The Σ Well Depth and the Proto Neutron Star Matter

The effect of the Σ well depth $U_{\varSigma}^{(N)}$ on a proto neutron star (PNS) is examined within the framework of relativistic mean field theory for the baryon octet system. It is found that the well depth $U_{\varSigma}^{(N)}$ will affect the structures of the PNS. With the well depth $U_{\varSigma}^{(N)}$ growing from 0 to 30 MeV, the field strength of meson ρ, the chemical potentials of electrons and neutrons, the relative number density of p, e, μ, Λ, Ξ ⁰, the mass and the pressure of a PNS all increase while the relative number density of n, Ξ ^?, Σ ^?, Σ ⁰, Σ ⁺ decrease. It is also found that the larger changes of the hyperon coupling constants, which is connected to the Σ well depth $U_{\varSigma}^{(N)}$ , will lead to the smaller changes in the neutron star mass and this shows the mass of PNS is not very sensitive to the hyperon coupling constants.     

Double Diffractive Process Factorization from ηc and γ Associated Production at Tevatron and LHC

We present a study of associated ηc and γ double diffractive production in pp^- collision based on Ingelman-Schlein model, and the framework of non-relativistic QOD factorization formalism for quarkonia production. The prediction of ηc and γ is more reliable than J/ψ production, because the associated ηc and γ production is a pure color-octet process, and the dominant contribution comes from color octet ^1S0^(8) subprocess, which is related to the color octet matrix element of ^1S0(8) of J/ψ by the heavy quark spin symmetry and the large PT J/ψ production data. We find that the ratio of diffractive to inclusive cross sections is independent of the values of color octet matrix elements, but is sensitive to the gluon factor of the Pomeron and renormalized Pomeron flux factors. So experimental measurement of this ratio can give us more information of the nature of Pomeron and test the assumption of hard diffractive factorization in hadron-hadron collisions.     

Nucleon Finite Volume Effect and Nuclear Matter Properties in a Relativistic Mean-Field Theory

Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy al and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility Ko much higher than expected. For most parameter sets there exists a critical point （pc, δc）, where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M⊙, which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass （1.2M⊙） is obtained for r ≌ 0.9 fro.     

Structures of rotating traditional neutron stars and hyperon stars in the relativistic $\sigma-\omega$ model

The influence of rotation on the total masses and radii of neutron stars is calculated by Hartles slow-rotation formalism, while the equation of state is considered in a relativistic - model. As the changes of the mass and radius of a real neutron star caused by rotation are very small in comparison with the total mass and radius, one can see that Hartles approximate method is rational to deal with the rotating neutron stars. If three property values, mass, radius and period, are observed for the same neutron star, then the EOS of this neutron star could be decided entirely.Received: 7 November 2003, Revised: 17 February 2004, Published online: 31 August 2004PACS: 04.40.Dg Relativistic stars: structure, stability, and oscillations - 95.30.Sf Relativity and gravitation - 97.10.Kc Stellar rotation - 97.60.Jd Neutron stars     

Constraint on nuclear symmetry energy imposed by f-mode oscillation of neutron stars

Due to improvements in the sensitivity of gravitational wave (GW) detectors, the detection of GWs originating from the fundamental quasi-normal mode (f-mode) of neutron stars has become possible. The future detection of GWs originating from the f-mode of neutron stars will provide a potential way to improve our understanding of the nature of nuclear matter inside neutron stars. In this work, we investigate the constraint imposed by the f-mode oscillation of neutron stars on the symmetry energy of nuclear matter using Bayesian analysis and parametric EOS. It is shown that if the frequency of the f-mode of a neutron star of known mass is observed precisely, the symmetry energy at twice the saturation density (E_sym(2ρ₀)) of nuclear matter can be constrained within a relatively narrow range. For example, when all the following parameters are within the given intervals: 220 ≤ K₀ ≤ 260 MeV, 28 ≤ E_sym(ρ₀) ≤ 36 MeV, 30 ≤ L ≤ 90 MeV, −800 ≤ J₀ ≤ 400 MeV, − 400 ≤ K_sym ≤ 100 MeV, −200 ≤ J_sym ≤ 800 MeV, E_sym(2ρ₀) will be constrained to within ${48.8}_{-5.5}^{+6.6}$ MeV if the f-mode frequency of a canonical neutron star (1.4 M_⊙) is observed to be 1.720 kHz with a 1% relative error. Furthermore, if only f-mode frequency detection is available, i.e. there is no stellar mass measurement, a precisely detected f-mode frequency can also impose an accurate constraint on the symmetry energy. For example, given the same parameter space and the same assumed observed f-mode frequency mentioned above, and assuming that the stellar mass is in the range of 1.2–2.0 M_⊙, E_sym(2ρ₀) will be constrained to within ${49.5}_{-6.8}^{+8.1}\,\mathrm{MeV}$. In addition, it is shown that a higher slope of 69 ≤ L ≤ 143 MeV will give a higher posterior distribution of E_sym(2ρ₀), ${53.8}_{-6.4}^{+7.0}\,\mathrm{MeV}$.     

On gl（2｜2）（2）k Current Superalgebra and Twisted Conformal Field Theory

Motivated by the recently discovered hidden symmetry of the type IIB Green-Schwarz superstring on certain background, the non-semisimple Kac-Moody twisted superalgebra gl（2｜2）（2）k is investigated by means of the vector coherent state method and boson-fermion realization. The free field realization of the twisted current superalgebra at general level k is constructed. The corresponding Conformai Field Theory （CFT） has zero central charge. According to the classification theory, this CFT is a nonunitary field theory. After projecting out a U（1） factor and an outer automorphism operator, we get the free field representation of psl（2｜2）（2）k, which is the a/gebra of gl（2｜2）（2）k modulo the Z4-outer automorphism, the CFT has central charge -2.     

Production properties of K^\star(892)^\pm vector mesons and their spin alignment as measured in the NOMAD experiment

First measurements of mesons production properties and their spin alignment in charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD experiment is performed in different kinematic regions. For and mesons produced in CC interactions and decaying into we have found the following yields per event: and respectively, while for the and mesons produced in interactions the corresponding yields per event are: and . The results obtained for the parameter, and for and produced in CC interactions, are compared to theoretical predictions tuned on LEP measurements in annihilation at the pole. For mesons produced in interactions the measured parameter is . PACS 13.15.+g, 13.60.Le, 13.87.Fh, 13.88.+e, 14.40.Ev     

Study of K*(892)0 and φ (1020) meson production in proton-proton and Pb-Pb collisions at $\sqrt{{s}_{NN}}$=2.76 TeV

In this paper, we describe a study of charged particle yield as a function of p_T for K^*(892)⁰ and φ (1020) mesons in proton-proton (pp) and Pb-Pb collisions at $\sqrt{{s}_{NN}}$=2.76 TeV in the central rapidity region of ∣y∣<0.5, in a p_T range of 0<p_T <15 GeV c⁻¹ in pp collisions and in a p_T range of 0<p_T<20 GeV c⁻¹ in Pb-Pb collisions. We also investigated a very important ratio, the nuclear modification factor, to study the effects of the medium in the most central region, i.e. 0%-5% centrality. For data simulation, we used the EPOS-LHC and EPOS-1.99 models. To check the validity of these models’ simulations, we compared the data obtained from these Monte Carlo simulation programs with ALICE experimental data for $\sqrt{{s}_{NN}}$=2.76 TeV. It was concluded that the models’ predictions for the φ-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data, and that the difference increased with p_T. This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For K^*0 mesons, both programs gave almost the same predictions, and with p_T in the interval p_T>3 GeV c⁻¹, the predictions were very close to the experimental data. Both models gave higher predictions for the soft p_T interval and lower predictions for the hard interactions. The values of the R_AA distributions were lower than unity and both models were very close to the ALICE data. It is very interesting that the models were not able to describe the p_T distributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of K^*0 at low values of p_T with respect to φ-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for R_AA in the region from p_T =10 GeV c⁻¹ to 20 GeV c⁻¹ observed by the ALICE experiment was absent for the φ-mesons.     

Different effect of the hyperons $\Lambda$ and $\Xi$ on the nuclear core

We demonstrate the different effect of strange impurities ( and ) on the static properties of nuclei within the framework of the relativistic mean-field model. Systematic calculations show that the glue-like role of the -hyperon is universal for all -hypernuclei considered. However, the -hyperon has a glue-like role only for the protons distribution in nuclei, while for the neutrons distribution it plays a repulsive role. On the other hand, the -hyperon attracts the surrounding neutrons and reveals a repulsive force to the protons. Possible explanations of the above observation are discussed.Received: 10 March 2003, Revised: 6 November 2003, Published online: 5 May 2004PACS: 21.80. + a Hypernuclei - 24.10.Cn Many-body theory     

Theory of nine elastic constants of biaxial nematics

In this paper, a rotational invariant of interaction energy between two biaxial-shaped molecules is assumed and in the mean field approximation, nine elastic constants for simple distortion patterns in biaxial nematics are derived in terms of the thermal average （Dmn^（l）） （Dm＇n＇^（l＇））, where Dmn^（l） is the Wigner rotation matrix. In the lowest order terms, the elastic constants depend on coefficients Γ,Γ＇, λ, order parameters Q0 = Q0（D00^（2）） ＋Q2（D02^（2）＋D0-2^（2）） and Q2 = Q0（D20^（2）） ＋ Q2（D22^（2）＋D2-2^（2））. Here Γ and Γ＇ depend on the function form of molecular interaction energy vj′j″j （τ12） and probability function fk′k″k （τ12）, where r12 is the distance between two molecules, and λ is proportional to temperature. Q0 and Q2 are parameters related to multiple moments of molecules. Comparing these results with those obtained from Landau-de Gennes theory, we have obtained relationships between coefficients, order parameters used in both theories. In the special case of uniaxial nematics, both results are reduced to a degenerate case where K11=K33.     

Search for the \phi1860 Pentaquark at COMPASS

Narrow and resonances produced by quasi-real photons have been searched for by the COMPASS experiment at CERN. The study was stimulated by the recent observation of an exotic baryonic state decaying into , at a mass of 1862 MeV, interpreted as a pentaquark. While the ordinary hyperon states and are clearly seen, no exotic baryon is observed in the data taken in 2002 and 2003.Received: 15 March 2005, Published online: 31 May 2005PACS: 13.60.Hb, 13.60.Rj, 14.20.Jn, 14.80.-j     

Uniqueness and Nondegeneracy of Positive Solutions of {(-\Delta)^s u + u = u^p \, {\rm in} \, \mathbb{R}^N} when s is Close to 1

We consider the equation ${(-\Delta)^s u + u = u^p}$ , with ${s \in (0, 1)}$ in the subcritical range of p. We prove that if s is sufficiently close to 1 the equation possesses a unique minimizer, which is nondegenerate.     

RAMAN SCATTERING OF α-ET3(ReO4)2 CHARGE-TRANSFER SALT

We describe the results of Haman studies on C=C stretch modes in α-ET₃(ReO₄)₂ charge-transfer salt with the incident laser beam polarised perpendicular and parallel to the large flat face of plate-like crystal. We have assigned central C=C stretch mode at 1454 cm^-1 and ring C=C stretch mode at 1470cm^-1. The change in ring C=C stretch vibration was observed at the metal-insulator transition of α-ET₃(ReO₄)₂ on warming due to the distortion of the ET molecules.     

Photoproduction of $ \eta$ -mesons off neutrons from a deuteron target

A formalism is developed for the partial-wave analysis of data on meson photoproduction off deuterons and applied to photoproduction of and mesons. Different interpretations of a dip-bump structure of the photoproduction cross-section in the 1670MeV region are presented and discussed. Helicity amplitudes for two low-mass S₁₁ states are determined.     

Pure annihilation decays of B_s~0→a_0~+a_0~- and B_d~0→K_0~(*+)K_0~(*-) in the PQCD approach

We study the CP-averaged branching fractions and the CP-violating asymmetries in the pure annihilation decays ofB _s~0→a_0~+a _0~-andB _d~0→K_0~(*+)K_0~(*-),where a_0[K_0~*]denotes the scalar a_0(980) and a_0(1450)[K_0~*(800)(ork)and K_0~*(1430)],with the perturbative QCD factorization approach under the assumption of two-quark structure for the a_0and K_0~*states.The numerical results show that the branching ratios of theB _d~0→K_0~(*+)K_0~(*-)decays are in the order of 10~(-6),while the decay rates of theB_s~0→a_0~+a _0~-modes are in the order of 10~(-5).In light of the measured modes with the same quark components in the pseudoscalar sector,namely,B _d~0→K~+K~-and B_s~0→p p~(+-),the predictions for the considered decay modes in this work are expected to be measured at the Large Hadron Collider beauty and/or Belle-Ⅱ experiments in the (near) future.Meanwhile,it is of great interest to find that the twist-3 distribution amplitudes φ~S and φ~T with inclusion of the Gegenbauer polynomials for the scalar a_0(1450) and K_0~*(1430)states in scenario2 contribute slightly to the branching ratios while significantly to the CP violations in the B_d~0→K_0~*(14 30)~+K_0*(14 30)~-and B_s~0→a_0(1450)~+a_0(1450)~-decays,which indicates that,compared to the asymptotic φ~Sand φ~T,these Gegenbauer polynomials could change the strong phases evidently in these pure annihilation decay channels.These predictions await for the future confirmation experimentally,which could further provide useful information to help explore the inner structure of the scalars and shed light on the annihilation decay mechanism.     

OPTICAL-OPTICAL DOUBLE-RESONANCE EXCITATION SPECTRA OF THE (6d)1Πg, (7d)1Πg HIGH-LYING RYDBERG STATES IN Na2

Two ¹Π_g states of Na₂ for v≤13 have been observed by using optical-optical double resonance (OODR) fluorescence excitation spectroscopy. The intermediate levels in B¹Π_u state are identified by the numerical calculations with the molec-ular constants for B¹Π_u←X¹Σ_g⁺ transitions and confirmed by the complemen-tary A¹Σ_g⁺←X¹Σ_g⁺ polarization spectra. Absolute vibrational numberings of the (6d)¹Π_g and (7d)¹Π_g states are determined by comparing the experimental OODR excitation intensities with the simulated Franck-Condon factors. The Dnnham coef-ficients and the Rydberg-Klein-Rees (RKR) potential energy curves of the (6d)¹Π_g, (7d)¹Π_g states are reported.     

The New Clue to Understanding fo(975) Meson From Ds Decays

Based on the understanding of nonleptonic decays of charmed meson, the relative ratio Br(D_s⁺→f₀(975)π⁺/Br(D_s⁺→фπ⁺) is calculated. We argue that only (ss) component of f₀(975) contributes to it dominantly. The numerical result proves f₀(975) to be almost a pure (ss) state if the newly measured resultant value of the decay is trustable, and the conclusion is very usefulinformation as a clue for clarifying up the puzzle of 0⁺⁺ meson f₀(975).