J/psi plus prompt-photon associated production in two-photon collisions at next-to-leading order

TL;DR

The paper develops a complete next-to-leading-order NRQCD framework for exclusive $J/\psi$ production in two-photon collisions, focusing on direct photoproduction of $J/\psi$ in association with a prompt photon and including feed-down from heavier charmonia. It derives and renormalizes the relevant NRQCD operators, treats ultraviolet, infrared, and Coulomb singularities, and builds the finite NLO cross section by combining virtual and real corrections with phase-space slicing. Numerical results for a TESLA-like $e^+e^-$ collider show substantial negative NLO corrections to the direct channel, with significant scale dependence and a strong suppression at high $p_T$, while the direct channel remains dominant over resolved contributions. The work also outlines the need to incorporate NLO corrections to resolved photoproduction for a complete phenomenological prediction and for testing NRQCD factorization, potentially guiding future collider analyses.

Abstract

We calculate the cross section of J/psi plus prompt-photon inclusive production in gamma gamma collisions at next-to-leading order within the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD) focusing on direct photoproduction. Apart from direct J/psi production, we also include the feed-down from directly-produced chi_{cJ} and psi' mesons. We discuss the analytical calculation, in particular the treatment of the various types of singularities and the NRQCD operator renormalization, in some detail. We present theoretical predictions for the future e^+e^- linear collider TESLA, taking into account both brems- and beamstrahlung.

Figures (5)

• Figure 1: Tree-level diagrams pertinent to the partonic subprocess (\ref{['eq:ccy']}).
• Figure 2: One-loop (a) self-energy, (b) triangle, (c) box, and (d) pentagon diagrams pertinent to the partonic subprocess (\ref{['eq:ccy']}).
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