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High Energy Physics Journal Club

High Energy Physics
Journal Club

The High Energy Particle Physics journal club meets weekly to present on recent research published in the field. Graduate students who are studying high energy physics at OU are expected to participate.


The seminar and journal club are being temporarily combined, to be held on Tuesdays at 1:00 pm in Lin Hall 105 on the OU Norman campus.

Spring 2025

Title: "Generalized Global Symmetries and Nonperturbative Quantum Flavodynamics"

Abstract: Generalized global symmetries are present in theories of particle physics, and understanding their structure can give insight into these theories and UV completions thereof.  We will identify noninvertible chiral symmetries in certain flavorful Z' extensions of the Standard Model, and our understanding of generalized symmetry breaking will lead us to short-distance theories of gauged non-Abelian flavor where nonperturbative effects can resolve important naturalness questions. For the leptons we will find naturally exponentially small Dirac neutrino masses, and in the quark sector we will construct a massless down-type quarks solution to strong CP in color-flavor unification. Intriguingly, the fact that we have three generations of fermions plays a crucial role in the existence of these noninvertible symmetries.

A small group from the High Energy Physics research group enjoying a meal at a restaurant.

Title: "Observable CMB B-Modes from Cosmological Phase Transitions"

Abstract: A B-mode polarization signal in the cosmic microwave background (CMB) is widely regarded as smoking gun evidence for gravitational waves produced during inflation. In this talk, I demonstrate that tensor perturbations from a cosmological phase transition can produce a B-mode signal whose strength rivals that from inflationary predictions across a range of observable scales. Although phase transitions arise from sub-horizon physics, they nevertheless exhibit a white noise power spectrum on super-horizon scales. Power is suppressed on the large scales relevant for CMB B-mode polarization, but it is not necessarily negligible. For appropriately chosen phase transition parameters, the maximal B-mode amplitude can compete with inflationary predictions that can be tested with current and future experiments. These scenarios can be differentiated by performing measurements on multiple angular scales, since the phase transition signal predicts peak power on smaller scales.

Title: "Cutting rule for in-in correlators and cosmological collider"

Abstract: Cosmological correlators, observed through the structures of the universe, contain rich information on the physics of the early universe. However, in general, the calculation of the cosmological correlators is quite involved due to the loss of the time translation invariance.

In this talk, I derive a cutting rule for equal-time in-in correlators, including cosmological correlators, which decomposes diagrams into fully retarded functions and cut-propagators consisting of Wightman functions. Our derivation relies only on basic assumptions such as unitarity and, therefore, holds for theories with arbitrary particle contents and local interactions at any loop order. As an application, we show that non-local cosmological collider signals, particle production signals in the correlators, arise solely from cut-propagators under the assumption of microcausality. The cut factorizes the conformal time integrals, simplifying practical calculations.