论文标题
重型离子碰撞中的中心性波动和去相关
Centrality fluctuations and decorrelations in heavy-ion collisions
论文作者
论文摘要
重离子碰撞中产生的系统的中心性或初始状态来源$ v $是一个未唯一定义的概念，并受到重要的理论和实验性不确定性。我们认为，可以从逐个事件的两个子事件中的两个子事件中的两个子事件（$ n_a $ vs $ n_b $之间的事件）中建立最终状态多重性的初始状态来源之间的更强的连接。这种相关性对每种源$ p（n）$的粒子产生的两种主要类型的中心性波动很敏感，这些粒子的产生涂抹了$ v $和$ v $和$ n_a $用于实验中心性的$ n_a $之间的关系，而2）在两个子事件$ v_b $ v_b $和$ v_a $之间的源之间的脱发。根据$ n_a $的函数（即用$ n_a $定义了实验中心性），对CF进行了分析。我们发现，平均值$ \ langle v_b \ rangle_ {n_a} $和$ \ langle n_b \ rangle_ {n_a} $在中央碰撞中与$ n_a $线性地增加，但在超中心碰撞中却扁平。这种非线性行为对$ n_a $的中心分辨率敏感。在存在中心性去相关的情况下，缩放的方差$ \ langle（ΔV_B）^2 \ rangle/\ langle v_b \ rangle $和$ \ langle（Δn_b）^2 \ rangle/\ langle n_b \ langle n_b \ rangle $ collisation y niD-c collision y niD-c collisional collisional collisional collision nid-c collisies nid collisional in niD-c in nid collisional collision y。 $ p（n）$导致超中央地区的另一幅急剧下降。 $ v_b $和$ n_b $的高阶累积物显示出有趣但相当复杂的行为，值得进一步研究。我们的结果表明，人们可以使用二维多重性相关性的累积物，尤其是均值和方差，以限制粒子生产机制以及初始状态源的纵向波动。
The centrality or the number of initial-state sources $V$ of the system produced in heavy ion collision is a concept that is not uniquely defined and subject to significant theoretical and experimental uncertainties. We argue that a more robust connection between the initial-state sources with final-state multiplicity could be established from the event-by-event multiplicity correlation between two subevents separated in pseudorapidity, $N_a$ vs $N_b$. This correlation is sensitive to two main types of centrality fluctuations (CF): 1) particle production for each source $p(n)$ which smears the relation between $V$ and $N_a$ used for experimental centrality, and 2) decorrelations between the sources in the two subevents $V_b$ and $V_a$. The CF is analyzed in terms of cumulants of $V_b$ and $N_b$ as a function of $N_a$, i.e. experimental centrality is defined with $N_a$. We found that the mean values $\langle V_b\rangle_{N_a}$ and $\langle N_b\rangle_{N_a}$ increase linearly with $N_a$ in mid-central collisions, but flatten out in ultra-central collisions. Such non-linear behavior is sensitive to the centrality resolution of $N_a$. In the presence of centrality decorrelations, the scaled variances $\langle(δV_b)^2\rangle/\langle V_b\rangle$ and $\langle(δN_b)^2\rangle/\langle N_b\rangle$ are found to decrease linearly with $N_a$ in mid-central collisions, while the $p(n)$ leads to another sharp decrease in the ultra-central region. The higher-order cumulants of $V_b$ and $N_b$ show interesting but rather complex behaviors which deserve further studies. Our results suggest that one can use the cumulants of the two-dimensional multiplicity correlation, especially the mean and variance, to constrain the particle production mechanism as well as the longitudinal fluctuations of the initial-state sources.
