Non-zero Value Of Θ13 Research Articles

Neutrino masses and mixings with non-zero [formula omitted] in type I + II seesaw models

We study the survivability of neutrino mass models with normal as well as inverted hierarchical mass patterns in the presence of both type I and type II seesaw contributions to neutrino mass within the framework of generic left–right symmetric models. At leading order, the Dirac neutrino mass matrix is assumed to be diagonal with either charged lepton (CL) type or up quark (UQ) type structure which gets corrected by non-leading effects giving rise to deviations from tri-bi-maximal (TBM) mixing and hence non-zero value of θ13. Using the standard form of neutrino mass matrix which incorporates such non-leading effects, we parametrize the neutrino mass matrix incorporating both oscillation as well as cosmology data. Also considering extremal values of Majorana CP phases such that the neutrino mass eigenvalues have the structure (m1,−m2,m3) and (m1,m2,m3), we then calculate the predictions for neutrino parameters in the presence of both type I and type II seesaw contributions, taking one of them dominant and the other sub-dominant. We show that these mass models can survive in our framework with certain exceptions.

Optimized Neutrino Factory for small and large θ13

Recent results from long baseline neutrino oscillation experiments point towards a non-zero value of θ13 at around 3σ confidence level. In the coming years, further ratification of this result with high significance will have crucial impact on the planning of the future long baseline Neutrino Factory setup aimed to explore leptonic CP violation and the neutrino mass ordering. In this talk, we discuss the baseline and energy optimization of the Neutrino Factory including the latest simulation results on the magnetized iron neutrino detector (MIND) in the light of both small and large θ13. We find that in case of small θ13, baselines of about 2500 to 5000 km is the optimal choice for the CP violation measurement with Eμ as low as 12 GeV can be considered. However, for large θ13, we show that the lower threshold and the backgrounds reconstructed at lower energies allow in fact for muon energies as low as 5 to 8 GeV at considerably shorter baselines, such as Fermilab to Homestake. This suggests that with the latest MIND simulation, low- and high-energy versions of the Neutrino Factory are just two different forms of the same experiment optimized for different regions of the parameter space.

NONZERO θ13 FROM THE TRIANGULAR ANSATZ AND LEPTOGENESIS

Recent experiments indicate a departure from the exact tri-bimaximal mixing by measure ring definitive nonzero value of θ13. Within the framework of type I seesaw mechanism, we reconstruct the triangular Dirac neutrino mass matrix from the μ - τ symmetric mass matrix. The deviation from μ - τ symmetry is then parametrized by adding dimensionless parameters yi in the triangular mass matrix. In this parametrization of the neutrino mass matrix, the nonzero value θ13 is controlled by Δy = y4 - y6. We also calculate the resulting leptogenesis and show that the triangular texture can generate the observed baryon asymmetry in the universe via leptogenesis scenario.

Intrinsic deviation from the tri-bimaximal neutrino mixing in a class of [formula omitted] flavor models

It is well known that the tri-bimaximal neutrino mixing pattern V0 can be derived from a class of flavor models with the non-Abelian A4 symmetry. We point out that small corrections to V0, which are inherent in the A4 models and arise from both the charged-lepton and neutrino sectors, have been omitted in the previous works. We show that such corrections may lead the 3×3 neutrino mixing matrix V to a non-unitary deviation from V0, but they cannot result in a nonzero value of θ13 or any new CP-violating phases. Current experimental constraints on the unitarity of V allow us to constrain the model parameters to some extent.

CP Violation in Neutrino Oscillation Due to Planck Scale Effects

We consider non renormalization 1/Mx interaction term as a perturbation of the neutrino mass matrix. We find that for the degenerate neutrino mass spectrum. We assume that the neutrino masses and mixing arise through physics at a scale intermediate between Planck Scale and the electroweak scale. We also assume, above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing is bimaximal. The perturbation generates a non zero value of θ13, which is within reach of the high performance neutrino factory. In this paper, we find that the non zero value of θ13 due to Planck scale effects indicates the possibility of CP violation.

Contrasting solar and reactor neutrinos with a non-zero value of θ13

When solar neutrino and KamLAND data are analyzed separately one finds that, even though allowed regions of neutrino parameters overlap, the values of δm2 and the mixing angle θ12 at the χ2 minima are different. We show that a non-zero, but small value of the angle θ13 can account for this behavior. From the joint analysis of solar neutrino and KamLAND data we find the best fit value of sin22θ13 = 0.01−0.01+0.09.

New neutrino experiments

Following incredible recent progress in understanding neutrino oscillations, many new ambitious experiments are being planned to study neutrino properties. The most important may be to find a non-zero value of θ13. The most promising way to do this appears to be to measurev μ →v e oscillations with anE/L near Δm atmo 2 . Future neutrino experiments are great.