Four generations, the electroweak phase transition, and supersymmetry

Abstract

We calculate the strength of the electroweak phase transition in a supersymmetric model with four chiral generations. The additional chiral fermions (and scalar partners) lower the critical temperature and thus strengthen the first-order phase transition. The scalar partners stabilize the potential, leading to an effective theory that is bounded from below. We identify the ensemble of parameters where φc/Tc > ∼ 1 simultaneous with obtaining a large enough Higgs mass. Our calculations focus on a subset of the full four generational supersymmetric parameter space: We take the pseudoscalar heavy, tan β = 1, and neglect all subleading contributions to the effective potential. We find that the region of parameter space with a strong first-order phase transition requires mq /m q < ∼ 1.1 while the constraint on the lightest Higgs mass requires mq /m q > ∼ 1 with m q > ∼ 300 GeV. We are led to an intriguing prediction of quarks and squarks just beyond the current Tevatron direct search limits that are poised to be discovered quickly at the LHC.

MSSM baryogenesis and electric dipole moments: an update on the phenomenology

“…One large class of such models are those that include a gauge singlet with couplings to the SU(2) Higgs doublets [22,23]. Other viable beyond-the-MSSM setups featuring a strongly first order EWPT also include models with a fourth fermion generation [24] and top-flavor models [25]; models with higher dimensional scalar representations of SU(2) (which might lead to a multistep EWPT [26]) provide yet another promising such framework [27,28]. In several of these models, the physical mechanism that drives a strongly first order EWPT is decoupled from EWB as the source of the BAU.…”

Higgs masses in the four generation minimal supersymmetric standard model

“…Last year, Murdock, et al [17] discussed ways of extending the validity of perturbation theory in the four generation MSSM. The only recent discussion of the lightest Higgs mass in the four generation MSSM was the work of Fok and Kribs [18], who plotted the lightest Higgs mass as a function of the heavy quark mass. They did restrict the model to the case in which the scalar t ′ and b ′ masses were within twenty percent of the t ′ and b ′ masses, since that was necessary to obtain sufficient electroweak baryogenesis.…”

“…The expression used by Fok and Kribs [18] in the limit in which mixing between scalar quarks is ignored, all squarks have the same mass, the heavier Higgs bosons are all very heavy and tan β = 1 is…”

Dynamical symmetry breaking with a fourth generation

“…Recent highlights on consequences of a fourth generation can be found in [10]. These include mechanisms of dynamical electroweak symmetry breaking by condensates of fourth generation quarks and leptons [11][12][13][14], convergence improvement of the three SM gauge couplings due to the Yukawa coupling contributions from the fourth generation [15], the possibility of electroweak baryogenesis through first-order electroweak phase transition with four generations [16][17][18], CP violation based on Jarlskog invariants generalized to four generations [19] and the hierarchy problem [20].…”