Supersymmetry (SUSY) is a groundbreaking theory in particle physics that offers solutions to some of the long-standing mysteries in the field. It proposes the existence of “superpartner” particles for every known particle, each with slightly different properties. For instance, the top quark of the Standard Model would have a superpartner known as the top squark or “stop.”
In 2021, the CMS collaboration conducted a comprehensive analysis of collision data collected between 2016 and 2018. The results hinted at the possible presence of stop particles within the data set. To validate this finding, the collaboration employed upgraded analysis techniques to reexamine the data, specifically focusing on the simultaneous production of pairs of stops.
One of the primary challenges in identifying stop particles lies in distinguishing their signal from the background noise generated by other Standard Model processes, such as top quark pair production. Traditional methods like the ABCD method, which rely on uncorrelated observables to estimate backgrounds, prove ineffective in the context of the stop search due to the correlated nature of the variables involved.
To address this issue, CMS physicists turned to advanced machine-learning techniques to identify two minimally correlated variables for data subdivision. By leveraging these variables, the data set was categorized into four distinct regions, enabling the accurate prediction of background levels without the reliance on simulation-based uncertainty.
The implementation of this novel approach led to a significant enhancement in analysis sensitivity, shedding light on the absence of the signal initially hinted at in the 2021 analysis. This absence suggests that in certain SUSY scenarios, stop particles decaying into top quarks and jets must possess a mass exceeding 700 GeV.
Armed with a more refined analysis method, physicists are now poised to delve deeper into the ongoing LHC Run 3 data, aiming to unravel further mysteries and uncover the elusive secrets of Nature. As the quest for understanding the intricacies of supersymmetry continues, the utilization of cutting-edge techniques promises to unlock new realms of knowledge and insight into the fundamental workings of the universe.
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