118387209
Phenomenology of the minimal supersymmetric $U(1)_{B-L}\times U(1)_R$ extension of the standard model
Abstract We discuss the minimal supersymmetric U(1)B−L × U(1)R extension of the standard model. Gauge couplings unify as in the MSSM, even if the scale of U(1)B−L × U(1)R breaking is as low as order TeV and the model can be embedded into an SO(10) grand unified theory. The phenomenology of the model differs in some important aspects from the MSSM, leading potentially to rich phenomenology at the LHC. It predicts more light Higgs states and the mostly left CP-even Higgs has a mass reaching easily 125 GeV, with no constraints on the SUSY spectrum. Right sneutrinos can be the lightest supersymmetric particle, changing all dark matter constraints on SUSY parameter space. The model has seven neutralinos and squark/gluino decay chains involve more complicated cascades than in the MSSM. We also discuss briefly low-energy and accelerator constraints on the model, where the most important limits come from recent Z ′ searches at the LHC and upper limits on lepton flavour violation.
119290526
Probing a supersymmetric model for neutrino masses at ultrahigh energy neutrino telescopes
Abstract A bilinear R-parity breaking SUSY model for neutrino mass and mixing predicts the lightest superparticle to decay mainly into a pair of tau leptons or b quarks along with a neutrino for relatively light SUSY spectra. This leads to a distinctive triple bang signature of SUSY events at ultrahigh energy neutrino telescopes like IceCube or Antares. While the expected signal size is only marginal at IceCube, it will be promising for a future multi-km 3 size neutrino telescope.
11803420
Majoron emission in muon and tau decays revisited
9 pages, 4 figures.-- ISI article identifier:000264762400078.-- ArXiv pre-print avaible at: http://arxiv.org/abs/0902.0525
53701384
Enhancing $l_i 3 l_j$ with the $Z^0$-penguin
Lepton flavor violation (LFV) has been observed in neutrino oscillations. For charged lepton FV 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 $l_i \to 3 l_j$ are roughly a factor $\alpha$ maller than the corresponding decays $l_i \to l_j \gamma$. Here we demonstrate that the $Z^0$-penguin diagram can give an enhancement for decays $l_i \to 3 l_j$ in many extensions of the 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.
53865432
Hefty MSSM-like light Higgs in extended gauge models
A bstractIt is well known that in the MSSM the lightest neutral Higgs h0 must be, at the tree level, lighter than the Z boson and that the loop corrections shift this stringent upper bound up to about 130 GeV. Extending the MSSM gauge group in a suitable way, the new Higgs sector dynamics can push the tree-level mass of h0 well above the tree-level MSSM limit if it couples to the new gauge sector. This effect is further pronounced at the loop level and h0 masses in the 140GeV ballpark can be reached easily. We exemplify this for a sample setting with a low-scale U(1)R × U(1)B−L gauge symmetry in which neutrino masses can be implemented via the inverse seesaw mechanism.
35525710
Phenomenology of neutrinoless double beta decay
Neutrinoless double beta decay ( 0 ν β β ) violates lepton number by two units, a positive observation therefore necessarily implies physics beyond the standard model. Here, three possible contributions to 0 ν β β decay are briefly reviewed: (a) The mass mechanism and its connection to neutrino oscillations; (b) Left-right symmetric models and the lower limit on the right-handed W boson mass; and (c) R-parity violating supersymmetry. In addition, the recently published “extended black box” theorem is briefly discussed. Combined with data from oscillation experiments this theorem provides proof that the 0 ν β β decay amplitude must receive a non-zero contribution from the mass mechanism, if neutrinos are indeed Majorana particles.
16340817
IM3SHAPE: A maximum-likelihood galaxy shear measurement code for cosmic gravitational lensing
We present and describe IM3SHAPE, a new publicly available galaxy shape measurement code for weak gravitational lensing shear. IM3SHAPE performs a maximum likelihood fit of a bulgeplus-disc galaxy model to noisy images, incorporating an applied point spread function. We detail challenges faced and choices made in its design and implementation, and then discuss various limitations that affect this and other maximum like lihood methods. We assess the bias arising from fitting an incorrect galaxy model using simple n oise-free images and find that it should not be a concern for current cosmic shear surveys. We test IM3SHAPE on the GREAT08 Challenge image simulations, and meet the requirements for upcoming cosmic shear surveys in the case that the simulations are encompassed by the fitted model, using a simple correction for image noise bias. For the fiducial branch of GREAT08 we obt ain a negligible additive shear bias and sub-two percent level multiplicative bias, which i s suitable for analysis of current surveys. We fall short of the sub-percent level requirement for upcoming surveys, which we attribute to a combination of noise bias and the mis-match between our galaxy model and the model used in the GREAT08 simulations. We meet the requirements for current surveys across all branches of GREAT08, except those with small or high noise galaxies, which we would cut from our analysis. Using the GREAT08 metric we we obtain a score of Q=717 for the usable branches, relative to the goal of Q=1000 for futur e experiments. The code is freely available from https://bitbucket.org/joezuntz/im3shap e.