The Impact of Quark/Gluon Tagging on Searches for Dark Matter in Dijet Event Data with the ATLAS Detector

Peskett, Joe and Bertram, Iain (2021) The Impact of Quark/Gluon Tagging on Searches for Dark Matter in Dijet Event Data with the ATLAS Detector. Masters thesis, Lancaster University.

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Abstract

Differentiating between quark-and-gluon initiated events can be a useful tool for increasing the signal to noise ratio in searches of new physics. This thesis presents an analysis of the impact of quark-gluon tagging on the dijet invariant mass spectrum. Monte Carlo simulated data were compared with the ATLAS data from Run-2 of the LHC at 13 TeV. Truth information from the simulations was used to make a simple quark-gluon tagger based on the sum of the multiplicities of the two leading jets in a dijet event. A range of gluon-gluon selection efficiencies were applied to a H′ signal and 95% CL upper limits were found and compared between tagged and untagged samples. No improvements in the H′ upper limits were observed for any tested efficiency.