HEE Seminar: Exploring ALPs under the Alps: The Search for a Diphoton Resonance with the CMS Experiment in an Unexplored Mass Range (A. Tsatsos)

In 2012, the ATLAS and CMS experiments at the Large Hadron Collider (LHC) confirmed the existence of a particle that coincides with the Standard Model (SM) Higgs boson. With this discovery, the LHC has an avenue for exploring new physics beyond the Standard Model (BSM). Several theoretical models, such as the axion-like particle (ALP), predict a Higgs-like particle with a mass lower than the SM Higgs. ALPs may even solve symmetry problems such as the strong charge-parity (CP) problem, which addresses the lack of CP violation within quarks. The diphoton final state at CMS is sensitive to many of these BSM models, presenting new prospects for an ALP search. In this departmental seminar, I will present the theory, analysis, and expected exclusion limits on the cross-section of diphoton resonances in the invariant mass range of 10-70 GeV using Run 2 data from the CMS experiment. We utilize a dataset with an integrated luminosity of 54.4 fb⁻¹, applying new multivariate analyses and fitting strategies to further improve results. Additionally, I will present new developments in the CMS trigger system made for the ongoing data-taking in Run 3 to further investigate the nature of diphoton resonances.