Research
Current Activities - In Brief
- Bottom-jet-initiated trigger signature operations tasks (algorithm and code validation for Run 3)
- Higgs physics with H → bb with emphasis on gluon-fusion, vector-boson associated, and vector-boson fusion Higgs production
- Development of new machine learning-based approaches to quark jet identification
Higgs Physics
My highest priority right now is the pursuit of a deeper understanding of the newly discovered Higgs Boson (see publications below) and the search for additional Higgs bosons using the ATLAS Experiment located at the Large Hadron Collider in Geneva, Switzerland. I am part of the SMU ATLAS team and joined the effort in 2009. Since then, I have been involved or a leader in several key areas:
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Experimental Particle Physics:
- Trigger-Level Flavor Tagging: Heavy quarks (bottom and charm) are expected to be key players in Higgs boson physics, as well as many beyond-the-Standard Model physics scenarios. "Triggering" on events containing heavy quark flavors is therefore a crucial element in the ATLAS physics portfolio. SMU makes leading contributions to the implementation, validation, and development of jet tagging algorithms deployed in the realtime data-taking environment. I serve as co-leader of the ATLAS b-jet Trigger Signature Group. Learn more on my ATLAS Research Page.
- Standard Model Higgs Physics:
- Higgs-Bottom Quark Interaction: This is my primary research activity during LHC Run 2 and for the foreseeable future. The Higgs interaction with the bottom quark is the second-largest Yukawa coupling in the Standard Model and results in the largest branching fraction for the Higgs boson of mass 125 GeV/c2, BR(H → bb) = 59%. As I proposed to the Department of Energy Office of Science in 2016, the goal was to make a definitive observation of this decay process by the end of Run 2. SMU is part of a much larger team of ATLAS physicists intent on achieving this goal, and we have made significant contributions to the modelling of top quark events (a large background process) and the analysis software framework. Learn more on my ATLAS Research Page.
- Higgs Properties in Run 1: In Run 1, I collaborated with my faculty colleague Jingbo Ye to initiate and complete the first ATLAS search for H0(125) → Zγ. My Ph.D. student, Tingting Cao, contributed to the first comprehensive quantum number measurement of the newly discovered boson with a mass of 125 GeV/c2, establishing that the CP-even, spin-0 hypothesis was favored by the data. Learn more on my ATLAS Research Page.
- Beyond-the-Standard Model (BSM) Higgs Physics: a key question has been opened by the discovery of a Higgs Boson. "Are there more Higgs bosons in nature?" I co-led the ATLAS BSM Higgs subgroup, along with Nikos Rompotis, then at the University of Washington. I provided intellectual leadership to our BSM Higgs team in the search for the existence of additional Higgs-like bosons in nature. My biggest contribution has been as a leader of the effort to search for an electrically charged Higgs boson, an uneqivocal sign of physics beyond the Standard Model. This work is challenging Supersymmetry, one of the leading proposals for explaining what BSM physics might look like. Learn more on my ATLAS Research Page.
Quark and Lepton Physics
I have led or conducted research in several areas here while serving as a member of the BaBar Collaboration, whose experiment was located on the PEP-II Accelerator at the SLAC National Accelerator Laboratory.
- As co-leader of the BaBar working group on leptonic decays of bottom and charm mesons, I was deeply involved in the search for such decays of these mesons. My Ph.D. thesis was on the rare decay B0 → τ ν, which the BaBar and Belle collaborations have evidence for after analyzing all of their available data. In addition, I made significant contributions to the study of other relates decays, such as those of Ds mesons.
- As co-leader of the BaBar Collaboration's "Task Force on the Upsilon Mesons," I was responsible for insuring the efficient collection of data on the Υ(3S) and Υ(2S) mesons and the analysis of the large data samples that resulted from this. I led the most sensitive search for low-mass dark matter using decays of these mesons, and was part of the team that discovered the ground state of the bottomonium system, which had been predicted but not observed for 31 years.
- I contributed to the first BaBar measurement of CP violation in the B meson system and to a subsequent search for CP violation in the rare decay b → s γ
Other Activities
As a graduate student, I developed a C++/ROOT-based interface to the Stuttgart Neural Network Simulation (SNNS), based on FORTRAN work my advisor had done previously. This interface was called RooCARDS.
As an early graduate student, I worked on the discrimination of Higgs and Z bosons at the LEP Collider (ALEPH Experiment) using methods inspired by the paper, hep-ph/9803410.
As an undergraduate, I worked with Yale Prof. Michael Schmidt and the Yale CDF group on the feasibility of triggering on Electrons at CDF Run II (Senior Thesis, 1998) and performed the techical layout of the
Done, Error, and Busy cross-point chips for the CDF Run II Trigger Supervisor boards.
Publications and Papers
My INSPIREHEP Author Profile: http://inspirehep.net/author/profile/S.J.Sekula.1