Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions
Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions
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DOI：
10.1103/physrevc.92.034911
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发表时间：
2015-03
期刊：
影响因子：
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通讯作者：
V. Khachatryan;A. Sirunyan;A. Tumasyan;W. Adam;E. Asilar;T. Bergauer;J. Brandstetter;M. Dragicevic-M.-Dr
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文献类型：
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作者：
V. Khachatryan;A. Sirunyan;A. Tumasyan;W. Adam;E. Asilar;T. Bergauer;J. Brandstetter;M. Dragicevic-M.-Dr
长程方位角两粒子相关分解成单粒子各向异性的产物的系统研究提出作为两个粒子的pt和eta的函数，并作为PbPb和pPb碰撞中粒子多重性的函数。这些数据是用CMS探测器在sqrt（s[NN]）= 2.76 TeV的PbPb碰撞和sqrt（s[NN]）= 5.02 TeV的pPb碰撞中获得的，覆盖了非常宽的多重性范围。观察到分解作为粒子pt和eta的函数被破坏。当测量不同的粒子的PT，第二傅立叶谐波的分解击穿的幅度达到20%非常中心的PbPb碰撞，但迅速减少的多重性降低。这些数据与粘性流体动力学预测一致，这表明因子分解破缺的影响主要对初始状态条件敏感，而不是对输运性质敏感（例如，剪切粘度）。因子分解也计算与粒子的不同η。这种影响被认为是最弱的中中心PbPb事件，但变得更大的中心或外围PbPb碰撞，也为非常高的多重性pPb碰撞。依赖于η的因子分解数据为重离子碰撞中形成的介质的纵向演化提供了新的见解。
A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of pt and eta of both particles, and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at sqrt(s[NN]) = 2.76 TeV and pPb collisions at sqrt(s[NN]) = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pt and eta. When measured with particles of different pt, the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different eta. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very high-multiplicity pPb collisions. The eta-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions.