371 research outputs found

    Contact interactions in low scale string models with intersecting D6D6-branes

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    We evaluate the tree level four fermion string amplitudes in the TeV string mass scale models with intersecting D6D6-branes. The coefficient functions of contact interactions subsuming the contributions of string Regge resonance and winding mode excitations are obtained by subtracting out the contributions from the string massless and massive momentum modes. Numerical applications are developed for the Standard Model like solution of Cremades, Ibanez, and Marchesano for a toroidal orientifold with four intersecting D6D6-brane stacks. The chirality conserving contact interactions of the quarks and leptons are considered in applications to high energy collider and flavor changing neutral current phenomenology. The two main free parameters consist of the string and compactification mass scales, ms m_s and Mc M_c. Useful constraints on these parameters are derived from predictions for the Bhabha scattering differential cross section and for the observables associated to the mass shifts of the neutral meson systems KKˉ,BBˉ,DDˉ K-\bar K, B-\bar B, D-\bar D and the lepton number violating three-body leptonic decays of the charged leptons μ\mu and τ \tau .Comment: 34 pages, 7 figure

    Two-pion-exchange parity-violating potential and npdγ\vec{n} p \to d \gamma

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    We calculate the parity-violating nucleon-nucleon potential in heavy-baryon chiral perturbation theory up to the next-to-next-to-leading order. The one-pion exchange comes in the leading order and the next-to-next-to-leading order consists of two-pion-exchange and the two-nucleon contact terms. In order to investigate the effect of the higher order contributions, we calculate the parity-violating asymmetry in npdγ\vec{n} p \to d \gamma at the threshold. The one-pion dominates the physical observable and the two-pion contribution is about or less than 10% of the one-pion contribution.Comment: 3 pages, contribution to the workshop PAVI06 held in Milos island, Greece, May 16-20, 200

    Quenching of the Deuteron in Flight

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    We investigate the Lorentz contraction of a deuteron in flight. Our starting point is the Blankenbecler-Sugar projection of the Bethe-Salpeter equation to a 3-dimensional quasi potential equation, wqhich we apply for the deuteron bound in an harmonic oscillator potential (for an analytical result) and by the Bonn NN potential for a more realistic estimate. We find substantial quenching with increasing external momenta and a significant modification of the high momentum spectrum of the deuteron.Comment: 11 pages, 4 figure

    Study of a Neutrino Mass Texture Generated in Supergravity with Bilinear R-Parity Violation

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    We study a particular texture of the neutrino mass matrix generated in supergravity with bilinear R-Parity violation. The relatively high value of tanβ\tan\beta makes the one-loop contribution to the neutrino mass matrix as important as the tree-level one. The atmospheric angle is nearly maximal, and its deviation from maximal mixing is related to the smallness of the ratio between the solar and atmospheric mass scales. There is also a common origin for the small values of the solar and reactor angles, but the later is much smaller due the large mass ratio between the lightest two neutrinos. There is a high dependence of the neutrino mass differences on the scalar mass m0m_0 and the gaugino mass M1/2M_{1/2}, but a smaller one of the mixing angles on the same sugra parameters. Measurements of branching ratios for the neutralino decays can give important information on the parameters of the model. There are good prospects at a future Linear Collider for these measurements, but a more detailed analysis is necessary for the LHC.Comment: 21 pages, 9 figure

    Service user suicides and coroner's inquests

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    This is an Accepted Manuscript of an article published by Taylor & Francis in Criminal Justice Matters on 22nd May 2013, available online: DOI:10.1080/09627251.2013.805375The expansion of victimology in the 1980s produced a more nuanced understanding of victims and victimisation. Yet responses of government, criminal justice agencies, media and general public to victims are predictably and predominantly focused on victims of ‘conventional crime’. We challenge this perspective, thus widening the victimological lens. We discuss the impact of self-inflicted deaths and subsequent coronial inquests on practitioners working on behalf of the state

    Photoproduction and Radiative Decay of Spin 1/2 and 3/2 Pentaquarks

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    We study photoproduction and radiative decays of pentauqarks paying particular attention to the differences between spin-1/2 and spin-3/2, positive and negative parities of pentaquarks. Detailed study of these processes can not only give crucial information about the spin, but also the parity of pentaquarks.Comment: 14 pages, 7 figure

    Microscopic calculation of 6Li elastic and transition form factors

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    Variational Monte Carlo wave functions, obtained from a realistic Hamiltonian consisting of the Argonne v18 two-nucleon and Urbana-IX three-nucleon interactions, are used to calculate the 6Li ground-state longitudinal and transverse form factors as well as transition form factors to the first four excited states. The charge and current operators include one- and two-body components, leading terms of which are constructed consistently with the two-nucleon interaction. The calculated form factors and radiative widths are in good agreement with available experimental data.Comment: 9 pages, 2 figures, REVTeX, submitted to Physical Review Letters, with updated introduction and reference

    Oxidative photopolymerization of thiol-terminated polysulfide resins. Application in antibacterial coatings

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    A UV photoinduced cross-linking of non-modified commercial poly(disulfide) resins (Thioplast) is reported via the air oxidative photocoupling of terminal thiol functions. Catalyzed by a photogenerated guanidine base (TBD), this step-growth photopolymerization is useful to maximize disulfide functions content. The mechanism proceeds through thiol deprotonation into thiolate anions, further oxidized into thiyl radicals, eventually dimerizing into disulfide cross-links. Starting with a detailed structural characterization of the thiol-terminated resin, photooxidative kinetics are studied under exposure to a polychromatic medium-pressure Hg arc using Raman and infrared spectroscopy. The effects of irradiance, film thickness, photobase concentration, resin molar mass, and content of an additional polythiol monomer (reactive diluent) have been investigated. In an effort of upscaling, irradiation under a 365 nm LED panel has enabled the fast preparation of 1.5 μm thick cross-linked poly(disulfide) coatings in a matter of minutes. Capitalizing on the ability of residual thiol groups to react with silver cations, a post-functionalization has been successfully performed, leading to films exhibiting at their surface stable thiolate-silver bonds as proved by X-ray photoelectron spectroscopy. Despite the well-established biocide action of silver ions, no antibacterial action has been evidenced by confocal fluorescence microscopy because of insufficient release

    Cone Genesis Tracing by the Chrnb4-EGFP Mouse Line: Evidences of Cellular Material Fusion after Cone Precursor Transplantation.

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    The cone function is essential to mediate high visual acuity, color vision, and daylight vision. Inherited cone dystrophies and age-related macular degeneration affect a substantial percentage of the world population. To identify and isolate the most competent cells for transplantation and integration into the retina, cone tracing during development would be an important added value. To that aim, the Chrnb4-EGFP mouse line was characterized throughout retinogenesis. It revealed a sub-population of early retinal progenitors expressing the reporter gene that is progressively restricted to mature cones during retina development. The presence of the native CHRNB4 protein was confirmed in EGFP-positive cells, and it presents a similar pattern in the human retina. Sub-retinal transplantations of distinct subpopulations of Chrnb4-EGFP-expressing cells revealed the embryonic day 15.5 high-EGFP population the most efficient cells to interact with host retinas to provoke the appearance of EGFP-positive cones in the photoreceptor layer. Importantly, transplantations into the DsRed retinas revealed material exchanges between donor and host retinas, as >80% of transplanted EGFP-positive cones also were DsRed positive. Whether this cell material fusion is of significant therapeutic advantage requires further thorough investigations. The Chrnb4-EGFP mouse line definitely opens new research perspectives in cone genesis and retina repair

    Report of the GDR working group on the R-parity violation

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    This report summarizes the work of the "R-parity violation group" of the French Research Network (GDR) in Supersymmetry, concerning the physics of supersymmetric models without conservation of R-parity at HERA, LEP, Tevatron and LHC and limits on R-parity violating couplings from various processes. The report includes a discussion of the recent searches at the HERA experiment, prospects for new experiments, a review of the existing limits, and also theoretically motivated alternatives to R-parity and a brief discussion on the implications of R-parity violation on the neutrino masses.Comment: 60 pages, LaTeX, 22 figures, 2 table
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