Too many $X^{\prime }s$, $Y^{\prime }s$ and $Z^{\prime }s$?

Abstract

A large number of new states have been reported during the last few years in charmonium spectroscopy above the charmed meson production threshold. They have been called $X^{\prime }s$, $Y^{\prime }s$, and $Z^{\prime }s$. We reflect on the influence of thresholds on heavy meson spectroscopy comparing different flavor sectors and quantum numbers. The validity of a quark-model picture above open-flavor thresholds would severely restrict the number of channels that may lodge meson-meson molecules.

8 pages, 5 figures

References in corpus (9)

• Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays
• Constituent quark model study of the meson spectra
• $Z_b(10610{)}^{\pm }$ and $Z_b(10650{)}^{\pm }$ as the $B^{\ast }\bar{B}$ and $B^{\ast }{\bar{B}}^{\ast }$ molecular states
• Multi-quark hadrons from Heavy Ion Collisions
• An explanation of Belle states Z_b(10610) and Z_b(10650)
• Stability of multiquarks in a simple string model
• Charmonium spectroscopy above thresholds
• Relation between $T_{cc,bb}$ and $X_{c,b}$ from QCD
• Production of four-quark states with double heavy quarks at LHC

Cited by in corpus (18)

• The hidden-charm pentaquark and tetraquark states
• Phenomenology of $P_c(4380{)}^{+}$, $P_c(4450{)}^{+}$ and related states
• String dynamics and metastability of fully-heavy tetraquarks
• Spectroscopy of all charm tetraquark states
• Triple-charm molecular states composed of $D^{\ast }{D}^{\ast }D$ and $D^{\ast }{D}^{\ast }{D}^{\ast }$
• Heavy hadron spectroscopy: a quark model perspective
• Experimental Review of Structures in the $J/\psi \varphi$ Mass Spectrum
• Unraveling the pattern of the $XYZ$ mesons
• The Polyakov loop in various representations in the confined phase of QCD
• $T_{bbb}$: a three $B-$meson bound state
• Width of a two-body coupled-channel resonance
• Multiquark contributions to charm baryon spectroscopy
• Hadronic resonances enhanced by thresholds
• The $D{\bar{D}}^{\ast }$ interaction with isospin zero in an extended hidden gauge symmetry approach
• Effect of thresholds on the width of three-body resonances
• Hidden and open heavy-flavor hadronic states
• On the proliferation of X's, Y's and Z's candidates
• On the Origin of the $XYZ$ Mesons