Coupled Channels Effects on Hybrid Meson States
Coupled Channels Effects on Hybrid Meson States
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Date
2008-11-26
Auteurs
DALILE Ahmed
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Résumé
Theoretical investigations have unquestionably confirmed that the effects of coupled channels, corresponding to virtual two-meson decays, are unexpectedly large on the standard mesons spectrum. The masses of resonances, estimated including the coupling to hadronic channels, are considerably shifted with respect to the bare masses calculated treating mesons as stable qq bound states. Models that incorporate these effects are able to achieve satisfactory results in comparison with experiment, overcoming many inconsistencies with standard mesonic states that the naïve quark model appears to have difficulties in reproducing them, especially the light scalars which are experimentally well established, but their classification in terms of quasi-bound systems of quark and antiquark is still far from agreed upon. In this work, we explore these effects on the hybrid mesons masses, as being corrections to the hybrid spectrum obtained from the Quark-Gluon Constituent Model. The system describing a QGC-hybrid meson and the dominant OZI-allowed combinations of two-meson decay channels that have the correct quantum numbers are treated on an equal footing. The exploration is performed using two coupled channels approaches.The first one is based on studying the formation of an s-channel hybrid meson resonance in meson-meson scattering. The problem is modelled by a set of coupled Schrodinger equations where transitions between the hybrid system and the two-meson systems are governed by effective potentials suggested by Swanson and Barnes. We solve the coupled system numerically using the Noumerov technique, then; we apply it to study light hybrid mesons formation in s?wave b-1n° scattering. The second approach we use is to study mesonic thresholds contributions in the hybrid states. This approach is inspired by an earlier work of Cornell group that was elaborated to study charmonium spectroscopy. We adapt it to accommodate the case of hybrid meson. The model was applied to hybrid mesons with Jpc=1-+since several hybrid candidates have been identified with those exotic quantum numbers. We also investigate the possibility of the recently observed Y(4260) having Jpc=1--to be a ccg hybrid meson.
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Hybrid mesons, Coupled channels, QGC Model, Mesonic loops