ee0A GeV S+Au反应中光子产生的低横动量增强

用建立在LUND弦模型特别是PYTHIA事件产生器基础上的描写极端相对论性核一核碰撞的强子和弦级联模型—JPCIAE研究了入射能量为200A GeV的S+ Au中心碰撞中光子产生.模型同时考虑了部分子QCD散射过程、强子末态相互作用以及强子衰变等光子产生反应道并作了协调处理.JPCIAE模型计算结果很好再现了WA93实验数据所呈现的低横动量增强效应.     

Quantum chromodynamics: Working group report

This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering, and collider phenomenology are reported.     

THE NONLINEAR QCD DYNAMICAL EQUATIONS WITH HIGHER ORDER EFFECTIVE COUPLING

Through studying the nonlinear QCD dynamical equations with higher order effective coupling, we find that shadowing effect is substantially weaker than that neglecting higher order effective coupling. This conclusion is very important for explaining the data from DESY ep collider HERA.     

深度非弹性散射中小x区物理新进展

简单评述了近几年来轻子一核子(核)深度非弹性散射(1–N(A)DIS)在小x区的单举实验数据和唯象分析方面的进展.     

Vacuum Polarization Bubble Effects on the Triangle Relations for B Meson Charmless Decay Amplitudes

Assuming that factorization is valid and that contributions of the exchange, annihilation, and penguin-annihilation diagrams are negligible, we study the effects of the QCD vacuum polarization bubbles on the decay amplitudes of some B meson charmless decays into two light pseudoscalars. The bubbles have much less effects on B⁰→π⁺π^-, π^-K⁺, π⁰K⁰ than on B⁰→π⁰π⁰ thus the triangle relation √2A(B⁺→π⁺π⁰) = A(B⁰→π^-K⁺)/R_u+√2A(B⁰→π⁰K⁰)/R_u is changed slightly while √2A(B⁺→π⁺π⁰)=√2A(B⁰→π⁰π⁰)+A(B⁰→π⁺π^-) is altered significantly. This may indicate that in order to test or use these triangle relations other higher order QCD corrections should also be carefully taken into consideration.     

Calculation of a High Order QCD Process-gg to ttgg

We use the permutation group of order 4 to classify the fouith order tree QCD Feynman diagrams, which contribute to the gg to tfgg process. (There are 159 of them.) We also provide new methods to make the color sum, and to check the gauge symmetry of the matrix elements and Feynman parts.     

微扰QCD方法计算稀有衰变B+→D+s(-K)*0

在标准模型中,稀有衰变道B+→D+s(-K)*0只有通过纯湮没图才可以发生.这样这个衰变道的分支比很小.利用基于kT因子化的微扰方法给出分支比的预测,发现它在10-8的量级上.这个衰变道估计在将来的LHC上得到测量,对检验标准模型以及探寻新物理有着重要的意义.     

Deep inelastic scattering with proton target in the presence of gluon condensation using holography

We study the deep inelastic scattering (DIS) of a proton-targeted lepton in the presence of gluon condensation using gauge/gravity duality. We use a modified \begin{document}${\rm AdS}_5$\end{document} background where the modification parameter c corresponds to the gluon condensation in the boundary theory. First, by examining the electromagnetic field, we establish that a non-zero c can increase field magnitude. Our aim is to obtain the acceptable value of c for this scattering. Our method is based on setting the mass of the proton as an eigenvalue of the baryonic state equations of the DIS to find the acceptable value of the parameter c on the other side of the equations. Therefore, in the second step, we calculate wave function equations for the baryonic states where the mass of the proton target requires a value contribution of c as \begin{document}$ c=0.0120 \; \rm GeV^4 $\end{document}. Proceeding with the electromagnetic field and baryonic states, we derive the holographic interaction action related to the amplitude of the scattering. Finally, we compute the corresponding structure functions numerically as functions of x and q, which are Bj?rken variables and the lepton momentum transfers, respectively. Comparing the Jlab Hall C data with our theoretical calculations, our results are acceptable.     

Three-quark potential at finite temperature and chemical potential

Using gauge/gravity duality, we study the potential energy and the melting of triply heavy baryon at finite temperature and chemical potential in this paper. First, we calculate the three-quark potential and compare the results with quark-antiquark potential. With the increase of temperature and chemical potential, the potential energy will decrease at large distances. It is found that the three-quark potential will have an endpoint at high temperature and/or large chemical potential, which means triply heavy baryons will melt at enough high temperature and/or large chemical potential. We also discuss screening distance which can be extracted from the three-quark potential. At last, we draw the melting diagram of triply heavy baryons in the \begin{document}$ T-\mu $\end{document} plane.