On lepton flavor universality in top quark decays

Jernej F Kamenik,Andrey Katz,Daniel Stolarski

doi:10.1007/jhep01(2019)032

Abstract

We propose a novel strategy to test lepton flavor universality (LFU) in top decays, applicable to top pair production at colliders. Our proposal exploits information in kinematic distributions and mostly hinges on data-driven techniques, thus having very little dependence on our theoretical understanding of top pair production. Based on simplified models accommodating recent hints of LFU violation in charged current B meson decays, we show that existing LHC measurements already provide non-trivial information on the flavor structure and the mass scale of such new physics (NP). We also project that the measurements of LFU in top decays at the high-luminosity LHC could reach a precision at the percent level or below, improving the sensitivity to LFU violating NP in the top sector by more than an order of magnitude compared to existing approaches.

Highlights

This relatively poor precision, we find that these searches have comparable sensitivity to new physics for mediators lighter than the top mass
Based on simplified models accommodating recent hints of lepton flavor universality (LFU) violation in charged current B meson decays, we show that existing LHC measurements already provide non-trivial information on the flavor structure and the mass scale of such new physics (NP)
We project that the measurements of LFU in top decays at the high-luminosity LHC could reach a precision at the percent level or below, improving the sensitivity to LFU violating NP in the top sector by more than an order of magnitude compared to existing approaches

Summary

Introduction

This relatively poor precision, we find that these searches have comparable sensitivity to new physics for mediators lighter than the top mass. The key insight is that heavy (off-shell) NP contributions to t → bτ ν decays will result in final state distributions distinctly different from the SM two-body t → W b kinematics This can be used to probe tiny LFU violating effects in localized regions of phase-space which might be averaged out in the integrated total rate measurements.

Results

Discussion

Conclusion