Charmonia in an unquenched quark model

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 ${}^3{P}_0$ 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.

Comments: 24 pages, 3 figures, 15 tables