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arXiv 0910.1891nucl-th
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强子-强子和核-核碰撞中电荷平衡函数的纵向助推不变性

Longitudinal boost-invariance of charge balance function in hadron-hadron and nucleus-nucleus collisions

Na LI Zhiming LI Yuanfang WU

摘要:

利用强子-强子碰撞的PYTHIA模型和核-核碰撞的多相输运(AMPT)模型的Monte Carlo发生器,详细研究了电荷平衡函数的纵向增强不变性和横向动量依赖性.结果表明,在这两个模型中,电荷平衡函数在{ \it p}+{ \it p}和Au+Au碰撞中都具有升压不变性,与实验结果一致.以赝快度窗口宽度为尺度的平衡函数与窗口的位置和大小无关,对应于整个赝快度范围的平衡函数。平衡函数的这种纵向性质在PYTHIA和AMPT默认模型中也适用于小横向动量范围内的粒子,但在AMPT中违反了弦熔化。讨论了这些结果的物理来源。

英文摘要:

Using Monte Carlo generators of the PYTHIA model for hadron-hadron collisions and a multi-phase transport (AMPT) model for nucleus-nucleus collisions, the longitudinal boost-invariance of charge balance function and its transverse momentum dependence are carefully studied. It shows that the charge balance function is boost-invariant in both {\it p}+{\it p} and Au+Au collisions in these two models, consistent with experimental data. The balance function properly scaled by the width of the pseudorapidity window is independent of the position or the size of the window and is corresponding to the balance function of the whole pseudorapidity range. This longitudinal property of balance function also holds for particles in small transverse momentum ranges in the PYTHIA and the AMPT default models, but is violated in the AMPT with string melting. The physical origin of the results are discussed.

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