Probing anomalous tbW couplings in single-top production using top polarization at the Large Hadron Collider

TL;DR

This paper investigates how top polarization measurements at the LHC can be used to detect anomalous tbW couplings in single-top production, providing more sensitive limits than traditional methods.

Contribution

It introduces a novel approach using top polarization and decay product distributions to constrain anomalous tbW couplings at the LHC.

Findings

Asymmetries in decay distributions improve sensitivity to anomalous couplings.

Limits on anomalous couplings are significantly better than previous direct and indirect bounds.

Method works effectively at 14 TeV with 10 fb^{-1} luminosity.

Abstract

We study the sensitivity of the Large Hadron Collider (LHC) to anomalous tbW couplings in single-top production in association with a W^- boson followed by semileptonic decay of the top. We calculate top polarization and the effects of these anomalous couplings to it at two centre-of-mass (cm) energies of 7 TeV and 14 TeV. As a measure of top polarization, we look at various laboratory frame distributions of its decay products, viz., lepton angular and energy distributions and b-quark angular distributions, without requiring reconstruction of the rest frame of the top, and study the effect of anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to anomalous tbW couplings. We find that 1\sigma limits on real and imaginary parts of the dominant anomalous coupling Ref_{2R} which may be obtained by utilizing these asymmetries at the LHC with cm energy of 14 TeV and an integrated luminosity of 10 fb^{-1} will be significantly better than the expectations from direct measurements of cross sections and some other variables at the LHC and over an order of magnitude better than the indirect limits.