Abstract
We present results of the first calculation of next-to-leading-order electroweak corrections to W-boson pair production at the LHC that fully takes into account leptonic W-boson decays and off-shell effects. Employing realistic event selections, we discuss the corrections in situations that are typical for the study of W-boson pairs as a signal process or of Higgs-boson decays $H\to W W^*$, to which W-boson pair production represents an irreducible background. In particular, we compare the full off-shell results, obtained treating the W-boson resonances in the complex-mass scheme, to previous results in the so-called double-pole approximation, which is based on an expansion of the loop amplitudes about the W resonance poles. At small and intermediate scales, i.e. in particular in angular and rapidity distributions, the two approaches show the expected agreement at the level of fractions of a percent, but larger differences appear in the TeV range. For transverse-momentum distributions, the differences can even exceed the 10% level in the TeV range where "background diagrams" with one instead of two resonant W bosons gain in importance because of recoil effects.
Highlights
For invariant masses below the W-pair production threshold, where at least one of the W bosons is off its mass shell
We present results of the first calculation of next-to-leading-order electroweak corrections to W-boson pair production at the LHC that fully takes into account leptonic W-boson decays and off-shell effects
The above-mentioned phenomenological issues call for theoretical predictions for Wpair production at the LHC at the highest possible precision, which carefully take into account decay and off-shell effects of the W bosons including fully differential kinematics and phase-space regions below the W-pair threshold
Summary
2.1 Full off-shell calculation We consider the proton-proton collision process pp → νμμ+e−νe + X,. NLO EW corrections, i.e. corrections of O(α) with respect to LO, comprise purely EW virtual one-loop diagrams and real corrections with one additional external photon. We base our calculation on the full LO results including all partonic channels of eq (2.2) and on NLO corrections comprising all virtual EW and real-photonic bremsstrahlung contributions to the antiquark-quark annihilation channels as well as all the qγ contributions of eq (2.4). The recombination of leptons and collinear photons is necessary for a realistic treatment of electrons which are detected as showers in the electromagnetic calorimeter In this case, the mass-singular corrections are mitigated to corrections that are logarithmically sensitive to the resolution parameter of the recombination cone. We emphasize that the complexmass scheme maintains NLO precision everywhere in phase space, i.e. in regions with any number of resonant or non-resonant W bosons
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