The CMS Collaboration近日取得一项新成果。经过不懈努力，他们研究出全粲四夸克的自旋和宇称的测定。这一研究成果于2025年12月3日发表在国际顶尖学术期刊《自然》上。

在这里，该课题组研究人员报告了最近发现的三个全粲四夸克家族的量子数的首次测量，主题数据是2016年至2018年在大型强子对撞机上的CMS实验收集的。为发现和表征希格斯玻色子而开发的角分析技术已应用于新的奇异态。

这里研究人员证明了宇称P和电荷共轭C对称性的量子数是+1。这些奇异态的自旋J被确定为与2?一致，而在95%和99%的置信水平上分别排除了0?和1?。JPC= 2++赋值意味着组成自旋和轨道角动量的特殊构型，这限制了这些四夸克可能的内部结构。

据了解，传统的夸克模型解释了重子的存在，如质子和中子，它们由三个夸克组成，以及介子，由夸克-反夸克对组成。直到最近才开始积累大量证据，证明由4到5个夸克和反夸克组成的奇异态。它们内部结构的确切性质仍然不确定。

附：英文原文

Title: Determination of the spin and parity of all-charm tetraquarks

Author: anonymous

Issue&Volume: 2025-12-03

Abstract: The traditional quark model1,2 accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark–antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks3. The exact nature of their internal structure remains uncertain4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29. Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks30,31,32, using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018 (refs.33,34). The angular analysis techniques developed for the discovery and characterization of the Higgs boson35,36,37 have been applied to the new exotic states. Here we show that the quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is determined to be consistent with 2?, while 0? and 1? are excluded at 95% and 99% confidence levels, respectively. The JPC=2++ assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.

DOI: 10.1038/s41586-025-09711-7

Source: https://www.nature.com/articles/s41586-025-09711-7