During Run 2 of the Large Hadron Collider, the ATLAS experiment recorded proton-proton collision events at 13 TeV, the highest energy ever achieved in a collider. Analysis of this dataset has provided new opportunities for precision measurements of the Higgs boson, including its interaction with the top quark. The Higgs-top coupling can be directly probed through the production of a Higgs boson in association with a top-antitop quark pair (ttH). The Higgs to diphoton decay channel is among the most sensitive for ttH measurements due to the excellent diphoton mass resolution of the ATLAS detector and the clean signature of this decay. Event selection criteria were developed using novel Machine Learning techniques to target ttH events, yielding a precise measurement of the ttH cross section in the diphoton channel and a 6.3 $\sigma$ observation of the ttH process in combination with other decay channels, as well as stringent limits on CP violation in the Higgs-top coupling.

Jennet Dickinson began studying physics as an undergraduate student at Columbia University, where she got her first introduction to experimental particle physics while studying neutrino oscillations with the MicroBooNE experiment. As a graduate student at the University of California, Berkeley, she joined the ATLAS group at Lawrence Berkeley National Laboratory under the supervision of Professor Marjorie Shapiro. At the beginning of LHC Run 2, Jennet contributed to searches for new physics in multijet final states before shifting her focus to Higgs boson measurements. She was a key contributor to many ATLAS physics analyses focused on the Higgs to diphoton decay. Jennet also studied radiation damage in the innermost layers of the ATLAS detector. In order to participate in detector operations work, she spent two years working at CERN in Geneva, Switzerland during her graduate studies. She completed her PhD in 2020 and received an ATLAS thesis award for her work. Jennet is now a Research Associate at Fermi National Accelerator Laboratory, where she works on the CMS experiment. Her research continues to focus on Higgs boson measurements, as well as the planned upgrade to the CMS Outer Tracker.