Higgs boson couplings to top and bottom quarks – Hbb+ttH@LHC

The project is built on several techniques that will improve the sensitivity beyond the current state-of-the-art, notably: hadronic triggers to take advantage of fully hadronic decay channels as well as cope with the limitations of the lepton triggers at high-luminosity; jet-substructure techniques applied to high-momentum sub-channels; improvements to bottom and charm jet identification; use of color-flow and regression techniques to improve signal reconstruction. Those improvements
will lead to measurements of physics backgrounds, observation and measurements of Higgs boson production in association with a weak boson and a pair of top quarks, and extraction of Higgs boson
couplings.

Contributions to results of the ATLAS experiment:
- search for a new particle beyond the Standard Model decaying to a vector boson W or Z and a Higgs boson, with proton-proton collisions at 13 TeV at the LHC
- first evidence of the associate production of the Higgs boson with a vector boson W or Z in the b-quarks decay channel of the Higgs

Detailed characterization of the Higgs boson and electroweak symmetry breaking mechanism; indirect evidence for new physics beyond the Standard Model.

Contributions to published results of the ATLAS experiment:
- ATLAS Collaboration, “ Search for the bb decay of the Standard Model Higgs boson in associated (W/Z)H production with the ATLAS detector”, JHEP 01 (2015) 069
- ATLAS Collaboration, “ Search for the Standard Model Higgs boson decaying into bb produced in association with top quarks decaying hadronically in pp collisions at sqrt(s)=8 TeV with the ATLAS detector”, JHEP 05 (2016) 160
- ATLAS Collaboration, “ Search for new resonances decaying to a W or Z boson and a Higgs boson in the llbb, lnubb, and nunubb channels in pp collisions at sqrt(s)=13 TeV with the ATLAS detector”, ATLAS-CONF-2015-074
- ATLAS Collaboration, “Search for a CP-odd Higgs boson decaying to Zh in pp collisions at sqrt(s) =13 TeV with the ATLAS detector”, ATLAS-CONF-2016-015

The recent discovery at the Large Hadron Collider of a new particle consistent with the Higgs boson of the Standard Model is a major milestone for fundamental physics. One of the main priorities for the years to come is to study the exact nature of this new boson and in particular its couplings to Standard Model particles. The Hbb+ttH@LHC project has two main goals: establishing the observation of processes in which a Higgs boson is produced in association with a weak boson or with a pair of top quarks, and decays subsequently to a pair of bottom quarks; and studying the related Higgs couplings, in particular to the top quark to test the nature of the Higgs boson and probe new physics. A 4-year program was defined by a consortium gathering four teams to exploit the data collected between 2015 and 2018 by the ATLAS experiment at LHC. This run of LHC should quadruple the amount of data already collected, at an almost doubled centre-of-mass energy. The project is built on several techniques that will improve the sensitivity beyond the current state-of-the-art, notably: hadronic triggers to take advantage of fully hadronic decay channels as well as cope with the limitations of the lepton triggers at high-luminosity; jet-substructure techniques applied to high-momentum sub-channels; improvements to bottom and charm jet identification; use of color-flow and regression techniques to improve signal reconstruction. Those improvements will lead to measurements of physics backgrounds, observation and measurements of Higgs production in association with a weak boson and a pair of top quarks, and extraction of Higgs couplings.