R. Foot

Seesaw Neutrino Masses Induced by a Triplet of Leptons

Neutrinos can acquire mass through the see-saw mechanism by extending the lepton sector of the Standard Model. The most generalSU(2)L assignments allowed for the exotic leptons are the singlet and triplet representations. A model is constructed involving a triplet of exotic leptons. In this model lepton number is broken. Therefore lepton number violating processes, in particular those involving the lepton triplet, could provide distinctive experimental signatures.

Neutrino physics and the mirror world: How exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly, and the LSND experiment.

Important evidence for neutrino oscillations comes from the solar neutrino deficit and the atmospheric neutrino anomaly. Further evidence for \ensuremath{\nu}

Solution to the hierarchy problem from an almost decoupled hidden sector within a classically scale invariant theory

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Electroweak Higgs as a pseudo-Goldstone boson of broken scale invariance

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Neutrino mass in radiatively broken scale-invariant models

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Reconciling sterile neutrinos with Big Bang nucleosynthesis.

oscillations has been reported at LAMPF using the LSND detector. All of these anomalies require new physics. We show that all of these anomalies can be explained if the standard model is enlarged so that an unbroken parity symmetry can be defined. This explanation holds independently of the actual model for neutrino masses. Thus, we argue that parity symmetry is not only a beautiful candidate for a symmetry beyond the standard model, but it can also explain the known neutrino physics anomalies.

Large neutrino asymmetries from neutrino oscillations

If scale invariance is a classical symmetry then both the Planck scale and the weak scale should emerge as quantum effects. We show that this can be realized in simple scale invariant theories with a hidden sector. The weak/Planck scale hierarchy emerges in the (technically natural) limit in which the hidden sector decouples from the ordinary sector. In this limit, finite corrections to the weak scale are consequently small, while quadratic divergences are absent by virtue of classical scale invariance, so there is no hierarchy problem.

Mirror dark matter: Cosmology, galaxy structure and direct detection

We point out that it is possible to associate the electroweak Higgs boson with the pseudo-Goldstone boson of broken scale invariance, thus resolving the hierarchy problem in a technically natural way. We illustrate this idea with two specific gauge models. Besides being consistent with all currently available experimental data, both models maintain the predictive power of the standard model, since the first model has only one additional parameter beyond the Standard Model, and the second has the same number of free parameters as the Standard Model.

Implications of the dama/nai and cdms experiments for mirror matter-type dark matter

Scale invariance may be a classical symmetry which is broken radiatively. This provides a simple way to stabilize the scale of electroweak symmetry breaking against radiative corrections. The simplest phenomenologically successful model of this type involves the addition of one real scalar field to the standard model. In this minimal model the electroweak Higgs can be interpreted as the pseudo-Goldstone boson of broken scale invariance. We study the possible origin of neutrino mass in such models, both at tree-level and radiatively.

Phenomenology of a very light scalar (100 MeV < mh < 10 GeV) mixing with the SM Higgs

We reexamine the big bang nucleosynthesis (BBN) bounds on the mixing of neutrinos with sterile species. These bounds depend on the assumption that the relic neutrino asymmetry {ital L}{sub {nu}} is very small. We show that for {ital L}{sub {nu}} large enough (greater than about 10{sup {endash}5}) the standard BBN bounds do not apply. We apply this result to the sterile neutrino solution to the atmospheric neutrino anomaly and show that for {ital L}{sub {nu}}{approx_gt}7{times}10{sup {minus}5} it is consistent with BBN. The BBN bounds on sterile neutrinos mixing with electron neutrinos can also be weakened considerably. {copyright} {ital 1995 The American Physical Society.}