Robust Determination of the Higgs Couplings: Power to the Data

TL;DR

This paper performs a global fit to Higgs data using an effective Lagrangian approach, constraining Higgs couplings and testing consistency with the Standard Model within current experimental uncertainties.

Contribution

It introduces a basis choice for effective operators that optimally utilizes available data to determine Higgs coupling modifications in a model-independent framework.

Findings

Standard Model Higgs couplings are within 68% CL of current data.

Global fit constrains eight parameters related to Higgs interactions.

Results have implications for high-energy unitarity and future analyses.

Abstract

We study the indirect effects of new physics on the phenomenology of the recently discovered "Higgs-like" particle. In a model independent framework these effects can be parametrized in terms of an effective Lagrangian at the electroweak scale. In a theory in which the SU(2)_L x U(1)_Y gauge symmetry is linearly realized they appear at lowest order as dimension--six operators, containing all the SM fields including the light scalar doublet, with unknown coefficients. We discuss the choice of operator basis which allows us to make better use of all the available data on the new state, triple gauge boson vertex and electroweak precision tests, to determine the coefficients of the new operators. We illustrate our present knowledge of those by performing a global fit to the existing data which allows simultaneous determination of the eight relevant parameters quantifying the Higgs couplings to gluons, electroweak gauge bosons, bottom quarks, and tau leptons. We find that for all scenarios considered the standard model predictions for each individual Higgs coupling and observable are within the corresponding 68% CL allowed range. We finish by commenting on the implications of the results for unitarity of processes at higher energies. Note added: The analysis has been updated with all the public data available by October 2013. Updates of this analysis are provided at http://hep.if.usp.br/Higgs as well as new versions of this manuscript.