Rapidity gap survival factors caused by remnant fragmentation for $W^+ W^-$ pair production via $\gamma^*\gamma^* \to W^+ W^-$ subprocess with photon transverse momenta

TL;DR

This paper calculates the cross section for W+W- pair production in proton-proton collisions considering photon transverse momenta, focusing on remnant fragmentation effects on rapidity gap survival factors using a $k_T$-factorisation approach.

Contribution

It introduces a detailed calculation of gap survival factors due to remnant fragmentation in W+W- production, including proton dissociation and hadronisation effects with PYTHIA 8.

Findings

Gap survival factors vary with process and remnant mass.

Double dissociative processes have smaller gap survival factors than single dissociative.

Approximate factorisation $S_{R,DD} oughly (S_{R,SD})^2$ observed.

Abstract

We calculate the cross section for $p p \to W^{+} W^-$ in the recently developed $k_{\rm T}$-factorisation approach, including transverse momenta of the virtual photons. We focus on processes with single and double proton dissociation. First we discuss the gap survival on the parton level as due to the emission of extra jet. Both the role of valence and sea contributions is discussed. The hadronisation of proton remnants is performed with {PYTHIA 8} string fragmentation model, assuming a simple quark-diquark model for proton. Highly excited remnant systems hadronise producing particles that can be vetoed in the calorimeter. We calculate associated effective gap survival factors. The gap survival factors depend on the process, mass of the remnant system and collision energy. The rapidity gap survival factor due to remnant fragmentation for double dissociative (DD) collisions ($S_{R,DD}$) is smaller than that for single dissociative (SD) process ($S_{R,SD}$). We observe the approximate factorisation $S_{R,DD} \approx (S_{R,SD})^2$, however it is expected that this property will be violated by soft rescattering effects not accounted for in this letter.