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.
117100470
(B-L)-violating masses in supersymmetry and neutrinoless double beta decay
8030769
Leptogenesis with single right-handed neutrino dominance
We make an analytic and numerical study of leptogenesis in the framework of the (supersymmetric) standard model plus the seesaw mechanism with a U(1) family symmetry and single right-handed neutrino dominance. In presenting our analytic and numerical results we make a clear distinction between the theoretically clean asymmetry parameter ?1 and the baryon asymmetry YB. In calculating YB we propose and use a fit to the solutions to the Boltzmann equations which gives substantially more reliable results than parametrizations previously used in the literature. Our results show that there is a decoupling between the low energy neutrino observables and the leptogenesis predictions, but that nevertheless leptogenesis is capable of resolving ambiguities within classes of models which would otherwise lead to similar neutrino observables. For example we show that models where the dominant right-handed neutrino is the heaviest are preferred to models where it is the lightest and study an explicit example of a unified model of this type.
10450965
CP violation in decays of the lightest supersymmetric particle with bilinearly broken R parity
Supersymmetric models with broken R-parity induced by lepton number violating terms provide a calculable framework for neutrino masses and mixings. Within models with bilinear R-parity breaking six new physical phases appear which are potential sources of novel CP-violating phenomena compared to the minimal supersymmetric extension of the standard model. We consider CP-violating observables in the decays of the lightest supersymmetric particle in this class of models. We show that: (i) Neutrino physics requires a strong correlation between three different pairs of phases, thus reducing the effective number of new phases to three. (ii) CP-violating phenomena in decays of the lightest supersymmetric particle due to new R-parity breaking phases turn out to be small, once constraints from neutrino physics are taken into account. We demonstrate that this feature does not depend on the nature of the lightest supersymmetric particle.
10505280
Testing the mechanism of R-parity breaking with slepton LSP decays
In supersymmetric models R-parity can be violated through either bilinear or trilinear terms in the superpotential, or both. If charged scalar leptons are the lightest supersymmetric particles, their decay properties can be used to obtain information about the relative importance of these couplings. We show that in some specific scenarios it is even possible to decide whether bilinear or trilinear terms give the dominant contribution to the neutrino mass matrix.
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.
15297769
Measurement and calibration of noise bias in weak lensing galaxy shape estimation
Weak gravitational lensing has the potential to constrain cosmological parameters to high 
precision. However, as shown by the Shear Testing Programmes and Gravitational lensing 
Accuracy Testing challenges, measuring galaxy shears is a non-trivial task: various methods 
introduce different systematic biases which have to be accounted for. We investigate how 
pixel noise on the image affects the bias on shear estimates from a maximum likelihood 
forward model-fitting approach using a sum of co-elliptical Sersic profiles, in complement 
to the theoretical approach of an associated paper. We evaluate the bias using a simple but 
realistic galaxy model and find that the effects of noise alone can cause biases of the order of 
1–10 per cent on measured shears, which is significant for current and future lensing surveys. 
We evaluate a simulation-based calibration method to create a bias model as a function of 
galaxy properties and observing conditions. This model is then used to correct the simulated 
measurements. We demonstrate that, for the simple case in which the correct range of galaxy 
models is used in the fit, the calibration method can reduce noise bias to the level required for 
estimating cosmic shear in upcoming lensing surveys.