Graduate Program Events |
Events on Friday, December 5th, 2025
- 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
- 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
- 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