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We solve the equations of motion for a CP violating phase between the two Higgs doublets at the bubble wall of the MSSM electroweak phase transition. Contrary to earlier suggestions, we do not find indications of spontaneous ``transitional CP violation in the MSSM. On the other hand, in case there is explicit CP violation in the stop and chargino/neutralino sectors, the relative phase between the Higgses does become space dependent, but only mildly even in the maximal case. We also demonstrate that spontaneous CP violation within the bubble wall could occur, e.g., if the Higgs sector of the MSSM were supplemented by a singlet. Finally we point out some implications for baryogenesis computations.
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While the axion was originally introduced to wash out CP violation from strong interactions, new sources of CP violation beyond QCD might manifest themselves via a tiny scalar axion-nucleon component. The latter can be experimentally probed in axion-mediated force experiments, as suggested long ago by J.E. Moody and F. Wilczek. In the present note, I review the physical origin of CP-violating axion couplings and point out the special role of the QCD axion as a low-energy portal to high-energy sources of CP violation.
We investigate the sensitivity of the next generation of flavor-based low-energy experiments to probe the supersymmetric parameter space in the context of the phenomenological MSSM (pMSSM), and examine the complementarity with direct searches for Supersymmetry at the 13 TeV LHC in a quantitative manner. To this end, we enlarge the previously studied pMSSM parameter space to include all physical non-zero CP-violating phases, namely those associated with the gaugino mass parameters, Higgsino mass parameter, and the tri-linear couplings of the top quark, bottom quark and tau lepton. We find that future electric dipole moment and flavor measurements can have a strong impact on the viability of these models even if the sparticle spectrum is out of reach of the 13 TeV LHC. In particular, the lack of positive signals in future low-energy probes would exclude values of the phases between ${cal O}(10^{-2})$ and ${cal O}(10^{-1})$. We also find regions of parameter space where large phases remain allowed due to cancellations. Most interestingly, in some rare processes, such as BR($B_s to mu^+ mu^-$ ), we find that contributions arising from CP-violating phases can bring the potentially large SUSY contributions into better agreement with experiment and Standard Model predictions.
We introduce a scenario for CP-violating (CPV) dark photon interactions in the context of non-abelian kinetic mixing. Assuming an effective field theory that extends the Standard Model (SM) field content with an additional $U(1)$ gauge boson ($X$) and a $SU(2)_L$ triplet scalar, we show that there exist both CP-conserving and CPV dimension five operators involving these new degrees of freedom and the SM $SU(2)_L$ gauge bosons. The former yields kinetic mixing between the $X$ and the neutral $SU(2)_L$ gauge boson (yielding the dark photon), while the latter induces CPV interactions of the dark photon with the SM particles. We discuss experimental probes of these interactions using searches for permanent electric dipole moments (EDMs) and di-jet correlations in high-energy $pp$ collisions. It is found that the experimental limit on the electron EDM currently gives the strongest restriction on the CPV interaction. In principle, high energy $pp$ collisions provide a complementary probe through azimuthal angular correlations of the two forward tagging jets in vector boson fusion. In practice, observation of the associated CPV asymmetry is likely to be challenging.
We study an extension of the Standard Model (SM) in which two copies of the SM scalar $SU(2)$ doublet which do not acquire a Vacuum Expectation Value (VEV), and hence are textit{inert}, are added to the scalar sector. We allow for CP-violation in the textit{inert} sector, where the lightest textit{inert} state is protected from decaying to SM particles through the conservation of a $Z_2$ symmetry. The lightest neutral particle from the textit{inert} sector, which has a mixed CP-charge due to CP-violation, is hence a Dark Matter (DM) candidate. We discuss the new regions of DM relic density opened up by CP-violation, and compare our results to the CP-conserving limit and the Inert Doublet Model (IDM). We constrain the parameter space of the CP-violating model using recent results from the Large Hadron Collider (LHC) and DM direct and indirect detection experiments.
Using the holographic correspondence as a tool, we determine the steady-state velocity of expanding vacuum bubbles nucleated within chiral finite temperature first-order phase transitions occurring in strongly-coupled large $N$ QCD-like models. We provide general formulae for the friction force exerted by the plasma on the bubbles and for the steady-state velocity. In the top-down holographic description, the phase transitions are related to changes in the embedding of $Dq$-${bar Dq}$ flavor branes probing the black hole background sourced by a stack of $N$ $Dp$-branes. We first consider the Witten-Sakai-Sugimoto $D4$-$D8$-$bar D8$ setup, compute the friction force and deduce the equilibrium velocity. Then we extend our analysis to more general setups and to different dimensions. Finally, we briefly compare our results, obtained within a fully non-perturbative framework, to other estimates of the bubble velocity in the literature.
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