https://doi.org/10.1140/epja/s10050-022-00880-x
Regular Article - Theoretical Physics
Charmonium spectrum in an unquenched quark model
1
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
Received:
13
May
2022
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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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2022. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
