Events at Physics |
Events on Wednesday, December 3rd, 2025
- Preliminary Exam
- Measurement of the ZZ production cross-section and EFT constraints
- Time: 9:00 am - 11:00 am
- Place: 5310 Chamberlin or
- 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
- Fantastic signatures and how to find them: Long-lived particle searches in CMS
- Time: 12:00 pm - 1:00 pm
- Place: 5280CH &
- Speaker: Daniel Guerrero, Fermilab
- Abstract: Many theories beyond the Standard Model predict new particles with lifetimes long enough to travel measurable distances before decaying. These long-lived particles (LLPs) often produce unconventional and challenging signatures in the detector. To efficiently capture these signatures, dedicated trigger strategies and innovative use of detector capabilities are employed to enhance the sensitivity of LLP searches. In this seminar, I present results using CMS data from Run 2 and the ongoing Run 3 of the LHC, including a novel approach based on the Muon Detector Shower signature. I conclude with prospects for the High-Luminosity LHC, where upcoming detector and trigger upgrades will enable next-generation LLP searches.
- 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