# Probing the top-quark width using the charge identification of $b$ jets

## TL;DR

This paper introduces a novel method to measure the top-quark width at the LHC by analyzing the charge asymmetry of $b$ jets, which reduces background and systematic uncertainties, enabling high-precision measurements.

## Contribution

The paper presents a new approach using $b$-charge asymmetry ratios in $pp o Wbj$ to directly measure the top-quark width with minimized model dependence.

## Key findings

- Potential to achieve a few hundred MeV precision at high luminosity
- Method effectively reduces background and systematic uncertainties
- Complementary to existing cross section measurements

## Abstract

We propose a new method for measuring the top-quark width based on the on-/off-shell ratio of $b$-charge asymmetry in $pp\to Wbj$ production at the LHC. The charge asymmetry removes virtually all backgrounds and related uncertainties, while remaining systematic and theoretical uncertainties can be taken under control by the ratio of cross sections. Limited only by statistical error, in an optimistic scenario, we find that our approach leads to good precision at high integrated luminosity, at a few hundred MeV assuming 300-3000 fb$^{-1}$ at the LHC. The approach directly probes the total width, in such a way that model-dependence can be minimized. It is complementary to existing cross section measurements which always leave a degeneracy between the total rate and the branching ratio, and provides valuable information about the properties of the top quark. The proposal opens up new opportunities for precision top measurements using a $b$-charge identification algorithm.