Events at Physics |
Events on Wednesday, October 9th, 2024
- Preliminary Exam
- Connecting Multimessenger Observations to Theory in Particle Astrophysics from GeV to EeV
- Time: 11:00 am - 1:00 pm
- Place: 5280 Chamberlin Hall or
- Speaker: Angelina Partenheimer, Physics PhD Graduate Student
- Abstract: In my preliminary exam, I will discuss my paper on ultrahigh energy cosmic rays from gamma-ray sources. Ultra-high-energy cosmic rays (UHECRs) are the highest-energy particles ever observed. While the sources producing UHECRs are still unknown, the Pierre Auger Observatory has detected a large-scale dipole anisotropy in the arrival directions of cosmic rays above 8 EeV. My project explores whether resolved gamma-ray sources can reproduce the Auger dipole. I find that in all cases, the simulated dipole has an amplitude significantly larger than that measured by Auger, implying that the resolved gamma-ray sources are insufficient to account for the population of sources producing the highest-energy cosmic rays. Next, I will discuss my recent project on prospects of detecting GeV transients with IceCube DeepCore and Upgrade. A wide variety of transient sources have been predicted to emit GeV neutrinos. In light of the upcoming IceCube-Upgrade, which will extend the IceCube detector’s sensitivity down to a few GeV, I survey a variety of transient source models and compare the predictions and detector sensitivities. Finally, I will briefly discuss my intended thesis work, which involves using anticipated UHE neutrino data from the Payload for Ultrahigh Energy Observations balloon experiment to constrain the UHECR proton composition.
- Host: Ke Fang
- Theory Seminar (High Energy/Cosmology)
- 6220 Nesbitt Rd, Fitchburg, WI 53719
- Time: 4:00 pm - 5:00 pm
- Place: 5280 Chamberlin Hall
- Speaker: Cash Hauptmann, University of Nebraska–Lincoln
- Abstract: I will discuss ongoing work concerning cosmological phase transitions (PTs) and their possible roles in the production of dark matter (DM) and primordial black holes (PBHs). For DM, I have recently proposed a non-thermal production mechanism utilizing supercooled first-order PTs which can enhance the abundance of DM. This enhancement opens the viable DM parameter space to models with higher annihilation cross sections which would have otherwise produced too little DM in the standard thermal scenario. Another interesting consequence of first-order PTs could be an efficient trapping of DM in false vacuum domains, and their subsequent collapse to PBHs. Depending on the energy scale of the PT, these PBHs could make up significant fractions (if not all) of today’s DM abundance. Whatever their byproducts may be, first-order PTs are expected to source stochastic background signals of gravitational waves—potentially probeable by next-generation detectors. With this in mind, all phenomenological results are presented in a robust multi-messenger fashion; correlating DM or PBH constraints with gravitational wave signals.
- Host: Lisa Everett