Search for new resonances in mass distributions of jet pairs using 139 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper reports a search for new particle resonances decaying into jet pairs using 139 fb$^{-1}$ of proton-proton collision data at 13 TeV, finding no significant excess and setting upper limits on new physics models.

Contribution

It introduces an improved analysis of dijet and b-jet events with enhanced flavor identification, extending sensitivity beyond previous studies.

Findings

No significant excess observed in dijet mass spectrum.

Set 95% CL upper limits on cross sections for new resonances.

Enhanced sensitivity in b-jet analysis due to improved flavor tagging.

Abstract

A search for new resonances decaying into a pair of jets is reported using the dataset of proton-proton collisions recorded at $\sqrt{s}=13$ TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the Standard Model background. In addition to an inclusive dijet search, events with jets identified as containing $b$-hadrons are examined specifically. No significant excess of events above the smoothly falling background spectra is observed. The results are used to set cross-section upper limits at 95% confidence level on a range of new physics scenarios. Model-independent limits on Gaussian-shaped signals are also reported. The analysis looking at jets containing $b$-hadrons benefits from improvements in the jet flavour identification at high transverse momentum, which increases its sensitivity relative to the previous analysis beyond that expected from the higher integrated luminosity.