Abstract
The exploration of energies above the open-flavor threshold in the meson spectra has led to the appearance of unexpected states difficult to accommodate in the naive picture of a bound state of a quark and an antiquark. Many of such states are located close to meson-meson thresholds, which suggests that molecular structures may be a relevant component in the total wave function of such resonances. In this work, the state of meson-meson molecules calculations is reviewed, using a nonrelativistic constituent quark model that has been applied to a wide range of hadronic observables, and therefore all model parameters are completely constrained. The model has been able to reproduce, among others, the properties of the X(3872), described as a mixture of cc and DD* states, or the spectrum of the P-wave charm-strange mesons, which are well reproduced only if DK and D*K structures are taken into account. We show that such constituent quark model, which is able to describe the ordinary heavy meson spectra, is also capable of providing a good description of many new states recently reported.
Highlights
Between November 1974, when the J/ψ particle was discovered, until 2003, when the X(3872) resonance was observed by the Belle Collaboration, the quarkonium spectrum was satisfactorily described by naive quark models
The exploration of energies above the open-flavor threshold has led to the appearance of unexpected states difficult to accommodate in the naive picture of a bound state of a quark and an antiquark
In this work we review the results of a widely-used Constituent Quark Model (CQM) [1,2,3], which satisfactorily describes the meson spectra involving one or two heavy quarks, incorporating the effects of closeby meson-meson thresholds in a non-perturbative way
Summary
Between November 1974, when the J/ψ particle was discovered, until 2003, when the X(3872) resonance was observed by the Belle Collaboration, the quarkonium spectrum was satisfactorily described by naive quark models. In this work we review the results of a widely-used Constituent Quark Model (CQM) [1,2,3], which satisfactorily describes the meson spectra involving one or two heavy quarks, incorporating the effects of closeby meson-meson thresholds in a non-perturbative way This extension allowed to describe the inner structure of states with difficult assignment in the heavy quarkonium QQand Qqspectrum 1. The aforementioned CQM model is able to describe the baryonic phenomenology [4,5,6] and, at the same time, some of the exotic states discovered in the baryon spectrum, such as the P∗c(4380) and P∗c(4450) pentaquarks as D Σ∗c and D ∗Σc molecules [7], the Λc(2940)+ as D∗N bound state [8] or the Xc(3250) one as a D∗∆ molecule [9] Details for such calculations are out of scope for this review and the reader is kindly referred to the previous studies for further information
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