Department Colloquia
The Physics Department Colloquia are held at 11:30 am on Tuesdays in Abelson 131.
Spring 2026
TBD
TBD
February 3, 2026
Abstract: Only a small fraction of the collisions between ultra-relativistic heavy ions at the Large Hadron Collider (LHC) involve direct strong interactions between the nucleons of the colliding nuclei. In most cases, the nuclei interact via their electromagnetic fields in so-called ultra-peripheral collisions (UPCs), which produce an abundant rate of photon–nucleus and photon–photon collisions at the highest center-of-mass energies achievable at colliders. In this seminar, I will highlight how photon–nucleus events in UPCs can serve as a novel tool to probe the dynamics of gluons and quarks in nuclei, particularly in the small Bjorken-x regime. I will discuss recent experimental advances that have transformed the CMS detector into a high-performance instrument for studying heavy-flavor and jet production in UPCs. The seminar will present results from the first measurements of open-charm production in UPCs and provide an outlook for future analyses at the LHC in Run 3 and Run 4. The prospects for analogous measurements in electron-proton and electron-ion collisions at the Electron Ion Collider will also be discussed.
January 20, 2026
Abstract: I will describe recent results from the Dark Energy Spectroscopic Instrument (DESI) on the measurement of the cosmic distance scale with the baryon acoustic oscillation (BAO) method and its resulting implications for cosmology and dark energy. I'll start with an introduction to BAO physics and its use as a cosmological standard ruler, as well as to the design and status of the DESI project. Then I'll turn to the results from the first three years of data, which provide sub-percent measurements of cosmological distance and a tantalizing suggestion of a breakdown of the cosmological constant model. Cosmology is no longer at a moment of concordance, and I will close by attempting to summarize the current state of play.