Production of $t\bar t$ pairs via $\gamma\gamma$ fusion with photon transverse momenta and proton dissociation

TL;DR

This paper investigates the production of top quark pairs via photon-photon fusion in proton-proton collisions, considering various proton dissociation scenarios and using the $k_T$-factorisation approach to include photon transverse momenta.

Contribution

It provides a detailed calculation of $t\bar t$ production cross sections and distributions, incorporating inelastic processes with modern proton structure functions, which is a novel comprehensive analysis.

Findings

Total cross section ~2.36 fb at 13 TeV

Elastic contribution is smallest among processes

Inelastic contributions decrease with jet veto

Abstract

We discuss the production of $t\bar t$ quark-antiquark pairs in proton-proton collisions via the $\gamma\gamma$ fusion mechanism. We include topologies in which both protons stay intact or one or even both of them undergo dissociation. The calculations are performed within the $k_{\rm T}$-factorisation approach, including transverse momenta of intermediate photons. Photon fluxes associated to inelastic (dissociative) processes are calculated based on modern parameterisations of proton structure functions. We find an integrated cross section of about 2.36 fb at $\sqrt{s}=$ 13 TeV for all contributions. The cross section for the fully elastic process is the smallest. Inelastic contributions are significantly reduced when a veto on outgoing jets is imposed. We present several differential distributions in rapidity and transverse momenta of single $t$ or $\bar t$ quarks/antiquarks as well as distributions in invariant mass of both the $t\bar t$ and masses of dissociated systems. A few two-dimensional distributions are presented in addition.