The discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider (LHC) ushered in a new era of particle physics. A unique property of the Higgs boson is that relatively large fractions of Higgs bosons could decay to non-Standard Model final states and be consistent with the current experimental constraints. Furthermore, many theoretical models suggest that new particles may preferentially couple to the Higgs boson, making the Higgs boson a unique window sensitive to non-Standard Model physics. In particular, the Higgs boson may decay to a variety of unknown particles that could address a range of fundamental questions including dark matter.

My research goals cover broad areas of physics and respond to three key areas in the Report of the Particle Physics Project Prioritization Panel (P5):

1.) Using the Higgs boson as a new tool for discovery
2.) Identifying the new physics of dark matter
3.) Exploring unknown new particles, interactions, and physical principles.

My main interest is in exotic decays of the Higgs boson, including invisible final states. I have then extended this paradigm to include partially visible final states (e.g., missing transverse momentum with photons or leptons).

I co-led the search for Higgs bosons to invisible final states in the vector boson fusion channel with the first portion of LHC data published in 2018. Then I set the groundwork for the follow-up study with the full data published in 2022. I then co-led the search for dark photons in the invisible final state published in 2022. I am currently working on several related analyses of exotic Higgs decays.

The ATLAS trigger system is an amazing system of custom electronics, computing and software that underly the core of the experiment. The system allows ATLAS to achieve our core scientific goals by deciding in a fraction of second which events will be written to permanent storage.

My interest in the ATLAS trigger is primarily focused on the missing transverse momentum final state, or dark matter trigger. This trigger is fundamental for my physics interests at the intersection of the Higgs boson and dark matter.

I work on both the hardware and software components of the trigger. From 2016-2020 I lead the algorithm development and simulation for the L1 trigger upgrade. From 2020-2022 I led the missing transverse momentum trigger group.

The LHC began a new run in 2022 — and my undergraduate students have been involved in trigger operations at CERN. Performance results of the Run 3 trigger can be described in a paper submitted in 2024.

Modern high energy physics experiments, such as the ATLAS and CMS experiments generate a deluge of data that must be sifted through in microseconds. The first-level trigger system operates on Field Programmable Gate Arrays (FPGA) and determines which events to save. Improvements to the algorithms that operate in the FPGA-based trigger have the potential to dramatically increase the sensitivity of experiments. The advent of machine learning algorithms that can be evaluated on FPGA electronics has the potential to revolutionize the trigger by saving interesting events that would be rejected. I am interested in the very efficient implementation of decision tree models in FPGA. With my fwX collaborators, I have worked on the implementation of classification, regression and anomaly detection (described in three papers).

I am interested in the question: are there channels we could be sensitive to Higgs decays at the LHC, but we do not currently analyze the data because the appropriate trigger does not exist? I have performed phenomenological studies of challenging final states using Monte Carlo simulation to motivate new triggers for experiments like ATLAS. I published a study quantifying the sensitivity of decays to charm quarks using the VBF production mode with an associated photon. Most recently I expanded this study for exotic decays of the Higgs boson to four b-jets.

• ATLAS Collaboration, “The ATLAS Trigger System for LHC Run 3 and Trigger performance in 2022,” submitted to JINST, arXiv: 2401.06630.

• S. Hageboeck, A. Reinsvold Hall, N. Skidmore, G. A. Stewart, G. Benelli, B. Carlson, C. David, J. Davies, W. Deconinck, D. DeMuth Jr., P. Elmer, R. B. Garg, K. Lieret, V. Lukashenko, S. Malik, A. Morris, H. Schellman, J. Veatch, M. Hernandez Villanueva “Training and Onboarding initiatives in High Energy Physics experiments,” arXiv: 2310.07342

• Stephen Roche, Benjamin Carlson, Christopher Hayes, Tae Min Hong, “Illuminating all-hadronic final states with a photon: Exotic decays of the Higgs boson to four bottom quarks in vector boson fusion plus gamma at hadron colliders,” submitted (2023). arXiv: 2306.01901
• Stephen Roche, Quincy Bayer, Benjamin Carlson, William Ouligian, Pavel Serhiayenka, Joerg Stelzer, Tae Min Hong, “Nanosecond anomaly detection with decision trees for high energy physics and real-time application to exotic Higgs decays,” submitted (2023). arXiv: 2304.03836.
• B. T. Carlson, Q. Bayer, T.M. Hong, S.T. Roche, “Nanosecond machine learning regression with deep boosted decision trees in FPGA for high energy physics,” Journal of Instrumentation 17 P09039 (2022). arXiv: 2207.05602.
• ATLAS Collaboration, “Search for invisible Higgs-boson decays in events with vector-boson fusion signatures using 139 fb-1 of proton-proton data recorded by the ATLAS experiment,” Journal of High Energy Physics 08 (2022) 104. arXiv: 2202.07953.
• Benjamin Carlson, Tao Han, Sze Ching Iris Leung, “Higgs to charm quarks in vector boson fusion plus a photon,” Phys. Rev. D 104 073006 (2021). arXiv: 2105.08738.
• ATLAS Collaboration, “Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying to invisible particles at 13 TeV with the ATLAS detector,” The European Physical Journal C 82 105 (2022). arXiv: 2109.00925
• ATLAS Collaboration, “Performance of the ATLAS Level-1 topological trigger in Run 2,” The European Physical Journal C 82 7 (2022). arXiv: 2105.01416.
• Tae Min Hong, Benjamin Carlson, Brandon Eubanks, Stephen Racz, Stephen Roche, Joerg Stelzer, Daniel Stumpp, “Nanosecond machine learning event classification with boosted decision trees in FPGA for high energy physics,” Journal of Instrumentation 16 P08016 (2021). arXiv: 2104.03408.
• ATLAS Collaboration, “Performance of the ATLAS missing transverse momentum triggers for the ATLAS detector,” Journal of High Energy Physics 2020, 80 (2020). arXiv: 2005.09554.
• ATLAS Collaboration, “Performance of the upgraded PreProcessor of the ATLAS Level-1 Calorimeter Trigger,” Journal of Instrumentation 15 (2020) P11016, September 2020. arXiv: 2005.04179.
• ATLAS Collaboration, “Searches for electroweak production of supersymmetric particles with compressed mass spectra in sqrt(s) = 13 TeV pp collisions with the ATLAS detector,” Phys. Rev. D 101, 052005 (2020). arXiv: 1911.12606.
• ATLAS Collaboration, “Combination of searches for invisible Higgs boson decays with the ATLAS experiment,” Phys. Rev. Lett. 122, 231801 (2019). arXiv: 1904.05105.
• ATLAS Collaboration, “Search for invisible Higgs boson decays in vector boson fusion at sqrt(s) = 13 TeV with the ATLAS detector,” Phys. Lett. B 793 499-519 (2019). arXiv: 1809.06682.
• CMS Collaboration, “Search for R-parity violating decays of a top squark in proton-proton collisions at sqrt(s) = 8 TeV,” Phys. Lett. B 760 178-201 (2016). arXiv:1602.04334
• CMS Collaboration, “Measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections in pp collisions at sqrt(s) = 7 TeV,” Phys. Lett. B 749 14-34 (2015). arXiv:1501.07750.
• CMS Collaboration, “Search for supersymmetry in events with jets, either photons or leptons, and low missing transverse momentum in pp collisions at 8 TeV,” Phys. Lett. B 743 503-525 (2014). arXiv:1411.7255.
• J.P Sikora, B.T. Carlson, D.O. Duggins, K.C Hammond, S.D Santis, A.J. Tencate, “Electron cloud density measurements in accelerator beam-pipe using resonant microwave excitation,” Nucl. Instrum. Methods Phys. Res., Sect. A, 754, 28-25 (2014). arXiv:1311.5633
• Stefano De Santis, John.M. Byrd, Michael G. Billing, Mark A. Palmer, John P. Sikora, Benjamin T. Carlson, “Characterization of electron clouds in the Cornell Electron Storage Ring Test Accelerator using TE-wave transmission,” Phys. Rev. ST Accel. Beams, 13, 071002 (2010).

• Conference presentation, “New search strategies for exotic decays of the Higgs boson to four bottom quarks using vector boson fusion,” Phenomenology Symposium, 2023. May 9 2023. [link]
• Conference presentation (ATLAS), “Measurements of multi-boson production including vector-boson scattering at ATLAS,” Lake Louise Winter Institute, February 25, 2022. [link]
• Conference presentation (fwX), “Nanosecond machine learning with BDT for high energy physics,” APS Division of Particles and Fields, July 13, 2021. [link]
• Conference presentation (ATLAS), “Missing transverse momentum algorithm improvements for the ATLAS High Level Trigger for Run 3 for pp collisions,” APS Division of Particles and Fields, July 13, 2021. [link]
• Poster presentation (fwX), “Nanosecond machine learning with BDT for high energy physics,” Offshell July 6, 2021. [link]
• Conference presentation (ATLAS), “Missing transverse momentum algorithm improvements for the ATLAS Run 3 High Level Trigger”, APS April meeting (virtual), April 18, 2021.
• Conference presentation (ATLAS), “Dark Matter searches with the ATLAS detector,” International Conference on New Frontiers in Physics (virtual), September 7, 2020. [link]
• Conference presentation (ATLAS), “Triggering on hadronic signatures with the ATLAS detector,” ICHEP (virtual), July 29, 2020. [link]
• Conference presentation (ATLAS), “Searching for Dark Matter with the ATLAS detector,” ICHEP (virtual), July 28, 2020. [link]

Seminar presentation, The ATLAS missing transverse momentum trigger and searches for invisible decays of the Higgs boson, Argonne National Lab (virtual), June 23, 2020

Seminar, Invisible Higgs with ATLAS, TRIUMF (Vancouver, Canada), December 14, 2018

Seminar, Invisible Higgs with ATLAS, University of Illinois at Chicago, December 12, 2018

Seminar, Invisible Higgs with ATLAS, LHC Physics Center Topic of the Week (Fermilab, Chicago), December 11, 2018

Seminar, Invisible Higgs with ATLAS, University of Chicago, December 10, 2018

Seminar, Invisible Higgs with ATLAS, Cambridge University (U.K.), November 6, 2018

Seminar, VBF Higgs to Invisible with ATLAS, Collider Cross Talk (chalk board talk, compared with CMS speaker Siddharth Narayanan), CERN, October 18, 2018

Colloquium, “Using the Higgs boson to probe the unknown”, Departmental Colloquium University of Texas at Arlington (virtual), November 11, 2020.

Seminar, “Searches for invisible decays of the Higgs boson with the ATLAS detector,” Joint Experimental-Theoretical Physics Seminar (Fermilab), January 25, 2019

Colloquium, “The next steps in particle physics: Using the Higgs boson to probe the unknown,” Departmental Colloquium Baylor University (Waco, TX), January 23, 2019