Gravitational Waves dynamics with Higgs portal and U(1) X SU(2) interactions

Abstract

We show that a mixture of Higgs boson with a heavy scalar singlet with large vacuum expectation value ( vev) is a viable model of inflation that satisfy the existing observational data, the perturbativity constraints, avoiding in the same time the EW vacuum metastability as long as the Higgs portal interactions lead to positive tree-level threshold corrections for SM Higgs quartic coupling. The tree-level threshold corrections lead to the change of Hubble expansion rate during inflation with impact on the evolution of the axion-gauge field spectator sector, modifying the time-dependent mass parameter of the gauge field fluctuation. We evaluate this effect on the GW sourced tensor modes while accounting for the consistency and backreaction constraints and show that the Higgs portal interactions enhance the GW signal sourced by the gauge field fluctuations in the CMB B-mode ploarization power spectra. We address the detectability of the GW sourced by the gauge field fluctuations in presence of Higgs portal interactions for the experimental configuration of the future CMB polarization LiteBird space mission. We find that the sourced GW tensor-to-scalar ratio in presence of Higgs portal interactions is enhanced to a level that overcomes the vacuum tensor-to-scalar ratio by a factor of 10, much above the detection threshold of the LiteBird experiment, in agreement with the existing observational constraints on the curvature fluctuations and the allowed parameter space of Higgs portal interactions. We also show that a large enhancement of the sourced GW can be also detected by experiments such as pulsar timing arrays and laser/atomic interferometers. Moreover, a significant Higgs-singlet mixing can be probed by the LHC Higgs searchers.