1,424 research outputs found

    Higher dimensional models of light Majorana neutrinos confronted by data

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    We discuss experimental and observational constraints on certain models of higher dimensional light Majorana neutrinos. Models with flavor blind brane-bulk couplings plus three or four flavor diagonal light Majorana neutrinos on the brane, with subsequent mixing induced solely by the Kaluza-Klein tower of states, are found to be excluded by data on the oscillations of solar, atmospheric and reactor neutrinos, taken together with the WMAP upper bound on the sum of neutrino masses. Extra dimensions, if relevant to neutrino mixing, need to discriminate between neutrino flavors.Comment: 5 pages, Revtex4, 2 PS figures. Fig. 2a and 2b from earlier version are now combined into one figure. Minor modifications in the text. References adde

    Lattice QCD calculation of the proton decay matrix element in the continuum limit

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    We present a quenched lattice QCD calculation of the \alpha and \beta parameters of the proton decay matrix element. The simulation is carried out using the Wilson quark action at three values of the lattice spacing in the range a\approx 0.1-0.064 fm to study the scaling violation effect. We find only mild scaling violation when the lattice scale is determined by the nucleon mass. We obtain in the continuum limit, |\alpha(NDR,2GeV)|=0.0090(09)(^{+5}_{-19})GeV^3 and |\beta(NDR,2GeV)|=0.0096(09)(^{+6}_{-20})GeV^3 with \alpha and \beta in a relatively opposite sign, where the first error is statistical and the second is due to the uncertainty in the determination of the physical scale.Comment: 4 pages, 3 figure

    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

    Climate oscillations, glacial refugia, and dispersal ability: factors influencing the genetic structure of the least salmonfly, Pteronarcella badia (Plecoptera), in Western North America

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    Background: Phylogeographic studies of aquatic insects provide valuable insights into mechanisms that shape the genetic structure of communities, yet studies that include broad geographic areas are uncommon for this group. We conducted a broad scale phylogeographic analysis of the least salmonfly Pteronarcella badia (Plecoptera) across western North America. We tested hypotheses related to mode of dispersal and the influence of historic climate oscillations on population genetic structure. In order to generate a larger mitochondrial data set, we used 454 sequencing to reconstruct the complete mitochondrial genome in the early stages of the project. Results: Our analysis revealed high levels of population structure with several deeply divergent clades present across the sample area. Evidence from five mitochondrial genes and one nuclear locus identified a potentially cryptic lineage in the Pacific Northwest. Gene flow estimates and geographic clade distributions suggest that overland flight during the winged adult stage is an important dispersal mechanism for this taxon. We found evidence of multiple glacial refugia across the species distribution and signs of secondary contact within and among major clades. Conclusions: This study provides a basis for future studies of aquatic insect phylogeography at the inter-basin scale in western North America. Our findings add to an understanding of the role of historical climate isolations in shaping assemblages of aquatic insects in this region. We identified several geographic areas that may have historical importance for other aquatic organisms with similar distributions and dispersal strategies as P. badia. This work adds to the ever-growing list of studies that highlight the potential of next-generation DNA sequencing in a phylogenetic context to improve molecular data sets from understudied groups

    New contribution to dimension five operators on proton decay in anomaly mediation scenario

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    In supergravity, effective superpotential relevant to dimension five operators on proton decay processes also leads to supersymmetry breaking terms among sfermions, dimension four operators. These dimension four operators induce the dimension five operators through 1-loop diagrams dressed by gauginos. We find that, in a class of models with the anomaly mediation, the 1-loop contributions can be comparable to those at the tree level. Therefore, such operators have a great impact on proton decay rate. Depending on a universal phase of gaugino masses and soft mass spectrum, the proton decay rate can be enhanced or suppressed.Comment: 8 pages, no figure. A few minor changes have been mad
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