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arXiv 0907.3870nucl-th
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在RHIC上是否有p+p碰撞流?理解单粒子分布、多重性演化和守恒定律

Do p+p Collisions Flow at RHIC? Understanding One-Particle Distributions, Multiplicity Evolution, and Conservation Laws

Zbigniew Chajȩcki, Mike Lisa

摘要:

集体,爆炸流在中央重离子碰撞体现在$p_T$分布和飞秒尺度的质量依赖性,测量软部门($p_T\lesssim 1$ GeV/c)。测量的质子-质子碰撞的$p_T$分布明显不同于那些从重离子碰撞。这被认为是p+p碰撞几乎不产生集体流的证据,这一结论符合天真的预期。我们指出了可能的危险,忽略相空间的限制,由于守恒定律比较高,低多重性的最终状态。在两粒子关联函数中,我们已经看到了RHIC低多重碰撞中这种相空间限制的清晰信号。我们讨论这些相同的效果,然后,{ \it必须}出现在单粒子光谱。我们认为,能量和动量守恒的影响,实际上占主导地位的观察到的系统,和$p+p$碰撞可能更类似于重离子碰撞比一般认为的。

英文摘要:

Collective, explosive flow in central heavy ion collisions manifests itself in the mass dependence of $p_T$ distributions and femtoscopic length scales, measured in the soft sector ($p_T\lesssim 1$ GeV/c). Measured $p_T$ distributions from proton-proton collisions differ significantly from those from heavy ion collisions. This has been taken as evidence that p+p collisions generate little collective flow, a conclusion in line with naive expectations. We point out possible hazards of ignoring phase-space restrictions due to conservation laws when comparing high- and low-multiplicity final states. Already in two-particle correlation functions, we see clear signals of such phase-space restrictions in low-multiplicity collisions at RHIC. We discuss how these same effects, then, {\it must} appear in the single particle spectra. We argue that the effects of energy and momentum conservation actually dominate the observed systematics, and that $p+p$ collisions may be much more similar to heavy ion collisions than generally thought.

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