Higgs Precision (Higgcision) Era begins

TL;DR

This paper develops a framework for analyzing deviations in Higgs boson couplings from the Standard Model, performs global fits to experimental data, and finds that the SM Higgs provides the best fit with limited room for new physics contributions.

Contribution

It introduces a generic parameter-based framework for Higgs coupling deviations applicable to many beyond Standard Model theories and performs comprehensive fits to current collider data.

Findings

Nonstandard decay branching ratio less than 22%

Best fit achieved by additional particle contributions to loop functions

Electroweak symmetry breaking from observed Higgs is dominant

Abstract

After the discovery of the Higgs boson at the LHC, it is natural to start the research program on the precision study of the Higgs-boson couplings to various standard model (SM) particles. We provide a generic framework for the deviations of the couplings from their SM values by introducing a number of parameters. We show that a large number of models beyond the SM can be covered, including two-Higgs-doublet models, supersymmetric models, little-Higgs models, extended Higgs sectors with singlets, and fourth generation models. We perform global fits to the most updated data from CMS, ATLAS, and Tevatron under various initial conditions of the parameter set. In particular, we have made explicit comparisons between the fitting results BEFORE and AFTER the Moriond 2013 meetings. Highlights of the results include: (i) the nonstandard decay branching ratio of the Higgs boson is less than 22%; (ii) the most efficient way to achieve the best fit for the data before the Moriond update is to introduce additional particle contributions to the triangular-loop functions of H\gamma\gamma and Hgg vertices; (iii) the 1\sigma allowed range of the relative coupling of HVV is 1.01 +0.13 -0.14, which means that the electroweak-symmetry breaking contribution from the observed Higgs boson leaves only a small room for other Higgs bosons; (iv) the current data do not rule out pseudoscalar couplings nor pseudoscalar contributions to the H\gamma\gamma and Hgg vertices; and (v) the SM Higgs boson provides the best fit to all the current Higgs data.