# Measurement of the top-quark mass in $t\bar{t}+1$-jet events collected with the ATLAS detector in $pp$ collisions at $\sqrt{s}=8$ TeV

## TL;DR

This paper measures the top-quark mass using 8 TeV proton-proton collision data from the ATLAS detector, analyzing top-quark pair production with an additional jet to extract mass values in different schemes with high precision.

## Contribution

It introduces a novel method of determining the top-quark mass through differential cross section measurements in top-antitop plus jet events at the LHC.

## Key findings

- Top-quark pole mass: 171.1 ± 0.4 (stat) ± 0.9 (syst) +0.7/-0.3 (theo) GeV
- Running mass at scale m_t: 162.9 ± 0.5 (stat) ± 1.0 (syst) +2.1/-1.2 (theo) GeV
- Results are consistent across schemes and with previous measurements.

## Abstract

A determination of the top-quark mass is presented using 20.2 $\text{fb}^{-1}$ of 8 TeV proton-proton collision data produced by the Large Hadron Collider and collected by the ATLAS experiment. The normalised differential cross section of top-quark pair production in association with an energetic jet is measured in the lepton+jets final state and unfolded to parton and particle levels. The unfolded distribution at parton level can be described using next-to-leading-order QCD predictions in terms of either the top-quark pole mass or the running mass as defined in the (modified) minimal subtraction scheme. A comparison between the experimental distribution and the theoretical prediction allows the top-quark mass to be extracted in the two schemes. The value obtained for the pole-mass scheme is: \[ m_t^{\text{pole}} = 171.1 \pm 0.4 (\text{stat}) \pm 0.9 (\text{syst}) \substack{+0.7\\ -0.3} (\text{theo}) \text{ GeV}. \] The extracted value in the running-mass scheme is: \[ m_t(m_t) = 162.9 \pm 0.5 (\text{stat}) \pm 1.0 (\text{syst}) \substack{+2.1\\ -1.2} (\text{theo}) \text{ GeV}. \] The results for the top-quark mass using the two schemes are consistent, when translated from one scheme to the other.