$π^-p\toη^{(\prime)}\, π^- p$ in the double-Regge region

Abstract

The production of $η^{(\prime)}π$ pairs constitutes one of the golden channels to search for hybrid exotics, with explicit gluonic degrees of freedom. Understanding the dynamics and backgrounds associated to $η^{(\prime)}π$ production above the resonance region is required to impose additional constraints to the resonance extraction. We consider the reaction $π^-p\to η^{(\prime)} π^- \,p$ measured by COMPASS. We show that the data in $2.4 < m_{η^{(\prime)}π} < 3.0$ GeV can be described by amplitudes based on double-Regge exchanges. The angular distribution of the meson pairs, in particular in the $η' π$ channel, can be attributed to flavor singlet exchanges, suggesting the presence of a large gluon content that couples strongly to the produced mesons.

25 pages, 30 figures, 6 appendices. Version to appear in Eur. Phys. J. C