Constraints on the Higgs boson self-coupling from the combination of single and double Higgs boson production in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper constrains the Higgs boson self-coupling by combining single and double Higgs production data from proton-proton collisions at 13 TeV, providing limits on the coupling strength relative to the Standard Model.

Contribution

It presents the first combined analysis of single and double Higgs production to measure the self-coupling and constrain its deviation from the Standard Model prediction.

Findings

Excluded $ abla \, ext{interval}$ for $ abla_ ext{lambda}$ at 2$\sigma$ confidence level.

Measured $ abla_ ext{lambda}$ consistent with Standard Model within uncertainties.

Provided bounds on Higgs self-coupling with and without assuming SM couplings to other particles.

Abstract

The Higgs boson (H) trilinear self-coupling, $\lambda_3$, is constrained via its measured properties and limits on the HH pair production using the proton-proton collision data collected by the CMS experiment at $\sqrt{s}$ = 13 TeV. The combination of event categories enriched in single-H and HH events is used to measure $\kappa_\lambda$, defined as the value of $\lambda_3$ normalized to its standard model prediction, while simultaneously constraining the Higgs boson couplings to fermions and vector bosons. Values of $\kappa_\lambda$ outside the interval $-$1.2 $\lt$ $\kappa_\lambda$ $\lt$ 7.5 are excluded at 2$\sigma$ confidence level, which is compatible with the expected range of $-$2.0 $\lt$ $\kappa_\lambda$ $\lt$ 7.7 under the assumption that all other Higgs boson couplings are equal to their standard model predicted values. Relaxing the assumption on the Higgs couplings to fermions and vector bosons the observed (expected) $\kappa_\lambda$ interval is constrained to be within $-$1.4 $\lt$ $\kappa_\lambda$ $\lt$ 7.8 ($-$2.3 $\lt$ $\kappa_\lambda$ $\lt$ 7.8) at 2$\sigma$ confidence level.