标题： 关于高能碰撞中重夸克强子化的非普适性 显示英文标题

标题： On the non-universality of heavy quark hadronization in elementary high-energy collisions

摘要： 长期以来人们传统地假设重夸克（粲夸克，$c$和底夸克，$b$）碎裂在不同的碰撞系统中是普适的，这一假设基于强子化作为一个软过程应该发生在特征非微扰QCD尺度$\Lambda_{QCD}$上的想法。然而，最近这一普适性假设受到了挑战，因为在LHC能量下的最小偏倚质子-质子（$pp$）碰撞中，$c$- 和$b$-重子相对于其介子对应物的产生被观察到比电子-正电子（$e^+e^-$）碰撞中显著增强。 非普适性的概念通过 LHCb 实验在 LHC 的 $\sqrt{s}=13$ TeV $pp$ 能量下测量到的 $b$- 含重子跃迁到介子产额比值 $\Lambda_b/B$ 对电荷粒子多重性的依赖关系得到明确加强，在最小偏倚 $pp$ 碰撞中从饱和值开始，随着系统尺寸逐渐减小，不断演化至 $e^+e^-$ 碰撞中的较小值。 我们研究了在具有输入的 $b$- 强子谱的标准统计强子化模型中， $b$- 重子产生的多重性依赖关系，并补充了许多迄今为止未观测到的状态，这些状态来自夸克模型的预测。 我们证明了低多重性下 $\Lambda_b/B$ 的下降趋势可以通过小系统中由于严格守恒而导致的 $\Lambda_b$ 的产量的正则抑制来定量理解。 因此，我们提出了一种可能的情景来理解基本碰撞中重夸克碎裂非普适性的起源。 显示英文摘要

摘要： It has been traditionally hypothesized that the heavy quark (charm, $c$ and bottom, $b$) fragmentation is universal across different collision systems, based on the notion that hadronization as a soft process should occur at the characteristic non-perturbative QCD scale, $\Lambda_{QCD}$. However, this universality hypothesis has recently been challenged by the observation that the $c$- and $b$-baryon production relative to their meson counterparts in minimum bias proton-proton ($pp$) collisions at the LHC energies is significantly enhanced as compared to the electron-positron ($e^+e^-$) collisions. The conception of non-universality is unambiguously reinforced by the latest measurement of the charged-particle multiplicity dependence of the $b$-baryon-to-meson yield ratio, $\Lambda_b/B$, by the LHCb experiment in $\sqrt{s}=13$\,TeV $pp$ collisions at the LHC, evolving continuously from the saturation value in minimum bias $pp$ collisions toward the small value in $e^+e^-$ collisions as the system size gradually reduces. We address the multiplicity dependence of $b$-baryon production in the canonical statistical hadronization model with input $b$-hadron spectrum augmented with many hitherto unobserved states from quark model predictions. We demonstrate that the decreasing trend of the $\Lambda_b/B$ toward low multiplicities can be quantitatively understood from the canonical suppression on the yield of $\Lambda_b$, as caused by the requirement of strict conservation of baryon number in sufficiently small systems. We have therefore proposed a plausible scenario for understanding the origin of the non-universality of heavy quark fragmentation in elementary collisions.