According to the CPT theorem, which states that the combined operation of charge conjugation, parity transformation and time reversal must be conserved, particles and their antiparticles should have the same mass and lifetime but opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus containing a strange quark, more specifically in the hypertriton. This hypernucleus is the lightest one yet discovered and consists of a proton, a neutron and a Λ hyperon. With data recorded by the STAR detector^1,2,3 at the Relativistic Heavy Ion Collider, we measure the Λ hyperon binding energy B_Λ for the hypertriton, and find that it differs from the widely used value⁴ and from predictions^5,6,7,8, where the hypertriton is treated as a weakly bound system. Our results place stringent constraints on the hyperon–nucleon interaction^9,10 and have implications for understanding neutron star interiors, where strange matter may be present¹¹. A precise comparison of the masses of the hypertriton and the antihypertriton allows us to test CPT symmetry in a nucleus with strangeness, and we observe no deviation from the expected exact symmetry.

根据 CPT 定理，即电荷共轭、宇称变换和时间反演的联合操作必须守恒，粒子及其反粒子应具有相同的质量和寿命，但电荷和磁矩相反。在这里，我们在含有奇异夸克的原子核中测试 CPT 对称性，更具体地说是在超氚核中。这个超核是迄今为止发现的最轻的超核，由一个质子、一个中子和一个 Λ 超子组成。利用相对论重离子对撞机 STAR 探测器^1,2,3记录的数据，我们测量超氚核的 Λ 超子结合能B _Λ，发现它与广泛使用的值⁴和预测值^{5,6 不同， 7,8}，其中超氚被视为弱束缚系统。我们的结果对超子-核子相互作用^9,10施加了严格的限制，并且对理解可能存在奇怪物质的中子星内部具有重要意义¹¹。超氚和反超氚质量的精确比较使我们能够测试具有奇异性的原子核中的 CPT 对称性，并且我们观察到与预期的精确对称性没有偏差。