Abstract
A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of sqrt{s} = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into gamma gamma mathrm{b}overline{mathrm{b}} . The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κλ and the coupling between a pair of Higgs bosons and a pair of vector bosons c2V are constrained within the ranges −3.3 < κλ< 8.5 and −1.3 < c2V< 3.5 at 95% confidence level. Constraints on κλ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κλ and the top quark Yukawa coupling modifier κt.
Highlights
Following the discovery of the Higgs boson (H) by the ATLAS and CMS collaborations [1,2,3], there has been significant interest in thoroughly understanding the Brout-Englert-Higgs mechanism [4, 5]
Single Higgs boson production, where the Higgs boson decays to a pair of photons, is considered as a resonant background. These production processes are simulated at next-to-leading order (NLO) in quantum chromodynamics (QCD) precision using powheg 2.0 [47, 58,59,60] for gluon-gluon fusion (ggF) H and Vector boson fusion (VBF) H, and MadGraph5_amc@nlo v2.2.2 (2016) / v2.4.2 (2017 and 2018) for ttH, vector boson associated production (VH), and production associated with a single top quark
The ttHScore discriminant is implemented with a deep neural network (DNN) combining feed-forward and long short-term memory neural networks [81], based on the topology-classifier architecture introduced in ref
Summary
Following the discovery of the Higgs boson (H) by the ATLAS and CMS collaborations [1,2,3], there has been significant interest in thoroughly understanding the Brout-Englert-Higgs mechanism [4, 5]. The modification of the properties of nonresonant HH production via ggF from BSM effects can be parametrized through an effective Lagrangian that extends the SM one with dimension-6 operators [16, 17] This parametrization results in five couplings: λHHH, the coupling between the Higgs boson and the top quark (yt), and three additional couplings not present in the SM. This paper describes a search for nonresonant production of pairs of Higgs bosons decaying to γγbb using a data sample of 137 fb−1 collected by the CMS experiment from 2016 to 2018. After reducing the nonresonant γγbb background and the background coming from single Higgs boson production in association with a top quark-antiquark pair (ttH), the events are categorized into ggF- and VBF-enriched signal regions using a multivariate technique. The ttH production cross section depends on yt, and includes a trilinear Higgs boson self-coupling contribution from NLO electroweak corrections [33, 34].
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