196 research outputs found

    2540 km: Bimagic baseline for neutrino oscillation parameters

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    We show that a source-to-detector distance of 2540 km offers multiple advantages for a low energy neutrino factory with a detector that can identify muon charge. At this baseline, for any neutrino hierarchy, the wrong-sign muon signal is almost independent of CP violation and ΞΈ13\theta_{13} in certain energy ranges. This reduces the uncertainties due to these parameters and allows the identification of the hierarchy in a clean way. In addition, part of the muon spectrum is also sensitive to the CP violating phase and ΞΈ13\theta_{13}, so that the same setup can be used to probe these parameters as well.Comment: 4 pages, 4 figures, Revtex4. Text modified. Version to appear in PR

    Radiatively broken symmetries of nonhierarchical neutrinos

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    Symmetry-based ideas, such as the quark-lepton complementarity (QLC) principle and the tri-bimaximal mixing (TBM) scheme, have been proposed to explain the observed mixing pattern of neutrinos. We argue that such symmetry relations need to be imposed at a high scale Ξ›βˆΌ1012\Lambda \sim 10^{12} GeV characterizing the large masses of right-handed neutrinos required to implement the seesaw mechanism. For nonhierarchical neutrinos, renormalisation group evolution down to a laboratory energy scale λ∼103\lambda \sim 10^3 GeV tends to radiatively break these symmetries at a significant level and spoil the mixing pattern predicted by them. However, for Majorana neutrinos, suitable constraints on the extra phases Ξ±2,3\alpha_{2,3} enable the retention of those high scale mixing patterns at laboratory energies. We examine this issue within the Minimal Supersymmetric Standard Model (MSSM) and demonstrate the fact posited above for two versions of QLC and two versions of TBM. The appropriate constraints are worked out for all these four cases. Specifically, a preference for Ξ±2β‰ˆΟ€\alpha_2 \approx \pi (i.e. m1β‰ˆβˆ’m2m_1 \approx -m_2) emerges in each case. We also show how a future accurate measurement of ΞΈ13\theta_{13} may enable some discrimination among these four cases in spite of renormalization group evolution.Comment: 29 pages, 4 figures, revtex4. Minor changes in the Introduction, references added. Final version to be published in Phys. Rev.

    A Study of Invisible Neutrino Decay at DUNE and its Effects on ΞΈ23\theta_{23} Measurement

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    We study the consequences of invisible decay of neutrinos in the context of the DUNE experiment. We assume that the third mass eigenstate is unstable and decays to a light sterile neutrino and a scalar or a pseudo-scalar. We consider DUNE running in 5 years neutrino and 5 years antineutrino mode and a detector volume of 40 kt. We obtain the bounds on the rest frame life time Ο„3\tau_3 normalized to the mass m3m_3 as Ο„3/m3>4.50Γ—10βˆ’11\tau_3/m_3 > 4.50\times 10^{-11} s/eV at 90\% C.L. for a normal hierarchical mass spectrum. We also find that DUNE can discover neutrino decay for Ο„3/m3>4.27Γ—10βˆ’11\tau_3/m_3 > 4.27\times 10^{-11} s/eV at 90\% C.L. In addition, for an unstable Ξ½3\nu_3 with an illustrative value of Ο„3/m3\tau_3/m_3 = 1.2Γ—10βˆ’111.2 \times 10^{-11} s/eV, the no decay case gets disfavoured at the 3Οƒ3\sigma C.L. At 90\% C.L. the allowed range for this true value is obtained as 1.71Γ—10βˆ’11>Ο„3/m3>9.29Γ—10βˆ’121.71 \times 10^{-11} > \tau_3/m_3 > 9.29\times 10^{-12} in units of s/eV. We also study the correlation between a non-zero Ο„3/m3\tau_3/m_3 and standard oscillation parameters and find an interesting correlation in the appearance channel probability with the mixing angle ΞΈ23\theta_{23}. This alters the octant sensitvity of DUNE, favorably (unfavorably) for true ΞΈ23\theta_{23} in the lower (higher) octant. The effect of a decaying neutrino does not alter the hierarchy or CP discovery sensitivity of DUNE in a discernible way.Comment: accepted and published in JHEP with additional figures and few reference

    Threshold effects and renormalization group evolution of neutrino parameters in TeV scale seesaw models

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    We consider the threshold effect on the renormalization group (RG) evolution of the neutrino masses and mixing angles in TeV scale seesaw models. We obtain the analytic expressions using the factorization method in presence of threshold effects. We also perform numerical study of RG effects in two specific low scale seesaw models following the bottom-up approach and ascertain the role of seesaw thresholds in altering the values of masses and mixing angles during RG evolution.Comment: 31 pages, 8 figure
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