Events at Physics
Events on Thursday, April 15th, 2021
- Cosmology Journal Club
- Time: 12:00 pm
- Abstract: Each week, we start with a couple scheduled 15 minute talks about one's research, or an arXiv paper. The last 30 minutes will typically be open to the group for anyone to discuss an arXiv paper.
All are welcome and all fields of cosmology are appropriate.
Contact Ross Cawthon, cawthon@wisc, for more information.
Meeting ID: 93592708053, passcode: cmbadger
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Ultra-high-energy cosmic rays and neutrinos, expectations for diffuse fluxes and arrival-direction correlations
- Time: 2:30 pm
- Place: https://uwmadison.zoom.us/j/94502540064?pwd=c3p5ZmJuaGIzNDlsdG1Kc05CaVB6QT09
- Speaker: Arjen van Vliet, DESY Zeuthen, Germany
- Abstract: Astrophysical neutrinos can be produced by cosmic-ray interactions, either inside the sources of cosmic rays (source neutrinos) or during the propagation through extragalactic space (cosmogenic neutrinos). The expected cosmogenic neutrino flux in the EeV range depends strongly on the composition of ultra-high-energy cosmic rays (UHECRs). A larger fraction of protons will especially increase the expected cosmogenic neutrino flux. One scenario in which a significant proton fraction can be expected is if different classes of Active Galactic Nuclei (AGN) are the dominant sources of UHECRs. If that is the case, not only a large cosmogenic neutrino flux is expected, but a large source neutrino flux as well. It might therefore be interesting to look at correlations between neutrino and UHECR arrival directions. However, deflections of UHECRs in magnetic fields decrease the expected directional correlations. Even for the weakest extragalactic magnetic fields (EGMFs) the non-observation of high-energy neutrino multiplets strongly constrains the possibility to find neutrino-UHECR correlations. On the other hand, the Pierre Auger Collaboration has recently found indications for correlations between UHECR arrival directions and local star-forming galaxies or AGN. These results can be used to put limits on the EGMFs between these galaxies and the Milky Way. For a source density of star-forming galaxies relatively strong EGMFs are required to reproduce the level of anisotropy that Auger has observed.
- Host: Lu Lu
- Astronomy Colloquium
- Planets, Patterns, and the Origin of Life
- Time: 3:30 pm
- Place: Zoom meeting(see Abstract ) Coffee and tea 3:30pm, Talk 3:45 PM
- Speaker: Lauren Weiss, University of Hawaii at Monoa
- Abstract: Exoplanet science is an explosive new field catalyzed by the discovery of over 4000 extrasolar planets via the NASA Kepler and MIT-led TESS missions. The field will continue to evolve rapidly over the next several decades as we push observational techniques toward the discovery of Earth-like planets. Along the way, we are learning about diverse types of planets, their interior and atmospheric compositions, their orbital properties, the systems in which they reside, and how the planets form and change over time. Recent discoveries of patterns have reshaped our understanding of planet formation, with possible implications for the origins of Earth-like planets and life. I will discuss my past, present, and future experiments with observational astronomy to address these topics.
- Host: Professor Ellen Zweibel
- High Energy Seminar
- First results from the Muon g-2 experiment at Fermilab
- Time: 4:00 pm
- Place: https://uwmadison.zoom.us/j/99956350920
- Speaker: Liang Li, Shanghai Jiao Tong University
- Abstract: The Fermilab Muon g-2 experiment measures the muon anomalous magnetic moment with high precision. Together with recent improvements on the theory front, the first results of the experiment confirm the long-standing discrepancy between the experimental measurements and the Standard Model predictions. The combined significance of the discrepancy is at 4.2 sigma. This talk presents the first results and current status of the Muon g-2 experiment at Fermilab.
- Host: Yang Bai