Abstract

We study the accuracy with which the lowest order CP conserving anomalous Wtb couplings in the single top-quark production at the proposed large hadron electron collider can be probed. The one-dimensional distribution of various kinematic observables at the parton level MC and their asymmetries arising due to the presence of anomalous couplings both in the hadronic and leptonic W decay is examined. We find that at 95 % CL the anomalous coupling associated with the left-handed vector current can be measured at an accuracy of the order of $$\sim $$ 10 $$^{-2}$$ –10 $$^{-3}$$ , while those associated with the right-handed vector and left- as well as right-handed tensor currents have a sensitivity at the order of $$\sim $$ 10 $$^{-1}$$ –10 $$^{-2}$$ for the systematic uncertainty varying between 10–1 % at an integrated luminosity of 100 fb $$^{-1}$$ . A comprehensive analysis of the combined covariance matrix derived from all one-dimensional distributions of kinematical observables is used to compute the errors in the anomalous couplings.

Highlights

  • The top quark provides an excellent opportunity for the study of the electroweak symmetry breaking mechanism as well as it provides a glimpse of new physics (NP) beyond the standard model (SM)

  • Based on the one-dimensional histograms given in Figs. 5 and 6, we look for the asymmetry within a distribution generated due to the interplay of the SM, background channels and a given anomalous coupling for two distinct hadronic and leptonic modes of W − decay

  • We analyze the effect of anomalous couplings in the W tb vertex by examining its one-dimensional distributions

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Summary

Introduction

The top quark provides an excellent opportunity for the study of the electroweak symmetry breaking mechanism as well as it provides a glimpse of new physics (NP) beyond the standard model (SM). The sensitivity of anomalous W tb couplings can be measured from the W ± helicity distributions arising from top decays to their dominant W b mode in the top pair production processes [10] It can be measured from the observed single top quark production cross section through W -boson exchange and has both linear and quadratic terms in the effective couplings. DØ with 5.4 fb−1 data reported a combined analysis of W boson helicity studies and the single top-quark production cross section exclusively through the W tb vertex. This sets upper limits on the anomalous W tb couplings at 95 % CL viz.

Single antitop-quark production
Sensitivity in the hadronic mode
Sensitivity in the leptonic mode
Angular asymmetries from histograms
Exclusion contours from bin analysis
Errors and correlations
Luminosity error
Observations and discussion
Observations
Findings
Comparison and analysis
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