Singlet-catalyzed electroweak phase transitions in the 100 TeV frontier

We study the prospects for probing a gauge singlet scalar driven strong first-order electroweak phase transition with a future proton-proton collider in the 100 TeV range. Singlet-Higgs mixing enables resonantly enhanced di-Higgs production, potentially aiding discovery prospects. We perform Monte Carlo scans of the parameter space to identify regions associated with a strong first-order electroweak phase transition, analyze the corresponding di-Higgs signal, and select a set of benchmark points that span the range of di-Higgs signal strengths. For the b (b) over bar gamma gamma and 4 tau final states, we investigate discovery prospects for each benchmark point for the high-luminosity phase of the Large Hadron Collider and for a future pp collider with root s = 50, 100, or 200 TeV. We find that any of these future collider scenarios could significantly extend the reach beyond that of the high-luminosity LHC, and that with root s = 100 TeV (200 TeV) and 30 ab(-1), the full region of parameter space favorable to strong first-order electroweak phase transitions is almost fully (fully) discoverable.