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Events on Wednesday, August 24th, 2022

Theory Seminar (High Energy/Cosmology)
Two problems for strong CP: Topological quantization and the first postulate of quantum mechanics
Time: 12:00 pm
Place: Chamberlin 5280
Speaker: Bjorn Garbrecht, Munich Tech. U.
Abstract: In the path integral quantization of Yang-Mills theory, integer topological sectors follow only when Euclidean time is taken to infinity. This implies that the spacetime volume must be taken to infinity before interfering among the sectors. On the other hand, in canonical quantization, the standard theta-vacua are not properly normalizable without further ado. We revisit the well-known analogy with a point particle on a circle. It is sometimes argued that continuous energy bands corresponding to Bloch states exist for this problem. We show however that the states in these bands exhibit an inconsistent time evolution, unless narrowing the energy band to just one allowed state. From either perspective one can understand why no CP violation is seen in the strong interactions.
Host: George Wojcik
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Physics Summer Fun
Weekly Recess
Time: 12:30 pm
Place: Bascom Hill or 5310 Chamberlin Hall
Speaker: Sharon Kahn
Abstract: We hope you’ll take a 20-30 minute break on (some/all) Wednesdays this summer (12:30-1pm) to come play together! For nice days, we’ve arranged to borrow some lawn games from the L&S dean’s office and will likely bring along a frisbee and/or a hackeysack, too. Meet us on Bascom Hill (between Birge/South Hall).
In case of rain, we’ll meet indoors (5310 CH) for board games. Feel free to come play or just hang out!
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Thesis Defense
Measuring the Atmospheric Neutrino Oscillation Parameters with IceCube DeepCore
Time: 2:00 pm
Place: Chamberlin 4274
Speaker: Kayla DeHolton , Physics PhD Graduate Student
Abstract: The discovery of neutrino oscillations (and consequently the implication that neutrinos have mass) is one of the only confirmed pieces of evidence of physics beyond the Standard Model. Since this discovery, there has been a worldwide effort to measure the model parameters that describe these oscillations. The DeepCore sub-array within the IceCube Neutrino Observatory is a densely instrumented detector embedded in the Antarctic ice at the South Pole and detects Cherenkov light from the interactions of atmospheric neutrinos with energies down to 5 GeV. At these energies, Earth-crossing muon neutrinos have a high chance of oscillating to tau neutrinos. DeepCore is able to measure these oscillations with precision comparable to accelerator-based experiments, but it is also complementary to accelerator measurements because it probes longer distance scales and higher energies, peaking above the tau lepton production threshold. This dissertation presents the effort involved in curating one of the largest neutrino oscillation datasets in the world, with over 200,000 events spanning almost 10 years and a neutrino purity of over 99%. The nearly unprecedented level of statistics also requires unprecedented precision in the treatment of systematic uncertainties and other analysis techniques. I will present the status of an analysis to measure the atmospheric neutrino oscillation parameters using the full dataset, as well as the unblinded results of a measurement performed with a sub-sample containing 20% of the full dataset.
Host: Francis Halzen
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