Zhang Hui, Liao Jinfeng, Wang Enke, Wang Qian, Xing Hongxi
Guangdong Provincial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou 510006, China.
Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Southern Nuclear Science Computing Center, South China Normal University, Guangzhou 510006, China.
Phys Rev Lett. 2021 Jan 8;126(1):012301. doi: 10.1103/PhysRevLett.126.012301.
Exploring the nature of exotic multiquark candidates such as the X(3872) plays a pivotal role in understanding quantum chromodynamics (QCD). Despite significant efforts, consensus on their internal structures is still lacking. As a prime example, it remains a pressing open question to decipher the X(3872) state between two popular exotic configurations: a loose hadronic molecule or a compact tetraquark. We demonstrate a novel approach to help address this problem by studying the X(3872) production in heavy ion collisions, where a hot fireball with ample light as well as charm (anti-)quarks is available for producing the exotics. Adopting a multiphase transport model (AMPT) for describing such collisions and implementing appropriate production mechanism of either molecule or tetraquark picture, we compute and compare a series of observables for X(3872) in Pb-Pb collisions at the Large Hadron Collider. We find the fireball volume plays a crucial role, leading to a 2-order-of-magnitude difference in the X(3872) yield and a markedly different centrality dependence between hadronic molecules and compact tetraquarks, thus offering a unique opportunity for distinguishing the two scenarios. We also make the first prediction of X(3872) elliptic flow coefficient to be tested by future experimental measurements.
探索诸如X(3872)等奇特多夸克候选粒子的本质，对于理解量子色动力学（QCD）起着关键作用。尽管付出了巨大努力，但对于它们的内部结构仍未达成共识。作为一个典型例子，在两种常见的奇特构型（松散的强子分子或紧凑的四夸克）之间解读X(3872)态，仍然是一个紧迫的开放性问题。我们展示了一种新颖的方法来帮助解决这个问题，即研究重离子碰撞中X(3872)的产生，在这种碰撞中，一个具有充足轻夸克以及魅（反）夸克的热火球可用于产生这些奇特粒子。采用多相输运模型（AMPT）来描述此类碰撞，并实施分子或四夸克图景的适当产生机制，我们计算并比较了大型强子对撞机中铅 - 铅碰撞中X(3872)的一系列可观测量。我们发现火球体积起着关键作用，导致X(3872)产率出现两个数量级的差异，并且强子分子和紧凑四夸克之间的中心度依赖性明显不同，从而为区分这两种情况提供了独特的机会。我们还首次预测了X(3872)的椭圆流系数，以供未来的实验测量进行检验。
