Coupled-Channel and Screening Effects in Charmonium Spectrum

TL;DR

This study compares coupled-channel and screened potential models to predict the charmonium spectrum below 4 GeV, finding similar results and supporting their use for higher energies and understanding exotic mesons like X(3872).

Contribution

It demonstrates the equivalence of coupled-channel and screened potential models in describing charmonium spectra and applies this to interpret the X(3872) as a $ ext{χ}_{c1}(2P)$ state.

Findings

Models show similar global features in charmonium spectrum.

Screened potential model is promising for higher energy predictions.

S-wave decay coupling lowers $ ext{χ}_{c1}(2P)$ mass near $Dar{D}^*$ threshold.

Abstract

Using the same quenched limit as input, we compare the charmonium spectra predicted by the coupled-channel model and the screened potential model in the mass region below 4 GeV, in which the contributions from decay channels involving P-wave (as well as even higher excited) D mesons can be neglected. We find that the two models have similar global features in describing charmonium spectrum since they embody the same effect of the vacuum polarization of dynamical light quark pairs. This agreement is encouraging for using the screened potential to further describe the mass spectrum of higher charmonium in the region above 4 GeV. Applying both models will be helpful to clarify the nature of the newly discovered "X,Y,Z" mesons in B-factories and other experiments. In particular, we show the S-wave decay coupling effect on lowering the $\chi_{c1}(2P)$ mass towards the $D\bar {D^*}$ threshold, in support of the assignment of the X(3872) as a $\chi_{c1}(2P)$-dominated charmonium state.