The electroweak phase transition: a collider target

Abstract

Determining the thermal history of electroweak symmetry breaking (EWSB) is an important challenge for particle physics and cosmology. Lattice simulations indicate that EWSB in the Standard Model (SM) occurs through a crossover transition, while the presence of new physics beyond the SM could alter this thermal history. The occurrence of a first order EWSB transition would be particularly interesting, providing the needed pre-conditions for generation of the cosmic matter-antimatter asymmetry and sources for potentially observable gravitational radiation. I provide simple, generic arguments that if such an alternate thermal history exists, the new particles involved cannot be too heavy with respect to the SM electroweak temperature, nor can they interact too feebly with the SM Higgs boson. These arguments do not rely on the decoupling limit. I derive corresponding quantitative expectations for masses and interaction strengths which imply that their effects could in principle be observed (or ruled out) by prospective next generation high energy colliders. The simple, generic arguments provide a quantitative, parametric understanding of results obtained in a wide range of explicit model studies; relate them explicitly to the electroweak temperature; and delineate broad contours of collider phenomenology pertaining to a non-standard history of EWSB.

A critical look at the electroweak phase transition

“…Furthermore, the longitudinal-vector 1-loop contribution dominates all other tree-level terms, and forces the tree-level minimum to be at φ = 0. 4 A counting like λ ∼ e 4 -as in the Coleman-Weinberg model -is likewise dicey. To wit this counting implies eφ ∼ T which invalidates the high-temperature expansion.…”

“…where H and G are real scalar fields. This gives the tree-level potential V 0 (φ) = (1/2)m 2 φ 2 + (1/4)λφ 4 . Using the convenient notation that the squared mass of a particle is denoted with the name of that field, the squared masses -as functions of φ -are Ghosts are massless in Fermi gauges.…”

“…Describing these phenomena goes hand-in-hand with understanding phase transitions. Furthermore, it's also possible to indirectly probe the electroweak phase transition through particle colliders [4,5].…”

Cosmological phase transitions: is effective field theory just a toy?

“…with the last expression written in unitary gauge √ 2H = (0h), and c kin = 1 4 c HD − c H . We can define the approximate canonical field h =h + 1 3…”

“…The Standard Model (SM) predicts a crossover, but the transition may be different in extensions of the SM provided the new physics is important at the electroweak scale. Such new physics can be searched for at the LHC and, with more precision, in next generation colliders [1][2][3][4][5]. Especially interesting is the possibility of a strongly firstorder electroweak phase transition (SFO-EWPT).…”