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.

arXiv comment8 pages, 5 figures

References in corpus (22)

• Observation of a New Narrow Charmonium State in Exclusive B+-->K+ pi+pi- J/psi Decays
• Observation of a narrow charmonium-like state in exclusive B+ -> K+ pi+pi- J/psi decays
• Observation of the Narrow State $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}$ in $\bar{p}p$ Collisions at $\sqrt{s}=1.96 \TeV$
• Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays
• Observation and Properties of the X(3872) Decaying to J/psi pi+ pi- in p-p(bar) Collisions at sqrt(s) = 1.96 TeV
• Study of the B- --> J/psi K- pi+ pi- Decay and Measurement of the B- --> X(3872) K- Branching Fraction
• Constituent quark model study of the meson spectra
• Observation of two resonance-like structures in the pi+ chi_c1 mass distribution in exclusive B0-bar --> K- pi+ chi_c1 decays
• Evidence for the decay X(3872) --> J/psi omega
• $Z_b(10610{)}^{\pm }$ and $Z_b(10650{)}^{\pm }$ as the $B^{\ast }\bar{B}$ and $B^{\ast }{\bar{B}}^{\ast }$ molecular states
• Search for the Z(4430)^- at BABAR
• Multi-quark hadrons from Heavy Ion Collisions
• An explanation of Belle states Z_b(10610) and Z_b(10650)
• Observation of the chi_c2(2P) meson in the reaction gamma gamma -> D Dbar at BABAR
• Stability of multiquarks in a simple string model
• Charmonium spectroscopy above thresholds
• Relation between $T_{cc,bb}$ and $X_{c,b}$ from QCD
• Probabilities in nonorthogonal basis: Four--quark systems
• The End of the Constituent Quark Model?
• Beyond the Adiabatic Approximation: the impact of thresholds on the hadronic spectrum
• Production of four-quark states with double heavy quarks at LHC
• The covalent bond in Particle Spectroscopy

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