Search for Pair Production of Higgs Bosons

The measurement of di-Higgs production and its self-coupling will be one of the key goals of the High Luminosity LHC (HL-LHC) program. The measurement of the trilinear coupling allows the determination of the shape of the Higgs potential, which is connected to the phase of the early universe from the unbroken to the broken electroweak symmetry. This measurement can also be used to explore signs of new physics. The existence of an extended scalar sector or the presence of new dynamics at higher scales could modify the Higgs self-couplings.

At the LHC the dominant Standard Model (SM) di-Higgs production process is via gluon-gluon fusion. The pairs of Higgs boson can be produced via the heavy-quark loop (``box-diagram'') or through the Higgs self-interacting (``triangle-diagram''). These two diagrams interfere destructively. The trilinear coupling is from the Higgs self-interacting vertex in the ``triangle-diagram''. In beyond SM (BSM) the di-Higgs pair can be produced from the decay of a heavy resonance.

The Academia Sinica group at ATLAS participated in the resonant and non-resonant di-Higgs search by analyzing the ATLAS Run-2 data sample (L=139 fb-1). The search was performed in the HH→bbtautau decay channel. The search is further categorized into “lephad” (one of the tau lepton decays into an electron or muon, and the other tau lepton decays hadronically) and “hadhad” (both tau leptons decay hadronically). The results from both categories are then combined together. In the resonant analysis, we search for a heavy resonance that decays into a pair of Higgs bosons (X→HH) , and set an upper limit on the production cross section as a function of the heavy resonance mass. For the non-resonant analysis, we set an observed (expected) upper limit of 4.6 (3.9) times the SM predicted di-Higgs production cross section. The expected limit has the best sensitivity in the ATLAS experiment. The results from the non-resonant search is also used to extract the limits on the Higgs boson self-coupling modifier (KL), which we exclude the region outside this observed (expected) range of - 2.4 < KL < 9.2 ( - 2.0 < KL < 9.0 ).

Published Papers :

• “Search for resonant and non-resonant Higgs boson pair production in the bbtautau decay channel using 13 TeV pp collision data from the ATLAS detector”, ATLAS Collaboration, arXiv:2209.10910, accepted by JHEP

  • http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2018-40/

• “Combination of searches for non-resonant and resonant Higgs boson pair production in the bbgammagamma, bbtautau and bbbb decay channels using pp collisions at sqrt(s)=13$ TeV with the ATLAS detector”, ATLAS Collaboration, https://cds.cern.ch/record/2786865

Links :

• Higgs Searches at ATLAS

Last modification : April 2023, Song-Ming Wang