Here comes some of that shameless self-promotion I promised! On Friday, I had a new paper come out on the arXiv, written with my friend and collaborator Matt McCullough, who is now a postdoc at MIT. We present a mechanism to explain the observed tiny but non-zero neutrino masses, in the context of supersymmetric models which preserve an R-symmetry at the electroweak scale.
It is well known that when supergravity is taken into account, R-symmetry must be broken in order to cancel the large cosmological constant generated by supersymmetry breaking. This can happen well below the electroweak scale, leaving a good approximate R-symmetry, and all the advantages that brings (see below). But in the scenario we present, the R-symmetry is what forbids electroweak-scale Dirac neutrino masses, so when it is broken, Dirac neutrino masses are naturally generated at a much smaller scale. The particularly nice observation, made by Matt, is that once one demands TeV-scale soft masses for the squarks, the neutrino masses which are generated this way are of just the right magnitude, independent of the scale of supersymmetry breaking. We found this to be quite a compelling coincidence, so we wrote a paper about it!
This idea fits in nicely with a model we developed along with John March-Russell earlier this year, or with the perhaps better-known model of Kribs, Poppitz and Weiner from a few years earlier. These R-symmetric models have some very nice features, and have been gaining more attention recently; I will try to talk about them in more detail in a future post.