Speaker
Description
Precision measurements of Higgs boson couplings to SM particles is a central task at the LHC today and for the future HL-LHC. Due to the $\sim$ O(nb) $t\bar{t}$ cross section and large Yukawa coupling, measurements of the interaction of the Higgs with top quarks is particularly compelling. The $t\bar{t}HH$ signal can be used to probe this coupling and also provides a direct measurement of trilinear Higgs self-coupling. We search for $t\bar{t}HH$ production with the CMS detector at the LHC both in the SM and in an EFT model. In SM we look for semi-leptonic decay of the top-quark pair and the decay of both Higgs bosons to b-quarks using full Run 2 data. We also develop a simplified EFT model to study this signal independently of $t\bar{t}H$, in which 6D and 8D gauge-invariant operators are included to modify $t\bar{t}HH$ while keeping $t\bar{t}H$ unchanged at tree level. In this model, which includes a BSM $t\bar{t}HH$ vertex, Higgs bosons are produced at higher $p_T$ compared with those from SM production. Due to the resulting Lorentz boost, we observe an enhancement around the Higgs mass in the single b-jet mass spectrum.
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