52 research outputs found

    Neutrino mixing in the seesaw model

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    In the seesaw model with hierarchical Dirac masses, the neutrino mixing angle exhibits the behavior of a narrow resonance. In general, the angle is strongly suppressed, but it can be maximal for special parameter values. We delineate the small regions in which this happens, for the two flavor problem. On the other hand, the physical neutrino masses are hierarchical, in general, except in a large part of the region in which the mixing angle is sizable, where they are nearly degenerate. Our general analysis is also applicable to the RGE of neutrino mass matrix, where we find analytic solutions for the running of physical parameters, in addition to a complex RGE invariant relating them. It is also shown that, if one mixing angle is small, the three neutrino problem reduces to two, two flavor problems.Comment: 19 pages, 4 figures; added new sections on RGE effects and universal seesaw; version to appear in EPJ

    Density profiles of supernova matter and determination of neutrino parameters

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    The flavor conversion of supernova neutrinos can lead to observable signatures related to the unknown neutrino parameters. As one of the determinants in dictating the efficiency of resonant flavor conversion, the local density profile near the MSW resonance in a supernova environment is, however, not so well understood. In this analysis, variable power-law functions are adopted to represent the independent local density profiles near the locations of resonance. It is shown that the uncertain matter density profile in a supernova, the possible neutrino mass hierarchies, and the undetermined 1-3 mixing angle would result in six distinct scenarios in terms of the survival probabilities of νe\nu_{e} and νeˉ\bar{\nu_{e}}. The feasibility of probing the undetermined neutrino mass hierarchy and the 1-3 mixing angle with the supernova neutrinos is then examined using several proposed experimental observables. Given the incomplete knowledge of the supernova matter profile, the analysis is further expanded to incorporate the Earth matter effect. The possible impact due to the choice of models, which differ in the average energy and in the luminosity of neutrinos, is also addressed in the analysis.Comment: 27 pages, 10 figures. text and figures revised, references added, to appear in Phys. Rev.

    Probing neutrino mass hierarchies and ϕ13\phi_{13} with supernova neutrinos

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    We investigate the feasibility of probing the neutrino mass hierarchy and the mixing angle ϕ13\phi_{13} with the neutrino burst from a future supernova. An inverse power-law density ρrn\rho \sim r^{n} with varying nn is adopted in the analysis as the density profile of a typical core-collapse supernova. The survival probabilities of νe\nu_{e} and νˉe\bar{\nu}_{e} are shown to reduce to two-dimensional functions of nn and ϕ13\phi_{13}. It is found that in the nsin2ϕ13n-\sin^{2} \phi_{13} parameter space, the 3D plots of the probability functions exhibit highly non-trivial structures that are sensitive to the mass hierarchy, the mixing angle ϕ13\phi_{13}, and the value of nn. The conditions that lead to observable differences in the 3D plots are established. With the uncertainty of nn considered, a qualitative analysis of the Earth matter effect is also included.Comment: 16 pages, 3 figures. Ref [11] added, and some typos correcte

    Lorentz transformation and vector field flows

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    The parameter changes resulting from a combination of Lorentz transformation are shown to form vector field flows. The exact, finite Thomas rotation angle is determined and interpreted intuitively. Using phase portraits, the parameters evolution can be clearly visualized. In addition to identifying the fixed points, we obtain an analytic invariant, which correlates the evolution of parameters.Comment: 11 pages, 3 figures. Section IV revised and title change

    Ocimum gratissimum Aqueous Extract Protects H9c2 Myocardiac Cells from H2O2-Induced Cell Apoptosis through Akt Signalling

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    Increased cell death of cardiomyocyte by oxidative stress is known to cause dysfunction of the heart. O. gratissimum is one of the more well-known medicinal plants among the Ocimum species and widely used in treatment of inflammatory diseases. In this study, we hypothesized that aqueous extract of O. gratissimum leaf (OGE) may protect myocardiac cell H9c2 from oxidative injury by hydrogen peroxide (H2O2). Our results revealed that OGE pretreatment dose-dependently protects H9c2 cells from cell death when exposed to H2O2. Additionally, DNA condensation induced by H2O2 was also reduced by OGE pretreatment, suggesting that Ocimum gratissimum extract may attenuate H2O2-induced chromosome damage. Further investigation showed that OGE pretreatment inhibited H2O2-induced activation of caspase-3 and caspase-9, as well as H2O2-induced upregulation of proapoptotic Apaf-1 and the release of cytosolic cytochrome c, but has little effect on the activation of caspase-8. Additionally, OGE pretreatment significantly upregulated Bcl-2 expression and Akt phosphorylation, and slightly affected the phosphorylation of mitogen-activated protein kinases including p38 MAPK and JNK. Taken together, our findings revealed that Ocimum gratissimum extract effectively inhibited the mitochondrial pathway and upregulated Bcl-2 expression, which may be important in protecting H9c2 cells from H2O2-induced cell death

    Hermitian quark mass matrices with four texture zeros

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    We provide a complete and systematic analysis of hermitian, hierarchical quark mass matrices with four texture zeros. Using triangular mass matrices, each pattern of texture zeros is readily shown to lead to a definite relation between the CKM parameters and the quark masses. Nineteen pairs are found to be consistent with present data, and one other is marginally acceptable. In particular, no parallel structure between the up and down mass matrices is found to be favorable with data.Comment: 18 pages, no figure, references [8] and [10] adde

    Texture Specific Mass Matrices and CP violating asymmetry in B^o_d({\bar B}^o_d) -> \psi K_S

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    In the context of texture 4 - zero and texture 5 - zero hierarchical quark mass matrices, CP violating asymmetry in Bdo(Bˉdo)ψKSB^o_d({\bar B}^o_d) \to \psi K_S (sin2β\beta) has been evaluated by considering quark masses at mZm_Z scale. For a particular viable texture 4 - zero mass matrix the range of sin2\beta is: 0.27 - 0.60 and for the corresponding texture 5 - zero case it is 0.31 - 0.59. Further our calculations reveal a crucial dependence of sin2β\beta on light quark masses as well as the phase in this sector.Comment: 10 latex pages, 4 EPS figure
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