Regular Article - Theoretical Physics
The couplings of the Higgs boson and its CP properties from fits of the signal strengths and their ratios at the 7+8 TeV LHC
Laboratoire de Physique Théorique, Bât. 210, CNRS, Université Paris-sud 11, 91405, Orsay Cedex, France
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Revised: 17 June 2013
Published online: 7 September 2013
Using the full set of the LHC Higgs data from the runs at 7 and 8 TeV center of mass energies that have been released by the ATLAS and CMS collaborations, we determine the couplings of the Higgs particle to fermions and gauge bosons as well as its parity or CP composition. We consider ratios of production cross sections times decay branching fractions in which the theoretical (and some experimental) uncertainties as well as some ambiguities from new physics cancel out. A fit of both the signal strengths in the various search channels that have been conducted, H→ZZ,WW,γγ,ττ and , and their ratios shows that the observed ∼126 GeV particle has couplings to fermions and gauge bosons that are Standard Model-like already at the 68 % confidence level (CL). From the signal strengths in which the theoretical uncertainty is taken to be a bias, the particle is shown to be at most 68 % CP-odd at the 99 %CL and the possibility that it is a pure pseudoscalar state is excluded at the 4σ level when including both the experimental and theoretical uncertainties. The signal strengths also measure the invisible Higgs decay width which, with the same type of uncertainty analysis, is shown to be at the 68 %CL.
© Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica, 2013