On Lepton Flavor Universality in Top Quark Decays

TL;DR

This paper introduces a data-driven method to test lepton flavor universality in top quark decays at colliders, aiming to improve sensitivity to new physics beyond current limits.

Contribution

It presents a novel, minimally theory-dependent strategy for probing LFU in top decays, leveraging kinematic distributions and existing collider data.

Findings

Existing LHC data constrains flavor structure and mass scale of new physics.

Projected high-luminosity LHC measurements could reach sub-percent precision.

Method enhances sensitivity to LFU violation in top sector by over tenfold.

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.