Radiative Higgs-Sector CP Violation in the MSSM

We briefly review the phenomenological implications of the minimal supersymmetric standard model (MSSM) with explicit radiative breaking of CP invariance in the Higgs sector for the LEP2 and Tevatron colliders.Comment: 6 pages, talk given at PASCOS '99, Lake Tahoe, California, December 10-16, 199

Symmetries for SM Alignment in multi-Higgs Doublet Models

We derive the complete set of continuous maximal symmetries for Standard Model (SM) alignment that may occur in the tree-level scalar potential of multi-Higgs Doublet Models, with $n > 2$ Higgs doublets. Our results generalize the symmetries of SM alignment, without decoupling of large mass scales or fine-tuning, previously obtained in the context of two-Higgs Doublet Models.Comment: 12 pages, no figures, expanded version with significant clarifications adde

CP Violation in the Higgs Sector of the MSSM

Recently, it has been found that the tree-level CP invariance of the Higgs potential in the MSSM can be sizeably broken by loop effects due to soft-CP-violating trilinear interactions involving third generation scalar quarks. These soft-CP-violating couplings may be constrained by considering new two-loop contributions to the electron and neutron EDMs. The phenomenological consequences of such a minimal supersymmetric scenario of explicit CP violation at present and future colliders are briefly discussed.Comment: 11 pages, comments on the renormalization-scheme dependence of the radiatively-induced CP-odd Higgs phase adde

Anomalous Fermion Mass Generation at Three Loops

We present a novel mechanism for generating gauge-invariant fermion masses through global anomalies at the three loop level. In a gauge theory, global anomalies are triggered by the possible existence of scalar or pseudoscalar states and heavy fermions, whose masses may not necessarily result from spontaneous symmetry breaking. The implications of this mass-generating mechanism for model building are discussed, including the possibility of creating low-scale fermion masses by quantum gravity effects.Comment: 12 pages, 2 axodraw figures, to appear in MPL

Charged LFV in a low-scale seesaw mSUGRA model

We investigate the influence of the boundary conditions of minimal supergravity (mSUGRA) on the supersymmetric mechanism for lepton flavour violation (LFV) proposed recently [1], within the framework of the MSSM extended by TeV-scale singlet heavy neutrinos. We find that the consideration of the mSUGRA boundary condition may increase the branching ratios of the muon and tauon decaying into three charged leptons by up to a factor of 5, whereas the corresponding branching ratio for their photonic decays remains almost unchanged.Comment: 6 pages, 3 figures. Prepared for the Proceedings of the 11th International Workshop on Tau Lepton Physics, Manchester, UK, September 13-17, 2010. Presented by A. Ilakova

Thermal field theory to all orders in gradient expansion

We present a new perturbative formulation of non-equilibrium thermal field theory, based upon non-homogeneous free propagators and time-dependent vertices. The resulting time-dependent diagrammatic perturbation series are free of pinch singularities without the need for quasi-particle approximation or effective resummation of finite widths. After arriving at a physically meaningful definition of particle number densities, we derive master time evolution equations for statistical distribution functions, which are valid to all orders in perturbation theory and all orders in a gradient expansion. For a scalar model, we make a loopwise truncation of these evolution equations, whilst still capturing fast transient behaviour, which is found to be dominated by energy-violating processes, leading to non-Markovian evolution of memory effects.Comment: 8 pages, 4 figures. Prepared for the proceedings of DISCRETE2012: the Third Symposium on Prospects in the Physics of Discrete Symmetries, IST Lisbon, to appear in the Journal of Physics: Conference Series (JPCS). Presented by P. Millingto

Symmetry Improved 2PI Effective Action and the Infrared Divergences of the Standard Model

Resummations of infinite sets of higher-order perturbative contributions are often needed both in thermal field theory and at zero temperature. For instance, the behaviour of the Standard Model (SM) effective potential extrapolated to very high energies is known to be extremely sensitive to higher-order effects. The 2PI effective action provides a systematic approach to consistently perform such resummations. However, one of its major limitations was that its loopwise expansion introduces residual violations of possible global symmetries, thus giving rise to massive Goldstone bosons in the spontaneously broken phase of the theory. We review the recently developed symmetry-improved 2PI formalism for consistently encoding global symmetries in the 2PI approach, and discuss its satisfactory field-theoretical properties. We then apply the formalism to study the infrared divergences of the SM effective potential due to Goldstone bosons, which may affect the stability analyses of the SM. We present quantitative comparisons, for the scalar sector of the SM, with the approximate partial resummation procedure recently developed to address this problem, and show the quantitative discrepancy of the latter with the more complete 2PI approach, thus motivating further studies in this direction.Comment: 19 pages, 14 figures; Contribution to the Proceedings of DISCRETE 2014, London, United Kingdo

F_D-Term Hybrid Inflation with Electroweak-Scale Lepton Number Violation

We study F-term hybrid inflation in a novel supersymmetric extension of the SM with a subdominant Fayet-Iliopoulos D-term. We call this particular form of inflation, in short, F_D-term hybrid inflation. The proposed model ties the mu-parameter of the MSSM to an SO(3)-symmetric Majorana mass m_N, through the vacuum expectation value of the inflaton field. The late decays of the ultraheavy particles associated with the extra U(1) gauge group, which are abundantly produced during the preheating epoch, could lower the reheat temperature even up to 1 TeV, thereby avoiding the gravitino overproduction problem. The baryon asymmetry in the Universe can be explained by thermal electroweak-scale resonant leptogenesis, in a way independent of any pre-existing lepton- or baryon-number abundance. Further cosmological and particle-physics implications of the F_D-term hybrid model are briefly discussed.Comment: 20 pages, 1 eps figure, comments added to conclusion

Cumulative Non-Decoupling Effects of Kaluza-Klein Neutrinos in Electroweak Processes

In Kaluza-Klein theories of low-scale quantum gravity, gravitons and isosinglet neutrinos may propagate in a higher-dimensional space with large compact dimensions, whereas all particles of the Standard Model are confined on a (1+3)-dimensional subspace. After compactification of the extra dimensions, the resulting Yukawa couplings of the Kaluza-Klein neutrinos to the lepton doublets become naturally very suppressed by a higher-dimensional volume factor, in agreement with phenomenological observations. We show that one-loop effects induced by Kaluza-Klein neutrinos, albeit tiny individually, act cumulatively in electroweak processes, giving rise to a non-decoupling behaviour for large values of the higher-dimensional Yukawa couplings. Owing to the non-decoupling effects of Kaluza-Klein neutrinos, we can derive stronger constraints on the parameters of the theory that originate from the non-observation of flavour-violating and universality-breaking phenomena, which involve the W and Z bosons, and the e, $\mu$ and $\tau$ leptons.Comment: 31 pages, LaTeX, to appear in Physical Review