This will be our first virtual seminar, and will be hosted in Zoom
Meeting ID: 686 2959 4539
Direct link: https://uu-se.zoom.us/j/68629594539
Final PhD seminar
Abstract:
After the discovery of the Higgs boson, the ultimate test of the electroweak symmetry breaking is to establish evidence of Higgs boson self-coupling, which can be achieved by searching for pair production of Higgs bosons (di-Higgs). In the Standard Model (SM), di-Higgs is dominantly produced in the gluon-gluon fusion processes, namely via the loop of top-quarks (Yukawa coupling), or the Higgs boson self-coupling. These two production mechanisms interfere destructively, which leads to a very small di-Higgs production cross-section. It is not expected that the data recorded during the Run 2 of the LHC will be enough to observe di-Higgs if there are no deviations from the SM couplings. On the other hand, deviations in couplings of the Higgs boson could lead to a significant enhancement of the di-Higgs production rate. In addition, many beyond the SM (BSM) theories predict heavy resonances that would decay into pairs of SM Higgs bosons.
A search for non-resonant and resonant di-Higgs production in the bbττ channel is presented for 36.1 /fb of sqrt{s} = 13 TeV data recorded at the ATLAS experiment at the LHC. The observed (expected) upper limit on the non-resonant Higgs boson pair production cross-section times branching ratio corresponds to 12.7 (14.8) times the SM prediction. The ratio of the Higgs boson self-coupling to its SM expectation, κ_λ , is observed (expected) to be constrained at 95% CL to -7.3 < κ_λ < 15.7 (-8.8 < κ_λ < 16.7). The sensitivity is extrapolated to a 14 TeV center-of-mass energy and 3000 /fb, which is the target integrated luminosity of the High-Luminosity LHC. Various extrapolation assumptions are taken into account. Furthermore, potential improvements of the analysis techniques are discussed in the context of achieving even higher sensitivity with the full Run 2 data recorded by the ATLAS experiment.