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Hirsch, M., Morisi, S., Peinado, E., & Valle, J. W. F. (2010). Discrete dark matter. Phys. Rev. D, 82(11), 116003–5pp.
Abstract: We propose a new motivation for the stability of dark matter (DM). We suggest that the same non-Abelian discrete flavor symmetry which accounts for the observed pattern of neutrino oscillations, spontaneously breaks to a Z(2) subgroup which renders DM stable. The simplest scheme leads to a scalar doublet DM potentially detectable in nuclear recoil experiments, inverse neutrino mass hierarchy, hence a neutrinoless double beta decay rate accessible to upcoming searches, while theta(13) = 0 gives no CP violation in neutrino oscillations.
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De Romeri, V., Hirsch, M., & Malinsky, M. (2011). Soft masses in supersymmetric SO(10) GUTs with low intermediate scales. Phys. Rev. D, 84(5), 053012–15pp.
Abstract: The specific shape of the squark, slepton and gaugino mass spectra, if measured with sufficient accuracy, can provide invaluable information not only about the dynamics underpinning their origin at some very high scale such as the unification scale M(G), but also about the intermediate scale physics encountered throughout their renormalization group equations evolution down to the energy scale accessible for the LHC. In this work, we study general features of the TeV scale soft supersymmetry breaking parameters stemming from a generic mSugra configuration within certain classes of supersymmetry SO(10) GUTs with different intermediate symmetries below M(G). We show that particular combinations of soft masses show characteristic deviations from the mSugra limit in different models and thus, potentially, allow to distinguish between these, even if the new intermediate scales are outside the energy range probed at accelerators. We also compare our results to those obtained for the three minimal seesaw models with mSugra boundary conditions and discuss the main differences between those and our SO(10) based models.
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Dib, C., Helo, J. C., Hirsch, M., Kovalenko, S., & Schmidt, I. (2012). Heavy sterile neutrinos in tau decays and the MiniBooNE anomaly. Phys. Rev. D, 85(1), 011301–4pp.
Abstract: Current results of the MiniBooNE experiment show excess events that indicate neutrino oscillations, but only if one goes beyond the standard 3 family scenario. Recently a different explanation of the events has been given, not in terms of oscillations but by the production and decay of a massive sterile neutrino with large transition magnetic moment. We study the effect of such a sterile neutrino in the rare decays tau(-) -> mu(-)mu(+)pi(-)nu and tau(-) -> mu(-)mu(+)e(-)nu nu. We find that searches for these decays, featuring displaced vertices between the mu(-) and the other charged particles, constitute reliable tests for the existence of the sterile neutrino proposed to explain the MiniBooNE anomaly. These searches could be done with already existing experimental data.
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Hirsch, M., Staub, F., & Vicente, A. (2012). Enhancing l(i) -> 3l(j) with the Z(0)-penguin. Phys. Rev. D, 85(11), 113013–5pp.
Abstract: Lepton flavor violation has been observed in neutrino oscillations. For charged lepton flavor violation decays only upper limits are known, but sizable branching ratios are expected in many neutrino mass models. High-scale models, such as the classical supersymmetric seesaw, usually predict that decays l(i) -> 3l(j) are roughly a factor alpha smaller than the corresponding decays l(i) -> l(j)gamma. Here we demonstrate that the Z(0)-penguin diagram can give an enhancement for decays l(i) -> 3l(j) in many extensions of the minimal supersymmetric standard model (MSSM). We first discuss why the Z(0)-penguin is not dominant in the MSSM with seesaw and show that much larger contributions from the Z(0)-penguin are expected in general. We then demonstrate the effect numerically in two example models, namely, the supersymmetric inverse seesaw and R-parity violating supersymmetry.
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Campos, F., Eboli, O. J. P., Magro, M. B., Porod, W., Restrepo, D., Das, S. P., et al. (2012). Probing neutralino properties in minimal supergravity with bilinear R-parity violation. Phys. Rev. D, 86(7), 075001–8pp.
Abstract: Supersymmetric models with bilinear R-parity violation can account for the observed neutrino masses and mixing parameters indicated by neutrino oscillation data. We consider minimal supergravity versions of bilinear R-parity violation where the lightest supersymmetric particle is a neutralino. This is unstable, with a large enough decay length to be detected at the CERN Large Hadron Collider. We analyze the Large Hadron Collider potential to determine the lightest supersymmetric particle properties, such as mass, lifetime and branching ratios, and discuss their relation to neutrino properties.
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