2,144 research outputs found

    The two-pseudoscalar-meson decay of χcJ\chi_{cJ} with twist-3 corrections

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    The decays of χcJπ+π,K+K\chi_{cJ} \to \pi^+\pi^-, K^+K^- (J=0,2)(J=0,2) are discussed within the standard and modified hard scattering approach when including the contributions from twist-3 distribution amplitudes and wave functions of the light pseudoscalar meson. A model for twist-2 and twist-3 distribution amplitudes and wave functions of the pion and kaon with BHL prescription are proposed as the solution to the end-point singularities. The results show that the contributions from twist-3 parts are actually not power suppressed comparing with the leading-twist contribution. After including the effects from the transverse momentum of light meson valence-quark state and Sudakov factors, the decay widths of the χcJ\chi_{cJ} into pions or kaons are comparable with the their experimental data.Comment: 31 pages, 5 figures, 3 table

    Study of Chromium-Frit-Type Coatings for High-Temperature Protection of Molybdenum

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    The achievement of more compact and efficient power plants for aircraft is dependent, among other factors, on the perfection of heat-resisting materials that are superior to those in current use. Molybdenum is one of the high-melting metals (melting point, 4750 F). It is fairly abundant and also can be worked into many of the shapes required in modern power plants. To permit its widespread use at elevated temperatures, however, some means must first be found to prevent its rapid oxidation. The application of a protective coating is one method that might be used to achieve this goal. In the present work, a number of chromium-frit-type coatings were studied. These were bonded to molybdenum specimens by firing in controlled atmospheres to temperatures in the range of 2400 to 2700 F

    Twist-four Corrections to Parity-Violating Electron-Deuteron Scattering

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    Parity violating electron-deuteron scattering can potentially provide a clean access to electroweak couplings that are sensitive to physics beyond the Standard Model. However hadronic effects can contaminate their extraction from high-precision measurements. Power-suppressed contributions are one of the main sources of uncertainties along with charge-symmetry violating effects in leading-twist parton densities. In this work we calculate the twist-four correlation functions contributing to the left-right polarization asymmetry making use of nucleon multiparton light-cone wave functions.Comment: 12 pages, 3 figure

    Diffractive vector meson electroproduction at small Bjorken xx within GPD approach

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    We study light vector meson electroproduction at small xx within the generalized parton distributions (GPDs) model. The modified perturbative approach is used, where the quark transverse degrees of freedom in the vector meson wave function and hard subprocess are considered. Our results on the cross section and spin observables are in good agreement with experimentComment: 6 pages, 5 figures, presented at Symmetries and Spin meeting, Prague, 8- 14 July, 200

    Scattering of massive W bosons into gravitinos and tree unitarity in broken supergravity

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    The WW scattering into gravitino and gaugino is here investigated in the broken phase, by using both gauge and mass eigenstates. Differently from what is obtained for unbroken gauge symmetry, we find in the scattering amplitudes new structures, which can lead to violation of unitarity above a certain scale. This happens because, in the annihilation diagram, the longitudinal degrees of freedom in the propagator of the gauge bosons disappear from the amplitude, by virtue of the SUGRA vertex. We show that the longitudinal polarizations of the on-shell W become strongly interacting in the high energy limit, and that the inclusion of diagrams with off-shell scalars of the MSSM does not cancel the divergences.Comment: 26 pages, 17 figures. Uses JHEP3.cls, epsfig.sty and axodraw.sty. Some references, together with Ward identities in the basis of mass eigenstates, have been added. Version accepted for publication in JHE

    The consequences of compromising the EU's free movement of persons principle on Swiss research: how to survive constrained access to regional funding

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    Between 2014 and 2016, Switzerland's access to some of the EU funding was limited after a referendum against mass immigration was accepted and the country refused to sign the free movement accord to the EU's newest member, Croatia. It is well documented that Switzerland has suffered from a drop in participation, funding and a decrease in consortium lead positions. However, there is no account of the consequences on institutional level. We therefore aimed at describing the immediate- and longer-term impact of the partial association status to the Swiss Tropical and Public Health Institute (Swiss TPH) and to identify key strategies for minimizing institutional damage during a limited access period to a key regional funding source. A quantitative analysis of the institute's grants database, from 2007 to 2019, did not show any clear trends related to the partial association status of Switzerland for funding and projects awarded. The qualitative outcomes changed along the timeline assessed; whereas in 2014 a range of negative effects were stated by Swiss TPH researchers, a survey conducted in 2019 with Swiss TPH applicants and project partners to Horizon 2020, revealed that most project leaders felt that the partial association did neither affect their external partners' willingness to collaborate nor Swiss TPH's role in the proposal or consortium. On the other hand, the institutional strategic goal of taking on consortia leads was delayed by several years as a direct consequence of the partial association. Also, the exclusion from European research networks and the lack of consultation of expertise by the European partner institutions was widely seen as damaging. A policy of favouring long-term partnerships over ad-hoc collaborations, along with constant and trustful communication, as immediate mitigation measure, helped averting some of the reputational and access damage. Moreover, the Swiss TPH business model based on a three-way strategy of research, education and services has proven highly viable allowing to build a large pool of potential funding sources internationally, resulting in relative resilience in terms of income lost

    Intrinsic Transverse Size Effect

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    Two recently proposed concepts to improve the perturbative calculation of exclusive amplitudes, gluonic radiative corrections (Sudakov factor) and confinement size effects (intrinsic transverse momentum) are combined to study the neutron magnetic form factor in the space-like region. We find that nucleon distribution amplitudes modelled on the basis of current QCD sum rules indicate overlap with the existing data at the highest measured values of momentum transfer. However, sizeable higher-order perturbative corrections (K-factor) and/or higher-twist contributions cannot be excluded, although they may be weaker than in the proton case.Comment: 12 pages LATEX, 4 figures as compressed uu-encoded PS-file, preprint University of Wuppertal WU-B-94-16, University of Bochum RUB-TPII-04/94 (some typos eliminated

    HELAS and MadGraph with spin-3/2 particles

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    Fortran subroutines to calculate helicity amplitudes with massive spin-3/2 particles, such as massive gravitinos, which couple to the standard model and supersymmetric particles via the supercurrent, are added to the HELAS (HELicity Amplitude Subroutines) library. They are coded in such a way that arbitrary amplitudes with external gravitinos can be generated automatically by MadGraph, after slight modifications. All the codes have been tested carefully by making use of the gauge invariance of the helicity amplitudes.Comment: 12 pages, 4 figures; sections rearranged, typos corrected, version to appear in EPJ
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