Gluonic excitations of mesons: Why they are missing and where to find them

Abstract

We have studied the decays of the low-lying gluonic excitations of mesons (hybrids) predicted by a flux-tube model for chromodynamics. The probable reason for the absence to date of signals for such states is immediately explained: The lowest-lying hybrids decay preferentially to final states with one excited meson [e.g., B(1235)π, ${\mathrm{A}}_2$(1320)π, ${\mathrm{K}}^{\mathrm{*}}$(1420)K¯, π(1300)pi,. . .] rather than to two ground-state mesons (e.g., ππ, ρπ, ${\mathrm{K}}^{\mathrm{*}}$K¯,. . .). We make specific predictions of decay channels which will contain ${\mathrm{J}}^{\mathrm{PC}}$ exotic hybrid resonance signals and suggest some possibly fruitful production mechanisms.