We propose a model for neutrino masses that simultaneously results in a new dark matter candidate, the right-handed neutrino. We derive the dark matter abundance in this model, show how the hierarchy of neutrino masses is obtained, and verify that the model is compatible with existing experimental results. The model provides an economical method of unifying two seemingly separate puzzles in contemporary particle physics and cosmology.

A relation between anomaly coefficients and the group G 2The large neutrino mixing angles have generated interest in finite subgroups of SU͑3͒, as clues towards understanding the flavor structure of the standard model. In this work, we study the mathematical structure of the simplest non-Abelian subgroup, ⌬͑3n 2 ͒. Using simple mathematical techniques, we derive its conjugacy classes and character table, and build its irreducible representations, their Kronecker products, and its invariants.Excluding the values of k and l that lead to reducible representations, which happens if k = l and 3k = 0 mod͑n͒. 073501-5Flavor group ⌬͑3n 2 ͒

Long-lived colored particles with masses m > ∼ 200 GeV are allowed by current accelerator searches, and are predicted by a number of scenarios for physics beyond the standard model. We argue that such "heavy partons" effectively have a geometrical cross section (of order 10 mb) for annihilation at temperatures below the QCD deconfinement transition. The annihilation process involves the formation of an intermediate bound state of two heavy partons with large orbital angular momentum. The bound state subsequently decays by losing energy and angular momentum to photon or pion emission, followed by annihilation of the heavy partons. This decay occurs before nucleosynthesis for m < ∼ 10 11 GeV for electrically charged partons and m < ∼ TeV for electrically neutral partons. This implies that heavy parton lifetimes as long as 10 14 sec are allowed even for heavy partons with m ∼ TeV decaying to photons or hadrons with significant branching fraction.

The three flavor linear sigma model is studied as a "toy model" for understanding the role of possible light scalar mesons in the ππ, πK and πη scattering channels. The approach involves computing the tree level partial wave amplitude for each channel and unitarizing by a simple K-matrix prescription which does not introduce any new parameters. If the renormalizable version of the model is used there is only one free parameter. While this highly constrained version has the right general structure to explain ππ scatteirng, it is "not quite" right. A reasonable fit can be made if the renormalizability (for the effective Lagrangian) is relaxed while chiral symmetry is maintained.The occurence of a Ramsauer Townsend mechanism for the f 0 (980) region naturally emerges. The effect of unitarization is very important and leads to "physical" masses for the scalar nonet all less than about 1 GeV. The a 0 (1450) and K * 0 (1430) appear to be "outsiders" in this picture and to require additional fields. Comparison is made with a scattering treatment using a more general non-linear sigma model approach. In addition some speculative remarks and a highly simplified larger toy model are devoted to the question of the quark substructure of the light scalar mesons.