反质子间相互作用的研究

Study of Interaction Between Antiprotons

随着对反物质研究的深入,人们需要迫切知道反质子之间的相互作用力是怎样的,是否与质子之间的作用是对称的。对这个作用力的测量,有助于我们理解反物质原子核的形成机制以及对物质-反物质对称性的理解。为此,STAR合作组利用相对论重离子加速器中金核-金核碰撞中产生的丰富的反质子,通过反质子-反质子动量关联函数的测量,并扣除了通过其他粒子衰变过来的次级反质子与其他反粒子关联的污染,精确地构建了反质子-反质子关联函数。然后,结合量子多粒子关联理论,定量提取出反质子-反质子的有效力程和散射长度这两个基本作用参数。研究表明,在实验精度内,反质子间的相互作用与正质子保持一致。反质子-反质子之间的强相互作用存在着吸引,它们可以克服由于同号(负电荷)的反质子-反质子之间的库仑排斥而结合成反物质原子核。这项研究首次实现了对反物质间相互作用力的测量,为进一步研究反原子核的形成和属性奠定了基础。同时为CPT对称性的检验提供了一种新的方式,对人类深刻认识物质世界的构成及其运动规律具有重要意义。

With undergoing researches on antimatter physics, it is crucial to understand what the interaction between antiprotons is. Is it the same as the interaction between protons？ This measurement will definitely help us to understand the formation mechanism of antimatter nuclei as well as the symmetry of matter and antimatter.In this context, our STAR collaboration measured the correlation function of antiproton-antiproton pairs from200 Ge V/c Au＋Au collisions. After substracting the residual correlation due to the secondary antiprotons that decayed from other particles, the primary antiproton-antiproton correlation function is extracted. By applying the quantum theory of multi-particle correlation, two key parameters that characterize the corresponding strong interaction： namely, the scattering length（f0） and effective range（d0） were obtained. Within error bars, it is found that the f0 and d0 for the antiproton-antiproton interaction are consistent with their antiparticle counterparts–the ones for the proton-proton interaction. Like the force that holds ordinary protons together within the nuclei of atoms, the force between antiprotons is attractive and strong, which overcomes the tendency of the like（negatively） charged particles to repel one another, and allows the antiprotons to bind to form antinucleus. The current measurement is for the first time to measure the interaction between antimatter, it offers a foundation to understanding the structure of more-complex antinuclei and their properties. Also our measurement offers a new way to test the CPT symmetry, which has an important impact for human beings to understand the law of motion in our world.