Abstract
We study the charge asymmetry between the t and t¯ quarks at the LHC, when they are produced in association with a W boson. Though sizably reducing the cross section with respect to the inclusive production, requiring a W boson in the final state has two important implications. First, at leading order in QCD, tt¯W± production can only occur via qq¯ annihilation. As a result, the asymmetry between the t and t¯ generated at NLO in QCD is significantly larger than that of inclusive tt¯ production, which is dominated by gluon fusion. Second, the top quarks tend to inherit the polarization of the initial-state quarks as induced by the W-boson emission. Hence, the decay products of the top quarks display a sizable asymmetry already at the leading order in QCD. We study the relevant distributions and their uncertainties in the standard model, compare them to those obtained in a simple axigluon model and discuss prospects for measurements at the LHC and beyond.
Highlights
The charge asymmetry in ttproduction at pp colliders is defined by the quantity: Atc where t η
Results at the next-to-leading order (NLO) and NLO + PS for the processes ttV (V = W ±, Z ) have appeared in the literature [28,29,30,31,32,33,34] yet no special attention has been given to asymmetries, whether EW or Quantum chromodynamics (QCD)
In the previous sections we have argued that the polarization and asymmetry effects in ttW ± production are large enough to offer a useful handle to constrain new physics effects
Summary
The charge asymmetry in ttproduction at pp colliders is defined by the quantity: Atc. Model (SM) at the LHC is much smaller than AFB at the Tevatron. The smallness of the effect makes it difficult at the LHC to reach the sensitivity required to measure Atc , and to probe the possible existence of BSM contributions, unless the BSM departures from the SM prediction were rather large. The measurements of top charge asymmetry performed so far by the ATLAS and CMS Collaborations [15,16,17,18,19], have reached uncertainties at the level of δ Atc ∼ 0.01, which is of the order of the SM value of Atc .
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
