1,721,196 research outputs found
Addendum to: “The SNO solar neutrino data, neutrinoless double beta-decay and neutrino mass spectrum” [Phys. Lett. B 544 (2002) 239]
Full text linkAbstractWe update our earlier study [Phys. Lett. B 544 (2002) 239], which was inspired by the 2002 SNO data, on the implications of the results of the solar neutrino experiments for the predictions of the effective Majorana mass in neutrinoless double beta-decay, |〈m〉|. We obtain predictions for |〈m〉| using the values of the neutrino oscillation parameters, obtained in the analyzes of the presently available solar neutrino data, including the just published data from the salt phase of the SNO experiment, the atmospheric neutrino and CHOOZ data and the first data from the KamLAND experiment. The main conclusion reached in the previous study [Phys. Lett. B 544 (2002) 239] of the existence of significant lower bounds on |〈m〉| in the cases of neutrino mass spectrum of inverted hierarchical (IH) and quasi-degenerate (QD) type is strongly reinforced by fact that combined solar neutrino data (i) exclude the possibility of cos2θ⊙=0 at more than 5 s.d., (ii) determine as a best fit value cos2θ⊙=0.40, and (iii) imply at 95% C.L. that cos2θ⊙≳0.22, θ⊙ being the solar neutrino mixing angle. For the IH and QD spectra we get using, e.g., the 90% C.L. allowed ranges of values of the oscillation parameters, |〈m〉|≳0.010 eV and |〈m〉|≳0.043 eV, respectively. We also comment on the possibility to get information on the neutrino mass spectrum and on the CP-violation in the lepton sector due to Majorana CP-violating phases
Tetrahedron: crossing different energy scales
No full textWe summarise the content of the talks presented at the Tetrahedron parallel session of N0W2008 with a general overview of the plenary session as introduction to the argument "crossing different energy scales". Neutrino mass and mixing, leptogenesis and CP violation, cosmology hints to neutrino properties, lepton flavour violating processes could enlighten the puzzle of beyond the standard model theories from low to high energy scales. The status of present and future experiments at low and high energies are presented. © 2009 Elsevier B.V. All rights reserved
Understanding the performance of the low-energy neutrino factory: The dependence on baseline distance and stored-muon energy
No full textWe study the physics reach of a low-energy neutrino factory (LENF) and its dependence on the chosen baseline distance, L, and stored-muon energy, E-mu, in order to ascertain the configuration of the optimal LENF. In particular, we study the performance of the LENF over a range of baseline distances from 1000 km to 4000 km and stored-muon energies from 4 GeV to 25 GeV, connecting the early studies of the LENF (1300 km, 4.5 GeV) to those of the conventional, high-energy neutrino factory design (4000 km and 7000 km, 25 GeV). Three different magnetized detector options are considered: a Totally-Active Scintillator Detector (TASD) and two models of a liquid-argon detector distinguished by optimistic and conservative performance estimates. In order to compare the sensitivity of each set-up, we compute the full delta-dependent discovery contours for the determination of theta(13) not equal 0, delta(CP) is not an element of {0, pi} and sign(Delta m(13)(2)). For large values of theta(13), as recently confirmed by the Daya Bay and RENO experiments, the LENF provides a strong discovery potential over the majority of the L-E-mu parameter space and is a promising candidate for the future generation of long baseline experiments aimed at discovering CP-violation and the mass hierarchy, and at making a precise determination of the oscillation parameters
Matter-antimatter symmetry violated
No full textIn a mirror world, antiparticles should behave in the same way as particles. But it emerges that leptons - neutrinos, electrons and their more exotic cousins - might not obey this expected pattern
Quasi-degenerate neutrino mass spectrum, μ→e+γ decay and leptogenesis
No full textAbstractIn a large class of SUSY GUT models with see-saw mechanism of neutrino mass generation, lepton flavor violating (LFV) decays μ→e+γ, τ→μ+γ, etc., are predicted with rates that are within the reach of present and planned experiments. A crucial element in these predictions is the matrix of neutrino Yukawa couplings Yν which can be expressed in terms of the light and RH heavy neutrino masses, the neutrino mixing PMNS matrix U, and an orthogonal matrix R. Leptogenesis can take place only if R is complex. Considering the case of quasi-degenerate neutrinos and assuming that R is complex, we derive simple analytical expressions for the μ→e+γ, τ→μ+γ and τ→e+γ decay rates. Taking into account the leptogenesis constraints on the relevant parameters we show that the predicted rates of the LFV decays μ→e+γ, and τ→e+γ are generically enhanced by a factor of ∼103 to ∼106 with respect to the rates calculated for real R, while the τ→μ+γ decay rate is enhanced approximately by two orders of magnitude
Majorana neutrinos, neutrino mass spectrum, and the |m|∼10-3eV frontier in neutrinoless double beta decay
No full textIf future neutrino oscillation experiments show that the neutrino mass spectrum is with normal ordering, m(1) < m(2) < m(3), and the searches for neutrinoless double beta [(beta beta)(0 nu)] decay with sensitivity to values of the effective Majorana mass |< m >| greater than or similar to 10(-2) eV give negative results, the next frontier in the quest for (beta beta)(0 nu)-decay will correspond to |< m >| similar to 10(-3) eV. By assuming that massive neutrinos are Majorana particles and their exchange is the dominant mechanism generating (beta beta)(0 nu) - decay, we analyze the conditions under which |< m >|, in the case of three-neutrino mixing and a neutrino mass spectrum with normal ordering, would satisfy |< m >| >= 0.001 eV. We consider the specific cases of (i) a normal hierarchical neutrino mass spectrum, (ii) a relatively small value of the CHOOZ angle theta(13), as well as (iii) the general case of a spectrum with normal ordering, a partial hierarchy, and a value of theta(13) close to the existing upper limit. We study the ranges of the lightest neutrino mass m(1) and/or of sin(2)theta(13) for which |< m >| >= 0.001 eV and discuss the phenomenological implications of such scenarios. We provide also an estimate of |< m >| when the three-neutrino masses and the neutrino mixing originate from a neutrino mass term of the Majorana type for the (left-handed) flavor neutrinos and Sigma(3)(j)m(j)U(ej)(2) = 0, but there does not exist a symmetry which forbids the (beta beta)(0 nu)-decay
Addendum: The SNO Solar Neutrino Data, Neutrinoless Double Beta-Decay and Neutrino Mass Spectrum
No full textOn the Connection of Leptogenesis with Low Energy CP-Violation and LFV Charged Lepton Decays
Full text linkThe biunitary parametrization of the neutrino Dirac mass matrix m(D) of the seesaw mechanism of neutrino mass generation is considered in detail. Assuming a hierarchical structure of m(D) and of the heavy Majorana neutrino masses M-1,M-2,M-3>0, M-110(3)M(1)), we find that, in order to produce the observed baryon asymmetry of the Universe via leptogenesis, the scale of m(D) should be given by the up-quark masses, m(D)similar tom(up). It is also possible to reproduce the low-energy neutrino mixing phenomenology for m(D)similar tom(up) if one of the heavy Majorana neutrinos is much heavier than the other two and there exists only a rather mild hierarchy between the masses of the latter (M(2)congruent to10 M-1). In the case of a strong hierarchy between M-3 and M-1,M-2, successful leptogenesis requires a mild hierarchy between M-1 and M-2 as well. In this scenario, the effective Majorana mass in neutrinoless double beta decay depends on the CP violating phase controlling the leptogenesis if m(D1) is negligible. The lepton flavor violating decays mu-->e+gamma, tau-->mu+gamma and tau-->e+gamma are considered and a characteristic relation between their decay rates is predicted. The CP violation effects in neutrino oscillations can be observable. In general, there is no direct connection between the latter and CP violation in leptogenesis. If the CP violating phases of the seesaw model satisfy certain relations, the baryon asymmetry of the Universe and the rephasing invariant J(CP) which determines the magnitude of the CP violation effects in neutrino oscillations depend on the same CP violating phase and their signs are correlated
The Absolute Neutrino Mass Scale, Neutrino Mass Spectrum, Majorana CP-Violation and Neutrinoless Double-Beta Decay
No full textAssuming 3- mixing, massive Majorana neutrinos and neutrinoless double-beta (\betabeta-) decay generated only by the (V-A) charged current weak interaction via the exchange of the three Majorana neutrinos, we briefly review the predictions for the effective Majorana mass \meff in \betabeta-decay and reanalyse the physics potential of future \betabeta-decay experiments to provide information on the type of neutrino mass spectrum, the absolute scale of neutrino masses, and Majorana CP-violation in the lepton sector. Using as input the most recent experimental results on neutrino oscillation parameters and the prospective precision that can be achieved in future measurements of the latter, we perform a statistical analysis of a \betabeta-decay half-life measurement taking into account experimental and theoretical errors, as well as the uncertainty implied by the imprecise knowledge of the corresponding nuclear matrix element (NME). We show, in particular, how the possibility to discriminate between the different types of neutrino mass spectra and the constraints on the absolute neutrino mass scale depend on the mean value and the experimental error of \meff and on the NME uncertainty. The constraints on Majorana CP-violation phases in the neutrino mixing matrix, which can be obtained from a measurement of \meff and additional data on the sum of neutrino masses, are also investigated in detail. We estimate the required experimental accuracies on both types of measurements, and the required precision in the NME permitting to address the issue of Majorana CP-violation in the lepton sector.Assuming 3- ν mixing, massive Majorana neutrinos and neutrinoless double-beta ( (ββ)0ν -) decay generated only by the (V−A) charged current weak interaction via the exchange of the three Majorana neutrinos, we briefly review the predictions for the effective Majorana mass |〈m〉| in (ββ)0ν -decay and reanalyze the physics potential of future (ββ)0ν -decay experiments to provide information on the type of neutrino mass spectrum, the absolute scale of neutrino masses, and Majorana CP-violation in the lepton sector. Using as input the most recent experimental results on neutrino oscillation parameters and the prospective precision that can be achieved in future measurements of the latter, we perform a statistical analysis of a (ββ)0ν -decay half-life measurement taking into account experimental and theoretical errors, as well as the uncertainty implied by the imprecise knowledge of the corresponding nuclear matrix element (NME). We show, in particular, how the possibility to discriminate between the different types of neutrino mass spectra and the constraints on the absolute neutrino mass scale depend on the mean value and the experimental error of |〈m〉| and on the NME uncertainty. The constraints on Majorana CP-violation phases in the neutrino mixing matrix, which can be obtained from a measurement of |〈m〉| and additional data on the sum of neutrino masses, are also investigated in detail. We estimate the required experimental accuracies on both types of measurements, and the required precision in the NME permitting to address the issue of Majorana CP-violation in the lepton sector.Assuming 3- mixing, massive Majorana neutrinos and neutrinoless double-beta (\betabeta-) decay generated only by the (V-A) charged current weak interaction via the exchange of the three Majorana neutrinos, we briefly review the predictions for the effective Majorana mass \meff in \betabeta-decay and reanalyse the physics potential of future \betabeta-decay experiments to provide information on the type of neutrino mass spectrum, the absolute scale of neutrino masses, and Majorana CP-violation in the lepton sector. Using as input the most recent experimental results on neutrino oscillation parameters and the prospective precision that can be achieved in future measurements of the latter, we perform a statistical analysis of a \betabeta-decay half-life measurement taking into account experimental and theoretical errors, as well as the uncertainty implied by the imprecise knowledge of the corresponding nuclear matrix element (NME). We show, in particular, how the possibility to discriminate between the different types of neutrino mass spectra and the constraints on the absolute neutrino mass scale depend on the mean value and the experimental error of \meff and on the NME uncertainty. The constraints on Majorana CP-violation phases in the neutrino mixing matrix, which can be obtained from a measurement of \meff and additional data on the sum of neutrino masses, are also investigated in detail. We estimate the required experimental accuracies on both types of measurements, and the required precision in the NME permitting to address the issue of Majorana CP-violation in the lepton sector
Searching for the CP-violation associated with Majorana neutrinos
No full textAbstractThe effective Majorana mass which determines the rate of the neutrinoless double beta ((ββ)0ν-) decay, |〈m〉|, is considered in the case of three-neutrino mixing and massive Majorana neutrinos. Assuming a rather precise determination of the parameters characterizing the neutrino oscillation solutions of the solar and atmospheric neutrino problems has been made, we discuss the information a measurement of |〈m〉|≳(0.005–0.010) eV can provide on the value of the lightest neutrino mass and on the CP-violation in the lepton sector. The implications of combining a measurement of |〈m〉| with future measurement of the neutrino mass mνe in 3H β-decay experiments for the possible determination of leptonic CP-violation are emphasized
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