Experimental Status of Conventional Charmonium Spectroscopy

Xiongfei Wang,A Bondar,S Eidelman

doi:10.1051/epjconf/201920202002

Abstract

Based on data samples taken by the BESIII, Belle, KEDR and LHCb experiments, many measurements on conventional charmonium spectroscopy were finished in the past years. Some of recent results, such as precise measurements of J/ψ and ψ(2S ) masses, the J/ψ decay width, the J/ψ and ψ(2S ) electronic widths, two-photon width of χc0,2 meson, the χc1,2 resonance parameters with the decays χc0,2 → J/ψµ+µ−, the ηc resonance parameters and observations of X(3823) and X*(3860), were reported.

Highlights

After the discovery of J/ψ, Appelquist and Politer [1] proposed that if there existed a heavy charm quark, it should form a nonrelativistic bound state of charmed quark and anticharm quark with a similar spectrum of energy levels to the positronium, which was called charmonium taking into account beautifying the language
Many new charmonium states ηc(1S ), χcJ, ψ(2S ), ψ(3773), ψ(4040), ψ(4260), ψ(4360), ψ(4415), ψ(4660), etc., produced from e+e− annihilation via a virtual photon one after another were found [2], in which ψ(4260), ψ(4360) ψ(4660), were originally thought to be charmonium states, but some of current evidences and theoretical predictions suggested more exotic explanations, such as a tetraquark state, a molecule or a hybird meson [3]. Other states, such as ηc(1S ), χcJ, J/ψ, ψ(2S ), ψ(3773), ψ(4040), ψ(4160), ψ(4415), etc., were thought to be pure charmonium states, it is sometimes called conventional charmonium state (CCS) because for these CCS, the observations of their spectroscopies are basically consistent with the predictions from potential models and lattice quantum chromodynamics (QCD) [4]
The detector is a magnetic spectrometer and its cylindrical core consists of a helium-based multilayer drift chamber (MDC), a plastic scintillator time-of-flight system (TOF), and a CsI(Tl) electromagnetic calorimeter (EMC), which are all enclosed in a superconducting solenoidal magnet (SSM) providing a 1.0 T (0.9 T in 2012) magnetic field

Summary

Introduction

After the discovery of J/ψ, Appelquist and Politer [1] proposed that if there existed a heavy charm quark, it should form a nonrelativistic bound state of charmed quark and anticharm quark (cc) with a similar spectrum of energy levels to the positronium, which was called charmonium taking into account beautifying the language. The first member, J/ψ meson with hidden charm, which was quickly identified as the 13S 1 state of charmonium. Many new charmonium states ηc(1S ), χcJ, ψ(2S ), ψ(3773), ψ(4040), ψ(4260), ψ(4360), ψ(4415), ψ(4660), etc., produced from e+e− annihilation via a virtual photon one after another were found [2], in which ψ(4260), ψ(4360) ψ(4660), were originally thought to be charmonium states, but some of current evidences and theoretical predictions suggested more exotic explanations, such as a tetraquark state, a molecule or a hybird meson [3]. Other states, such as ηc(1S ), χcJ, J/ψ, ψ(2S ), ψ(3773), ψ(4040), ψ(4160), ψ(4415), etc., were thought to be pure charmonium states, it is sometimes called conventional charmonium state (CCS) because for these CCS, the observations of their spectroscopies are basically consistent with the predictions from potential models and lattice quantum chromodynamics (QCD) [4]

Experimental apparatus

Summary