The XYZ mesons: what they aren't

I discuss the properties of some representative $XYZ$ mesons in the context of the most commonly proposed models for their underlying nature.Comment: 8 pages, 6 figures, write-up of talks given at Charm2018 in Novosibirsk, May 2018 and New Physics in the Flavor Sector Workshop in Nagoya, November 2018. To appear in the Charm2018 proceeding

Recent Results from BaBar, Belle, BESIII and CDF

A brief report of some recent experimental developments concerning the $X$, $Y$ and $Z$ charmoniumlike mesons states and other puzzling states from the BaBar, Belle, BESIII and CDF experiments is presented.Comment: 7 pages, 13 figures, write-up of a plenary talk on XYZ mesons etc at Quark Confinement & Hadron Spectrum IX, Aug 30 - Sept 3, 2010, Madri

A New Hadron Spectroscopy

QCD-motivated models for hadrons predict an assortment of "exotic" hadrons that have structures that are more complex than the quark-antiquark mesons and three-quark baryons of the original quark-parton model. These include pentaquark baryons, the six-quark H-dibaryon, and tetraquark, hybrid and glueball mesons. Despite extensive experimental searches, no unambiguous candidates for any of these exotic configurations have been identified. On the other hand, a number of meson states, one that seems to be a proton-antiproton bound state, and others that contain either charmed-anticharmed quark pairs or bottom-antibottom quark pairs, have been recently discovered that neither fit into the quark-antiquark meson picture nor match the expected properties of the QCD-inspired exotics. Here I briefly review results from a recent search for the H-dibaryon, and discuss some properties of the newly discovered states --the proton-antiproton state and the so-called XYZ mesons-- and compare them with expectations for conventional quark-antiquark mesons and the predicted QCD-exotic states.Comment: 34 pages, 22 figures, a review article that will appear in Frontiers of Physic

Comment on the X(3915) nonstandard hadron candidate

I review the experimental evidence for the $X(3915)$, the candidate nonstandard meson associated with $\omega J\psi$ resonance-like peaks in $B\rightarrow K\omega J\psi$ and $\gamma\gamma\rightarrow\omega J\psi$ near $M(\omega J\psi)=3920$~MeV, and address the conjecture that it can be identified as the $\chi_{c2}^\prime$, the radial excitation of the $\chi_{c2}$ charmonium state. Since the partial decay width for $B\rightarrow K X(3915)$ is at least an order-of-magnitude larger than that for $B\rightarrow K\chi_{c2}$, its assignment as the $\chi_{c2}^\prime$ is dubious.Comment: 6 page, 5 figures, to appear in the proceedings of "e+e- Collisions From Phi to Psi 2019," Novosibirsk, February 201