arXiv subjects

Stephan J. Huber

Publications and source records attributed to Stephan J. Huber.

45 records · Page 3Linked to original sources

arXiv2002

Flavor Physics and Warped Extra Dimensions

We consider a five dimensional model with warped geometry where the standard model fermions and gauge bosons correspond to bulk fields. Fermion masses and CKM mixings can be explained in a geometrical picture, without hierarchical Yukawa couplings. We discuss various flavor violating processes induced by (excited) gauge boson exchange and non-renormalizable operators. Some of them, such as muon-electron conversion, are in the reach of next generation experiments.

hep-ph↗

arXiv2002

Majorana neutrinos in a warped 5D standard model

We consider neutrino oscillations and neutrinoless double beta decay in a five dimensional standard model with warped geometry. Although the see-saw mechanism in its simplest form cannot be implemented because of the warped geometry, the bulk standard model neutrinos can acquire the desired (Majorana) masses from dimension five interactions. We discuss how large mixings can arise, why the large mixing angle MSW solution for solar neutrinos is favored, and provide estimates for the mixing angle U_e3. Implications for neutrinoless double beta decay are also discussed.

hep-ph↗

arXiv2002

Kaluza-Klein Excitations of W and Z at the LHC?

Deviations from standard electroweak physics arise in the framework of a Randall-Sundrum model, with matter and gauge fields in the bulk and the Higgs field localized on the TeV brane. We focus in particular on modifications associated with the weak mixing angle. Comparison with the electroweak precision data yields a rather stringent lower bound of about 10 TeV on the masses of the lowest Kaluza-Klein excitation of the W and Z bosons. With some optimistic assumptions the bound could be lowered to about 7 TeV.

hep-ph↗

arXiv2001

Electroweak Baryogenesis: Concrete in a SUSY Model with a Gauge Singlet

SUSY models with a gauge singlet easily allow for a strong first order electroweak phase transition (EWPT) if the vevs of the singlet and Higgs fields are of comparable size. We discuss the profile of the stationary expanding bubble wall and CP-violation in the effective potential, in particular transitional CP-violation inside the bubble wall during the EWPT. The dispersion relations for charginos contain CP-violating terms in the WKB approximation. These enter as source terms in the Boltzmann equations for the (particle--antiparticle) chemical potentials and fuel the creation of a baryon asymmetry through the weak sphaleron in the hot phase. This is worked out for concrete parameters.

hep-ph↗

arXiv2001

Neutrino oscillations and rare processes in models with a small extra dimension

We discuss Dirac neutrino masses and mixings in a scenario where both the standard model fermions and right handed neutrinos are bulk fields in a non-factorizable geometry in five dimensions. We show how the atmospheric and solar neutrino anomalies can be satisfactorily resolved, and in particular how bimaximal mixing is realized. We also consider rare processes such as neutron-antineutron oscillations and mu --> e + gamma, which may occur at an observable rate.

hep-ph↗

arXiv2000

Baryogenesis at the Electroweak Phase Transition for a SUSY Model with a Gauge Singlet

SUSY models with a gauge singlet easily allow for a strongly first order electroweak phase transition (EWPT). We discuss the wall profile, in particular transitional CP violation during the EWPT. We calculate CP violating source terms for the charginos in the WKB approximation and solve the relevant transport equations to obtain the generated baryon asymmetry.

hep-ph↗

arXiv2000

Fermion Masses, Mixings and Proton Decay in a Randall-Sundrum Model

We consider a Randall-Sundrum model in which the Standard Model fermions and gauge bosons correspond to bulk fields. We show how the observed charged fermion masses and CKM mixings can be explained, without introducing hierarchical Yukawa couplings. We then study the impact on the mass scales associated with non-renormalizable operators responsible for proton decay, neutrino masses, and flavor changing neutral currents. Although mass scales as high as 10^{11}- 10^{12} GeV are in principle possible, dimensionless couplings of order 10^{-8} are still needed to adequately suppress proton decay. Large neutrino mixings seem to require new physics beyond the Standard Model.

hep-ph↗

arXiv2000

Higgs Mechanism and Bulk Gauge Boson Masses in the Randall-Sundrum Model

Assuming the breaking of gauge symmetries by the Higgs mechanism, we consider the associated bulk gauge boson masses in the Randall-Sundrum background. With the Higgs field confined on the TeV-brane, the W and Z boson masses can naturally be an order of magnitude smaller than their Kaluza-Klein excitation masses. Current electroweak precision data requires the lowest excited state to lie above about 30 TeV, with fermions on the TeV-brane. This bound is reduced to about 10 TeV if the fermions reside sufficiently close to the Planck-brane. Thus, some tuning of parameters is needed. We also discuss the bulk Higgs case, where the bounds are an order of magnitude smaller.

hep-ph↗

arXiv1998

SUSY Variants of the Electroweak Phase Transition

The MSSM with a light right-handed stop and supersymmetric models with a singlet whose vev is comparable to that of the SU(2)_W Higgs allow for a strongly first-order electroweak phase transition even for a mass of the lightest Higgs around 100 GeV. After a short review of the standard model situation we discuss these supersymmetric models. We also compare perturbative calculations based on the dimensionally reduced 3-dimensional action with lattice results and present an analytic procedure based on an analogue of the stochastic vacuum model of QCD to estimate the nonperturbative contributions.

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