Modeling W+W- production with rapidity gaps at the LHC

We present a new calculation of W+W- production in the semiexclusive channel, that is either with intact outgoing protons or rapidity gaps present in the final state, and with no color flow between the colliding protons. This study provides the first complete prediction of the W+W- semiexclusive cross section, as well as the breakdown between elastic and proton dissociative channels. It combines the structure function calculation for a precise modeling of the region of low momentum transfers with a parton-level calculation in the region of high momentum transfers; in the latter case the impact of additional diagrams that are not purely photon-initiated has been appropriately evaluated for the first time. The survival factor probability of no additional proton-proton interactions has for the first time been fully accounted for, including its kinematic and process dependence. We analyze in detail the role that the pure photon-initiated (gamma gamma -> W+W-) subprocess plays, a comparison that is only viable by working in the electroweak axial gauge. In this way, we find that the dominance of this is not complete in the proton dissociative cases, although once Z-initiated production is included a significantly better matching to the complete calculation is achieved. A direct consequence of this is that the relative elastic, single and double dissociative fractions are in general different in comparison to the case of lepton pair production. We present a direct comparison to the recent ATLAS data on semiexclusive W+W- production, finding excellent agreement within uncertainties. Our calculation is provided in the publicly available SuperChic 4.1 Monte Carlo (MC) generator, and can be passed to a general purpose MC for showering and hadronization of the final state.

Automated summary

This study provides a complete prediction of the W+W- semiexclusive cross section, and provides a breakdown between elastic and proton dissociative channels. The study combines structure function calculation and a parton-level calculation, evaluating the impact of additional diagrams that are not purely photon-initiated for the first time. The study also fully accounts for the survival factor probability of no additional proton-proton interactions.