Charmonia in an unquenched quark model

TL;DR

This paper investigates the charmonium spectrum using an unquenched quark model with coupled-channel effects, successfully describing known states and predicting higher states with estimated mass shifts and widths.

Contribution

It introduces a coupled-channel unquenched quark model that accurately describes known charmonium states and predicts higher states with specific mass shifts and widths.

Findings

Good description of established charmonium masses and widths.

Predictions for higher charmonium states up to 5.0 GeV.

Mass shifts due to coupled-channel effects are about 10s MeV.

Abstract

In this work, we study the charmonium spectrum within an unquenched quark model including coupled-channel effects. In couple-channel calculations, we include all of the opened charmed meson channels with the once-subtracted method, meanwhile adopt a suppressed factor to soften the hard vertices given by the $^3P_0$ model in the high momentum region. We obtain a good description of both the masses and widths for the well-established states in the charmonium spectrum. Furthermore, we give predictions for the higher $S$-, $P$- and $D$-wave charmonium states up to mass region of $\sim 5.0$ GeV. The magnitude of mass shifts due to the coupled-channel effects is estimated to be about $10s$ MeV. Although many decay channels are opened for the higher charmonium states, they are relatively narrow states. Their widths scatter in the range of $\sim 10s-100$ MeV. Many charmonium-like states, such as $\chi_{c1}(3872)$, $\chi_{c1}(4274)$, $\chi_{c0}(3915)$, $\chi_{c0}(4500)$, $\chi_{c0}(4700)$, $X(4160)$, $X(4350)$, $Y(4500)$, and $\psi(4660)$/$Y(4710)$, can be accommodated by the charmonium spectrum when the unquenched coupled-channel effects are carefully considered.