On 27 January 2016, at 11.00 am in the DLNP Conference Hall a seminar “Prompt/non-prompt lepton discrimination study with BDT in the ttH multilepton final states at ATLAS” will be held.

Speaker: Nazim Huseynov

Abstract

In the Standard Model (SM), fundamental fermions acquire mass through their interaction with the Higgs field. The Yukawa coupling governing this interaction isproportional to the mass of the fermion, as Yƒ = √2mƒ υ where υ is the vacuum expectation value of the Higgs field. Indirectly, the fermion Yukawa coupling can be inferred from the measured mass of the particle, which in the case of the top quark Yt =0.996±0.005 yields at leading order.

However, this measure is indirect, and is uncertain due to the nature of the theoretical mass being measured. Alternatively, the top Yukawa coupling could be measured via a fermion loop processes (e.g. gg → H and H → γγ). However, the presence of other particles entering loop diagrams affect precise determination of the Yt measurement. Such approach is also based on the assumption that there is no physics beyond the standard model contributing to the loop. Therefore, it is important to measure the top quark Yukawa coupling directly through a tree-level process, and the most effective way to do this is through production of top quark pairs in conjunction with the Higgs boson.