STAR合作组发现了重离子碰撞中φ和K*⁰介子的全局自旋对准模式。相关论文于2023年1月18日发表于国际顶尖学术期刊《自然》杂志上。

该研究团队表明，在相对论重离子碰撞中，夸克和胶子在一个扩展的体积上被释放，两种产生的矢量(自旋1)介子，即φ和K*⁰，出现了令人惊讶的全局自旋对准模式。特别是，全局自旋对准的值出乎意料地大，而K*⁰的值与0一致。

观测到的自旋对准模式和幅度不能用常规机制解释，而与强力场连接的模型，即标准模型和量子色动力学中的有效代理描述，可以容纳当前数据。这种联系如果完全建立起来，将为研究强力场的行为开辟一条潜在的新途径。

据悉，尽管自汤川第一次从介子交换的角度描述核子间的作用力以来已有几十年的进展，但对强相互作用的全面理解在现代科学中仍然是一个相当大的挑战。剩下的一个困难来自于强作用力的非摄动性质，这导致了夸克在质子大小量级的距离上受到限制的现象。

附：英文原文

Title: Pattern of global spin alignment of ? and K*0 mesons in heavy-ion collisions

Author: anonymous

Issue&Volume: 2023-01-18

Abstract: Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange1, a full understanding of the strong interaction remains a considerable challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distances on the order of the size of the proton. Here we show that, in relativistic heavy-ion collisions, in which quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely and K*0, emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for is unexpectedly large, whereas that for K*0 is consistent with zero. The observed spin-alignment pattern and magnitude for cannot be explained by conventional mechanisms, whereas a model with a connection to strong force fields2,3,4,5,6, that is, an effective proxy description within the standard model and quantum chromodynamics, accommodates the current data. This connection, if fully established, will open a potential new avenue for studying the behaviour of strong force fields.

DOI: 10.1038/s41586-022-05557-5

Source: