Lepton flavor violation in low-scale seesaw models: SUSY and non-SUSY contributions

Taking the supersymmetric inverse seesaw mechanism as the explanation for neutrino oscillation data, we investigate charged lepton flavor violation in radiative and 3-body lepton decays as well as in neutrinoless $\mu-e$ conversion in muonic atoms. In contrast to former studies, we take into account all possible contributions: supersymmetric as well as non-supersymmetric. We take CMSSM-like boundary conditions for the soft supersymmetry breaking parameters. We find several regions where cancellations between various contributions exist, reducing the lepton flavor violating rates by an order of magnitude compared to the case where only the dominant contribution is taken into account. This is in particular important for the correct interpretation of existing data as well as for estimating the reach of near future experiments where the sensitivity will be improved by one to two orders of magnitude. Moreover, we demonstrate that ratios like BR($\tau\to 3 \mu$)/BR($\tau\to \mu e^+ e^-$) can be used to determine whether the supersymmetric contributions dominate over the $W^\pm$ and $H^\pm$ contributions or vice versa.Comment: 75 pages, 7 figures. v3: references and comments added. Matches published versio

The Blast Energy Efficiency of GRBs

Using data mostly assembled by previous authors, we consider the linear correlation between the apparent radiative efficiency $\epsilon_{\gamma}$ (defined as the ratio of isotropic equivalent radiative output to inferred isotropic equivalent kinetic energy of the blast) and $E_{peak}^{\alpha}$ where $1.4<\alpha<2$, for 17 of 22 GRBs (Lloyd-Ronning and Zhang, 2004). We note in a quantitative manner that this is consistent with the hypothesis that $\epsilon_{\gamma}$ and $E_{peak}$ are influenced by viewing angle. We suggest a more general theoretically derived expression for this correlation that could be tested with a richer data set. If the reduction in both $\epsilon_{\gamma}$ and $E_{peak}$ is due to viewing angle effects, then the actual radiative efficiency is $\sim 7$. We also find preliminary evidence (with a small sample) for a separate class of weak GRB afterglows.Comment: Submitted to ApJL Feb. 10, 200