4,839 research outputs found

    Parallel hybrid textures of lepton mass matrices

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    We analyse the parallel hybrid texture structures in the charged lepton and the neutrino sector. These parallel hybrid texture structures have physical implications as they cannot be obtained from arbitrary lepton mass matrices through weak basis transformations. The total sixty parallel hybrid texture structures can be grouped into twelve classes, and all the hybrid textures in the same class have identical physical implications. We examine all the twelve classes under the assumption of non-factorizable phases in the neutrino mass matrix. Five out of the total twelve classes are found to be phenomenologically disallowed. We study the phenomenological implications of the allowed classes for 1-3 mixing angle, Majorana and Dirac-type CPCP violating phases. Interesting constraints on effective Majorana mass are obtained for all the allowed classes.Comment: Physical Review D (To appear

    Probing the deviation from maximal mixing of atmospheric neutrinos

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    Pioneering atmospheric muon neutrino experiments have demonstrated the near-maximal magnitude of the flavor mixing angle θ23\theta_{23}. But the precise value of the deviation D1/2sin2θ23D \equiv 1/2 - \sin^2 \theta_{23} from maximality (if nonzero) needs to be known, being of great interest -- especially to builders of neutrino mass and mixing models. We quantitatively investigate in a three generation framework the feasibility of determining DD in a statistically significant manner from studies of the atmospheric νμ,νˉμ\nu_\mu,\bar\nu_\mu survival probability including both vacuum oscillations and matter effects. We show how this determination will be sharpened by considering the up-down ratios of observed νμ\nu_\mu- and νˉμ\bar\nu_\mu-induced events and the differences of these ratios in specified energy and zenith angle bins. We consider 1 Megaton year of exposure to a magnetized iron calorimeter such as the proposed INO detector ICAL, taking into account both energy and zenith angle resolution functions. The sensitivity of such an exposure and the dependence of the determination of DD on the concerned oscillation parameters are discussed in detail. The vital use of matter effects in fixing the octant of θ23\theta_{23} is highlighted.Comment: Version to appear in PR

    Prospects of measuring the leptonic CP phase with atmospheric neutrinos

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    We have studied the prospects of measuring the CP violating phase with atmospheric neutrinos at a large magnetized iron calorimeter detector considering the muons (directly measurable) of the neutrino events generated by a MonteCarlo event generator Nuance. The effect of θ13\theta_{13} and δCP\delta_{CP} appears dominantly neither in atmospheric neutrino oscillation nor in solar neutrino oscillation, but appears as subleading in both cases. These are observable in range of E1E \sim 1 GeV for atmospheric neutrino, where solar and atmospheric oscillation couple. In this regime, the quasi-elastic events dominate and the energy resolution is very good, but the angular resolution is very poor. Unlike beam experiments this poor angular resolution acts against its measurements. However, we find that one can be able to distinguish δCP0\delta_{CP}\approx 0^\circ and 180180^\circ at 90% confidence level. We find no significant sensitivity for δCP90\delta_{CP}\approx 90^\circ or 270270^\circ.Comment: 9 pages, 7 figures, clarifying discussions on results added; accepted in Phys. Rev.

    Renormalization group evolution of neutrino mixing parameters near θ13=0\theta_{13} = 0 and models with vanishing θ13\theta_{13} at the high scale

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    Renormalization group (RG) evolution of the neutrino mass matrix may take the value of the mixing angle θ13\theta_{13} very close to zero, or make it vanish. On the other hand, starting from θ13=0\theta_{13}=0 at the high scale it may be possible to generate a non-zero θ13\theta_{13} radiatively. In the most general scenario with non-vanishing CP violating Dirac and Majorana phases, we explore the evolution in the vicinity of θ13=0\theta_{13}=0, in terms of its structure in the complex Ue3{\cal U}_{e3} plane. This allows us to explain the apparent singularity in the evolution of the Dirac CP phase δ\delta at θ13=0\theta_{13}=0. We also introduce a formalism for calculating the RG evolution of neutrino parameters that uses the Jarlskog invariant and naturally avoids this singular behaviour. We find that the parameters need to be extremely fine-tuned in order to get exactly vanishing θ13\theta_{13} during evolution. For the class of neutrino mass models with θ13=0\theta_{13}=0 at the high scale, we calculate the extent to which RG evolution can generate a nonzero θ13\theta_{13}, when the low energy effective theory is the standard model or its minimal supersymmetric extension. We find correlated constraints on θ13\theta_{13}, the lightest neutrino mass m0m_0, the effective Majorana mass meem_{ee} measured in the neutrinoless double beta decay, and the supersymmetric parameter tanβ\tan\beta.Comment: 24 pages, 6 figures, revtex

    Non-standard interaction effects on astrophysical neutrino fluxes

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    We investigate new physics effects in the production and detection of high energy neutrinos at neutrino telescopes. Analysing the flavor ratios \phi_\mu/\phi_\tau and \phi_\mu/(\phi_\tau+\phi_e), we find that the Standard Model predictions for them can be sensibly altered by new physics effects.Comment: 21 pages, 9 figures, REVTeX

    Leptogenesis bound on neutrino masses in left-right symmetric models with spontaneous D-parity violation

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    We study the baryogenesis via leptogenesis in a class of left-right symmetric models, in which DD-parity is broken spontaneously. We first discuss the consequence of the spontaneous DD-parity breaking on the neutrino masses. Than we study the lepton asymmetry in various cases, from the decay of right handed neutrino as well as the triplet Higgs, depending on their relative masses they acquire from the symmetry breaking pattern. The leptogenesis bound on their masses are discussed by taking into account the low energy neutrino oscillation data. It is shown that a TeV scale leptogenesis is viable if there are additional sources of CP violation like domain wall originating from the spontaneous DD-parity violation.Comment: 32 pages (revtex), 12 eps figures, clarifications are added in section VII, A new section VIII is added, useful references are added. Journal version, To appear in Phys. Rev.

    Determining the Neutrino Mass Hierarchy and CP Violation in NOvA with a Second Off-Axis Detector

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    We consider a Super-NOvA-like experimental configuration based on the use of two detectors in a long-baseline experiment as NOvA. We take the far detector as in the present NOvA proposal and add a second detector at a shorter baseline. The location of the second off-axis detector is chosen such that the ratio L/E is the same for both detectors, being L the baseline and E the neutrino energy. We consider liquid argon and water-Cherenkov techniques for the second off-axis detector and study, for different experimental setups, the detector mass required for the determination of the neutrino mass hierarchy, for different values of theta13. We also study the capabilities of such an experimental setup for determining CP violation in the neutrino sector. Our results show that by adding a second off-axis detector a remarkable enhancement on the capabilities of the current NOvA experiment could be achieved.Comment: 20 p

    Possible textures of the fermion mass matrices

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    Texture specific fermion mass matrices have played an important role in understanding several features of fermion masses and mixings. In the present work, we have given an overview of all possible cases of Fritzsch-like as well as non Fritzsch-like texture 6 and 5 zero fermion mass matrices. Further, for the case of texture 4 zero Fritzsch-like quark mass matrices, the issue of the hierarchy of the elements of the mass matrices and the role of their phases have been discussed. Furthermore, the case of texture 4 zero Fritzsch-like lepton mass matrices has also been discussed with an emphasis on the hierarchy of neutrino masses for both Majorana and Dirac neutrinos.Comment: 21 pages, 3 figure

    Supersymmetric Jarlskog Invariants: the Neutrino Sector

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    We generalize the notion of the Jarlskog invariant to supersymmetric models with right--handed neutrinos. This allows us to formulate basis--independent necessary and sufficient conditions for CP conservation in such models.Comment: 10 pages, no figure

    Neutrino mass generation in the SO(4) model

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    Generation of neutrino mass in SO(4) model is proposed here. The algebraic structure of SO(4) is same as to that of SU(2)L×SU(2)RSU(2)_{L}\times SU(2)_{R}. It is shown that the spontaneous symmetry breaking results three massive as well as three massless gauge bosons. The standard model theory according to which there exist three massive gauge bosons and a massless one is emerged from this model. In the framework of SU(2)L×SU(2)RSU(2)_{L}\times SU(2)_{R} a small Dirac neutrino mass is derived. It is also shown that such mass term may vanish with a special choice. The Majorana mass term is not considered here and thus in this model the neutrino mass does not follow seesaw structure.Comment: 7 pages, no figur
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