The Z\gamma{} transverse-momentum spectrum at NNLO+N3LL

TL;DR

This paper provides the most precise theoretical prediction for the Zγ transverse-momentum spectrum at the LHC by combining advanced resummation techniques with fixed-order calculations, matching NNLO and N3LL accuracy.

Contribution

It introduces a novel combination of NNLO fixed-order calculations with N3LL resummation for the Zγ p_T spectrum, including full differential effects and realistic cuts.

Findings

Agreement with 13 TeV ATLAS data at a few percent level.

Most advanced prediction for Zγ p_T spectrum to date.

Inclusion of spin correlations, interferences, and off-shell effects.

Abstract

We consider the transverse-momentum ($p_T$) distribution of $Z\gamma$ pairs produced in hadronic collisions. Logarithmically enhanced contributions at small $p_T$ are resummed to all orders in QCD perturbation theory and combined with the fixed-order prediction. We achieve the most advanced prediction for the $Z\gamma$ $p_T$ spectrum by matching next-to-next-to-next-to-leading logarithmic (N$^3$LL) resummation to the integrated cross section at next-to-next-to-leading order (NNLO). By considering $\ell^+\ell^-\gamma$ 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 $13$\,TeV ATLAS data at the few-percent level.