Search for long range flow-like correlation in hadronic $e^{+}e^{-}$ collisions with Belle

Yu-Chen Chen, Chengjian Lin, Yen-Jie Lee, P. Chang
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引用次数: 1

Abstract

The enhancement of charged-particle pairs with large pseudorapidity difference and small azimuthal angle difference, often referred to as the “ridge signal”, is a phenomenon widely observed in high multiplicity proton-proton, proton-ion and deutron-ion collisions, which is not yet fully understood. In heavy-ion collisions, the hydrodynamic expansion of the Quark-Gluon Plasma is the most popular explanation of the ridge signal. Measurements in the 4+4− collision system, without the complexities introduced by hadron structure in the initial state, can be a new opportunity to examine the formation of a ridge signal. The first measurement of two-particle angular correlation functions in high multiplicity 4+4− collisions at √ B = 10.52 GeV is reported. About 31.5 fb−1 hadronic 4+4− annihilation data collected by the Belle detector at KEKB are used in this study. Two-particle angular correlation functions are measured over the full azimuth and large pseudorapidity intervals which are defined by either the electron beam axis or the event thrust as a function of charged particle multiplicity. The measurement in the event thrust analysis, with mostly quark and anti-quark pairs determining the reference axis, is sensitive to soft gluon emissions associated with the outgoing (anti-)quarks. No significant ridge signal is observed with analyses performed in either coordinate system. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various 4+4− event generators and expected to provide new constraints to the phenomenological models in the low collision energy regime.
在强子$e^{+}e^{-}$与Belle的碰撞中寻找长程流状关联
赝快差大、方位角差小的带电粒子对的增强,通常被称为“脊信号”,是在高多重质子-质子、质子-质子和氘核-离子碰撞中广泛观察到的现象,目前尚未完全理解。在重离子碰撞中,夸克-胶子等离子体的流体动力学膨胀是对脊信号最流行的解释。在4+4−碰撞系统中进行测量,没有初始状态下强子结构带来的复杂性,可以成为研究脊信号形成的新机会。报道了在√B = 10.52 GeV高多重度4+4−碰撞中首次测量到的两粒子角相关函数。本研究使用了KEKB Belle探测器收集的约31.5 fb−1强子4+4−湮灭数据。测量了两粒子角相关函数在全方位角和大伪快度区间上的分布,伪快度区间由电子束轴或事件推力定义为带电粒子多重度的函数。在事件推力分析中,主要由夸克和反夸克对确定参考轴的测量对与出射(反)夸克相关的软胶子发射很敏感。在两种坐标系下均未观测到明显的脊信号。在推力轴分析中,近侧喷流相关性似乎不存在。将测量结果与各种4+4−事件发生器的预测结果进行了比较,并期望为低碰撞能量状态下的现象学模型提供新的约束。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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