Threshold effects in heavy quarkonium spectroscopy

Abstract

In this contribution, we discuss the possible importance of continuum-coupling (or threshold) effects in heavy quarkonium spectroscopy. Our calculations are carried out in a coupled-channel model, where meson-meson higher Fock (or molecular-type) components are introduced in $Q\bar{Q}$ bare meson wave functions by means of a pair-creation mechanism. After providing a quick resume of the main characteristics of the coupled-channel model, we briefly discuss its application to the calculation of the masses of heavy quarkonium-like ${\chi }_{\mathrm{c}}(2P)$ and ${\chi }_{\mathrm{b}}(3P)$ states with threshold corrections. We show that the introduction of pair-creation effects in the Quark Model (QM) formalism makes it possible to explain the deviations of ${\chi }_{\mathrm{c}}(2P)$ states' masses from the experimental data, without affecting the good QM description of the properties of ${\chi }_{\mathrm{b}}(3P)$ states.

Comments: Proceedings of the Symposium "Symmetries and Order: Algebraic Methods in Many Body Systems" in honor of Professor Francesco Iachello on the occasion of his retirement, October 5-6 2018, Yale University