26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Discriminating Four-Top Production with Recursive Jigsaw Reconstruction at the ATLAS Experiment

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Nuclear and Particle Physics (NUPP)

Description

The simultaneous production of four top-quarks (four-top) is a rare physics process predicted by the Standard Model, suspected to be sensitive to Beyond Standard Model (BSM) effects. If these BSM contributions were to exist, their effects would manifest in the form of an amplified cross section and enhanced yield of four-top, and in 2021 and 2023, four-top excess was repeatedly observed, indicative of such an occurrence. However, with the signal region being polluted with similar backgrounds, ambiguities remain as to whether the observed excesses are new physics or a convolution of known processes. As such, the development of new background discrimination techniques is motivated.

Recursive Jigsaw Reconstruction (RJR) is one such technique, by which one may resolve and assess the parent states of observed decay products. By identifying all visible products of a particle collision event, minimising the ambiguities of missing energy, and enforcing their recombination, the intermediate decay states of each event may be interrogated for their resemblance to a four-top decay.

Using the LHC Run-3 dataset as acquired by the ATLAS Experiment, this talk will discuss the efficacy of these RJR variables in separating four-top production from background, owing to their sensitivity to the reconstructed masses and angular dynamics of the decay.