Exclusive heavy vector meson production at next-to-leading order in the dipole picture

Heikki Mäntysaari,Jani Penttala

doi:10.1016/j.physletb.2021.136723

Heikki Mäntysaari, Jani Penttala

Open Access

https://doi.org/10.1016/j.physletb.2021.136723

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Abstract

We calculate exclusive production of a longitudinally polarized heavy vector meson at next-to-leading order in the dipole picture. The large quark mass allows us to separately include both the first QCD correction proportional to the coupling constant αs, and the first relativistic correction suppressed by the quark velocity v2. Both of these corrections are found to be numerically important in J/ψ production. The results obtained are directly suitable for phenomenological calculations. We also demonstrate how vector meson production provides complementary information to structure function analyses when one extracts the initial condition for the energy evolution of the proton small-x structure.

Highlights

Deep inelastic scattering (DIS) processes enable precision studies of proton and nuclear structure thanks to the pointlike structure of the electron probe
In this Letter we present the first calculation of the exclusive heavy vector meson production at next-to-leading order (NLO) in photon-proton collisions
The total NLO amplitude is shown in Eq (7), and should be compared to the leadingorder result including the small-x BK evolution defined in Eq (10) and denoted by LO(Ydip) in the figures

Summary

INTRODUCTION

Deep inelastic scattering (DIS) processes enable precision studies of proton and nuclear structure thanks to the pointlike structure of the electron probe. A subset of higher-order corrections to the evolution equation is included in terms of the running coupling corrections [20, 21] These applications include, for example, a successful description of the structure function [22, 23] and vector meson production data [24,25,26,27,28,29,30,31,32,33] measured at HERA [34,35,36] and in Ultra Peripheral collisions [17, 37] at the LHC [38,39,40,41,42]. We focus on J/ψ production, in which case both contributions can be expected to be parametrically important as for the charm quark velocity one can estimate v2 ∼ αs [65] These developments are crucial to enable precision studies of nonlinear dynamics in exclusive scattering processes in the CGC framework. In this work we consider the case where the photon is longitudinally polarized, but note that it will be possible to extend the identity, the operator for the qqg-target scattering can results to the transverse photon case in the future

EXCLUSIVE SCATTERING AT HIGH

NUMERICAL RESULTS

CONCLUSIONS

Longitudinal photon wave function

Vector meson wave function

Exclusive vector meson production cross section at next-to-leading order