CERN-PH-TH-2015-106, LPT-Orsay-15-32 Golden Probe of the Top Yukuwa

We perform a preliminary study of the ability of the Higgs decay to four leptons to shed light on the top quark Yukawa couplings. In particular we examine whether the h → 4` ‘golden channel’ is sensitive to the CP properties of the top quark couplings to the Higgs boson. We show that kinematic distributions are sensitive to interference of the next-to-leading order electroweak corrections with the tree level ZZ contribution. This translates into a sensitivity to the top quark Yukawa couplings such that meaningful constraints on their CP properties can begin to be obtained once ∼ 300 fb−1 of data has been collected at ∼ 14 TeV, with significant improvements at higher luminosity or with a higher energy hadron collider. This makes the h → 4` channel a useful probe of the top quark Yukawa couplings that is qualitatively different from already established searches in h → V γ two body decays, tth, and gg → h. We also briefly discuss other potential possibilities for probing the top Yukawa CP properties in h→ 2`γ and `+`− → hZ, hγ.