NLO QCD+EW predictions for $2\ell 2\nu$ diboson signatures at the LHC

Abstract

We present next-to-leading order (NLO) calculations including QCD and electroweak (EW) corrections for $2\ell 2\nu$ diboson signatures with two opposite-charge leptons and two neutrinos. Specifically, we study the processes $pp\to e^{+}{\mu }^{-}{\nu }_e{\bar{\nu }}_{\mu }$ and $pp\to e^{+}{e}^{-}\nu \bar{\nu }$, including all relevant off-shell diboson channels, $W^{+}{W}^{-}$, $ZZ$, $\gamma Z$, as well as non-resonant contributions. Photon-induced processes are computed at NLO EW, and we discuss subtle differences related to the definition and the renormalisation of the coupling $\alpha$ for processes with initial- and final-state photons. All calculations are performed within the automated Munich/Sherpa+OpenLoops frameworks, and we provide numerical predictions for the LHC at 13 TeV. The behaviour of the corrections is investigated with emphasis on the high-energy regime, where NLO EW effects can amount to tens of percent due to large Sudakov logarithms. The interplay between $WW$ and $ZZ$ contributions to the same-flavour channel, $pp\to e^{+}{e}^{-}\nu \bar{\nu }$, is discussed in detail, and a quantitative analysis of photon-induced contributions is presented. Finally, we consider approximations that account for all sources of large logarithms, at high and low energy, by combining virtual EW corrections with a YFS soft-photon resummation or a QED parton shower.

Comments: 25 pages + appendices, 22 figures