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

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

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