120092931
Sub-eV limit for the neutrino mass from 76Ge double beta decay by the HEIDELBERG-MOSCOW experiment
Abstract The HEIDELBERG-MOSCOW double beta decay experiment using HP germanium semiconductor detectors enriched in 76Ge is the first ββ experiment to penetrate into the sub-eV range. After a measuring time of 10.2 kg·a (117.0 mol·a) the half-life limit for 76Ge 0νββ decay is T 1 2 ≥ 5.6×10 24 a (90% C. L.) or T 1 2 ≥9.4×10 24 a (68% C.L.) which corresponds to an upper limit for the effective Majorana neutrino mass 〈mν〉 ≤ 0.65 eV (90% C.L.) or 〈mν〉 ≤ 0.50 eV (68% C. L.). For a superheavy neutrino, as it occurs, e. g., in seesaw models, we extract a limit of 〈mH〉 ≥ 5.1×107 GeV. These numbers are of importance in the context of presently discussed indications of physics beyond the Standard Model.
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.
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.
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.
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.
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
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.