1,137 research outputs found

    Neutrino Physics

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    The Standard Model has been incredibly successful in predicting the outcome of almost all the experiments done up so far. In it, neutrinos are mass-less. However, in recent years we have accumulated evidence pointing to tiny masses for the neutrinos (as compared to the charged leptons). These masses allow neutrinos to change their flavour and oscillate. In these lectures I review the properties of neutrinos in and beyond the Standard Model.Comment: 19 pages, contribution to the 2012 European School of High-Energy Physics, La Pommeraye, Anjou, France, 06-19 Jun 2012, edited by C. Grojean and M. Mulders. arXiv admin note: text overlap with arXiv:hep-ph/0506165 by other author

    Neutrinos: Fast & Curious

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    The Standard Model has been effective way beyond expectations in foreseeing the result of almost all the experimental tests done up so far. In it, neutrinos are massless. Nonetheless, in recent years we have collected solid proofs indicating little but non zero masses for the neutrinos (when contrasted with those of the charged leptons). These masses permit neutrinos to change their flavor and oscillate, indeed a unique treat. In these lectures, I discuss the properties and the amazing potential of neutrinos in and beyond the Standard Model.Comment: 22 pages, contribution to the 2016 European School of High-Energy Physics, Skeikampen, Norway , 15 - 28 June 2016, to appear as a CERN Yellow Report. arXiv admin note: substantial text overlap with arXiv:1504.0703

    On the Effective Mass of the Electron Neutrino in Beta Decay

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    In the presence of mixing between massive neutrino states, the distortion of the electron spectrum in beta decay is, in general, a function of several masses and mixing angles. For 3ν3\nu-schemes which describe the solar and atmospheric neutrino data, this distortion can be described by a single effective mass, under certain conditions. In the literature, two different definitions for the effective mass have been suggested. We show that for quasi-degenerate mass schemes (with an overall mass scale mm and splitting Δm2\Delta m^2) the two definitions coincide up to (Δm2)2/m4(\Delta m^2)^2/m^4 corrections. We consider the impact of different effective masses on the integral energy spectrum. We show that the spectrum with a single mass can be used also to fit the data in the case of 4ν4\nu-schemes motivated, in particular, by the LSND results. In this case the accuracy of the mass determination turns out to be better than (10−15)(10 - 15)%.Comment: 15 pages, Version to appear in Phys. Lett.

    Neutrinos that violate CPT, and the experiments that love them

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    Recently we proposed a framework for explaining the observed evidence for neutrino oscillations without enlarging the neutrino sector, by introducing CPT violating Dirac masses for the neutrinos. In this paper we continue the exploration of the phenomenology of CPT violation in the neutrino sector. We show that our CPT violating model fits the existing SuperKamiokande data at least as well as the standard atmospheric neutrino oscillation models. We discuss the challenge of measuring CP violation in a neutrino sector that also violates CPT. We point out that the proposed off-axis extension of MINOS looks especially promising in this regard. Finally, we describe a method to compute CPT violating neutrino effects by mocking them up with analog matter effects.Comment: 17 pages, 3 eps figure

    Quintessence, inflation and baryogenesis from a single pseudo-Nambu-Goldstone boson

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    We exhibit a model in which a single pseudo-Nambu-Goldstone boson explains dark energy, inflation and baryogenesis. The model predicts correlated signals in future collider experiments, WIMP searches, proton decay experiments, dark energy probes, and the PLANCK satellite CMB measurements.Comment: 16 pages, 3 color figure

    Tau neutrinos from muon storage rings

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    Charged tau leptons emerging in a long baseline experiment with a muon storage ring and a far-away detector will positively establish neutrino oscillations. We study the conversion of νμ\nu_\mu (νˉμ\bar{\nu}_\mu) and of νˉe\bar{\nu}_e (νe\nu_e) to ντ\nu_\tau or νˉτ\bar{\nu}_\tau for neutrinos from a 20 GeV muon storage ring, within the strong mixing scheme and on the basis of the squared mass differences which are compatible with all reported neutrino anomalies, including the LSND data. In contrast to other solutions which ignore the Los Alamos anomaly, we find charged tau production rates which should be measurable in a realistic set up. As a consequence, determining the complete mass spectrum of neutrinos as well as all three mixing angles seems within reach. Matter effects are discussed thoroughly but are found to be small in this situation.Comment: 11 pages, 5 postscript figures (eps

    Distributed Deterministic Edge Coloring using Bounded Neighborhood Independence

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    We study the {edge-coloring} problem in the message-passing model of distributed computing. This is one of the most fundamental and well-studied problems in this area. Currently, the best-known deterministic algorithms for (2Delta -1)-edge-coloring requires O(Delta) + log-star n time \cite{PR01}, where Delta is the maximum degree of the input graph. Also, recent results of \cite{BE10} for vertex-coloring imply that one can get an O(Delta)-edge-coloring in O(Delta^{epsilon} \cdot \log n) time, and an O(Delta^{1 + epsilon})-edge-coloring in O(log Delta log n) time, for an arbitrarily small constant epsilon > 0. In this paper we devise a drastically faster deterministic edge-coloring algorithm. Specifically, our algorithm computes an O(Delta)-edge-coloring in O(Delta^{epsilon}) + log-star n time, and an O(Delta^{1 + epsilon})-edge-coloring in O(log Delta) + log-star n time. This result improves the previous state-of-the-art {exponentially} in a wide range of Delta, specifically, for 2^{Omega(\log-star n)} \leq Delta \leq polylog(n). In addition, for small values of Delta our deterministic algorithm outperforms all the existing {randomized} algorithms for this problem. On our way to these results we study the {vertex-coloring} problem on the family of graphs with bounded {neighborhood independence}. This is a large family, which strictly includes line graphs of r-hypergraphs for any r = O(1), and graphs of bounded growth. We devise a very fast deterministic algorithm for vertex-coloring graphs with bounded neighborhood independence. This algorithm directly gives rise to our edge-coloring algorithms, which apply to {general} graphs. Our main technical contribution is a subroutine that computes an O(Delta/p)-defective p-vertex coloring of graphs with bounded neighborhood independence in O(p^2) + \log-star n time, for a parameter p, 1 \leq p \leq Delta

    MINOS and CPT-violating neutrinos

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    We review the status of CPT violation in the neutrino sector. Apart from LSND, current data favors three flavors of light stable neutrinos and antineutrinos, with both halves of the spectrum having one smaller mass splitting and one larger mass splitting. Oscillation data for the smaller splitting is consistent with CPT. For the larger splitting, current data favor an antineutrino mass-squared splitting that is an order of magnitude larger than the corresponding neutrino splitting, with the corresponding mixing angle less-than-maximal. This CPT-violating spectrum is driven by recent results from MINOS, but is consistent with other experiments if we ignore LSND. We describe an analysis technique which, together with MINOS running optimized for muon antineutrinos, should be able to conclusively confirm the CPT-violating spectrum proposed here, with as little as three times the current data set. If confirmed, the CPT-violating neutrino mass-squared difference would be an order of magnitude less than the current most-stringent upper bound on CPT violation for quarks and charged leptons.Comment: 18 pages, title change, version to appear in Physical Review
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