• Volume 54, Issue 1

      January 2000,   pages  1-214

    • Preface

      Anjan S Joshipura Palash B Pal

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    • Neutrino mass and oscillation: An introductory review

      D P Roy

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      After a brief introduction to neutrino mass via the see-saw model I discuss neutrino mixing and oscillation, first in vacuum and then its matter enhancement. Then the solar and atmospheric neutrino oscillation data are briefly reviewed. Finally I discuss the problem of reconciling hierarchical neutrino masses with at least one large mixing, as implied by these data. A minimal see-saw model for reconciling the two is discussed.

    • Transmission of neutrinos through matter

      L Wolfenstein

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      Neutrinos travel through matter with negligible absorption except in very extreme situations. However, the index of refraction of neutrinos can play an important role in the oscillation of one type of neutrino to another when passing through matter.

    • Solar neutrino problem in light of super-Kamiokande data

      S Uma Sankar

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      I discuss the status of the accepted solutions to the solar neutrino problem in light of the super-Kamiokande data.

    • Neutrino oscillations: Recent results and future directions

      Amitava Raychaudhuri

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      A brief introduction to the phenomena of vacuum neutrino oscillations and resonant flavour conversion is presented with a heavy pedagogic leaning. Variants of these ideas, e.g., neutrino helicity flip in a magnetic field, violation of the equivalence principle, etc. are outlined. A few vexing issues pertaining to the quantum mechanics of neutrino oscillations are discussed. Expectations from some of the future experiments are summarized.

    • Parametric resonance in neutrino oscillations in matter

      E Kh Akhmedov

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      Neutrino oscillations in matter can exhibit a specific resonance enhancement — parametric resonance, which is different from the MSW resonance. Oscillations of atmospheric and solar neutrinos inside the earth can undergo parametric enhancement when neutrino trajectories cross the core of the earth. In this paper we review the parametric resonance of neutrino oscillations in matter. In particular, physical interpretation of the effect and the prospects of its experimental observation in oscillations of solar and atmospheric neutrinos in the earth are discussed.

    • Neutrino anomalies without oscillations

      Sandip Pakvasa

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      I review explanations for the three neutrino anomalies (solar, atmospheric and LSND) which go beyond the ‘conventional’ neutrino oscillations induced by mass-mixing. Several of these require non-zero neutrino masses as well.

    • Determination of cosmological parameters: An introduction for non-specialists

      Palash B Pal

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      I start by defining the cosmological parameters H0, Θm and ΘA. Then I show how the age of the universe depends on them, followed by the evolution of the scale parameter of the universe for various values of the density parameters. Then I define strategies for measuring them, and show the results for the recent determination of these parameters from measurements on supernovas of type 1a. Implications for particle physics is briefly discussed at the end.

    • Cosmic microwave background anisotropy constraints on relict neutrinos

      Subhendra Mohanty

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      I discuss basic theory of effect of the properties of the cosmological relict neutrinos on the observations of the cosmic microwave background anisotropy.

    • Models of neutrino masses and baryogenesis

      Utpal Sarkar

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      Majorana masses of the neutrino implies lepton number violation and is intimately related to the lepton asymmetry of the universe, which gets related to the baryon asymmetry of the universe in the presence of the sphalerons during the electroweak phase transition. Assuming that the baryon asymmetry of the universe is generated before the electroweak phase transition, it is possible to discriminate different classes of models of neutrino masses. While see-saw mechanism and the triplet Higgs mechanism are preferred, the Zee-type radiative models and the R-parity breaking models requires additional inputs to generate baryon asymmetry of the universe during the electroweak phase transition.

    • Neutrino spectrum from theory and experiments

      Anjan S Joshipura

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      The observed deficits in the solar and atmospheric neutrino fluxes along with the accelerator results on neutrino oscillations significantly constrain possible mass and mixing patterns among neutrinos. We discuss possible patterns emerging from the experimental results and review theoretical attempts to understand them.

    • Neutrino masses from SUSY: Different contributions and their implications

      Sudhir K Vempati

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      We discuss the various sources of neutrino masses in supersymmetric standard models with explicit lepton number violation. We show that the bilinear lepton number violating soft terms in models with either bilinear or trilinear lepton number violating couplings in the superpotential, play an important role in determining the neutrino mass spectrum. A comparative study of the neutrino mass spectrum and its implications for the present neutrino anomalies in these models is presented.

    • Neutrino mass patterns, R-parity violating supersymmetry and associated phenomenology

      Biswarup Mukhopadhyaya

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      Motivated by the recent super-Kamiokande results on atmospheric neutrinos, we incorporate massive neutrinos, with large angle oscillation between the second and third generations, in a theory with R-parity violating supersymmetry. The general features of such a theory are briefly reviewed. We emphasize its testability through the observation of comparable numbers of muons and taus, produced together with the W-boson, in decays of the lightest neutralino. A distinctly measurable decay gap is another remarkable feature of such a scenario.

    • Constraints on three flavor neutrino mixing

      Mohan Narayan

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      We summarize the constraints on three flavor neutrino mixing coming from data. We first map out the allowed region in the three neutrino parameter space using solar and atmospheric neutrino data. We then incorporate the results of reactor and long baseline experiments in our analysis and show that the parameter space is drastically reduced. We conclude by pointing out that the results of Borexino and SNO will further help in constraining the parameter space.

    • Supernova constraints on neutrino mass and mixing

      Srubabati Goswami

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      In this article I review the constraints on neutrino mass and mixing coming from type-II supernovae. The bounds obtained on these parameters from shock reheating, r-process nucleosynthesis and from SN1987A are discussed. Given the current constraints on neutrino mass and mixing the effect of oscillations of neutrinos from a nearby supernova explosion in future detectors will also be discussed.

    • Variables for probing neutrino oscillation at super-Kamiokande and the Sudbury Neutrino Observatory

      Debasish Majumdar

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      We propose several new variables, insensitive to the absolute flux of the incident solar or supernova neutrino beam, which probe the shape of the observed spectrum at super-Kamiokande and Sudbury Neutrino Observatory experiments and can sensitively signal neutrino oscillations. One class of such variables involve moments of the distributions recorded at the two facilities while another variable, specific to SNO, utilises the integrated charged and neutral current signals. The utility of these variables in the context of supernova neutrinos both from the collapse epoch and the post-bounce era is also discussed.

    • Introduction to a field-theoretical treatment of neutrino oscillations

      P Stockinger

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      We discuss the main features of the field-theoretical approach to neutrino oscillations where one combines neutrino production and detection processes in a single Feynman graph. The ‘oscillating neutrinos’ are represented by inner lines of this graph and appear in the calculation of the cross section of the total process as propagators of the neutrino mass eigenfields. We show that this field-theoretical approach leads to a transparent treatment of neutrino oscillations without ambiguities and provides the correct answer in cases where the standard approach fails.

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