High Energy Physics Seminars This Term

Di-Higgs production directly probes the Higgs self-coupling, a crucial parameter for testing the Higgs potential and the Standard Model. With a small cross section of ∼33 fb, it remains currently unobserved at the LHC. The High-Luminosity LHC (HL-LHC), expected to start in 2030, will deliver 3000 fb−1 and improve sensitivity to this rare process. This talk presents CMS searches for resonant and non-resonant di-Higgs production in the bbτ τ final state, which represents a good balance between high branching ratio and reduced background contamination. An optimized categorization has been developed for targeting boosted topologies, where the Higgs decay products become collimated, resulting in an improved separation of signal from background using new dedicated tagging algorithms. Higher luminosity will also bring harsher conditions, including increased radiation and pileup. To mitigate pileup, CMS upgrades include the addition of the MIP Timing Detector (MTD), which will enable 4D event reconstruction by associating precise time information of 30–60 ps to charged particles. This is expected to improve analysis sensitivity, especially those involving multi-object final states like di-Higgs searches, where the impact is equivalent to 2–3 additional years of data. This work focuses on the design optimization and performance validation of the Barrel Timing Layer (BTL), consisting of LYSO crystals coupled to Silicon Photomultipliers. These efforts were conducted via extensive test beam and laboratory measurement campaigns. Results confirm that the BTL meets its performance goal and its mass production is underway.

The Mu2e experiment at Fermilab is designed to search for charged lepton flavor violation through neutrinoless muon-to-electron conversion in aluminum. Observation of this process would provide direct evidence for physics beyond the Standard Model. Mu2e aims to improve sensitivity by four orders of magnitude relative to previous experiments. This presentation will outline the scientific motivation, describe the experimental design, and summarize the status, including the recent transportation and installation of detector components into the Mu2e hall. The experiment remains on track for initial data collection in 2027.

Neutrinos are among the most mysterious particles in nature. Over the past few decades, experiments have revealed that neutrinos change their identity as they travel—a phenomenon called oscillation—which proved that they have mass and opened a window to new physics beyond the Standard Model. Today, the Short-Baseline Neutrino (SBN) program at Fermilab and the future Deep Underground Neutrino Experiment (DUNE) are pushing this frontier, searching for new neutrino states and seeking clues to why the universe is made of matter instead of antimatter. In this talk, I will discuss the challenges of precision neutrino oscillation measurements, the status of the SBN (SBND and ICARUS) program in the search of neutrino steriles as well as the performance of the detectors, and highlight the role that these experiments play to fully realize DUNE's discovery potential in the coming years.

As LHC Run 3 winds down in the next year or so, Effective Field Theory (EFT) is heating up as a technique to search for new physics.  During the HL-LHC period and beyond, EFT will become even more powerful because of the enormous data sets that will become available.  As a means to explore a possible future in which signs of BSM physics are discovered via EFT, we can turn to the past.  A retrospective exploration of EFT techniques to data below the electroweak scale allows us to see how EFT could have performed in terms of discovering and understanding the electroweak physics.  This case study offers tremendous hope for how much a future EFT discovery might tell us about BSM physics.

The discovery of the Higgs boson in 2012 completed the Standard Model of particle physics, yet key questions such as the nature of dark matter and the origin of the matter–antimatter asymmetry remain unresolved. A central goal of the LHC physics program is to probe the Higgs potential, as any deviation from the Standard Model expectation could alter the dynamics of the electroweak phase transition in the early universe, potentially offering insight into the origin of the matter–antimatter asymmetry and the mechanism of baryogenesis. This potential can be experimentally accessed through measurements of Higgs boson self-interactions in Higgs boson pair (HH) production. This seminar presents the results of the ATLAS Run-2 search for non resonant di-Higgs production in the bbˉτ+τ− final state using 140 fb−1 of proton–proton collision data collected between 2015 and 2018. The talk will discuss key analysis techniques, highlight improvements introduced for Run-3, and provide an outlook for future analysis at the High-Luminosity LHC.