Molecular effects in Charmonium Spectrum

TL;DR

This paper investigates how molecular structures influence the charmonium spectrum, identifying potential molecular states and explaining experimental decay ratios through coupled-channel calculations involving charmonium and meson-meson interactions.

Contribution

It introduces a coupled-channel approach to identify molecular states in the charmonium spectrum and explains experimental decay ratios, including the G(3900) and Y(4008) states.

Findings

Identified molecular states compatible with X(3945) and Y(3940).

Predicted a new molecular state possibly corresponding to G(3900) or Y(4008).

Reconciled decay branching ratios of $ ext{BABAR}$ measurements.

Abstract

We study the influence of possible molecular structures in the charmonium spectrum. We focus on the $0^{++}$ and $1^{--}$ sectors. In the first one we coupled the $2 ^3P_0$ $q\bar q$ pair with $DD$, $J/\psi \omega$, $D_sD_s$ and $J/\psi\phi$ channels and we obtain two states compatibles with the X(3945) and the Y(3940). In the second one we include the $3^3S_1$ and $2^3D_1$ charmonium states coupled to $DD$, $DD^*$, $D^*D^*$, $D_sD_s$, $D_sD_s^*$ and $D_s^*D_s^*$. In this calculation we obtain a new molecular state that could be the G(3900) or the controversial Y(4008) and two $c\bar c$ states dressed by the molecular components assigned to the $\psi(4040)$ and the $\psi(4160)$. The two $c\bar c$ states show interesting properties and in particular they solve the strong disagreement of the decay branching ratios measured by BABAR.