New Emerging Results in Higgs Precision Analysis Updates 2018 after Establishment of Third-Generation Yukawa Couplings

TL;DR

This paper presents a comprehensive global fit of Higgs boson couplings using data up to 2018, revealing a slight excess over the Standard Model, establishing third-generation Yukawa couplings, and constraining nonstandard decay modes.

Contribution

It provides the first global fit including third-generation Yukawa couplings and new measurements at 13 TeV, offering updated insights into Higgs interactions and potential deviations from the Standard Model.

Findings

Higgs signal strength is 2σ above SM expectation.

First evidence that the bottom-quark Yukawa coupling is positive.

Negative top-quark Yukawa coupling is ruled out unless additional particles contribute.

Abstract

We perform global fits of the Higgs boson couplings to all the 7 TeV, 8 TeV, and 13 TeV data available up to the Summer 2018. New measurements at 13 TeV extend to include the Higgs signal strengths exclusively measured in associated Higgs production with top-quark pair and the third-generation Yukawa couplings now have been established. Some important consequences emerge from the global fits. (i) The overall average signal strength of the Higgs boson stands at $2\sigma$ above the SM value ($\mu = 1.10 \pm 0.05 $). (ii) For the first time the bottom-quark Yukawa coupling shows a preference of the positive sign to the negative one. (iii) The negative top-quark Yukawa coupling is completely ruled out unless there exist additional particles running in the $H$-$\gamma$-$\gamma$ loop with contributions equal to two times the SM top-quark contribution within about 10 \%. (iv) The branching ratio for nonstandard decays of the Higgs boson is now below 8.4\% at the 95\% confidence level.