124674175
In-medium properties of eta in chiral perturbation theory
17626348
Some Calculations for Cold Fusion Superheavy Elements
The Q value and optimal exciting energy of the hypothetical superheavy nuclei in cold fusion reaction are calculated with relativistic mean field model and semiemperical shell model mass equation(SSME) and the validity of the two models is tested. The fusion barriers are also calculated with two different models and reasonable results are obtained. The calculations can give useful references for the experiments in the superheavy nuclei synthesized in cold fusion reactions. The formation of compound nuclei by cold fusion reaction is one of the outstanding problem of low-energy nuclear reactions. Such processes play a key role in the production of superheavy elements(SHEs)[1–4]. Experiments or intensive preparatory work are in progress at the laboratories such as Dubna, Berkeley, RIKEN and GANIL etc. Theoretical support of these very expensive experiments is vital in the choice of fusing nuclei and their collision energy, and for the estimation of the cross sections and identification of evaporation residues. The quantum mechanical fragmentation theory(QMFT) which was developed by Gupta et al. to describe the synthesis of new and superheavy elements gives us a method for selecting an optimum cold target-projectile combination. Cold compound systems were considered to be formed for all those target+projectile combinations that lie at the bottom of the potential energy minima[5–7]. On the basis of the QMFT, recently, Gupta lists all the possible target+projectile combinations, referring to minima in PES, in particular, the use of radioactive nuclear beams and targets. There are several important physical values such as Q values, the heights of the fusion barrier Bfu and the optimal excitation energies E ∗ for the cold fusion reaction. The aims of this paper are to find some proper methods to predict the ground-state Q values, the heights of the fusion barrier Bfu and the optimal excitation energies E ∗ for the cold fusion reaction. Then, following the work of Gupta et al. in Ref. we calculate Q, Bfu and E ∗ for the possible target+projectile combinations to give some significative references for the future experiments. Supported by National Natural Science Foundation of China (10275037) and Specialized Research Fund for the Doctoral Program of Higher Education of China (20010055012) E-mail: zhongxianhui@mail.nankai.edu.cn E-mail: lilei@nankai.edu.cn E-mail: ningpz@nankai.edu.cn
50826737
The hyperon mean free paths in the relativistic mean field
The Λ- and Ξ−-hyperon mean free paths in finite nuclei are firstly calculated in the relativistic mean-field theory. The real optical potentials are derived from the RMF approach, while the imaginary parts are obtained from the assumptions: USIY = ασY·USIN and UVIY = αωY·UVIN. With these assumptions, the depth of the imaginary potential for Ξ− is WΞ − 3.5 MeV, and for Λ is WΛ − 7 MeV at low incident energy. We find that the hyperon MFP decreases with the increment of the incident energies of the hyperon (from 200 MeV to 800 MeV); and in the nuclear interior, the MFP is about 2–3 fm for Λ, and about 4–8 fm for Ξ−, depending on the incident energy of the hyperon.
5718926
Thermodynamics with density and temperature dependent particle masses and properties of bulk strange quark matter and strangelets
Thermodynamic formulas for investigating systems with density- and/or temperature-dependent particle masses are generally derived from the fundamental derivation equality of thermodynamics. Various problems in the previous treatments are discussed and modified. Properties of strange quark matter in bulk and strangelets at both zero and finite temperature are then calculated based on the new thermodynamic formulas with a new quark mass scaling, which indicates that low-mass strangelets near {beta} equilibrium are multiquark states with an antistrange quark, such as the pentaquark (u{sup 2}d{sup 2}s) for baryon number 1 and the octaquark (u{sup 4}d{sup 3}s) for dibaryon, etc.
118925554
Lambda Lambda interactions in finite-density QCD sum rules
The properties of Lambda hyperons in pure Lambda matter are studied with the finite-density quantum chromodynamics (QCD) sum rule approach. The first-order quark and gluon condensates in Lambda nuclear matter are deduced from the chiral perturbation theory. The sum-rule predictions are sensitive to the four-quark condensates, (2)(rho) and (rho) (rho), and the pi N sigma term. When (2)(rho) is nearly independent of density and (rho) (rho) depends strongly on density, we can obtain weakly attractive Lambda Lambda potentials (about several MeV) in the low Lambda density region, which agrees with the information from the latest double Lambda hypernucleus experiments. The nearly no-density dependence of (2)(rho) and strong density dependence of (rho) (rho) can be explained naturally if the properties of (2)(rho) and rho (rho) are assumed to be similar to those of pi pi and (K) over barK in nuclear medium, respectively.
120641266
$K^-$-Nuclear Bound States in Relativistic Mean-Field Theory
122861815
Beam test of the CsI(Tl) calorimeter for the BELLE detector at the KEK-B factory
We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25-3.5 GeV. The prototype consisted of an array of 6 x 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm x 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/pi separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector.
121190690
Study of the radiation hardness of CsI(Tl) crystals for the BELLE detector
Abstract The radiation hardness of prototype CsI(Tl) crystals has been tested for the barrel electromagnetic calorimeter for the BELLE detector of the KEK B factory. Although samples made by one of the producers were found to be soft under irradiation, the problem was quickly improved when this information was fed back. All the tested crystals were found to meet our requirement. The light output was found to be almost uniform along a crystal, even when the front part was damaged by radiation. The damage causes a degradation of the attenuation length due to the formation of color centers; this conclusion was confirmed by a Monte Carlo ray-tracing study.