The Electro-Weak Phase Transition at Colliders: Confronting Theoretical Uncertainties and Complementary Channels

Abstract

We explore and contrast the capabilities of future colliders to probe the nature of the electro-weak phase transition. We focus on the real singlet scalar field extension of the Standard Model, representing the most minimal, yet most elusive, framework that can enable a strong first-order electro-weak phase transition. By taking into account the theoretical uncertainties and employing the powerful complementarity between gauge and Higgs boson pair channels in the searches for new scalar particles, we find that a even though a 27 TeV proton collider can probe a large fraction of the parameter space, it will not conclusively discover nor exclude its totality. On the other hand, a 100 TeV proton collider can confirm or falsify a strong first-order transition, relatively early in its lifetime. Such an early discovery would allow for precise measurements of the new phenomena to be obtained and would pave the way to definitively verify whether this is indeed the physical remnant of a scalar field that catalyses a strong first-order transition.

Singlet-assisted electroweak phase transition at two loops

“…We will study the theory near its Z 2 symmetric limit, see the discussion in Section IV below, taking | sin θ| < 0.1 and assuming the new excitation to be heavier than the SM Higgs. The remaining parameter space is then relatively unconstrained by current experiments [13,18,21,32]. We will not consider experimental constraints further in this paper as our focus is on the finite-T behavior of the theory.…”

“…We work in the real-singlet extension of the Standard Model which we shall refer to as xSM, following [9]. Several one-loop analyses of the EWPT exist in this minimalistic yet realistic BSM model, see [9][10][11][12][13][14][15][16][17][18][19][20][21] and references therein, but we are not aware of existing two-loop calculations in the finite-T context. Two-loop studies in other scalar extensions and in the MSSM have reported on considerable deviations from the one-loop behavior [22][23][24][25][26][27], motivating a detailed two-loop investigation of the xSM as well.…”

Gravitational waves from first-order electroweak phase transition in a model with light sgoldstinos

“…in [84][85][86]. It will be interesting to perform such an analysis within the model in question to study complementarity between collider and gravitational wave experiments [87][88][89]. We leave study of these and similar processes for future.…”

The Electro-Weak Phase Transition at Colliders: Discovery Post-Mortem

“…Determining the true nature of EWSB therefore requires ruling out or discovering any such new states. In the context of the minimal, but challenging to detect, real singlet extension to the SM as a test case, it has been demonstrated that a proton-proton collider with a centre-of-mass energy of 100 TeV [1,[46][47][48][49][50][51], or perhaps even 27 TeV [51], can exclude or discover the presence of a singlet field, provided it couples to the SM sufficiently strongly to induce a SFO-EWPT. This statement has been shown to remain true even when taking a liberal approach to the theoretical uncertainties involved [51].…”

“…In the context of the minimal, but challenging to detect, real singlet extension to the SM as a test case, it has been demonstrated that a proton-proton collider with a centre-of-mass energy of 100 TeV [1,[46][47][48][49][50][51], or perhaps even 27 TeV [51], can exclude or discover the presence of a singlet field, provided it couples to the SM sufficiently strongly to induce a SFO-EWPT. This statement has been shown to remain true even when taking a liberal approach to the theoretical uncertainties involved [51]. A potentially complementary approach towards discovery [49,50,[52][53][54] is to observe a gravitational wave background which would be present if the transition were strong enough.…”