Finn Rebassoo | 18-LW-061
The 2012 Nobel Prize-winning discovery of the Higgs boson particle at the Large Hadron Collider (LHC) provided a large missing piece in the standard model of particle physics, but has left many unanswered questions. Problems related to the Higgs boson and dark matter lead to the strong expectation for new undiscovered particles at the LHC. Despite a massive international effort, no new particles have been found at the LHC.
In this project, we developed a novel technique to search for the first evidence of new particles. Our technique involved tagging the outgoing protons from the proton collisions to explore events where photons fuse to form a final state containing new particles. During 2017 and 2018, approximately one quadrillion collisions were delivered by the LHC to the main detector. We leveraged data collected using the newly installed Proton Precision Spectrometer (PPS) subdetectors, located in the LHC tunnel, to tag the outgoing protons. We analyzed data from these photon fusion events to search for new physics models using a novel approach. In addition, this analysis will lay the groundwork for future studies with photon fusion at the LHC.
This project puts Lawrence Livermore National Laboratory at the forefront of an important new approach in discovery science within the highest priority mission of the DOE Office of High Energy Physics and establishes the Laboratory's ability to participate in future major collider projects, such as the High Luminosity LHC upgrade and the International Linear Collider. A highly visible role at the frontier of particle physics will allow the Laboratory to expand core capabilities that have direct benefits to Livermore programs, including Livermore's mission research challenge in nuclear threat reduction.
Publications, Presentations, and Patents
Rebassoo, F. 2019. "Results and prospects with the CMS Precision Proton Spectrometer," Meeting of the Division of Particles & Fields of the APS, Boston, MA. LLNL-PRES-818532
Sirunyan, A. M., et al. 2020. "Identification of heavy, energetic, hadronically decaying particles using machine-learning techniques." Journal of Instrumentation, 15. doi: 10.1088/1748-0221/15/06/P06005. LLNL-JRNL-819445
——— 2019. "Combined measurements of Higgs boson couplings in proton–proton collisions at √ s = 13TeV." Eur. Phys. J., 79:421 doi: 10.1140/epjc/s10052-019-6909-y. LLNL-JRNL-819450
——— 2018a. "Observation of proton-tagged, central (semi)exclusive production of high-mass lepton pairs in pp collisions at 13TeV with the CMS-TOTEM precision proton spectrometer." Journal of High Energy Physics, 153. doi: 10.1007/JHEP07(2018)153. LLNL-JRNL-819451
——— 2018b. "Observation of Higgs Boson Decay to Bottom Quarks." Phys Rev Lett, 121(12):121801.
doi: 10.1103/PhysRevLett.121.121801. LLNL-JRNL-819448
——— 2018c. "Search for high-mass resonances in dilepton final states in proton-proton collisions at ?√=13
TeV." Journal of High Energy Physics, 120. https://doi.org/10.1007/JHEP06(2018)120. LLNL-JRNL-819446