EPJ Web of Conferences 113, 01016 (2016)
https://doi.org/10.1051/epjconf/201611301016

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

^a e-mail: shencp@buaa.edu.cn

Published online: 11 July 2016

Abstract

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 X_b 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), Z_c(3900), Z_c(4020), Z_c(4200); the evidence for the Z_c(4050)^± → π^±ψ(2S ); search for the Z_cs in e⁺e⁻ → K⁺K⁻J/ψ.