Abstract
A programme of Higgs boson characterisation studies is already
well underway at the LHC experiments but, currently, one of the least
understood aspects of its behaviour is how it couples to the heavy Standard
Model fermions, including the top quark. In the SM, the coupling of fermions
to the Higgs boson is proportional to the fermion mass and so accurate
measurements of these Yukawa couplings is crucial. Any deviation from the
predicted coupling strengths would be a powerful indication of new physics
beyond the SM, with far-reaching consequences for our understanding of
physics at large scales. Given its particularly large mass, the top Yukawa
coupling is of special interest. But it is precisely its large mass which
makes the top quark coupling to the Higgs boson the most difficult to pin
down experimentally. A direct measurement of the top quark Yukawa coupling
is possible through Higgs boson production in association with a top quark
pair (ttH). In this seminar, the ATLAS ttH analysis at cm energy 13 TeV is
presented.