色玻璃凝聚近似下极端相对论重离子碰撞中的双轻子和光子产生(英文)

Key words: 
• dilepton /
• photon /
• color glass condensate /
• heavy ion collision

Abstract: 

在色玻璃凝聚胶子饱和框架下，研究了相对论重离子碰撞中的双轻子和光子产生。在胶子饱和区域，在微扰近似(kT-因子化近似) 下低转移动量双轻子和光子的主要产生机制是胶子-胶子相互作用。在RHIC 和LHC 能量区域的相对论重离子碰撞中，饱和动量的值远远大于量子色动力学禁闭标度ΛQCD，这使得αs≪1。此时，当转移动量小于饱和动量Qs 时质子和原子核的胶子密度值就会很高，双轻子和光子的不变产生横截面会由于饱效应而得到增强。数值结果给出在RHIC 和LHC 能量区域的pp, pA 和AA碰撞中，来源于色玻璃凝聚的低转移动量双轻子和光子产生贡献是显著的。

We investigate inclusive dileptons and photons production in relativistic heavy ion collisions based on the idea of gluon saturation in the color glass condensate (CGC) framework. In the gluon saturation region, the dominant mechanism for low-pT dileptons and photons production in the perturbative approach (the kT-factorization approach) is gluon-gluon interaction. At Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies, the value of saturation momentum becomes larger than the Quantum Chromodynamics (QCD) confinement scale ΛQCD for relativistic heavy ion collisions, which implies that αs≪1. In this state, the gluon density for proton and nucleus with transverse momentum less than the saturation momentum Qs will reach a high value, and the invariant cross-section for dileptons and direct photons is further enhanced by saturation effects. The numerical results indicate that the production of low-pT dileptons and photons from the color glass condensate becomes prominent in pp, pA, and AA collisions at RHIC and LHC  Energies.