Search for non-resonant production of hadronic semivisible jets with a novel anomaly detection algorithm in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS experiment
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Date
2025
Publication Type
Doctoral Thesis
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yes
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Abstract
A search for non-resonant production of hadronic jets partially visible, semivisible jets, is conducted using 138 fb$^{−1}$ of proton-proton collision data collected by the Compact Muon Solenoid experiment at the CERN Large Hadron Collider between 2016 and 2018. Semivisible jets arise from strongly coupled models, where a dark sector made of dark quarks and gluons exists and a scalar bifundamental mediator acts as a portal between the standard model and the dark sector. Dark quarks or gluons produced in the final state of the collisions hadronize and produce jets of dark hadrons. Unstable ones decay to standard model quarks, which in turn hadronize and form standard model hadrons. The latter are visible to detectors, while the stable dark hadrons escape detection. Stable dark hadrons are good dark matter candidates and could explain the dark matter relic abundance. Searching for strongly coupled dark sectors is however experimentally challenging and such searches have only recently begun. A novel anomaly detection algorithm, called Wasserstein normalized autoencoder, is developed in order to identify these exotic jets of particles while remaining agnostic to the unknown details of the parton shower in the dark sector. A state-of-the-art machine learning technique is employed to estimate the standard model backgrounds. No statistically significant excess is found and exclusion limits on the cross section of the considered new physics hypotheses are set.
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Examiner : de Cosa, Annapaola
Examiner : Klute, Markus
Examiner : Sgalaberna, Davide
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ETH Zurich
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Subject
High Energy Physics; Dark matter searches; Anomaly detection; CMS Experiment
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09720 - de Cosa, Annapaola / de Cosa, Annapaola