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)\ensuremath{\pi}, ${\mathrm{A}}_{2}$(1320)\ensuremath{\pi}, ${\mathrm{K}}^{\mathrm{*}}$(1420)K\ifmmode\bar\else\textasciimacron\fi{}, \ensuremath{\pi}(1300)pi,. . .] rather than to two ground-state mesons (e.g., \ensuremath{\pi}\ensuremath{\pi}, \ensuremath{\rho}\ensuremath{\pi}, ${\mathrm{K}}^{\mathrm{*}}$K\ifmmode\bar\else\textasciimacron\fi{},. . .). 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.