Non-conventional mesons at PANDA

Non-conventional mesons, such as glueballs and tetraquarks, will be in the focus of the PANDA experiment at the FAIR facility. In this lecture we recall the basic properties of QCD and describe some features of unconventional states.\ We focus on the search of the not-yet discovered glueballs and the use of the extended Linear Sigma Model for this purpose, and on the already discovered but not-yet understood $X,Y,Z$ states.Comment: 5 pages. Lecture prepared for FAIRNESS 2014 (3rd International Workshop for young scientists with research interests focused on physics at FAIR), 22-27/9/2014. Contribution to appear in the workshop proceeding

Chiral anomaly and strange-nonstrange mixing

As a first step, a simple and pedagogical recall of the $\eta$-$\eta'$ system is presented, in which the role of the axial anomaly, related to the heterochiral nature of the multiplet of (pseudo)scalar states, is underlined. As a consequence, $\eta$ is close to the octet and $\eta'$ to the singlet configuration. On the contrary, for vector and tensor states, which belong to homochiral multiplets, no anomalous contribution to masses and mixing is present. Then, the isoscalar physical states are to a very good approximation nonstrange and strange, respectively. Finally, for pseudotensor states, which are part of an heterochiral multiplet (just as pseudoscalar ones), a sizable anomalous term is expected: $\eta_2 (1645)$ roughly corresponds to the octet and $\eta_2 (1870)$ to the singlet.Comment: 4 pages. Prepared for the proceedings of MESON 2018, 15th International Workshop on Meson Physics, KRAK\'OW, POLAND, 7th - 12th June 201

Revisiting the axial anomaly for light mesons and baryons

The axial anomaly is responsible for the masses and mixing of the mesons $\eta$ and $\eta'$. An open question is if (and to what extent) it affects also other hadrons. We show that anomalous terms can be important to understand the spectroscopy of the pseudotensor mesons $\eta_2 (1645)$ and $\eta_2 (1870)$. In fact, pseudotensor mesons belong to a so-called heterochiral multiplet, for which a quadratic mixing term between nonstrange and strange isoscalar members arises. On the contrary, for so-called homochiral multiplets, such as the ground-state (axial-)vector and tensor mesons, this mixing is not possible, hence one can easily understand why the isoscalar members of these multiplets are almost purely nonstrange and strange, respectively. Moreover, the axial anomaly can be also coupled to baryons (within the mirror assignment), and thus it helps to explain the large decay width $N^{\ast }(1535)\rightarrow N\eta$ and to clarify which baryons are chiral partners.Comment: 6 pages. Prepared for the proceedings of the XVII International Conference on Hadron Spectroscopy and Structure - Hadron2017, 25-29 September, 2017, University of Salamanca, Salamanca, Spai

f_{2}(1270), a_{1}(1260)and and f_{0}(1370)$ as dynamically reconstructed quark-antiquark states

It is explained why the interpretation of the resonances $f_{2}(1270),$ $a_{1}(1260)$ and $f_{0}(1370)$ as quark-antiquark states is legitimate. The result of the quark model and of recently performed Bethe-Salpeter studies are not (necessarily) in conflict and can be understood as two different approaches toward the description of the same quark-antiquark resonances.Comment: 8 pages, 2 figures. Based on the contribution given at the Chiral10 Workshop, Valencia (Spain), June 21-24, 201