Diffractiveηcandηbproductions by neutrinos via neutral currents

Abstract

We report on a first theoretical study for neutrino-induced diffractive production of heavy pseudoscalar mesons ${\ensuremath{\eta}}_{c}$ and ${\ensuremath{\eta}}_{b}$ off a nucleon. Based on the factorization formalism for exclusive processes, we evaluate the forward diffractive production cross section in perturbative QCD in terms of the light-cone $Q\overline{Q}$ wave functions (WFs) of ${\ensuremath{\eta}}_{c,b}$ mesons and the gluon distribution of the nucleon. The light-cone WFs of the ${\ensuremath{\eta}}_{c}({\ensuremath{\eta}}_{b})$ meson are constructed to satisfy the spin symmetry relations with those of the $J/\ensuremath{\psi}(\ensuremath{\Upsilon})$ meson. The diffractive ${\ensuremath{\eta}}_{c}$ production is governed by the axial-vector coupling of the longitudinally polarized Z boson to a $Q\overline{Q}$ pair, and the resulting ${\ensuremath{\eta}}_{c}$ production rate is larger than that for the $J/\ensuremath{\psi}$ by one order of magnitude. We also discuss the production of bottomonium ${\ensuremath{\eta}}_{b},$ which shows up for a higher beam energy.