Prof. Christopher G. Tully

Research Activities and Interests

Our two-pronged approach in collider physics and table-top physics allows us to benefit from the highest end large-scale experimental methods of the LHC while at the same time investing in creative new ways to make measurements on physical systems that have largely remained invisible to direct detection.  Collider physics has the gift of discovery.  Given the energy scale and intensity of beams, Nature tells us all that it knows about particle interactions and new mass states.  The more we can do to maximize the information context extracted from high energy particle collisions, the more likely we will be to fish out deviations or extensions to the Standard Model of Particle Physics.  Relic neutrino physics witness the entire history of matter and radiation in the Universe.  The neutrinos are so odd-ball with respect to the rest of the matter content of the Standard Model that the possibility they couple into new sectors is still very plausible.  We learn as much about the neutrino and elementary interactions when probing the relic neutrinos as we do about the thermal history of the Universe.

On the CMS Experiment at CERN, Tully's group leads the development of new methods for probing the physics of high mass scales beyond the scales of the manifestly broken symmetries of the Standard Model of particle physics.  To reach the scales of 1000 TeV and above, displaced jet searches have been applied to detect the production of long-lived particle states suppressed by massive intermediate states.  Tully's group has developed the triggers and analyses for these searches.  More recently, we have learned how to time-in the Upgraded Hadron Calorimeter and have implemented hardware-level delayed energy triggers to trigger on displaced, extended path length, long-lived particle decays.  To push the search to the ultimate mass reach for production via the strong interaction, approximately 2.5 TeV for the gluino, at the High-Luminosity LHC a new Phase 2 Upgrade has been proposed to install a MIP Timing Detector (MTD) for the purpose of 4D vertex reconstruction and telescoping time-of-flight measurements of short-lived, finite velocity, long-lived particles.  The MTD in the barrel region is pursuing LYSO crystals and SiPM readout hosted within the Tracker Support Tube (TST) of the central tracking system.  The Princeton group leads the crystal and sensor development and test beam evaluations, while preparing for detector construction in 2024-2025.

Based on our over three decade of research in collider physics and calorimetry, our group also contributes to the development of calorimeters that are co-designed to maximize information content at future colliders.  Our group develops particle flow methods or hybrid dual readout segmented crystal and fiber calorimeters.

Collider physics is an invaluable probe of the relativistic quantum universe, but it is not the whole story.  The Universe is filled with matter and radiation - the essence of what we observe with the naked eye when we peer to the heavens at night.  The more we understand the dynamical history of the Universe the more we believe that matter and radiation dominance is but a fleeting moment in its existence.  What conditions led to the creation of matter and radiation and can we search for present-day relics of this early time?

The Universe has expanded by a factor of over one billion between the present-day and the early thermal epoch known as the neutrino decoupling.  We observe this dynamics in many forms:  the recession of galaxies (Hubble Expansion), the dim afterglow of the hot plasma epoch (Cosmic Microwave Background) and the abundances of light elements (Big Bang Nucleosynthesis).  The epoch of neutrino decoupling produced a fourth pillar of confirmation – the Cosmic Neutrino Background. These early universe relics have cooled under the expansion of the Universe and are sensed indirectly through the action of their diminishing thermal velocities on large-scale structure formation.  Experimental advances have opened up new opportunities to directly detect the CNB, an achievement which would profoundly confront and extend the sensitivity of precision cosmology data.

Tully leads a new experimental effort, called PTOLEMY, to directly detect neutrinos from the Big Bang.  At the Gran Sasso Underground Laboratory with its unparalleled strengths in high radio-purity, low background experiments, the PonTecorvo Observatory for Light, Early-universe Massive-neutrino Yield (PTOLEMY) will focus on demonstrating high radio-purity Carbon-12 2D target surfaces, fabricated from Graphene, that will form a basis for a future large-scale relic neutrino detector.


ORCiD: 0000-0001-6771-2174

Brief Biography

Chris Tully earned his PhD in high-energy physics from Princeton University (*98) and his B.S. at Caltech (‘92).  He is a professor of physics at Princeton University and has served as associate chair of the physics department.  His research in particle physics spans three decades of energy-frontier particle colliders at Fermilab and CERN, and he was part of the team that discovered the Higgs boson at the LHC.  He was awarded NSF, CERN, Sloan and IBM-Einstein Fellowships.  He is the author of a popular textbook “Elementary Particle Physics in a Nutshell” and is a contributing author to “100 Years of Subatomic Physics.”