V. Barger

CERN LHC phenomenology of an extended standard model with a real scalar singlet

Gauge singlet extensions of the standard model (SM) scalar sector may help remedy its theoretical and phenomenological shortcomings while solving outstanding problems in cosmology. Depending on the symmetries of the scalar potential, such extensions may provide a viable candidate for the observed relic density of cold dark matter or a strong first order electroweak phase transition needed for electroweak baryogenesis. Using the simplest extension of the SM scalar sector with one real singlet field, we analyze the generic implications of a singlet-extended scalar sector for Higgs boson phenomenology at the Large Hadron Collider (LHC). We consider two broad scenarios: one in which the neutral SM Higgs and singlet mix and the other in which no mixing occurs and the singlet can be a dark matter particle. For the first scenario, we analyze constraints from electroweak precision observables and their implications for LHC Higgs phenomenology. For models in which the singlet is stable, we determine the conditions under which it can yield the observed relic density, compute the cross sections for direct detection in recoil experiments, and discuss the corresponding signatures at the LHC.

BI-MAXIMAL MIXING OF THREE NEUTRINOS

Abstract We show that if the solar and atmospheric data are both described by maximal vacuum oscillations at the relevant mass scales then there exists a unique mixing matrix for three neutrino flavors. The solution necessarily conserves CP and automatically implies that there is no disappearance of atmospheric ν e , consistent with indications from the Super-Kamiokande experiment. We also investigate the consequences for three-neutrino mixing if the solar and atmospheric oscillations exhibit mixing that is large but not maximal. For non-maximal mixing ν e ↔ ν τ and ν e ↔ ν μ oscillations are predicted that may be observable in future long-baseline experiments.

Breaking eight fold degeneracies in neutrino CP violation, mixing, and mass hierarchy

We identify three independent twofold parameter degeneracies

Physics at a future Neutrino Factory and super-beam facility

(\ensuremath{\delta},{\ensuremath{\theta}}_{13}),

Supersymmetric particle spectrum

\mathrm{sgn}(\ensuremath{\delta}{m}_{31}^{2})

Complex singlet extension of the standard model

and

Radiative natural supersymmetry with a 125 GeV Higgs boson.

({\ensuremath{\theta}}_{23},\ensuremath{\pi}/2\ensuremath{-}{\ensuremath{\theta}}_{23})

CP violating phases in SUSY, electric dipole moments, and linear colliders

inherent in the usual three-neutrino analysis of long-baseline neutrino experiments, which can lead to as much as an eightfold degeneracy in the determination of the oscillation parameters. We discuss the implications these degeneracies have for detecting

Higgs bosons: Intermediate mass range at e+e- colliders.

\mathrm{CP}