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Colloquia & Seminars, Fall 2022

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Planetesimal Formation in Circumstellar Disks

Speaker: Dr. Jacob B. Simon
Date: Thursday, November 3, 2022
Time: 3:00 P.M. Central Standard Time
Room: 402 Currens Hall

Abstract: Abstract: Planetesimals are small rocky (and sometimes icy) objects, typically 1-100 km in diameter (e.g., asteroids and comets in the Solar System). One of the largest unanswered questions in planetary astrophysics is: how do these planetesimals form in the disks that orbit young, newly formed stars (“circumstellar disks”)? In this talk, I will discuss progress that my group has recently made in answer- ing this important question. In particular, using large-scale fluid and particle dynamics simulations run on national level supercomputers, we have studied an aerodynamic clumping mechanism, known as the streaming instability, as the route toward forming these bodies. In comparing the properties of plan- etesimals formed via this mechanism with observations of bodies in our own Solar System (i.e., the icy comet-like objects beyond the orbit of Pluto), we have shown that the streaming instability is a very strong candidate for producing these bodies. I will also discuss current and ongoing work to further compare theory and observations, namely within the context of the size distribution of planetesimals, and I will conclude by discussing how our results fit within our current understanding of planet formation.

About the speaker: Jake Simon is currently an Assistant Professor in the Department of Physics and Astronomy at Iowa State University. He received his Ph.D. in Astronomy (2010) at the University of Virginia, and his B.S. in Physics (2004) at the University of Illinois. Before arriving at ISU, he served in several postdoctoral (including a NASA Sagan Fellowship) and research associate positions at the University of Colorado and the Southwest Research Institute. His research is focused on a number of topics related to the earliest stages of planet formation, and he is also interested in how hot, ionized gas orbits and accretes onto black holes.

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Searches for rare Higgs decays with ATLAS at the Large Hadron Collider

Speaker: Dr. William Heidorn
Date: Thursday, October 20, 2022
Time: 3:00 P.M. Central Standard Time
Room: 402 Currens Hall

Abstract: An overview of particle physics with a focus on my graduate research within the ATLAS Collaboration at CERN. The two main topics will be my research on thermal imaging systems for quality assurance and quality control of stave cores for the ATLAS Phase 2 upgrade and a search for the exclusive decays of the Higgs and Z bosons to a meson and a photon using the full LHC Run 2 data set.

About the speaker: Dr. Heidorn is an Assistant Professor at Iowa Lakes Community College. He did his MS in physics from Western Illinois University. He received his Ph.D. in high energy physics at Iowa State University in 2021. He became a member of the ATLAS collaboration (one of the general- purpose detectors on the Large Hadron Collider at CERN) by developing thermal imaging systems for quality assurance and quality control of stave cores for the ATLAS strips detector upgrade. In collaboration with the University of Birmingham, UK using the full Run 2 data set of the ATLAS detector they searched for the rare Higgs and Z boson decays to a meson plus a photon.

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