Abstract
We consider the top quark charge asymmetry in the process pp rightarrow t{bar{t}}+gamma at the 13 TeV LHC. The genuine tree level asymmetry in the q{bar{q}} channel is large with about -12%. However, the symmetric gg channel, photon radiation off top quark decay products, and higher order corrections wash out the asymmetry and obscure its observability. In this work, we investigate these effects at next-to-leading order QCD and check the robustness of theoretical predictions. We find a sizable perturbative correction and discuss its origins and implications. We also study dedicated cuts for enhancing the asymmetry and show that a measurement is possible with an integrated luminosity of 150,mathrm {fb}^{-1}.
Highlights
The charge asymmetry in the fermion annihilation process f f → f fis a well-studied phenomenon of Quantum Electrodynamics (QED) [1,2] and Quantum Chromodynamics (QCD) [3,4]
The top quark charge asymmetry enjoyed a revival at the Large Hadron Collider (LHC) because the delicate interference effects can be used as a sensitive probe for new physics searches, see e.g. Refs. [12,13,14,15,16] and references in [17]
We study the top quark charge asymmetry in the lepton+jet final state of tt+γ production at the 13 TeV LHC
Summary
The charge asymmetry in the fermion annihilation process f f → f fis a well-studied phenomenon of Quantum Electrodynamics (QED) [1,2] and Quantum Chromodynamics (QCD) [3,4]. We investigate the charge asymmetry for top quark pair production in association with a photon at the LHC. We elevate previous studies at LO to NLO QCD precision This is motivated by a foreseeable measurement in the near future and by the importance higher order corrections played in the similar process pp → tt + jet. In this work put special attention to a realistic description of the process, accounting for the full decay chain in the lepton+jets final state, bbν j j +γ , including all spin correlations, photon emission off all charged particles, and NLO QCD corrections in production and decay. Only a complete off-shell calculation will yield an accurate error estimate
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