A new approach to modelling elastic and inelastic photon-initiated production at the LHC: SuperChic 4

TL;DR

This paper introduces SuperChic 4, a Monte Carlo tool for photon-initiated production at the LHC, accurately modeling various dissociation channels and rapidity gap effects, validated against ATLAS data.

Contribution

SuperChic 4 provides a comprehensive Monte Carlo implementation for photon-initiated processes, including dissociation and rapidity gap effects, with detailed validation and background estimation.

Findings

Good agreement with ATLAS 7 TeV data

Accurate modeling of dissociation channels and rapidity gaps

Low background from semi-exclusive lepton pair production for SUSY searches

Abstract

We present the results of the new SuperChic 4 Monte Carlo implementation of photon-initiated production in proton-proton collisions, considering as a first example the case of lepton pair production. This is based on the structure function calculation of the underlying process, and focusses on a complete account of the various contributing channels, including the case where a rapidity gap veto is imposed. We provide a careful treatment of the contributions where either (single dissociation), both (double dissociation) or neither (elastic) proton interacts inelastically and dissociates, and interface our results to Pythia for showering and hadronization. The particle decay distribution from dissociation system, as well the survival probability for no additional proton-proton interactions, are both fully accounted for; these are essential for comparing to data where a rapidity gap veto is applied. We present detailed results for the impact of the veto requirement on the differential cross section, compare to and find good agreement with ATLAS 7 TeV data on semi-exclusive production, and provide a new precise evaluation of the background from semi-exclusive lepton pair production to SUSY particle production in compressed mass scenarios, which is found to be low.