Transverse momentum and transverse mass distributions of charged hadrons produced in Au--Au collisions at high energies

The transverse momentum distribution and the transverse mass distribution of charged hadrons produced in nucleus nucleus collisions at high energies are described by using a two-cylinder model. The results calculated by the model are compared and found to be in agreement with the experimental data of the STAR and E895 Collaborations, measured in A~Au collisions at the relativistic heavy ion collider （RHIC） and alternating-gradient synchrotron （AGS） energies, respectively. In the energy range concerned, the excitation degree of emission source close to the central axis of cylinders increases obviously with the collision centrality and incident energy increasing, but it does not show any obvious change with the increase of the （pseudo）rapidity in central collisions. The excitation degree of emission source close to the side-surface of cylinders does not show any obvious change with the collision centrality, the （pseudo）rapidity, and the incident energy increasing.     

Thermoelectric Performances of Free-Standing Polythiophene and Poly（3-Methylthiophene） Nanofilms

Thermoelectric performances of free-standing polythiophene （PT） and poly（3-methylthiophene） （PMeT） nanofilms with high tensile strength electrosynthesized from boron trifluoride diethyl etherate （BFEE） are systematically investigated. They display decent electric conductivity （47 and 73S.cm^-1）, high Seebeck coefficient （130 and 76μV.K^-1） and low thermal conductivity （0.17 and 0.15 W.m^-1.K^-1） at room temperature. Their figure of merit can reach 3.0 × 10^-2 at 250K, higher than that of many other conducting polymers. The decrease of charge carrier concentration resulting from volatile and water-sensitive dopants from BFEE leads to the decrease of electrical conductivity but a substantial increase of the Seebeck coet~cient, making their figure-of-merit values maintained at more than 10-2 even after prolonged storage （two months）. Moreover, free-standing PT and PMeT exhibit much better thermoelectric performances than those in pressed pellets due to the good arrangement of the polymer chains and preferably oriented structure in films. It therefore provides a way to improve the thermo- electric performances of conducting polymers by controlling regularity of the extended conjugated chain structure and/or the chain packing to achieve high charge mobility.     

Branching Ratios of α Decay for Nuclei near Deformed Shell Closures

The generalized liquid drop model （GLDM） is extended to the region around deformed shell closure ^270Hs by taking into account the excitation energy EI＋ of the residual daughter nucleus and the centrifugal potential energy Vcen（r）. The branching ratios of a decays from the ground state of a parent nucleus to the ground state 0^＋ of its deformed daughter nucleus and to the first excited state 2^＋ are calculated in the framework of the GLDM. The results support the proposal that a measurement of a spectroscopy is a feasible method to extract information on nuclear deformation of superheavy nuclei around the deformed nucleus ^270Hs.     

Possible existence of triaxial superdeformation in ^172,174,176W

Two-dimensional total routhian surface （TRS） calculations are carried out to determine the triaxial superdeformation （TSD） of the even-even nucleus 174W, and the result indicates that TSD state exists with deformation parameters ε2=0.42 andγ=34.7°. In the same way, the total routhian surfaces for the nuclei ^172,176W are also calculated. It shows that the neutron shell correction energy plays a key role in the formation of TSD nuclei ^172,174,176W, while the high j intruder orbitals and rotational energy are also crucial in the formation mechanism.     

△-Resonances in Ground State Properties of ^40 20Ca Spherical Cold Finite Nucleus at Equilibrium and under Compression

The ground state properties of the spherical nucleus ^40Ca have been investigated by using constrained spherical Hartree Fock （CSHF） approximation at equilibrium and under high radial compression in a six major shells. The effective baryon-baryon interaction that includes the △（1236） resonance freedom degrees to calculate nuclear properties is used. The nucleon-nucleon （N-N） interaction is based on Reid soft core （RSC） potential. The results of calculations show that much of increase in the nuclear energy generated under compression is used to create the massive △ particles. The number of △ ＇s can be increased to about 2.1% of constituents of nucleus when nuclear density reaches about 1.34 times of normal density. The single particle energy levels are calculated and their behavior under compression is also examined. △ good agreement has been found between current calculations and phenomenological shell model for low lying single-particle spectra. The gap between shells is very clear and L-S coupling become stronger as increasing the static load on the nucleus. The results show a considerable reduction in compressibility when freedom degrees of △＇s are taken into account. It has been found that the total nuclear radial density becomes denser in the interior and less dense in the exterior region of nucleus. The surface of nucleus becomes more and more responsive to compression than outer region.     

Multiband Non-Thermal Radiation from the Crab Nebula and the Pulsar Wind Nebula in MSH 15-52

We study the multiband non-thermal emission from two pulsar wind nebulae （PWNe）, the Crab nebula and the PWN in MSH 15-52. Both of them have been recently detected by the Fermi large area telescope （LAT） and powered by central gamma-ray pulsars. Motivated by the Fermi LAT results, we use a simplified time-dependent injection model to study the non-thermal emission from radio to very high energy gamma-ray radiation from these two sources. In this model, the relativistic electrons are accelerated in pulsar magnetosphere and at pulsar wind termination shocks and can be described by a broken power law. Those high energy particles evolve with time and produce non-thermal emission through synchrotron radiation and inverse Compton scattering of soft photons. For Crab nebula, using the GeV emission from 100 MeV to 10 GeV given by Fermi LAT, we can constrain the maximum energy of the electrons and other parameters. The non-thermal emission can be well explained by this model. We also use this model to explain the non-thermal emission from the PWN in MSH 15-52.     

Transverse Momentum and Rapidity Distributions of Φ Mesons Produced in Pb-Pb Collisions at SPS Energies

To investigate the excitation degree of the interacting system and the penetrating power of the projectile nucleus and to understand their dependences on incident energy, the transverse momentum and rapidity distributions of particles produced in nucleus-nucleus collisions at high energies are studied by using a multisource ideal gas model. The calculated results are compared with the most recent NA49 experimental data of φ mesons produced in Pb-Pb collisions at the Super Proton Synchrotron （SPS） energies.     

Low-lying states and isospin excitation in the Ge isotopes

The level structure of ^64-70Ge isotopes has been studied within the framework of the interacting boson model-3（IBM-3） . The symmetry character in the proton and neutron degrees of freedom of the energy levels has been investigated. The isospin excitation states（T 〉 Tz） have been assigned for the ^64Ge（N = Z） nucleus. Some intruder states in these nuclei have been suggested. The calculated energy levels and transition probabilities are in good agreement with recent experimental data. The study indicates that the Ge isotopes are in transition from γ-unstable to vibrational.     

K^- Condensation in Neutron Star Matter with △ Quartet

In the framework of relativistic mean field theory, the condensations of K^- and K^0 in neutron star matter including baryon octet and △ quartet are studied. We find that in this case K^- and K^0 condensations can occur at relative shallow optical potential depth of K^ from -80 MeV to -160 MeV. Both K^- and K^0 condensations favor the appearances of △ resonances. With K^- condensations all the △ quartet can appear well inside the maximum mass stars. The appearances of △ resonances change the composition and distribution of particles at high densities. The populations of △ resonances can enhance K^- condensation. It is found that in the core of massive neutron stars, neutron star matter includes rich particle species, such as antikaons, baryon octet, and △ quartet. In the presence of △ resonances and K^- condensation, the EOS becomes softer and results in smaller maximum mass stars. Furthermore the impact of antikaon condensations, hyperons, and △ resonances on direct Urca process with nucleons is also discussed briefly.     

Simulation of a modified neutron detector applied in CSNS

We simulate the response of a modified Anderson-Braun rem counter in the energy range from thermal energy to about 10 GeV using the FLUKA code. Also, we simulate the lethargy spectrum of CSNS outside the beam dump. Traditional BF3 tube is replaced by the 3He tube, a layer of 0.6 cm lead is added outside the boron doped plastic attenuator and a sphere configuration is adopted. The simulation result shows that its response is exactly fit to H＊（10） in the neutron energies between 10 keV and approximately 1 GeV, although the monitor slightly underestimates H＊（10） in the energy range from thermal energy to about 10 keV. According to the characteristics of the CSNS, this modified counter increases the neutron energy response by 30% compared with the traditional monitors, and it can be applied in other kinds of stray field rich of high eeergy neutrons.     

K+核散射中的反阴影效应

核散射中罕见的反阴影效应在K~+介子与核的散射中出现了,1988～1990年BNL的系列实验确认了这一反常现象,然而,在核子层次上对此所作的各种理论解释几乎均告失败,因此人们不得不到夸克层次上寻找原因。 Unusual antishadowing appeared in K~+-nucleus scattering, which was reconfirmed byBrookhaven experiments in 1988～1991. Almost all of the conventional explanations of this effectat nucleon level are not successful. One has to search for new interpretations at quark level.     

Does the D(-)/D(+) production asymmetry decrease at large x(F)?

We have applied the meson cloud model to calculate the asymmetries in D and D(s) meson production in high-energy Sigma(-)-nucleus and pi(-)-nucleus collisions. We find a good agreement with recent data. Our results suggest that the asymmetries may decrease at large x(F).     

Precision measurements of strangeness photoproduction at threshold energies with the Crystal Ball at MAMI-C

The photoproduction of K~+ mesons from the nucleon provides important constraints on the nucleon excitation spectrum and at threshold energies challenges effective field theories based on chiral perturbation in the strange quark sector. Preliminary cross-section measurements for γ(p, K~+)A are presented at an unprece-dented beam energy resolution. The data was collected at the MAMI-C facility in Mainz using the Crystal Ball Detector. A new method of K~+ detection was used in which the K~+ is tagged from its weak decay products in the detector crystals. This technique has application with other calorimeters at present and future hadron facilities.     

Unified approach to alpha decay calculations

With the discovery of a large number of superheavy nuclei undergoing decay through α emissions, there has been a revival of interest in α decay in recent years. In the theoretical study of α decay the α-nucleus potential, which is the basic input in the study of α-nucleus systems, is also being studied using advanced theoretical methods. In the light of these, the Wentzel–Kramers–Brillouin (WKB) approximation method often used for the study of α decay is critically examined and its limitations are pointed out. At a given energy, the WKB expression uses barrier penetration formula for the determination of the transmission coefficient. This approach utilizes the α-nucleus potential only at the barrier region and ignores it elsewhere. In the present era, when one has more precise experimental information on decay parameters and better understanding of α-nucleus potential, it is desirable to use a more precise method for the calculation of decay parameters. We describe the analytic S-matrix (SM) method which gives a procedure for the calculation of decay energy and mean life in an integrated way by evaluating the resonance pole of the S-matrix in the complex momentum or energy plane. We make an illustrative comparative study of WKB and S-matrix methods for the determination of decay parameters in a number of superheavy nuclei.     

SPIN EFFECT AND π-N OFF SHELL AMPLITUDE CORRECTION ON π-NUCLEUS DOUBLE CHARGE EXCHANGE REACTION

We study the influence. of the spin terms and off shell correction of π-N amplitudeπ-nucleus double charge exchange reaction. It is showed that both greatly reduce thecross sections and improve the theoretical result to fit the experimental data better.Spin effect is importance in the (3,3) resonance energy region, but it is less importantin the higher energy.     

孤子中的再激发研究

本文在准一维紧束缚近似下,研究了孤子中的再激发。得到 , ,, , , 。其中 , 和 分别代表中性孤子、带电孤子和带电极化子, 表示链中出现的扭结。     

4.2 GeV α-^12C Elastic Scattering Based on α-Particle Model

Based on the α-particle model of ^12C nucleus, the differential cross sections for α-^12C elastic scattering at incident energy of 4.2 GeV have been calculated within the framework of Glauber multiple scattering theory. The results show that the main features of the measured angular distribution of the cross sections can be reasonably described. The parameterized α-α scattering amplitude, which is the basic input to construct the α-^12 C scattering Glauber amplitude in the a-particle model, is obtained by fitting the α-α scattering data.     

A potential for the description of alpha-alpha interactions

In an investigation into the α-α and α-nucleus interaction the former is studied employing for the effective interaction a potential with a repulsive core embedded into a long range attractive part. Calculations with this potential reproduce the energies and widths of the levels of the α-α system⁸Be and the phases for α-α scattering quite well thus pointing to an applicability of the model to α-α and α-nucleus scattering for light nuclei.     

Baryon-baryon spin-orbit interaction in a quark model

The baryon-baryon spin-orbit interactions are studied within the framework of a nonrelativistic quark-cluster model. The origin of the spin-orbit interactions is taken to be the Galilei-invariant part of the spin-orbit term in the one-gluon-exchange potential between quarks. It gives, for example, the NN spin-orbit interaction which is qualitatively similar to the empirical ones. The baryon-nucleus spin-orbit interactions are also considered along this line. The N- and Σ-nucleus spin-orbit interactions are of comparable strength, while the Λ-nucleus spin-orbit interaction is weak. The main origin of the difference between the Λ -nucleus and Σ-nucleus spin-orbit interactions is the presence of the comparatively strong antisymmetric LS (ALS) terms for both NΛ and NΣ interactions but with opposite signs. Other sources of the spin-orbit interactions are briefly discussed in connection with the problem of the spin-orbit effect in the excited baryon spectra.