Events on Friday, November 21st, 2025
- Preliminary Exam
- Measuring the Flavor Composition of the Cosmic Neutrino Flux at High Energies with IceCube
- Time: 10:00 am - 12:00 pm
- Place: Chamberlin Hall Room 5280
- Speaker: Hannah Erpenbeck
- Abstract: The IceCube Neutrino Observatory detects neutrinos by instrumenting 1 km3 of deep glacial ice with photomultiplier tubes. These detections allow for the study of possible astrophysical neutrino sources and the measurement of the diffuse astrophysical neutrino flux. The flavor composition of the measured flux is a very important component in understanding and modeling the astrophysical neutrino flux. In addition, an improved measurement of the flavor composition of the astrophysical neutrino flux at Earth allows us to infer the flavor composition at the sources and thus provides insights into neutrino production mechanisms. I will present the plan for a new flavor analysis using a combination of datasets used within the IceCube Collaboration. Previous flavor measurements with IceCube focused on individual samples targeting distinct event types, mostly dominated by events with interaction vertices inside the detector. Building on existing efforts, I plan to perform such a measurement on an expanded dataset. Such a sample includes contained and uncontained events, incorporates improved ice modeling, and achieves the highest statistics for the high-energy neutrino flux. These updates in event classification promise improvement in the sensitivity of the flavor measurement. Identifying double-cascades among tracks and cascades is a continuous effort, and the main focus of my talk.
- Host: Albrecht Karle
- Physics Department Colloquium
- Have we observed neutron star rockets?
- Time: 3:30 pm - 4:30 pm
- Place: Chamberlin 2241
- Speaker: Yuri Levin, Columbia University
- Abstract: Neutron stars are incredible playgrounds for theoretical physicists and observational astrophysicists, featuring the most intense concentrations of all four known force-fields of nature. In this talk, I will highlight a peculiar effect that leads to a prediction of an electromagnetic rocket force. I will explain how recent Gaia observations allow us to probe this force. I will show an exact computation of the rocket force in Force-Free Electrodynamics, which is a good theory describing magnetospheres of many, but not all neutron stars (no knowledge of plasma physics will be assumed). Gaia's neutron stars may well have to be described by a different theory.
- Host: Vladimir Zhdankin