Events at Physics |
Events During the Week of November 30th through December 6th, 2025
Sunday, November 30th, 2025
- Academic Calendar
- Thanksgiving Recess
- Abstract: *Note: actual end time may vary.* CONTACT: admin@secfac.wisc.edu
Monday, December 1st, 2025
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Title to be announced
- Time: 12:00 pm - 1:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Dave Gates, Thea
- Host: Cary Forest
- Theory Seminar (High Energy/Cosmology)
- New Opportunities to Search for Long-Lived Particles
- Time: 1:00 pm - 2:30 pm
- Place: Chamberlin 5280
- Speaker: Matheus Hostert, U. Iowa, Iowa City
- Abstract: I will discuss new opportunities to search for weakly-coupled, long-lived particles (LLP) produced in rare meson and lepton decays. We derive new limits and sensitivity to the visible decays of these LLPs at spallation sources and neutrino experiments. As a prototypical example, we focus on axion-like particles coupled to leptons. Time permitting, I will also link some of these signatures with ultra-high energy events at neutrino telescopes. Together, these approaches map a broad and rich landscape for discovering a wide range of weakly-coupled particles.
- Preliminary Exam
- Quantum Electrodynamics of Dual Superconducting Circuits
- Time: 1:00 pm - 3:00 pm
- Place: B343 Sterling Hall
- Speaker: Priya Rajkumar, Physics PhD Graduate Student
- Abstract: The 2025 Nobel Prize honors the discovery of Macroscopic Quantum Tunneling (MQT). However, standard superconducting qubits, such as the transmon, are engineered to suppress this phenomenon in a Josephson Junction (JJ), thereby localizing its phase to create a nonlinear inductor. We investigate the opposite regime where MQT proliferates, and the junction undergoes a quantum phase transition to an insulating state. Here, the phase delocalizes while its conjugate variable—charge—becomes localized, effectively turning the junction into a nonlinear "Bloch" capacitor. We experimentally realize this underexplored insulating state by galvanically connecting a junction to a high-impedance transmission line composed of thousands of large-area JJs. This line achieves characteristic impedances of 5*Resistance quantum while creating a bath of accessible standing wave modes, for which the junction acts as a nonlinear capacitive termination. Consequently, the junction scatters incoming photons, inducing measurable frequency shifts and spectral broadening. We further combine microwave spectroscopy with DC excitation to probe charging effects, such as Coulomb blockade. With our hybrid DC-RF setup, we elucidate the quantum electrodynamics of dual superconducting circuits, which holds promise for advancing quantum circuit theory and metrological techniques.
- Host: Roman Kuzmin
Tuesday, December 2nd, 2025
- Preliminary Exam
- MRI Methods for Imaging and Analysis of Neurofluid Dynamics
- Time: 12:00 pm - 2:00 pm
- Place: Chamberlin Hall Room 5280
- Speaker: Zaynab Yardim
- Abstract: Characterizing neurofluid dynamics is crucial, as it plays essential roles in maintaining cerebral homeostasis through nutrient delivery, waste clearance, and other vital functions. Disruption of these systems has been linked to a range of neurological disorders such as Alzheimer’s disease, small vessel disease, and dementia. Understanding these systems in the living human brain has been a significant challenge due to the lack of safe and reliable imaging methods, which has limited the potential for early diagnosis and preventive care. Recent advancements in MRI have enabled safe, repeatable, and high-resolution visualization of neurofluid dynamics. However, characterizing cerebrospinal fluid (CSF) dynamics still faces challenges due to the difficulties in accurately delineating CSF. In this talk, I will present MRI methods for noninvasive, high-contrast, and artifact-reduced CSF imaging, along with noninvasive cerebral blood flow analysis.
- Host: Sridhara Dasu and Kevin Johnson
Wednesday, December 3rd, 2025
- Preliminary Exam
- Measurement of the ZZ production cross-section and EFT constraints
- Time: 9:00 am - 11:00 am
- Place: Chamberlin Hall Room 5310
- Speaker: Justin Marquez
- Abstract: This research studies the production of Z boson pairs in proton-proton collisions with the CMS detector at the CERN LHC. The cross-section of this production is measured by observing four-lepton final states using early Run 3 data (2022-2023) witih center-of-mass energy of 13.6 TeV, considering only electrons and muons in the final state. In addition to the cross-section measurement, various relevant parameters in the standard model effective field theory will be investigated to obtain statistical limits on their effects on ZZ production.
- Host: Matthew F. Herndon
- Preliminary Exam
- Probing primordial non-gaussianity with large-scale velocity reconstruction using ACT and DESI-LS data
- Time: 11:00 am - 1:00 pm
- Place: Chamberlin Hall Room 5310
- Speaker: Anderson Lai
- Abstract: The large-scale velocity field of matter is a sensitive probe in several exciting areas of cosmology and astrophysics, including cosmological parameters, dark matter halo models, and electron profiles. In addition, by combining it with the large-scale velocity and galaxy overdensity fields, one can obtain competitive constraints on local primordial non-Gaussianity. In this talk, I will introduce kinematic Sunyaev–Zeldovich (kSZ) tomography, a modern technique for reconstructing the large-scale velocity field, followed by a novel development in an optimal power-spectrum estimator that outperforms conventional approaches with highly compressed computation time. I will present its latest application to observations from the Atacama Cosmology Telescope and DESI-LS (Legacy Survey), yielding a ~12σ detection of the kSZ signal—an improvement factor of ~3 compared to earlier studies. With upcoming data from the Simons Observatory and the Vera C. Rubin Observatory, there is a promising outlook for kSZ velocity reconstruction.
- Host: Moritz Muenchmeyer
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Long-lived particle searches
- Time: 12:00 pm - 1:00 pm
- Place: 5280CH &
- Speaker: Daniel Guerrero, Fermilab
- Host: Sridhara Dasu
- Preliminary Exam
- Magnetically driven plasma jet experiments on the Big Red Ball
- Time: 2:30 pm - 4:30 pm
- Place: Chamberlin Hall Room 5310
- Speaker: Shreya Dwivedi
- Abstract: Plasma jet experiments using planar coaxial electrodes with bias magnetic field, emulating the central object–accretion disk system, are conducted on the BRB at WiPPL. Hydrogen plasma jets (density ∼ 1e+19m−3 at 11 ± 2eV) at high bias voltage (2–3kV) are injected into different H plasma backgrounds (density ∼ 1e+17m−3 at ∼ 5eV). Axial component Bz propagates downstream from the gun, undergoing collimation while elongating. The induced toroidal field Bϕ shows pinching near the column axis, indicative of plasma compression or helicity injection. The current density Jz is strongly collimated, extending up to ∼ 90–100cm from the gun, approximately propagating along collimated Bz lines. Later, both Bz and Jz distributions broaden and weaken, suggesting relaxation or enhanced interaction with the background plasma. This J − B topology is consistent with earlier plasma jet experiments. Bz with average peak amplitude ∼ 240G remain collimated for longer durations when jets are launched into lower density plasma.: lasting ∼ 34μs at 1.0 × 1e+17m−3 compared to ∼ 24μs at 6.2 × 1e+17m−3 (each at 3kV bias). The propagation speed of Bz [90, 76, 46]km/s decreases with increasing background density ∼ [2.1, 3.1, 5.2] × 1e+17m−3, for jets biased at 2kV.
- Host: Albrecht Karle
Thursday, December 4th, 2025
- R. G. Herb Condensed Matter Seminar
- Experiments on Non-equilibrium Josephson Systems in One and Two Dimensions
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Andrew Higginbotham, University of Chicago
- Abstract: Experimental progress in quantum computing has yielded exciting new tools for probing and manipulating superconducting circuits. I will present our recent work on driven behavior of 1D and 2D Josephson junction arrays. In one dimension, we have recently studied the lifetime and dynamics of plasmons, which makes some interesting connections to the physics of one-dimensional quantum liquids and classical nonlinear systems. In two dimensions, I will show our discovery of non-equilibrium microwave radiation and non-equilibrium noise scaling near the superconductor-insulator quantum phase transition.
- Host: Roman Kuzmin
- Thesis Defense
- Measurement of the Three Top Quarks Process with the CMS Detector at the LHC
- Time: 10:00 am - 12:00 pm
- Place: 5280 Chamberlin
- Speaker: Dylan Teague, Physics PhD Graduate Student
- Abstract: This thesis presents the first analysis measuring the three top quark decay process at the Large Hadron Collider. The measurement was performed on events with two same-sign leptons and three or more leptons on data taken by the Compact Muon Solenoid detector during the 2016–2018 data taking period corresponding to 137 fb-1 of data with √𝑠 = 13 TeV. The analysis found the three top process to have an overall significance of 0.182𝜎 and a CLs 95 % upper limit of 28.1 fb. These results were also uses to reinterpret the data to place limits on possible beyond Standard Model physics models that predict enhancements to the three top quark cross-section.
- Host: Kevin Black
- Preliminary Exam
- Spiral Arm–Driven Star Formation in the FIRE Simulations
- Time: 11:00 am - 1:00 pm
- Place: 2532 Sterling
- Speaker: Hannah Woodward
- Abstract: Recent observations have traced the trajectories of nearby star clusters backward in time, revealing that many have converging paths and likely shared common origins. This trend spans clusters across a wide range of ages, providing evidence for sequential star formation. While stellar feedback is often invoked to explain such propagation, the dynamics of spiral arms may also compress gas and trigger new star formation. To explore this mechanism, we searched for signatures of spiral arm–induced star formation in the Feedback In Realistic Environments (FIRE) simulations. We applied the HDBSCAN clustering algorithm to identify groups of star particles with similar positions and velocities within selected regions of a simulated galaxy, and then analyzed their kinematic evolution over time. I will compare the motions of FIRE star particles to the observed trajectories of nearby stellar clusters to investigate whether spiral structure can drive sequential star formation.
- Host: Elena Donghia
- Astronomy Colloquium
- Single-lined Eclipsing Binary Stars: A Stellar Astronomy Multi-Tool
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Dan Stevens, University of Minnesota-Duluth
- Abstract: Precisely and accurately measured stellar properties such as mass and radius are important for a wide range of science cases, from characterizing nearby exoplanets to inferring properties of distant galaxies. Double-lined eclipsing binary stars (DLEBs) have long been the gold standard for making such measurements, as the two similar-luminosity stars’ individual masses and radii can routinely be measured to percent-level precision. By combining space-based observations from the TESS and Gaia space telescopes with archival datasets, it is now possible to measure fundamental stellar parameters precisely and accurately for single-lined EBs (SLEBs), in which only the more luminous star’s spectrum is seen. I will summarize the advantages of studying SLEBs for specific science cases, focusing on recent efforts by my research group and others to resolve the longstanding problem of radius inflation in low-mass stars. I will also highlight a few “superlative” SLEB discoveries and their potential for probing stellar physics across the HR diagram. I will discuss the obstacles we have encountered to characterize SLEBs to percent-level precision and accuracy, then preview the near-term prospects for overcoming them.
- Host: Nicholas Stone
Friday, December 5th, 2025
- Preliminary Exam
- Measurement of the Cross Section for Higgs Boson Production in Association with a Z Boson with the CMS Detector
- Time: 9:00 am - 11:00 am
- Place: Chamberlin Hall Room 5280
- Speaker: Ryan Simeon
- Host: Sridhara Dasu
- Thesis Defense
- Study of ZZ+jets and Electroweak ZZ+2jets Production in Proton-Proton Collisions at √s = 13 TeV in Four-Lepton Events Using the CMS Detector at the LHC
- Time: 11:30 am - 1:30 pm
- Place: 5280 Chamberlin
- Speaker: He He, Physics PhD Graduate Student
- Abstract: Two studies are presented on di-boson production in association with jets in the fully leptonic final states, pp → (Z/γ∗)(Z/γ∗) + jets → 2ℓ2ℓ′ + jets, (ℓ, ℓ′ = e or μ) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb−1 collected with the CMS detector at the LHC. In the first study, search is performed for the electroweak (EW) production of two Z bosons in association with two jets (EW ZZ+2jets) using a deep neural network (DNN) approach, and the production is measured with an observed (expected) significance of 4.4 (3.4) standard deviations, consistent with the published CMS results based on a matrix element likelihood approach (MELA). In the second study, differential distributions and normalized differential cross sections of di-boson ZZ production associated with different numbers of jets (ZZ+jets) are measured as a function of jet multiplicity, transverse momentum pT, pseudorapidity η, invariant mass and ∆η of the highest-pT and second-highest-pT jets, and as a function of invariant mass of the four-lepton system for events with various jet multiplicities. These differential cross sections are compared with theoretical predictions that mostly agree with the experimental data. However, in a few regions we observe discrepancies between the predicted and measured values. Further improvement of the predictions is required to describe the ZZ+jets production in the whole phase space.
- Host: Matthew Herndon
- Preliminary Exam
- Oblique dipole rotator to emulate a pulsar wind
- Time: 2:00 pm - 4:00 pm
- Place: Chamberlin Hall Room 5310
- Speaker: Rene Flores Garcia
- Abstract: We are building a dipolar rotating magnetic field (RMF) system to emulate the magnetosphere of an obliquely rotating pulsar and demonstrate production of an outgoing plasma wind. We intend to form a striped plasma wind similar to that surrounding a neutron star and potentially to observe magnetic reconnection within the stripes. The driver will consist of an orthogonal pair of Helmholtz-like drive coils powered by IGBT H-bridges producing 5 kA per turn on each coil generating ~10 G of magnetic field half a meter away from the center of the coils. The coils will be placed at atmospheric pressure in an alumina-coated fiberglass pressure vessel within the high-vacuum plasma chamber. Fuel gas will be puffed from outlets on the surface of the vessel, and the RMF will ionize the gas, hydrogen, helium and deuterium being possible fuel options. Experimental hardware is in development. Fueling system is currently being tested to ensure that the driver receives enough neutral gas to ionize and form a plasma, while additional plasmas sources are also being considered. Diagnostics will consist of an existing magnetic Hall probe array and a triple-Langmuir-Mach probe array currently being manufactured. Key next steps are to test the new solid-state RMF drivers at full power, to implement the fueling system, and to test plasma production in a cylindrical vacuum chamber, with plasma experiments on the Big Red Ball with spherical geometry and edge magnetic confinement as a longer-term objective.
- Host: Cary Forest
- Physics Department Colloquium
- Title to be announced
- Time: 3:30 pm - 4:30 pm
- Place: Chamberlin 2241
- Speaker: Andrew Long, Rice University
- Host: Daniel Chung