Particle Physics seminars

Benoit Assi examines limits on reliable theoretical predictions for present and future particle colliders. Low-order simulations of QCD radiation carry large uncertainties, hadronization is commonly modeled rather than derived, and effective theories contain more operators than measurements can constrain. Information theory and machine learning can incorporate improved calculations into simulations, quantify uncertainty, choose informative observables and advance hadronization theory. Geometry of effective-theory field space combines infinite operator families into finite physical quantities, while information measures identify the combinations experiments can resolve. The talk develops these complementary approaches to extracting the available information from LHC and future-collider data.

Claudio Manzari connects astrophysical observations and precision flavor measurements to two unresolved aspects of CP symmetry. For the strong CP problem, the talk considers QCD axions produced in a supernova core and converted to gamma rays by surrounding magnetic fields. A Galactic supernova could expose this distinctive transient, motivating the GALAXY network of telescopes monitoring the full sky. The second part examines the origin of flavor-sector CP violation through precise measurements of the CKM unitarity triangle. Possible hints of spontaneous CP violation are discussed alongside their implications for quark flavor and the fundamental symmetries of matter.

Tien-Tien Yu examines observational signatures of ultralight scalar dark matter with quadratic couplings to Standard Model fields. The couplings change fundamental constants over time, affecting primordial light-element production, the microwave-background power spectrum and tests of the equivalence principle. The talk follows these effects from the early Universe to present experiments and explains how current cosmological measurements constrain this class of scalar-dark-matter models.

Seth Koren shows how global symmetry structure and field-space topology affect particle-physics predictions beyond the usual analysis of small field fluctuations. Different possible global forms of the Standard Model gauge group imply different model-independent predictions for fractionally charged particles. Collider searches for these particles could identify the gauge-group structure and exclude unification models. The talk then examines axion theories, using the DFSZ model to show how the global properties of scalar fields and gauge symmetries modify axion strings and can resolve the cosmological domain-wall problem.

Benjamin Safdi studies the axion mass constraints obtained when grand unification and string theory are considered together with the QCD axion. Unitarity reasoning and explicit string compactifications, including examples from the Kreuzer–Skarke type-IIB ensemble, favor masses between 10^-11 and 10^-8 electronvolts. The talk explains how these theoretical frameworks combine to restrict a candidate extension of the Standard Model.

Francis Halzen explains how the IceCube telescope uses detectors buried deep in Antarctic ice to observe high-energy neutrinos from the cosmos. The lecture describes construction of the observatory, the measurement of particle energies and directions, and the distinction between atmospheric backgrounds and neutrinos arriving from distant astrophysical sources. It connects the discovery of cosmic neutrinos with the search for the powerful accelerators that produce cosmic rays. Examples include the association with a flaring blazar and evidence identifying the active galaxy NGC 1068 as a neutrino source. Halzen discusses the role of rotating supermassive black holes, coordination with other observatories, and prospects for extending the detector.