Hybrid phenomenology in a chiral approach

Abstract

We calculate masses and decays of the (lightest) hybrid nonet with exotic quantum numbers $J^{PC}=1^{-+}$ and the nonet of their chiral partners with $J^{PC}=1^{+-}$ in the framework of the extended Linear Sigma Model (eLSM). As an input, we identify $\pi_{1}^{hyb}=\pi_{1}(1600)$ as a low-lying hybrid. We investigated interaction terms which fulfil chiral symmetry. For what concerns $\pi_{1}^{hyb},$ the most important decays are $\pi_{1}^{hyb}\rightarrow b_{1}\pi,$ $\pi_{1}(1600)\rightarrow\rho\pi\eta,$ $\pi_{1}^{hyb}% \rightarrow\rho\pi,$ and $\pi_{1}^{hyb}\rightarrow KK^{\ast}(892).$ The decays $\pi_{1}^{hyb}\rightarrow\eta\pi$ and $\pi_{1}^{hyb}\rightarrow\eta^{\prime }\pi$ are expected to be small but non-zero: they follow from a chirally symmetric interaction term that breaks explicitly the axial anomaly. For all the other members of the two hybrid nonets (for which no experimental candidates exist yet) we report decay ratios that may guide ongoing and future experiments.