Abstract
Recent discrepancies between theoretical predictions and experimental data in multi-lepton plus b-jets analyses for the t{bar{t}}W^pm process, as reported by the ATLAS collaboration, have indicated that more accurate theoretical predictions and high precision observables are needed to constrain numerous new physics scenarios in this channel. To this end we employ NLO QCD computations with full off-shell top quark effects included to provide theoretical predictions for the mathcal{R}= sigma _{t{bar{t}}W^+}/sigma _{t{bar{t}}W^-} cross section ratio at the LHC with sqrt{s}=13 TeV. Depending on the transverse momentum cut on the b-jet we obtain 2–3% theoretical precision on mathcal{R}, which should help to shed some light on new physics effects that can reveal themselves only once sufficiently precise Standard Model theoretical predictions are available. Furthermore, triggered by these discrepancies we reexamine the charge asymmetry of the top quark and its decay products in the t{bar{t}}W^pm production process. In the case of charge asymmetries, that are uniquely sensitive to the chiral nature of possible new physics in this channel, theoretical uncertainties below 15% are obtained. Additionally, the impact of the top quark decay modelling is scrutinised by explicit comparison with predictions in the narrow-width approximation.
Highlights
Tofhe√Lsar=ge1H3aTderoVnCollider (LHC) with the Run has opened up the possibilityII of energy studying various top quark production and decay mechanisms at larger mass scales than previously explored in any experiment
In this paper we provided the state-of-the-art theoretical predictions for observables, which might be used to constrain numerous new physics scenarios in the ttW ± channel
We considered the ttW ± production process in th√e multi-lepton decay channel for the LHC Run II energy of s = 13 TeV for which discrepancies in the overall normalisation and in the modelling of the top quark decays have been recently reported by the ATLAS collaboration
Summary
Tofhe√Lsar=ge1H3aTderoVnCollider (LHC) with the Run has opened up the possibilityII of energy studying various top quark production and decay mechanisms at larger mass scales than previously explored in any experiment. The ttpair production associated with the W ± gauge boson is among the most interesting signatures that can be studied with high precision at the LHC. . The framework relies on the idea that new physics is too heavy to be directly produced and observed at the LHC, only deviations from the Standard Model (SM) can be probed in various ATLAS and CMS top quark measurements. Compared with top quark pair production and single top quark production, the associated ttW ± process does not bring sensitivity to new operators, it helps to resolve blind directions in the SMEFT parameter space that occur in the current LHC fits. Since the W ± gauge boson is radiated from the initial state, ttW ± is sensitive to a subset of the possible four-quark operators only. In the SM, ttW ± is dominated by quark–antiquark interactions, while ttis dominated by the gg initial state
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