标题： 用自旋纠缠探测QCD禁闭 显示英文标题

标题： Probing QCD Confinement with Spin Entanglement

摘要： 一度被视为纯粹虚空的真空，如今被认为具有丰富而复杂的结构，其特征是波动的能量场和虚夸克-反夸克对的凝聚态。这些对导致自发的手征对称性破缺，这是一种基本现象，被认为是生成可见宇宙中超过99%质量的原因。 然而，手征对称性破缺与夸克禁闭相关的质量生成的确切机制仍然是物理学中最深刻未解的问题之一。 在这里，我们研究了布鲁克海文国家实验室相对论重离子对撞机（RHIC）中的高能质子-质子碰撞，在那里这些碰撞可能从真空中释放出虚夸克-反夸克对。 这些虚对，特别是奇异夸克-反奇异夸克对，最初是量子自旋纠缠的，并随后经历夸克禁闭以形成诸如$\Lambda$超子之类的强子。 在这篇信中，我们报告了由RHIC的STAR实验首次观测到的$\Lambda\bar{\Lambda}$超子对的自旋关联证据——一种相对极化信号$(18 \pm 4)\%$，它将量子色动力学（QCD）真空中的自旋纠缠夸克对与其最终态强子对应物联系起来。 至关重要的是，当超子对在角度上被广泛分离时，这种关联消失，这与量子系统的退相干一致。 我们的发现为探索夸克禁闭和纠缠的动力学及其相互作用提供了一个新的实验范式。 显示英文摘要

摘要： Once regarded as mere emptiness, the vacuum is now understood to possess a rich and complex structure, characterized by fluctuating energy fields and a condensate of virtual quark-antiquark pairs. These pairs cause spontaneous chiral symmetry breaking, a fundamental phenomenon that is believed to generate over 99% of the mass in the visible universe. However, the precise mechanism linking the chiral symmetry breaking to the mass generation associated with quark confinement remains one of the most profound open questions in physics. Here, we investigate high energy proton-proton collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory, where those collisions could liberate virtual quark-antiquark pairs from the vacuum. These virtual pairs, particularly the strange quark-antiquark pairs, are initially quantum spin-entangled and later undergo quark confinement to form hadrons such as $\Lambda$ hyperons. In this Letter, we report the first evidence of spin correlation of $\Lambda\bar{\Lambda}$ hyperon pairs measured by the STAR experiment at RHIC - a relative polarization signal of $(18 \pm 4)\%$ that links the spin-entangled quark pairs of the Quantum Chromodynamic (QCD) vacuum to their final-state hadron counterparts. Crucially, this correlation vanishes when the hyperon pairs are widely separated in angle, consistent with the decoherence of the quantum system. Our findings provide a new experimental paradigm for exploring the dynamics and interplay of quark confinement and entanglement.