重离子碰撞中的轻矢量介子光生过程(英文)

计算了相对论重离子碰撞中轻矢量介子(ρ,ω和φ)的光生过程。基于窄-宽近似,严格推导了相对论重离子碰撞中ρ,ω和φ半弹性和非弹性光生过程的遍举和单举横截面。从数值结果可以看出对于p-p碰撞,光生过程的贡献是不重要的,但是对于pT2.5 GeV Au-Au碰撞和pT3 GeV Pb-Pb碰撞,轻矢量介子光生过程的贡献是明显的。     

J/ψ衰变中f0(975)的实验研究

本文基于北京正负电子对撞机(BEPC)上北京谱仪(BES)所收集到的国家自然科学基金资助.7.8×10⁶J/ψ事例,系统研究了J/ψ→φπ⁺π^－和J/ψ→ωπ⁺π^－两个衰变道,给出了过程的分支比以及f₀的位置和宽度参数,并对J/ψ→φf₀,f₀→π⁺π^－过程的角分布进行了拟合,首次确定出该过程的螺旋度振幅比.     

轴矢量介子E/f1(1420)的一种可能的解释

本文讨论了轴矢量介子f₁(1285),f₁(1530)和E/f₁(1420)的混合,结果表明,E/f₁(1420)的主要成份是胶子球.在此基础上给出了E/f₁(1420)的螺旋性振幅之比x的值,有待实验的检验.     

K介子的光生和相应的辐射俘获过程的研究

分析了由交叉对称性相联系的K介子光生过程(γP→K+)和相应的辐射俘获过程(K-P→γA).即从低能QCD拉氏量出发,在手征夸克模型中,统一地描述了K介子的光生过程,进而又利用交叉对称性对相关的K-介子的辐射俘获过程做了深入的研究,得到了与实验结果符合得相当好的辐射俘获过程的分支比.     

LHC光生过程中的核遮蔽效应

给出了关于LHC实光子核遮蔽效应的一些结果.证明了遮蔽随光子能量Er的增加而变强.给出了反应过程γ+A→V+A中的ρ,ω,φ总截面对质心系能量的依赖性.结果表明,存在一个能量的临界点,在该点以上的核遮蔽强到足可以被测到.     

对31S0介子九重态中ss成员的质量分析

利用雷吉轨迹理论和介子九重态质量混合公式两种方案，对3^１Ｓ_０介子九重态中同位旋标量态(主要是ss—成分)的质量给出预言，两种方案分别给出1853MeV和1849±1.2MeV.两种方案自洽的结果，将为实验上寻找该态的候选者提供帮助. 关键词： 雷吉轨迹 介子混合 同位旋标量态     

pp和pÞ碰撞中J/ψ的光生过程(英文)

计算了pp和pÞ碰撞中J/ψ的领头阶光生过程的产额。运用非相对论量子色动力学回顾了重夸克偶素产生的色单态机制与色八重态机制,并将它们分别用于处理直接光子过程和分解光子过程。通过与J/ψ产生的领头阶结果的对比可以看出,光生过程对J/ψ产额的修正在大横动量区域变得明显。The production of J/ψ originating from photoproduction processes in pp and pÞ collisions at leading order is calculated. The color singlet and color octet mechanisms for heavy quarkonium production are reviewed within nonrelativistic QCD, and be used to deal with the direct photon and resolved photon processes respectively. Comparing with the leading order results of J/ψ production, the numerical results show that the modification of photoproduction processes for J/ψ production become obvious at large p-T region.     

二步过程生成(ΩΩ)0+机制的研究

研究了一个生成(ΩΩ)0+的二步过程第一步过程为N+Ω→(NΩ)022+γ,或N+Ω→(NΩ)022+π;第二步为Ω+(NΩ)022→(ΩΩ)000+N. 结果表明这个二步过程的每一步的截面都比较大,有可能是一个生成(ΩΩ)0+的重要途径.     

关于B0→π－l+ν l衰变过程分支比的计算

通过构造适当的关联函数,计算B→π跃迁形状因子f⁺_Bπ(q²),f _{Bπ(q²)和标量形状因子f⁰(q²),从而就能研究轻子质量对B⁰→π}     

通过基矢光前量子化方法对π介子的研究

为研究介子的性质,通过基矢光前量子化方法获得介子的光前波函数。基失光前量子化是一种在哈密顿量体系下基于量子场论的非微扰方法。在哈密顿量中我们考虑了动能项、基于全息色动力学的横向禁闭势、与横向禁闭势互补的纵向禁闭势和基于QCD的夸克-胶子相互作用。我们的基矢空间包括最低阶的两个Fock空间,即领头阶■与次领头阶■。根据所得的光前波函数我们计算了介子衰变常数以及(基于领头Fock空间的)电磁半径,这些结果与粒子数据手册(PDG)上的结果相近。此外,我们计算了(基于领头Fock空间的)介子部分子分布,QCD演化后,与原先的结果相近(蓝江山等,Phys Rev Lett,2 019,122:172 001.),能够很好地描述费米国家实验室(FNAL)与欧洲核子中心(CERN)的实验数据。     

Photoproduction of Vector Meson ø off Deuteron in QCD Inspired Model

Based on the quark-gluon contents of nucleon and strongly believing that the force mediators, Pomeron and its counterpart in the conventional approach of Regge theory, for high energy diffractive process would be the tensor glueball and Odderonrespectively, we discuss photo-production of vector meson ø off the deuteron at energy less than 3 GeV in the QCD inspired model in which the quark gluon degrees of freedom and glueball, Odderon exchange are taken into account. A calculation isperformed for γ+D → ø+D, and the theoretical predictions of the differential cross section dσ ^γD/dt, are presented and compared with available experimental data. Our QCD inspired model reproduces data quite well in the whole range of the experimental measurements up to |t|≌ 0.4~GeV. Our results can be used toextract γn →øn data, which cannot be measured in experiment.     

B_s → f_0 (980) Transition Form Factors Within the k_T Factorization Approach

In the paper, we apply the kT factorization approach to deal with the Bs → f0 (980) transition form factors in the large recoil regions, i.e. the small q 2 regions. For the purpose, we adopt the B-meson wave-functions ΨB , ΨB and δ that include the three-Fock states contributions to do our discussion. Although the scalar meson f0 (980) is widely perceived as the 4-quark bound state (scenario 2), but the distribution amplitudes of 4-quark states are still unknown to us, so we adopt 2-quark model (scenario 1) for scalar meson f0 (980) in our discussion. By varying the B-meson wave-function parameters within their reasonable regions, we obtain F0(0) = F+(0) = 0.20 ± 0.02, FT(0) = 0.24 ± 0.02. Our present results for these form factors are consistent with the light-cone sum rule results obtained in the literature.     

Investigation of light scalar resonances a0(980)/ƒ0(980) with ANKE

A program to investigate the light scalar resonances a₀(980)/ƒ₀(980) in hadronic interactions via their decay into the πη and channels has started at the ANKE spectrometer of COSY-Jülich. As the first step the reactions pp → dπ⁺X and pp → dK⁺X have been measured at two energies, T_p = 2.65 GeV and 2.83 GeV. The status of the analysis at T_p = 2.65 GeV is presented. A total cross section of about 50 nb has been determined for the reaction .     

(γ, π0γ) reaction on a nucleus in the GeV region

π⁰γ invariant mass distribution spectrum has been calculated for the (γ, π⁰γ) reaction on¹²C nucleus at 2.5 GeV beam energy. These π⁰ and γ are assumed to originate due to the decay of vector mesons produced in the photonuclear reaction. The nuclear medium effect on vector mesons and the effect of π⁰ rescattering on the π⁰γ invariant mass spectrum have been investigated     

B→K_0~*(1430)η~(') decays in the pQCD approach

Based on the assumption of two-quark structure of the scalar meson K*0(1430),we calculate the CP-averaged branching ratios for B→K0*(1430)η(') decays in the framework of the perturbative QCD(pQCD) approach here.We perform the evaluations in two scenarios for the scalar meson spectrum.We find that:(a) the pQCD predictions for Br(B→K*0(1430)η(')) which are about 10-5-10-6,basically agree with the data within large theoretical uncertainty;(b) the agreement between the pQCD predictions and the data in Scenario I is better than that in Scenario II,which can be tested by the forthcoming LHC experiments;(c) the annihilation contributions play an important role for these considered decays.     

B→a0(1450)ρ(ω) Decays in Perturbative QCD Approach

In the two-quark model supposition for the meson a₀(1450), which can be viewed as either the first excited state (scenario I) or the lowest lying state (scenario II), the branching ratios and the direct CP-violating asymmetries for decays B→ a₀(1450)ρ(ω) are studied by employing the perturbative QCD factorization approach. We find the following results: (a) For the decays B^- → a⁰₀(1450)ρ^- and \bar{B}⁰ → a⁺₀(1450)ρ^-, their branching ratios have large
difference between two scenarios. Although their branching ratios are larger than other considered decay modes, their direct CP-violatingasymmetries in both scenarios are small. (b) For the decays B^-→ a^-₀(1450)ρ⁰ and \bar{B}⁰→ a^-₀(1450)ρ⁺, a⁰₀(1450)ρ⁰, a⁰₀(1450)ω, their branching ratios are close to each other between two scenarios, respectively. (c) Comparing with the decays \bar{B}⁰ →π⁰ρ⁰,π⁰π⁰, the decay \bar{B}⁰→ a⁰₀(1450)ρ⁰ receives a
larger branching ratio in each scenario, which is sensitive to the variation of the Cabibbo-Kobayashi-Maskawa angleα.     

Meson loops in the f0(980) and a0(980) radiative decays into ρ , ω

We calculate the radiative decay widths of the a ₀(980) and f ₀(980) scalar mesons into ργ and ωγ considering the dynamically generated nature of these scalar resonances within the realm of the chiral unitary approach. The main ingredient in the evaluation of the radiative width of the scalar mesons are the loops coming from the decay into their constituent pseudoscalar-pseudoscalar components and the subsequent radiation of the photon. The dominant diagrams with only pseudoscalar mesons in the loops are found to be convergent while the divergence of those with a vector meson in the loop are written in terms of the two-meson loop function easily regularizable. We provide results for all the possible charge channels and obtain results, with uncertainties, which differ significantly from quark loops models and some version of vector meson dominance.     

The (1f7/2) multiplet in Ca

The states of ⁴²Ca below 3.2 MeV excitation are studied by the ⁴¹Ca(d,p)⁴²Ca reaction at 12 MeV bombarding energy. The experimental spectroscopic factors are compared to predictions based on Gerace and Green's coexistence model.     

Reaction of O2 with the boron-terminated TaB2(0 0 0 1) surface

X-ray photoelectron spectroscopy has been used to study the clean TaB₂(0 0 0 1) surface and its reaction with O₂. In agreement with previous studies, XPS indicates that the clean surface is boron terminated. The topmost boron layer shows a chemically shifted B 1s peak at 187.1 eV compared to a B 1s peak at 188.6 eV for boron layers below the surface. The 187.1-188.6 eV peak intensity ratio and its variation with angle between the crystal normal and the detector is well described by a simple theoretical model based on an independently calculated electron inelastic mean free path of 15.7 Å for TaB₂. The dissociative sticking probability of O₂ on the boron-terminated TaB₂(0 0 0 1) surface is lower by a factor of 10⁴ than for the metal-terminated HfB₂(0 0 0 1) surface.