Abstract
We explore the capabilities of a future proton collider to probe the nature of the electro-weak phase transition, following the hypothetical discovery of a new scalar particle. We focus on the real singlet scalar field extension of the Standard Model, representing the most minimal, and challenging to probe, framework that can enable a strong first-order electro-weak phase transition. By constructing detailed phenomenological methods for measuring the mass and accessible couplings of the new scalar particle, we find that a 100 TeV proton collider has the potential to explore the parameter space of the real singlet model and provide meaningful constraints on the electro-weak phase transition. We empirically find some necessary conditions for the realization of a strong first order electroweak phase transition and conjecture that additional information, including through multi-scalar processes and gravitational wave detectors, are likely needed to gauge the nature of the cosmological electro-weak transition. This study represents the first crucial step towards solving the inverse problem in the context of the electro-weak phase transition.
Highlights
Complementary approach towards discovery [52, 53, 55,56,57] is to observe a gravitational wave background which would be present if the transition were strong enough
We explore the capabilities of a future proton collider to probe the nature of the electro-weak phase transition, following the hypothetical discovery of a new scalar particle
By constructing detailed phenomenological methods for measuring the mass and accessible couplings of the new scalar particle, we find that a 100 TeV proton collider has the potential to explore the parameter space of the real singlet model and provide meaningful constraints on the electro-weak phase transition
Summary
When the SM is extended by a real singlet scalar field, the most general form of the scalar potential that depends on the Higgs doublet field, H, and a gauge-singlet scalar field, S,. The two states h and s mix through both the Higgs portal parameters K1 and K2 as well as the singlet vev and they do not represent mass eigenstates. We identify the eigenstate h1 with the SM-like Higgs boson state observed at the LHC, and set m1 = 125.1 GeV. Note that, following the minimisation conditions for EWSB to occur and the requirement for one of the scalar particles to yield the observed Higgs boson mass, the seven coupling parameters of eq (2.1) are reduced down to five free parameters. With XX being any SM final state, i.e. fermions or gauge bosons These allow for constraints to be imposed on the mixing angle θ through the measurements of SM-like Higgs boson (i.e. h1) signal strengths and for searches of h2 decaying to SM particles. Where V (h1 − h1 − h2) ⊃ λ112h2h1h1.2 In the studies of the present article, we will assume that m2 > 2m1, such that h2 → h1h1 is open, with both SM-like Higgs boson h1 scalars being on shell
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