Search for SU(2) _V singlet Higgs boson in the Georgi–Machacek model at the LHC

Abstract In this paper, we study in detail the phenomenology of the non-SM SU (2) V singlet Higgs boson H 1 0 at the 14 TeV Large Hadron Collider (LHC) in the Georgi–Machacek (GM) model. We present a systematic comparison of the production mechanisms and decay modes of H 1 0 , especially the vector-boson fusion (VBF) and gluon–gluon fusion ( gg F) production mechanisms and the decays to W + W − , ZZ , H 5 H 5 , H 3 H 3 , H 3 ± W ∓ and H 3 0 Z . After performing a comprehensive scan over the seven-dimensional parameter space of the GM model, we find that the H 1 0 → H 3 ± W ∓ , H 1 0 → H 3 0 Z and H 1 0 → H 3 H 3 decay channels are almost excluded by the theoretical and experimental constraints, while H 1 0 can decay into H 5 H 5 in an appreciable region of the GM parameter space. Based on the scanning results, we discuss detailedly the H 1 0 production via gg F and VBF with subsequent decays of H 1 0 → H 5 H 5 → W + W − W + W − → l ± ν ( − ) l ± ν ( − ) + 4 j e t s , H 1 0 → Z Z → l + l − l + l − and H 1 0 → W + W − → e ± μ ∓ ν ν ¯ at the 14 TeV LHC. The integrated cross sections and some kinematic distributions of final products for both the signals at some benchmark points of the GM parameter space and the corresponding SM backgrounds are provided. If the decay to H 5 H 5 is kinematically allowed, H 1 0 can be detected in the H 1 0 → H 5 H 5 → W + W − W + W − → l ± ν ( − ) l ± ν ( − ) + 4 j e t s decay channel at high-luminosity LHC unless B R ( H 1 0 → H 5 H 5 ) is too small or m H 1 0 is too high. In the mass range of 2 m V ≲ m H 1 0 < 2 m H 5 , the vector-boson fusion is the most promising production channel in search of H 1 0 due to the two hard tagging jets in the final state, and we may expect to discover H 1 0 in both H 1 0 → W + W − → e ± μ ∓ ν ν ¯ and H 1 0 → Z Z → 4 l decay channels with O ( 1 0 2 ) f b − 1 of data if the decay branching ratio of H 1 0 to a pair of weak gauge bosons is sufficiently large.