Recent empirical developments in the study and understanding of XYZ states
School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, People’s Republic of China
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Published online: 11 July 2016
Exotic hadronic states beyond the conventional quark model (called charmoniumlike/bottomoniumlike states or XYZ particles) have been searched for and many candidates were proposed including glueballs, hybrids, multi-quark states, hadron molecules, etc. Dramatic progress was made in the study of the exotic states after the running of the two B-factories, i.e., Belle at KEK and BaBar at SLAC. In my review report, I present the most recent results on the study of the XYZ states from the BESIII, Belle, BaBar, LHCb, CMS experiments, etc., including (1) X states: the observation of the X(3872) in e+e− → γX(3872) at around 4.26 GeV; searches for the Xb state; (2) Y states including the updated results for the Y(4008), Y(4260), Y(4360), Y(4660), etc; (3) Z states including the observations of the Z(4430), Z1(4050), Z2(4250), Zc(3900), Zc(4020), Zc(4200); the evidence for the Zc(4050)± → π±ψ(2S ); search for the Zcs in e+e− → K+K−J/ψ.
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