The High Energy Elementary Particle Physics Group

Faculty: Delgado - Hildreth - Jessop - Kolda - Lannon - LoSecco - Martin - Ruchti - TsaiWayne
Research Faculty: Marinelli
Visiting Faculty: 
Emeritus Faculty: BigiCasonMcGlinn

Postdoctoral Research Associates: Band - Ghosh - Goldouzian

How Notre Dame physicists are helping us understand our universe: YouTube video link (written and produced by Don Lincoln)

Experimental Program

What are the fundamental building blocks that make up the universe we live in?  In what ways can those building blocks interact with one another?  Cosmological observations show that we can only explain roughly 5% of the energy content of the universe using known particles and interactions; what makes up the rest?  Why is the universe made up of only matter with almost no antimatter?  Why does the most massive known particle, the top quark, have a mass comparable to that of a gold nucleus while neutrinos have such small masses that we haven’t been able to measure them yet?  The experimental high energy physics (HEP) program at Notre Dame (ND) is focused on answering these questions and others like them using detectors operating at both energy frontier and intensity frontier facilities.  We design, construct, and operate detectors for these experiments and develop software and computational facilities for analyzing the data.  We apply sophisticated data analysis techniques to extract small signals from challenging backgrounds.  Ultimately we hope to uncover evidence of new particles or interactions to work towards resolving the mystery of what particles and interactions make up the other 95% of the universe that we live in.

The ND experimental HEP group has a long history of important contributions to leading HEP experiments around the world, including numerous fixed-target experiments and the D0 experiment on the Tevatron Collider at Fermilab, the Babar experiment at SLAC, but the current focus of our program centers on the CMS Experiment on the LHC as well as several neutrino experiments

  • Compact Muon Solenoid (CMS):  The CMS experiment records proton-proton collisions generated by the Large Hadron Collider (LHC) located at the CERN laboratory in Geneva, Switzerland.  The LHC is the world’s most energetic particle collider, enabling scientists from across the globe to explore phenomena at the highest accessible energy scales—what we call the “energy frontier” of particle physics.  We played a leading role in the construction of the electromagnetic calorimeter (ECAL) and hadronic calorimeter (HCAL), and continue to make important contributions to the operation and upgrading of the ECAL, HCAL, and trigger systems.  This detector R&D work is facilitated by on and off campus lab facilities, including a 5,000 sq. ft. detector development lab adjacent to campus and work areas at CERN.  A technical staff of three electrical engineers and four technicians assists faculty and graduate students in this work. We also play an important role in the development of software for simulating the detector and analyzing the data.  We operate one of the largest Tier-3 computing facilities in the world, and in partnership with the ND Center for Research Computing, provide the opportunity for ND group members to access in bursts extremely large-scale computing resources (on the order of 20,000 CPU cores) for CMS data analysis.  ND researchers made key contributions to the discovery of the Higgs Boson, and continue to drive important physics analyses such as the search for supersymmetry and  the search for new phenomena involving top quarks or Higgs bosons.

  • Neutrino Experiments:  ND is a member of three collaborations engaged in studies of neutrino physics. The Double Chooz experiment is in its completion phase, after successfully measuring a crucial parameter in the mixing of different types of neutrinos. The Deep Underground Neutrino Experiment (DUNE), which will commence operations circa 2026, will continue to expand our understanding of neutrino mixing to look for evidence that the laws of physics are subtly different between matter and antimatter.  Insights from DUNE could help to clarify why we live in a universe made up of matter, rather than antimatter.  Finally, the IceCube experiment, located at the South Pole, seeks to detect neutrinos traveling to earth from some of the most extreme astrophysical phenomena known, such as supernovae, neutron stars, or black holes.

In addition to these ongoing scientific experiments, ND plays an active role in research and development both for detectors and computational technology for future HEP experiments.

We are also founding members of the QuarkNet education and outreach program, established to bring cutting edge particle physics experiences to high school teachers and students.  In addition to our local QuarkNet center, we continue to lead the national QuarkNet program, consisting of 53 centers at universities and labs around the country, reaching roughly 60,000 high school students nationwide.



Theoretical Program

The theoretical high energy physics group at Notre Dame works on a broad range of topics, including model-building beyond the Standard Model, collider phenomenology, and tests and applications of particle physics models within the realm of astrophysics and cosmology. 

Historically, the group has played a major role in extending our understanding of CP violation, particularly through studies of the b-quark system at LHCb and the B-factories. Today, in the era of the LHC, the group continues to work on the forefront of CP violation and flavor physics, as well as their applications to fundamental questions of baryogenesis. Of utmost importance are questions such as: Are there sources of CP violation beyond the CKM matrix? Are there available tests for models of baryogenesis and leptogenesis? How else can we use precision measurements to augment the high-energy searches at the LHC?

The group is equally strong in the phenomenology of physics beyond the standard model, including searches for, and tests of, supersymmetry and extra spacetime dimensions. Studies are motivated both by theoretical drivers (such as the hierarchy problem) and by the most recent results coming from the LHC. Careful phenomenological studies of LHC collider physics allows the group to connect abstract theory to observable signatures and signals. In all of these topics, discussion and collaboration with our experimental colleagues is frequent and ongoing, benefitting both groups.

Finally, the connections to astrophysics (especially in studies of dark matter candidates) and to cosmology (including models for inflation) are deep, with much interaction with the Notre Dame astrophysics group. Recent work includes non-canonical approaches to dark matter creation in the early universe, effects of dark matter on pulsar populations, and finding ways to test realistic dark matter models at the LHC.