QCD corrections to associated production of $t\bar tγ$ at hadron colliders

TL;DR

This work delivers the complete NLO QCD corrections to associated top-quark pair production with a photon ($t\bar t\gamma$) at the LHC and Tevatron Run II, addressing the dominant theoretical uncertainties in LO predictions. It employs real-emission, virtual, and PDF-counterterm contributions with dimensional regularization and the TCPSS method to obtain finite cross sections and differential distributions. The results show K-factors of about 1.52 at the LHC and 0.98 at the Tevatron for μ=mt, demonstrating reduced scale dependence and clarified impact on $p_T$ spectra and on the top-quark forward-backward asymmetry at the Tevatron. These precise SM predictions are essential for probing the $t\bar t\gamma$ coupling and for interpreting collider measurements of top EW interactions.

Abstract

We report on the next-to-leading order(NLO) QCD computation of top-quark pair production in association with a photon at the Fermilab Tevatron RUN II and CERN Large Hadron Collider(LHC). We describe the impact of the complete NLO QCD radiative corrections to this process, and provide the predictions of the leading order(LO) and NLO integrated cross sections, distributions of the transverse momenta of top-quark and photon for the LHC and Tevatron, and the LO and NLO forward-backward top-quark charge asymmetries for the Tevatron. We investigate the dependence of the LO and NLO cross sections on the renormalization/factorization scale, and find the scale dependence of the LO cross section is obviously improved by the NLO QCD corrections. The K-factor of the NLO QCD correction is $0.977(1.524)$ for the Tevatron(LHC).

Figures (12)

• Figure 1: The LO Feynman diagrams for the $q\bar{q} \to t\bar{t}\gamma~$($q=u,d,s,c$) partonic process.
• Figure 2: The LO Feynman diagrams for the $gg \to t\bar{t}\gamma~$ partonic process.
• Figure 3: The LO Feynman diagrams for the real gluon emission partonic process $q\bar{q} \to t\bar{t}\gamma g~$$(q=u,d,s,c)$.
• Figure 4: The LO Feynman diagrams for the real gluon emission partonic process $gg \to t\bar{t}\gamma g~$. The diagrams obtained by exchanging two initial gluon lines in (11)-(30) are not drawn.
• Figure 5: The pentagon Feynman diagrams for the partonic process $q\bar{q} \to t\bar{t}\gamma~$($q\bar{q}=u\bar{u},d\bar{d}$).