Abstract
We consider the transverse-momentum (pT) distribution of Zγ pairs produced in hadronic collisions. Logarithmically enhanced contributions at small pT are resummed to all orders in QCD perturbation theory and combined with the fixed-order prediction. We achieve the most advanced prediction for the ZγpT spectrum by matching next-to-next-to-next-to-leading logarithmic (N3LL) resummation to the integrated cross section at next-to-next-to-leading order (NNLO). By considering ℓ+ℓ−γ production at the fully differential level, including spin correlations, interferences and off-shell effects, arbitrary cuts can be applied to the leptons and the photon. We present results at the LHC in presence of fiducial cuts and find agreement with the 13TeV ATLAS data at the few-percent level.
Highlights
Enhanced contributions at small pT are resummed to all orders in QCD perturbation theory and combined with the fixed-order prediction
In the upper frame of panel (b) and (d) we show the difference of the next-to-next-to-leading order (NNLO) cross section and NNLO expansion of the N3LL cross section at the cumulative level
Looking at the scale uncertainties, we observe a substantial reduction in the size of the respective bands when moving from next-to-leading order (NLO)+next-to-leading logarithmic (NLL) to NNLO+N3LL: At large pT, γ they decrease by roughly a factor of tiplicative matching is numerically more stable at small transverse momenta, and, more importantly, it includes the constant contributions in pT through the matching when those are not available in the resummation component, cf
Summary
Enhanced contributions at small pT are resummed to all orders in QCD perturbation theory and combined with the fixed-order prediction. Z γ pT spectrum by matching next-to-next-to-next-to-leading logarithmic (N3LL) resummation to the integrated cross section at next-to-next-to-leading order (NNLO).
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