Past Event

Devin Mahon - Columbia University

February 10, 2021
12:30 PM - 1:30 PM
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"ATLAS Search for Non-Pointing and Delayed Photons"

Years of dedicated searches for supersymmetry (SUSY) and other well-motivated extensions of the Standard Model (SM) have so far all come up empty. But what if we’re just looking in the wrong places? Most beyond the SM (BSM) searches tend to focus on prompt signals, but just as there are long-lived particles in the SM, BSM physics may too feature such particles. In this talk, I introduce a novel search for displaced photons with the ATLAS detector. Our search specifically targets the relatively unconstrained branching ratio of the Higgs boson to invisible particles, where there is still ample room for BSM phenomena. Exploiting the longitudinal segmentation and the excellent precision timing capabilities of the ATLAS detector’s liquid argon electromagnetic calorimeter, we are able to extract the striking, smoking-gun signature of a displaced photon that both fails to point back to the interaction point and arrives significantly delayed. I discuss in detail the optimization of the event selection and binning strategy in the context of our completely data-driven background estimation method. To provide in-depth context to the measurement of our analysis variables, I also present my work on the calorimeter itself including the development of the front-end readout electronics, the offline timing calibration procedure, and Run 2 operations.