504 research outputs found

    Neutrinos Have Mass - So What?

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    In this brief review, I discuss the new physics unveiled by neutrino oscillation experiments over the past several years, and discuss several attempts at understanding the mechanism behind neutrino masses and lepton mixing. It is fair to say that, while significant theoretical progress has been made, we are yet to construct a coherent picture that naturally explains non-zero, yet tiny, neutrino masses and the newly revealed, puzzling patterns of lepton mixing. I discuss what the challenges are, and point to the fact that more experimental input (from both neutrino and non-neutrino experiments) is dearly required - and that new data is expected to reveal, in the next several years, new information. Finally, I draw attention to the fact that neutrinos may have only just begun to reshape fundamental physics, given the fact that we are still to explain the LSND anomaly and because the neutrino oscillation phenomenon is ultimately sensitive to very small new-physics effects.Comment: invited brief review, 15 pages, 1 eps figure, typo corrected, reference adde

    Anarchy and Hierarchy

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    We advocate a new approach to study models of fermion masses and mixings, namely anarchy proposed in hep-ph/9911341. In this approach, we scan the O(1) coefficients randomly. We argue that this is the correct approach when the fundamental theory is sufficiently complicated. Assuming there is no physical distinction among three generations of neutrinos, the probability distributions in MNS mixing angles can be predicted independent of the choice of the measure. This is because the mixing angles are distributed according to the Haar measure of the Lie groups whose elements diagonalize the mass matrices. The near-maximal mixings, as observed in the atmospheric neutrino data and as required in the LMA solution to the solar neutrino problem, are highly probable. A small hierarchy between the Delta m^2 for the atmospheric and the solar neutrinos is obtained very easily; the complex seesaw case gives a hierarchy of a factor of 20 as the most probable one, even though this conclusion is more measure-dependent. U_{e3} has to be just below the current limit from the CHOOZ experiment. The CP-violating parameter sin delta is preferred to be maximal. We present a simple SU(5)-like extension of anarchy to the charged-lepton and quark sectors which works well phenomenologically.Comment: 26 page

    Comparação dos modelos digitais de elevação gerados com dados SRTM e cartas IBGE na escala 1:250.000 na região da Bacia do Camanducaia no Estado de São Paulo.

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    O estudo comparou os MDEs, os mapas de declividade e os mapas hipsomĂ©tricos produzidos pela SRTM com aqueles gerados pelas cartas do IBGE. A ĂĄrea estudada integra a bacia do Camanducaia, que limita-se como Estado de SĂŁo Paulo a leste e JaguariĂșna a oeste, abrangendo Holambra, JaguariĂșna, Santo AntĂŽnio de Posse, Pedreira, Amparo, Serra Negra, Monte Alegre do Sul, Socorro, Pinhalzinho e Pedra Bela

    On the complementarity of Hyper-K and LBNF

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    The next generation of long-baseline experiments is being designed to make a substantial step in the precision of measurements of neutrino-oscillation probabilities. Two qualitatively different proposals, Hyper-K and LBNF, are being considered for approval. This document outlines the complimentarity between Hyper-K and LBNF.Comment: 5 pager

    Initial report from the ICFA Neutrino Panel

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    In July 2013 ICFA established the Neutrino Panel with the mandate "To promote international cooperation in the development of the accelerator-based neutrino-oscillation program and to promote international collaboration in the development a neutrino factory as a future intense source of neutrinos for particle physics experiments". This, the Panel's Initial Report, presents the conclusions drawn by the Panel from three regional "Town Meetings" that took place between November 2013 and February 2014. After a brief introduction and a short summary of the status of the knowledge of the oscillation parameters, the report summarises the approved programme and identifies opportunities for the development of the field. In its conclusions, the Panel recognises that to maximise the discovery potential of the accelerator-based neutrino-oscillation programme it will be essential to exploit the infrastructures that exist at CERN, FNAL and J-PARC and the expertise and resources that reside in laboratories and institutes around the world. Therefore, in its second year, the Panel will consult with the accelerator-based neutrino-oscillation community and its stakeholders to: develop a road-map for the future accelerator-based neutrino-oscillation programme that exploits the ambitions articulated at CERN, FNAL and J-PARC and includes the programme of measurement and test-beam exposure necessary to ensure the programme is able to realise its potential; develop a proposal for a coordinated "Neutrino RD" programme, the accelerator and detector R&D programme required to underpin the next generation of experiments; and to explore the opportunities for the international collaboration necessary to realise the Neutrino Factory.Comment: ICFA Neutrino Panel 2014(01

    MeV sterile neutrinos in low reheating temperature cosmological scenarios

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    It is commonly assumed that the cosmological and astrophysical bounds on the mixings of sterile with active neutrinos are much more stringent than those obtained from laboratory measurements. We point out that in scenarios with a very low reheating temperature T_RH << 100 MeV at the end of (the last episode of) inflation or entropy creation, the abundance of sterile neutrinos becomes largely suppressed with respect to that obtained within the standard framework. Thus, in this case cosmological bounds become much less stringent than usually assumed, allowing sterile neutrinos to be ``visible'' in future experiments. Here, we concentrate on massive (mostly sterile) neutrinos heavier than 1 MeV.Comment: 14 pp, 7 fig
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