Eur. Phys. J. C (2011) 71: 1545
https://doi.org/10.1140/epjc/s10052-011-1545-1

Regular Article - Theoretical Physics

Central exclusive quarkonium production with tagged forward protons at RHIC

¹ Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge, CB3 0HE, UK
² Department of Physics and Institute for Particle Physics Phenomenology, University of Durham, Durham, DH1 3LE, UK
³ School of Physics & Astronomy, University of Manchester, Manchester, M13 9PL, UK
⁴ Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg, 188300, Russia

^* e-mail: lh367@cam.ac.uk

Received: 3 November 2010
Revised: 19 December 2010
Published online: 8 February 2011

Abstract

We study the Central Exclusive Production (CEP) of χ _cJ and η _c mesons at RHIC in proton–proton collisions. We consider the χ _cJ →J/ψ + γ decay channels and, recalling that the J _z =0 suppression of the J=1,2 states can be compensated by their larger branchings to J/ψ + γ, present predictions of rates and distributions for χ _c(0,1,2) production. Particular attention is paid to the impact of p _⊥ cuts applied to the outgoing protons, which can influence the relative rates significantly. The distribution in the azimuthal angle difference between the outgoing protons and the proton is also studied, and shown to depend sensitively on the spin and parity of the centrally produced meson, as well as being affected by the soft-survival factors, S ². Two- and four-body decays, which are particularly relevant for χ _c0 production, are also considered. We show that in the two-body case, backgrounds from ‘direct’ QCD production based on both perturbative and non-perturbative models are expected to be under control.