The Globe of Innovation at CERN, photo by Allison Deiana The ATLAS Detector Barrel, photo by Maximilien Brice, CC-BY-4.0 "Accelerating Science" Display Pipe, photo by Allison Deiana

My research focus is the “Energy Frontier” of particle physics. I am a member of the ATLAS Collaboration, and I use proton-proton collision events produced by the Large Hadron Collider (LHC) to study the fundamental particles of our universe and how they interact with one another. My current top priority is the study of the Higgs boson’s ability to couple with itself, and I am probing this through Higgs production and decays involving top quarks and tau leptons. I’m also involved in the trigger and data acquisition of the ATLAS detector, working on the Fast Tracker (FTK) updgrade for Run-3 in 2021. The below is a brief summary of current activities.

Di-Higgs Production

The measurement of the mass of the Higgs boson is strong evidence to support the Brout-Englert-Higgs mechanism, but it is also necessary to measure the Higgs self-coupling in order to experimentally determine the Higgs potential field. Towards this goal, a high priority for me has been the search for HH production. Searches for two Standard-Model-like Higgs bosons are sensitive not only to Standard Model production, but to potential resonant or non-resonant enhancements to the process from sources beyond the SM. More information about Higgs boson pairs can be found in this ATLAS physics briefing.

My primary focus is the search for Di-Higgs with one Higgs boson decaying to bottom quarks and the other to tau leptons. This is currently the strongest channel in ATLAS, due to its relatively high branching fraction and low backgrounds, as well as to the beneficial application machine learning techniques to the search. I am also involved in the search for the decay mode into multiple leptons.

Top-associated Production

A second and complementary way to approach constraining the Higgs self-coupling is through higher-order corrections to single Higgs production cross sections. In particular, the largest expected effect of the Higgs self-coupling can be found in measurements of the top-associated production cross section. A second focus of my research program is in the measurement of multiple lepton decay modes of top-associated Higgs boson production. This production mode was observed in 2018, opening up the possibility now for interesting new measurements.

Fast Tracker (FTK)

The ATLAS trigger system reduces the input rate of events (40 MHz) to the level that the ATLAS detector is able to record (~1.5 kHz). It is very important for the trigger system to be able to efficiently select events of interest to physics analyzers. The FTK upgrade relies on parallelization and pattern-matching to supply fast, high-quality information about the paths particles take as they travel through the detector from the collision point. My team is working on the Second Stage Board, where 12-track pattern matching and duplicate track removal is performed.

Current Collaborators

  • Rohin Narayan, post-doctoral researcher: 2019-present. Currently focuses on ttH production to multi-lepton final states, di-Higgs to multi-lepton final states, and FTK.
  • Lloyd Hasley, senior engineer: Currently focuses on firmware development of the HitWarrior for the FTK project.

Previous Research

Dr. Deiana’s CV in pdf format is available here.

Header Photos

Photos at top of page are taken on site at CERN by Allison Deiana (left, right) and Maximilien Brice (center). The center photo is used under a CC-BY-4.0 license and is available on the CERN Document Server.