Abstract
Radiative decays of are studied in single-channel approximation (SCA) and in the coupled-channel (CC) approach, where the decay channels are described with the string-breaking mechanism. In SCA the transition rate and large are obtained, giving for their ratio the value . In the CC approach, three factors are shown to be equally important: First, the admixture of the component in the normalized wave function of due to the CC effects. Its weight is calculated. Second, the use of the multipole function instead of in the overlap integrals, determining the partial widths. Third, the choice of the gluon-exchange interaction for , as well as for other states above threshold. If for the gluon-exchange potential is taken to be the same as for low-lying charmonium states, then in the CC approach is very small, giving the large ratio . Arguments are presented why the gluon-exchange interaction may be suppressed for and in this case , , and are predicted for the minimal value , while for the maximal value we obtain , , and , which agrees with the LHCb data.
- Received 6 January 2015
DOI:https://doi.org/10.1103/PhysRevD.91.056001
© 2015 American Physical Society