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关于QCD临界点的相关性探讨

Correlation Probes of a QCD Critical Point

T. Csorgo

备注：
Typos fixed, including an important misprint in the definition of the order parameter after eq. (3.1). This is the final version. 19 pages, 4 figures, 1 table, to appear in the proceedings of "High pt physics at LHC", March 16-19, 2008, Tokaj, Hungary, based partly on an earlier talk at NN2006, August 28 - September 1, 2006, Rio de Janeiro, Brazil
发表信息：
PoS HIGH-pTLHC08:027,2008
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摘要：

临界乳光是固态物理学中二级相变的一个特征实验信号。本文提出了一种新的、实验上可以达到的测量重离子反应中不透明度和衰减长度的方法，它是HBT半径和核修正因子的结合。当$\sqrt{s_{NN}}$、系统大小和中心性对应于QCD临界点时，这种不透明度最大。为了表征该临界点处的相变，可以通过测量玻色-爱因斯坦或HBT关联的Lévy稳定性指数来确定关联函数的临界指数。相关长度的指数可以从拟合的多重性分布中确定在各种赝快度间隔，也作为碰撞能量，系统大小，中心性和（化学）冻结温度的函数。这两个临界指数决定了剩余的四个临界指数和这个二阶相变的普适类。作为一个控制实验，建议的比热容的临界指数的确定，从事件的波动测量。为了精确测量不透明度，需要校准良好的高横向动量探针，例如由$γ$ +喷流关联函数的激发函数给出。

英文摘要：

Critical opalescence is a characteristic experimental signature of a second order phase transition in solid state physics. A new, experimentally accessible measure of opacity and of attenuation length in heavy ion reactions is suggested, as a combination of HBT radii and nuclear modification factors. This opacity is maximal when $\sqrt{s_{NN}}$, the system size and centrality correspond to the critical point of QCD. To characterize the phase transition at this critical point, the critical exponent of the correlation function can be determined by measuring the Lévy index of stability of the Bose-Einstein or HBT correlations. The exponent of the correlation length can be determined from fits to the multiplicity distribution in various pseudorapidity intervals, also as a function of colliding energy, system size, centrality and (chemical) freeze-out temperature. These two critical exponents determine the remaining four critical exponents and the universality class of this second order phase transition. As a control experiment, the determination of the critical exponent of the specific heat capacity is proposed, from event-by-event fluctuation measurements. To measure opacity precisely, well calibrated high transverse momentum probes are needed, such as given by the excitation function of $γ$ + jet correlation functions.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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