4,122 research outputs found

    Monte-Carlo Generator Photon Jets for the process e+e- -> gamma gamma

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    Monte-Carlo generator with photon jets radiation in collinear regions for the process \eegg is described in detail. Radiative corrections in the first order of α\alpha are treated exactly. Large leading logarithmic corrections coming from collinear regions are taken into account in all orders of α\alpha by applying the Structure Function approach. Theoretical precision of the cross section with radiative corrections is estimated to be 0.2%. This process is considered as an additional tool to measure luminosity in forthcoming experiments with the CMD-3 detector at the e+ee^+e^- collider VEPP-2000.Comment: 6 pages, 5 figure

    The running of the electromagnetic coupling alpha in small-angle Bhabha scattering

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    A method to determine the running of alpha from a measurement of small-angle Bhabha scattering is proposed and worked out. The method is suited to high statistics experiments at e+e- colliders, which are equipped with luminometers in the appropriate angular region. A new simulation code predicting small-angle Bhabha scattering is also presentedComment: 15 pages, 3 Postscript figure

    Parton distribution functions from the precise NNLO QCD fit

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    We report the parton distribution functions (PDFs) determined from the NNLO QCD analysis of the world inclusive DIS data with account of the precise NNLO QCD corrections to the evolution equations kernel. The value of strong coupling constant \alpha_s^{NNLO}(M_Z)=0.1141(14), in fair agreement with one obtained using the earlier approximate NNLO kernel by van Neerven-Vogt. The intermediate bosons rates calculated in the NNLO using obtained PDFs are in agreement to the latest Run II results.Comment: 8 pages, LATEX, 2 figures (EPS

    Methodological aspects of advertising activity efficiency evaluation

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    © Medwell Journals, 2016.The study describes the methodological approaches to the essence of advertising effectiveness. Theoretical and methodological basis of advertising activity evolution is given and its specificity in various stages of operation is determined. It is substantiated that advertising as it changes in the social and historical conditions and the development of commodity production transformed from a special type of information in the field of advertising as a specific market segment with a developed infrastructure. Supplemented and refined classification of advertising as a system of education is based on different criteria. The features display advertising in a modification of the competition, consisting of individualization advertising and changing its forms; the interactive nature of advertising; the concentration of the individual segments of the advertising market. The factors and methodological approaches of the effectiveness of advertising are determined

    Branching ratios of the decays of psi(3770) and Upsilon(10580) into light hadrons

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    Taking into account the new data on the full width of D^{\ast\pm}(2010) and the mass difference of the charged and neutral beauty mesons B^\pm, B^0,\bar B^0, the branching ratios of the decays psi(3770), Upsilon(10580) to pi^+pi^-, K bar K, rho(omega)pi, rho(omega)eta, rho(omega)eta^prime, K^ast bar K+ c.c, rho^+ rho^-, and K^ast bar K^ast are re-evaluated in the model in which the Okubo-Zweig-Iizuka rule is violated due to the real intermediate state D\bar D in case of psi(3770) and B\bar B in case of Upsilon(10580). The inclusive annihilation of psi(3770) and Upsilon(10580) into light hadrons is discussed.Comment: 10 page

    Hadronic Vacuum Polarization and the Lamb Shift

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    Recent improvements in the determination of the running of the fine-structure constant also allow an update of the hadronic vacuum-polarization contribution to the Lamb shift. We find a shift of -3.40(7) kHz to the 1S level of hydrogen. We also comment on the contribution of this effect to the determination by elastic electron scattering of the r.m.s. radii of nuclei.Comment: 7 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty require

    The running mass msm_s at low scalefrom the heavy-light meson decay constants

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    It is shown that a 25(20)% difference between the decay constants fDs(fBs)f_{D_s}(f_{B_s}) and fD(fB)f_D(f_B) occurs due to large differences in the pole masses of the ss and d(u)d(u) quarks. The values ηD=fDs/fD1.23(15)\eta_D =f_{D_s}/f_D\approx 1.23(15), recently observed in the CLEO experiment, and ηB=fBs/fB1.20\eta_B=f_{B_s}/f_B\approx 1.20, obtained in unquenched lattice QCD, can be reached only if the running mass msm_s at low scale is ms(0.5m_s(\sim 0.5 GeV)=170200= 170 - 200 MeV. Our results follow from the analytical expression for the pseudoscalar decay constant fPf_{\rm P} based on the path-integral representation of the meson Green's function.Comment: 6 pages, no figures; revtex

    New high order relations between physical observables in perturbative QCD

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    We exploit the fact that within massless perturbative QCD the same Green's function determines the hadronic contribution to the τ\tau decay width and the moments of the e+ee^+e^- cross section. This allows one to obtain relations between physical observables in the two processes up to an unprecedented high order of perturbative QCD. A precision measurement of the τ\tau decay width allows one then to predict the first few moments of the spectral density in e+ee^+e^- annihilations integrated up to smτ2s\sim m_\tau^2 with high accuracy. The proposed tests are in reach of present experimental capabilities.Comment: 7 pages, Latex, no figure

    Tangling clustering of inertial particles in stably stratified turbulence

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    We have predicted theoretically and detected in laboratory experiments a new type of particle clustering (tangling clustering of inertial particles) in a stably stratified turbulence with imposed mean vertical temperature gradient. In this stratified turbulence a spatial distribution of the mean particle number density is nonuniform due to the phenomenon of turbulent thermal diffusion, that results in formation of a gradient of the mean particle number density, \nabla N, and generation of fluctuations of the particle number density by tangling of the gradient, \nabla N, by velocity fluctuations. The mean temperature gradient, \nabla T, produces the temperature fluctuations by tangling of the gradient, \nabla T, by velocity fluctuations. These fluctuations increase the rate of formation of the particle clusters in small scales. In the laboratory stratified turbulence this tangling clustering is much more effective than a pure inertial clustering that has been observed in isothermal turbulence. In particular, in our experiments in oscillating grid isothermal turbulence in air without imposed mean temperature gradient, the inertial clustering is very weak for solid particles with the diameter 10 microns and Reynolds numbers Re =250. Our theoretical predictions are in a good agreement with the obtained experimental results.Comment: 16 pages, 4 figures, REVTEX4, revised versio
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