Investigating the Electroweak phase transition with a real scalar singlet at a muon collider

Abstract A strong first-order electroweak phase transition (SFOEWPT) is essential for explaining baryogenesis, and for potentially generating observable gravitational waves. In the present study, we investigate the potential of a high-energy muon collider to examine the occurrence of SFOEWPT within the context of a Standard Model extended by a real scalar singlet (xSM). We present an analysis of all viable decay modes of a singlet-like scalar particle, in order to constrain the valid parameter space of SFOEWPT, which was extracted numerically at different renormalization scales to account for theoretical uncertainties. This allowed us to determine the sensitivity of a muon collider to the production and decay channels of new heavy scalar singlet-like particles that emerge in the xSM. Our findings demonstrate that a 3 TeV muon collider could directly probe the nature of electroweak symmetry breaking by efficiently detecting new scalar particles associated with a first-order electroweak phase transition through jet-rich final states, thus complementing the indirect constraints from gravitational wave experiments.