Light inflaton Hunter's Guide
F. Bezrukov, D. Gorbunov
TL;DR
This work proposes a minimal, scale-free extension of the Standard Model in which a light inflaton χ mixes with the Higgs and drives inflation via a quartic potential, fixing most parameters with cosmological data. The inflaton is light (270 MeV–1.8 GeV) and couples to SM fields through Higgs mixing, enabling observable signatures in low-energy experiments: two-body kaon and B-meson decays produce χ with branching ratios around 10^-9 and 10^-6, respectively, while χ decays predominantly into leptons, photons, and pions with lifetimes around 10^-9–10^-10 s. The paper provides detailed decay rates, production mechanisms in hadron decays and high-intensity collisions, and reinterprets CHARM constraints to delineate the viable mass range; it also forecasts inflaton yields for several beam facilities. The results demonstrate that inflationary physics can be directly tested in realistic SM extensions, potentially linking early-Universe dynamics to collider and beam-dump experiments and to νMSM scenarios with sterile neutrinos. This establishes a concrete experimental program to probe the inflaton sector and its cosmological implications at EW scales.
Abstract
We study the phenomenology of a realistic version of the chaotic inflationary model, which can be fully and directly explored in particle physics experiments. The inflaton mixes with the Standard Model Higgs boson via the scalar potential, and no additional scales above the electroweak scale are present in the model. The inflaton-to-Higgs coupling is responsible for both reheating in the Early Universe and the inflaton production in particle collisions. We find the allowed range of the light inflaton mass, 270 MeV<~m_chi<~1.8 GeV, and discuss the ways to find the inflaton. The most promising are two-body kaon and B-meson decays with branching ratios of orders 10^{-9} and 10^{-6}, respectively. The inflaton is unstable with the lifetime 10^{-9}--10^{-10} s. The inflaton decays can be searched for in a beam-target experiment, where, depending on the inflaton mass, from several billions to several tenths of millions inflatons can be produced per year with modern high-intensity beams.