAST

Plasma in a typically elongated cross-section tokamak （for example, EAST） is inherently unstable against vertical displacement. When plasma loses the vertical position control, it moves downward or upward, leading to disruption, and a large halo current is generated helically in EAST typically in the scrape-off layer. When flowing into the vacuum vessel through in-vessel components, the halo current will give rise to a large J × B force acting on the vessel and the in-vessel components. In EAST VDE experiment, part of the eddy current is measured in halo sensors, due to the large loop voltage. Primary experimental data demonstrate that the halo current first lands on the outer plate and then flows clockwise, and the analysis of the information indicates that the maximum halo current estimated in EAST is about 0.4 times the plasma current and the maximum value of TPF × Ih/Ip0 is 0.65, furthermore Ih/Ipo and TPF × Ih/Ipo tend to increase with the increase of Ip0. The test of the strong gas injection system shows good success in increasing the radiated power, which may be effective in reducing the halo current.     

Octet baryon masses with two-gluon exchange effect

We report our investigation on the octet baryon spectrum in the nonrelativistic quark model by taking into account the two-gluon exchange effect. The calculated octet baryon masses agree better with the experimental data. It is also shown that the two-gluon exchange interactions bring a significant correction to the Gell-Mann-Okubo mass formula.     

Neutrino Mass Generation in SO（4） Model

Generation of neutrino mass in SO（4） model is proposed here. The algebraic structure of SO （4） is same as to that ofSU（2）L x SU（2）R. It is shown that the spontaneous symmetry breaking results three massive as well as three massless gauge bosons. The standard model theory according to which there exist three massive gauge bosons and a massless one is emerged from this model. In the framework ofSU（2）L x SU（2）R a small Dirac neutrino mass is derived. It is also shown that such mass term may vanish with a special choice. The Majorana mass term is not considered here and thus in this model the neutrino mass does not follow seesaw structure.     

Conformal Invariance and a New Type of Conserved Quantities of Mechanical Systems with Variable Mass in Phase Space

Conformal invariance and a new type of conserved quantities of mechanical systems with variable mass in phase space are studied. Firstly, the definition and determining equation of conformal invariance are presented. The relationship between the conformal invariance and the Lie symmetry is given, and the necessary and sufficient condition that the conformal invarianee would be the Lie symmetry under the infinitesimal transformations is provided. Secondly, a new type of conserved quantities of the conformal invariance are obtained by using the Lie symmetry of the system. Lastly, an example is given to illustrate the application of the results.     

A higher-dimensional model of the nucleon-nucleon central potential

Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25（2）： 177], a simple model of a nucleon nucleon （NN） central potential is derived which quantitatively reproduces tile radial profile of other models, without adjusting any free pa- rameters. It is postulated that a higher-dimensional simple harmonic oscillator confining potential localizes particles into three-dimensional （3D） space, but allows for an ewmescent penetration of the particles into two higtmr spatial dimensions. Producing an effect identical with the relativistic quan- tum phenolnenon of zitterbewegung, the higher-dimensional oscillations of amplitude h（mc） call be alternatively viewed as a localized curvature of 3D space back and forth into the higher dimensions. The overall spatial curvature is proportional to the particle＇s extra-dimensional ground state wave function in tile higher-dimensional harmonic confining potential well. Minimizing the overlapping curvature （proportional to the energy） of two particles in proximity to each other, subject to the constraint that for the two particles to occupy the same spatial location one of them must be excited into the 1st excited state of the harmonic potential well, gives the desired NN potential. Specifying only the imcleon masses, the resulting potential well and repulsive core reproduces the radial profile of several published NN central potential models. In addition, the predicted height of the repulsive core, when used to estimate the maximum neutron star mass, matches well with the best estimates from relativistic theory incorporating standard nuclear matter equations of state. Nucleon spin, Coulomb interactions, and internal nucleon structure are not considered in the theory as presented in this article.     

τ lepton decays

We discuss recent results on τ lepton physics obtained at the BABAR, Belle and KEDR detectors They include tests of lepton universality using new measurements of T lepton mass and some branching fractions Also described are selected results on τ lepton hadronic decays coming from BABAR and Belle.     

Interference phase of mass neutrino in Reissner-NordstrSm-de Sitter space-time

The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B < 1011 T, but electron chemical potential will decrease greatly when B > 1011 T. The effects of a strong magnetic field on electron capture rates for 60Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.     

Primary result of ^236U measurement with accelerator mass spectrometry at CIAE

The rare isotope ^236U has a half-life of 2.342（3）×107 years, and is produced principally by thermal neutron capture on ^235U. The isotopic atom ratio of ^236U/^238U depends on the integral thermal neutron flux received by the material of interest. ^236U is potentially useful as a ＂fingerprint＂ for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity. By extracting negative molecular ion UO^- from the uranium oxide target, simulating the ^236U^16O^- beam transport with ^238U^16O^- and ^208Pb2^16O^- pilot molecular ion beam, transporting the ^236U-containing ion beam with a high resolution injection magnet analyzer and electrostatic analyzer system, and finally identifying and detecting ^236U with a time-of-flight detector （TOF）, a method for AMS （Accelerator Mass Spectrometry） measurement of ^236U was established on the HI-13 Accelerator AMS system at China Institute of Atomic Energy.     

Measurement of J/ψ→ηcγ at KEDR

We present a study of the inclusive photon spectra from 5.9 million J/ψ decays collected with the KEDR detector at the VEPP-4M e＋e collider. We measure the branching fraction of radiative decay J/ψ→ηcγ, ηc width and mass. Our preliminary results are： M（ηc） = 2979.4± 1.5 ± 1.9 MeV/c^2, Г（ηc） = 27.8±5.1 ±3.3 MeV, B（Jψ→ηcγ） = （2.34±0.15±0.40）%.     

Study of various charged ρ-meson masses in asymmetric nuclear matter

We study the effective masses of p-mesons for different charged states in asymmetric nuclear matter （ANM） using the Quantum Hadrodynamics II model. The closed form analytical results are presented for the effective masses of p-mesons. We have shown that the different charged p-mesons have mass splitting similar to various charged pions. The effect of the Dirac sea is also examined, and it is found that this effect is very important and leads to a reduction of the different charged p-meson masses in ANM.     

Study of the data taking strategy for a high precision τ mass measurement

To achieve a high precision τ mass measurement at the high luminosity experiment BESIII,Monte Carlo simulation and sampling technique are utilized to simulate various data taking cases for single and multiparameter fits by virtue of which the optimal scheme is determined. The optimized proportion of luminosity distributed at selected points and the relation between precision and luminosity are obtained. In addition,the optimization of the fit scheme is confirmed by scrutinizing a variety of fit possibilities.     

Effective Mass of Strong-Coupling Bound Polaron in a Triangular Quantum Well Induced by Rashba Effect

In this paper, on the basis of Huybrechts＇ strong-coupling polaron model, the Tokuda modified linearcombination operator method and the unitary transformation method are used to study the properties of the strongcoupling bound polaron considering the influence of Rashba effect, which is brought by the spin-orbit （SO） interaction, in the semiconductor triangular quantum well （TQW）. Numerical calculation on the RbCI TQW, as the example, is performed. The expressions for the effective mass of the polaron as a function of the vibration frequency, the velocity, the Coulomb bound potential and the electron areal density are derived. Numerical results show that the total effective mass of the polaron is composed of three parts. The interactions between the orbit and the spin with different directions have different effects on the effective mass of the bound polaron.     

QCD Approach to B →Dπ Decays and CP Violation

The branching ratios and CP violations of the B →Dπ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams that lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass μg is regarded as a universal sca/e, it is extracted to be around μg = 440 MeV from one of the well-measured B →Dπ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct CP asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the B →D^±π^±↓ decays to be consistent with the experimental data at 1-σ level. More precise measurements will be helpful to extracting weak angle 2β＋γ.     

{Qs}{Q（＇）s} Molecular States in QCD Sum Rules

We systematically investigate the mass spectra of {Qs}{Q（＇）s} molecular states in the framework of QCD sum rules. The interpolating currents representing the molecular states are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion （OPE）. The masses for molecular states with various {Qs}{Q（＇）s} configurations are presented. The result 4.36 ± 0.08 Ge V for theDs＊ Ds0- ＊ molecular state is consistent with the mass 4350＋4.6 -5.1± 0.7 MeV of the newly observed X（4350）, which could support X（4350） interpreted as a D＊D＊so molecular state.