Regular Article - Theoretical Physics
Charmonium spectrum in an unquenched quark model
Centre For High Energy Physics, University of the Punjab, 54590, Lahore, Pakistan
2 Department of Physics and Astronomy, University of Pittsburgh, PA, 15260, Pittsburgh, USA
Accepted: 1 November 2022
Published online: 14 November 2022
The effects of virtual light quark pairs on the charmonium spectrum are studied. Pair creation is modelled with a “” vertex and intermediate states are summed up to 2S excitations. Quark model parameters are obtained by fitting to 12 well-known charmonium states, allowing for feedback between the decaying particle and the induced mass shifts. Both of these technical steps are new and improve agreement with the experimental spectrum. In general, the masses receive small shifts once model parameters are refit. This is true in almost cases except the multiplet, which experiences upwards mass shifts of order 150 MeV, has the ordering of the multiplet rearranged, and pushes the erstwhile state well above threshold–observations that clarify the nature of the enigmatic X(3872).
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