介质对部分子劈裂几率的影响

利用部分子在热密QCD介质中的辐射谱, 研究部分子在热密介质中的演化规律. 研究结果表明, 在相同能量下介质诱导效应使得部分子在介质中的劈裂几率大于部分子在真空中的劈裂几率; 高密度介质中的部分子劈裂几率大于低密度介质中的劈裂几率. 本文研究结果与美国BNL/RHIC相对论重离子碰撞实验中观测到的高横动量强子产额压低现象一致, 揭示了在RHIC能区已经生成高温高密物质.     

色玻璃凝聚中Sudakov效应对矢量介子产生的影响

在色玻璃凝聚框架下,将Sudakov效应运用到矢量介子产生中,计算了衍射遍举和衍射离解两种过程中轻(φ)和重(J/ψ)介子产生的微分截面和总截面。首先,利用数值方法求解微分积分形式的领头阶偶极子演化方程和Sudakov抑制的次领头阶偶极子演化方程,得到相应的偶极子散射振幅,研究发现Sudakov抑制的次领头阶偶极子散射振幅小于同一快度下领头阶的偶极子散射振幅,随着快度增加两者之间的差距越来越大,由此表明Sudakov效应压低了偶极子散射振幅的演化速度。其次,将这些偶极子散射振幅应用到衍射矢量介子产生模型中,描述HERA(hadron electron ring accelerator)能区φ和J/ψ介子产生相关实验数据,得到Sudakov抑制时的χ²/N_p=1.26远小于领头阶时的χ²/N_p=1.87,由此Sudakov效应提高了模型的精度,使得修正后的偶极子散射振幅能较好地描述相关数据,表明了Sudakov效应在矢量介子产生中起着重要的作用。     

色偶极子模型中深度虚康普顿散射过程研究

在色偶极子模型框架下,首次将共线改进的偶极子散射振幅用于研究深度虚康普顿散射(deeply virtual compton scattering,DVCS)过程实光子的产生。首先,利用计算机程序求解微积分形式的共线改进偶极子演化方程,用数值方法求得偶极子散射振幅的解。其次,将共线改进的偶极子散射振幅用于拟合HERA能区DVCS过程实光子产生的实验数据,通过拟合得到微分截面下的χ²/d.o.f=0.51和总截面下的χ²/d.o.f=0.89。最后,利用微分截面分布的理论值,基于dσ/d|t|∝e^-Bt抽取了DVCS过程的斜率,所得结果与HERA能区H1实验组测量结果一致。结果表明,共线改进的偶极子散射振幅能很好地描述DVCS实验数据。     

Hadron Multiplicities in Pb＋Pb Collisions at the Large Hadron Collider and Pomeron Loop Effects

We study the pseudo-rapidity distribution of hadron multiplicities of high energy Pb＋Pb collisions by using color glass condensate dynamics at LHC/ALICE in the fixed coupling case. It is found that after including the pomeron loop effects the charged hadron multiplicities at central rapidity are about 1500 for central Pb＋Pb collisions, which are significantly smaller than the saturation based calculations, ～ 1700 ÷ 2500 and compatible with that based on a study of multiplicities in the fragmentation region.     

Surface Emission of Quark Gluon Plasma at RHIC and LHC

Within the framework of a factorization model, we study the behaviour of nuclear modification factor in Au Au collisions at RHIC and Pb-Pb collisions at LHC. We find that the nuclear modification factor is inversely proportional to the radius of the quark-gluon plasma and is dominated by the surface emission of hard jets. We predict the nuclear modification factor R^LHC AA - 0.15 in central Pb-Pb collisions at LHC. The study shows that the factorization model can be used to describe the centrality dependence of nuclear modification factor of the high transverse momentum particles produced in heavy ion collisions at both RHIC and LHC.