$CP$ violation from $τ$, $t$ and $b$ dimension-6 Yukawa couplings -- interplay of baryogenesis, EDM and Higgs physics

Abstract

We explore the implications of the Standard Model effective field theory (SMEFT) with dimension-six terms involving the Higgs boson and third-generation fermion fields on the rate of Higgs boson production and decay into fermions, on the electric dipole moments (EDMs) of the electron, and on the baryon asymmetry of the Universe. We study the consequences of allowing these additional terms for each flavor separately and for combinations of two flavors.We find that a complex τ Yukawa coupling can account for the observed baryon asymmetry Y obs B within current LHC and EDM bounds. A complex b (t) Yukawa coupling can account for 4% (2%) of Y obs B , whereas a combination of the two can reach 12%. Combining τ with either t or b enlarges the viable parameter space owing to cancellations in the EDM and in either Higgs production times decay or the total Higgs width, respectively. Interestingly, in such a scenario there exists a region in parameter space where the SMEFT contributions to the electron EDM cancel and collider signal strengths are precisely SM-like, while producing sufficient baryon asymmetry. Measuring CP violation in Higgs decays to τ leptons is the smoking gun for this scenario.

Catalyzed Baryogenesis

“…For this to make a difference in Y B , T form must be close to the EWPT temperature T EWPT . The reason: if T form is much larger, then Y (T T form ) is constant, reducing to the previous The solid blue curve shows the constraint assuming the EWS ball abundance is set by annihilations and includes an enhancement factor ξ(y) = 10 by assuming annihilations are taking place during baryogenesis and T form = T i ; see (25). The dashed blue curve shows the constraint if f DM is fixed to unity, with no enhancement factor for annihilations; see (15).…”

“…The coefficient of this operator is constrained by the current upper limit on the electron dipole moment |d e | < 1.1 × 10 −29 e cm by the ACME collaboration [24]. Thus, Λ > v (λ/0.13) 1/2 [25].…”

“…Figure 2: Bounds on the parameter space for EWS balls to catalyze baryogenesis. Blue curves show the constraints from requiring sufficient baryogenesis to explain the observed asymmetry.The solid blue curve shows the constraint assuming the EWS ball abundance is set by annihilations and includes an enhancement factor ξ(y) = 10 by assuming annihilations are taking place during baryogenesis and T form = T i ; see(25). The dashed blue curve shows the constraint if f DM is fixed to unity, with no enhancement factor for annihilations; see(15).…”

Searching for BSM Physics in Yukawa Couplings and Flavour Symmetries

“…Most recent studies such as Ref. [55], assuming only one third generation fermion running in the loop at a time, give…”

A New bound on CP Violation in the $τ$ Lepton Yukawa Coupling and electroweak baryogenesis

“…CP violating third generation Yukawa couplings would be an important source of baryon-antibaryon asymmetry in the electroweak baryogenesis [1][2][3][4][5][6]. However, there is certain tension between their magnitude required by the observed baryon asymmetry in the Universe (BAU) and the bounds following mainly from the experimental upper limit on the electron Electric Dipole Moment (EDM) [7].…”