Nuclear Matter Density,Collision Number and Entropy in Dynamics Process of Intermediate High Energy Heavy Ion Collision

The nuclear matter density,collision number and entropy in the dynamic process of heavy ion collision ⁴⁰Ca+⁴⁰Ca at E_L=400MeV/A for very central collision were calculated.The results show that the nuclear spatial density distributions depend mainly on the mean field but rarely on the nucleonnucleon collisions.The density distribution in the momentum space,collision number and entropy are influenced by the mean field and nucleon-nucleon collision,especially the medium effects.     

Study of Ds±→μ±νμ at Belle

We present a preliminary measurement of the B(D_s→μν_μ) with the Belle
experiment at the KEKB collider. We select D_s→μν_μ decays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction. The results are based on a data sample of 550fb^－1 and are compared to similar measurements by other experiments as well as to the predictions of LQCD. We conclude with short prospects for improvements in the accuracy of the measurement.

     

Size distribution of sulfur species in fine and ultrafine aerosol particles using sulfur K-edge XANES

The sulfur species existing in different size aerosol particles were determined based on the `white line' energy shift and the features of post edge structure of sulfur K-edge XANES (X-ray Absorption Near Edge Structure). The results indicated that sulfates were dominant sulfur species in aerosol particles. However, small amount of reductive sulfur species were also found in the ultrafine aerosol particles(<0.1 μm). Sulfates in aerosols mostly exhibited as (NH₄)₂SO₄ and gypsum. Most (NH₄)₂SO₄ distributed in aerosol particles finer than 0.952 μm, while gypsum was the dominant sulfate in coarse aerosols.

     

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→η_cγ, η_c width and mass. Our preliminary results are: M(η_c)=2979.4±1.5±1.9 MeV/c², Γ(η_c) = 27.8±5.1±3.3 MeV, B(J/ψ→η_cγ)=(2.34±0.15±0.40)%.

     

Study of Kso Reconstruction and Lifetime Measurement at BESⅡ

The beam collision center of the BEPC has slightly shifted from geometrical origin of the BES detector and the beam bunch of the BEPC also has certain size. For these reasons, to measure K_s^o lifetime, primary vertex reconstruction must be carried out. After the investigation of di-muon, bhabha and hadron events, the beam collision center for each run is determined by bhabha and di-muon events. For the large branching ratio of and the existence of the resonance of KⅡ0 , this channel is chosen to provide much pure K_s^o signal. With the aid of M. C. tools at BES Ⅱ , existing software for secondary vertex reconstruction is adjusted and improved. A new method of secondary vertex determination is used and a better position resolution of secondary vertex is obtained. The lifetime of Ks0 is measured with channel and the inclusive K_s^o mass is investigated with BES Ⅱ 's 50M J/ψ data sample, which give consistent Ks0 lifetime and mass with PDG' s value within error. 1C fit on K⁰_s mass is also studied with M. C. events. The resolution of momentum and energy of 7π+ , π- and K, is improved too.     

Pressure-induced phase transition of wulfenite

The in-situ high-pressure structures of wulfenite have been investigated by means of angular dispersive X-ray diffraction with diamond anvil cell and synchrotron radiation. In the pressure up to 22.9 GPa, a pressure-induced scheelite-to-fergusonite transition is observed at about 10.6 GPa. The pressure dependence for the lattice parameters of wulfenite is reported, and the axial compression coefficients Ka₀=－1.36×10^－3 GPa^－1 and Kc₀= －2.78×10^－3 GPa^－1 are given. The room-temperature isothermal bulk modulus is also obtained by fitting the P-V data using the Murnaghan equation of state.

     

Rare decays B0s,d→l+l－ in a top quark two-Higgs-doublet model

In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of B⁰_s,d→l⁺l^－ (l=e, μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(B⁰_d→l⁺l^－) give the upper bound on tanβ: tanβ≤22, while Br(B⁰_s→l⁺l^－) give tanβ≤12 for fixed δ=0°, m_H+=350 GeV, m_H0=160 GeV, m_h0=115 GeV and m_A0=120 GeV; (b) A light neutral Higgs boson mass m_h0 (m_A0) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for B⁰_s,d→l⁺l^－(l=μ) decays with tanβ=10; (c) The bounds on m_h0 and tanβ, or m_A0 and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson.

     

HIGH ENERGY DEUTERON-DEUTERON SCATTERING

The differential cross section of deuteron-deuteron elastic scattering at P_d=5.76 GeV/c is calculated based on the Glauber multiple scattering theory in nucleus-nucleus collision. The theoretical result is compared with the experimental data and the agreement is satisfactory. In addition, the influence of the input amplitude is discussed.     

STRATO-GLUON MECHANISM FOR HADRONIC MULTIPLE PRODUCTION AND AVERAGE CHARGED MULTIPLICITY

By assuming that in a high energy hadronic collision process,N pairs of stratonsare produced together with gluons,the number of which is supposed to be propor-tional to the number of“bonds”between any two stratons,we are able to get a rela-tion between the Q-value and the number of pairs N:N=（α²+βQ）^1/2-α.The average charged multiplicity〈n_ch〉_theo is calculated,and is compared withthe experiments.The data of pp、π^±p、K^±p collisions all coincide with the theoreticalcurve in a wide range of energies.The deviation between the energy vs.chargedmultiplicity relations for meson-proton and proton-proton collision processes are ex-plained quantitatively.The average straton mass estimated from the theory is ingood agreement with that.given by other authors.     

THE BEHAVIOURS OF F2ep(X,Q2)-F2en(X,Q2) AND THE SCALE-BREAKING PARAMETER

The scale-breaking parameter F₂^ep(x, Q²) of non-singlet component F₂^ep-F₂^en and some other quantities in the electro-production process are discussed by usinb the analytic expression for the distribution function of valence quarks in ha.drons up to leading log approximation given by a, previous paper^[1]. Comparisons with data are also given.

     

Observation of a pp mass threshold enhancement in ψ′→π+π－J/ψ(J/ψ→γpp) decay

The decay channel ψ′→π⁺π^－J/ψ(J/ψ→γpp) is studied using a sample of 1.06×10⁸ ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the pp invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M=1861⁺⁶_－13 (stat)⁺⁷_－26 (syst) MeV/c² and a narrow width that is Γ<38 MeV/c² at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.

     

Eccentricity and elliptic flow at fixed centrality in Au+Au collisions at sNN=200 GeV in AMPT model

In this paper, elliptic flow is studied at fixed centrality in Au+Au collision at √s_NN=200 GeV in the AMPT model. It is observed that with the participant increasing, elliptic flow has an increase or a decrease at different fixed impact parameter, but it does not have a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions(b=5 fm) and mid-central collisions(b=8 fm), while the interaction between particles can mainly answer for the behavior of elliptic flow with participant in peripheral collisions (b=12 fm). To distinguish the pure geometrical effect, elliptic flow scaled by initial eccentricity is studied. It is found that the ratio v₂/ε increases with participant and reaches a saturation when the participant is large enough, indicating that the collision system may reach the local equilibrium.     

Measurement of Angular Cross Correlation of the Cross Section Fluctuation in Dissipative Collision 27Al+27Al

The excitation function was measured from θ_lab=10.4° to 57.4° in dissipative collision ²⁷Al+²⁷Al with incident energy ranging from 114 to 123 MeV in step of 200 keV. The Angular-cross Correlation Functions (ACFs) of cross section fluctuation within large angle region were obtained through experiment for the first time. It is found that the angular coherent width is at least 40°. It is interesting that the ACFs is not simple bell shape but shows strong asymmetry. The over-all behavior is that ACF varies more quickly for the backward angles. Itis also noticed that the cross section fluctuation in the forward angle region (θ_cm<70°) shows much stronger angular coherence than in the backward angle region (θ_cm>70°). This angular dependence may be attributed to the coherent rotation effect of intermediate dinuclear system.     

QCD PREDICTION FOR THE REACTION γ+p→2γ+X

In the framework of the perturbative QCD, the two-fold differential cross section d²σ/dx_Tdx_L of the reaction γ+p→2γ+X and its two backgrounds (γ+p→γ++X, γ+p→γ++X) are calculated in c.m.s.. The results show that, in a large range of (x_T, x_L), the calculated reaction cross section can be measured in current laboratory condition. And due to the properties of this reaction, i.e., large p_T photoproduction and direct photon pair emission, all of the backgrounds can be greatly suppressed.

     

PAPIDITY DISTRIBUTIONS IN UNEQUAL NUCLEI COLLISION AT HIGH ENERGIES AND HYDRODYNAMICAL MODEL

The mechanism of high-energy A'－A collision (A>A',A'^1/3>>1) and the space-time evolution of the fluid formed in the collision are analysed. The corresponding 1+1 dimensional hydrodynamical equations are established. The average rapidity distributions are estimated and compared with some cosmic ray events. The origin of the nonsymmetry of rapidity distribution is explained.

     

纳米氧化钛团聚结构的研究

爆轰形成的高温、高压持续时间短,使得新生的氧化钛来不及长成较大的晶粒,只能形成大量的类球形纳米微粒。在潮湿的爆生气体环境中,这些纳米氧化钛颗粒间的相互作用(如碰撞、摩擦、挤压、渗透和粘附等)比较剧烈,极易聚集成团聚体。初步分析了以硫酸氧钛为钛源、采用爆轰法合成的纳米氧化钛的团聚结构和分散形态,对经过加热至500℃、保温1 h热处理后的纳米氧化钛的团聚结构也进行了分析。研究结果表明:用爆轰法合成的纳米氧化钛存在软团聚和硬团聚两种形式,而经过热处理(500℃、1 h)的纳米氧化钛的团聚程度得到了一定的改善。此外,还分析了纳米粉体的特性、爆轰特点和爆生气体环境等因素对产生纳米氧化钛团聚结构的影响。     

Dielectronic Recombination of Sn^10＋ Ions and Related Satellite Spectra

Based on the multi-configuration Dirac-Fock method, theoretical calculations are carried out for the dielectronic recombination （DR） rate coefficients and the collision excitation rate coefficients of Sn^10＋ ions. It is found that the total DR rate coefficient has its maximum value between 10eV and 100eV and is greater than either the radiative recombination or three-body recombination rate coefficients （the number of free electrons per unit is 10^21 cm^3） for the ease of Te 〉 1 eV. Therefore, DR can strongly influence the ionization balance of laser produced multi-charged tin ions. The related dieleetronie satellite cannot be ignored at low temperature Te 〈 5 eV.     

Identification of New Isotope 238Th

Unreported heavy neutron-rich nuclide ²³⁸Th has been produced via a multinucleon transfer reaction by 60MeVIu ¹⁸0 ions bombardment of natural uranium.Thorium was radiochemically separated from the mixture of uranium and reaction products. ²³⁸Pa as a daughter nucleus of ²³⁸Th has been identified according to the growth and decay of ²³⁸Pa γ rays which has been observed. The half-life of ²³⁸Th was determined to be (9.4 + 2.0) min. At the same time, a new γ ray of (89.0 + 0.3) keV with T_1/2= (8.9 + 1.5)min was found in the γ spectrum gated with the K_α1, X ray of Pa and assigned to ²³⁸Th decay based on the measurements of its transition energy and the half-life.

     

A Simulation of Emitted Nucleons:An Extended BUU Model

On the basis of the old BUU method,the neutrons and protons of the projectile and target nucleus was distinguished,meanwhile,the droplet model which included the surface diffusion parameter,neutron skin and deformation parameter etc.was considered during simulating original nucleon's distribution.Condersing the fact σ_np≈3σ_nn≈3σ_pp in intermediate energy domain,it was incorapated into the collision term of BUU.Before studying 44MeV/A ⁸⁶Kr+¹⁹⁷Au reaction by the improved BUU model,the stability of the model has been checked,then the condition of nucleons emission was defined,finally the impact parameter dependence of the abraded neutrons and protons from the projectile was obtained,so was the correlation of TLF and PLF.