Research Seminars @ Illinois

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Tailored for undergraduate researchers, this calendar is a curated list of research seminars at the University of Illinois. Explore the diverse world of research and expand your knowledge through engaging sessions designed to inspire and enlighten.

To have your events added or removed from this calendar, please contact OUR at ugresearch@illinois.edu

Nuclear Physics Seminar - Gordon Baym (UIUC) "The puzzle of angular momentum conservation in beta decay and related processes"

Event Type: Seminar/Symposium
Sponsor: Physics Department
Location: 464 Loomis
Date: Apr 21, 2025 1:00 pm
Speaker: Gordon Baym (UIUC)
Contact: Brandy Koebbe
E-Mail: bkoebbe@illinois.edu
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Originating Calendar: Physics - Nuclear Physics Seminar; We ask the question of how angular momentum is conserved in a number of related processes, from elastic scattering of a circularly polarized photon by an atom, where the scattered photon has a different spin direction than the original photon; to scattering of a fully relativistic spin-1/2 particle by a central potential; to inverse beta decay in which an electron is emitted following the capture of a neutrino on a nucleus, where the final spin is in a different direction than that of the neutrino – an apparent change of angular momentum.

The seeming non-conservation of angular momentum arises, in fact, in the quantum measurement process in which the measuring apparatus does not have an initially well-defined angular momentum, but is localized in direction in the outside world. We generalize the discussion to massive neutrinos and electrons, and examine nuclear beta decay and electron-positron annihilation processes through the same lens, enabling physically transparent derivations of angular and helicity distributions in these reactions.

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