发现Z_C(3900)——一个带电类粲偶素共振结构

Observation of a charged charmonium-like state Z_C(3900)

北京谱仪(BESⅢ)实验和Belle实验利用两种不同的方法对e^+e^-→π^+ π^-J/y过程进行了研究。在π~±J/y系统中,同时观测到了一个新的带电类粲偶素结构——Z_C(3900)。Z_C(3900)耦合到粲偶素末态,因此其内部夸克组分应该含有正反粲夸克;同时它还带有电荷,故不可能仅由正反粲夸克组成。Z_C(3900)共振态中最少含有4个夸克,极有可能是一个奇特态强子。

Abstract U sing data samples collected with the BESⅢ detector at an e＋e centre-of-mass en- ergy of 4.26 GeV and with the Belle detector on or near the γ（nS）, n= 1,……, 5, resonances, the e＋e-→π＋π-J/ψ process was investigated through different approaches. Both detectors observed a charged char- monium-like state in the invariant mass distribution of π±J/ψ. This new structure, called Z,.（3900）, couples strongly to a charmonium and is charged, so it cannot be a conventional charmonium state, but can be interpreted as an exotic hadron with at least four quarks.