VHH production at the high-luminosity LHC

Karl Nordström,Andreas Papaefstathiou

doi:10.1140/epjp/i2019-12614-2

Abstract

.We study the phenomenology of associated production of a vector boson with a pair of Higgs bosons (VHH at the High-Luminosity LHC (HL-LHC). Despite the low rate of this channel, the scaling of the cross section suggests a measurement could be a useful probe of modifications of the trilinear Higgs boson coupling and anomalous interactions in the gauge-Higgs sector. We focus on both WHH and ZHH production, using the leptonic ( Wrightarrow l nu, Z rightarrow ll, Zrightarrow nu nu decay modes of the vector bosons and the HH rightarrow 4b di-Higgs decay mode. We show that top pair backgrounds are problematic for the Wrightarrow l nu and Zrightarrow nu nu channels, leaving Z rightarrow ll as the most promising decay mode. However, even for this channel, we find limited sensitivity due to a low signal rate. We discuss some potential avenues for improvement.

Highlights

Since the discovery of a scalar resonance with the properties of a Standard Model-like Higgs boson by the ATLAS and CMS collaborations in 2012 [1,2], the focus of the experiments and phenomenological community has shifted towards precise measurements of the properties of this new particle and its interactions [3]
That single Higgs production channels are sensitive to the trilinear coupling at one-loop [5,6,7] and these may turn out to be competitive with direct production, especially at future lepton colliders where single Higgs-strahlung can provide the most sensitive channel overall
Foreshadowing the results of our analysis, we choose to work in a simple “anomalous” coupling framework, where the Standard Model (SM) couplings are modified by simple rescaling: λ = λSM (1 + c3), where λSM is the SM value of the triple Higgs boson coupling and c3 parametrises the modifications coming from new physics

Summary

Introduction

Since the discovery of a scalar resonance with the properties of a Standard Model-like Higgs boson by the ATLAS and CMS collaborations in 2012 [1,2], the focus of the experiments and phenomenological community has shifted towards precise measurements of the properties of this new particle and its interactions [3]. Another potentially interesting feature of V HH production is that it gives us sensitivity to the W W HH and ZZHH vertices, which could be modified in strongly coupled and extra-dimensional models of electroweak symmetry breaking [45] These are probed very efficiently by vector boson fusion qq → qqHH production [35,36,38] since the contributing diagrams are such that the high di-Higgs invariant mass (mHH ) region is only suppressed by valence quark parton density functions which leads to large sensitivity when using boosted reconstruction techniques. Since the signal processes are qq-initiated at tree-level the cross sections grow more slowly when going to higher collider energies as compared to gluon fusion-initiated di-Higgs production channels; for this reason the qualitative changes that can be expected by considering, e.g., a 100 TeV proton-proton collider will be limited to a potentially larger data samples and detector improvements

Setup of calculation and analysis

ZHH production

WHH production

Projected limits

Avenues for improvement

Conclusions