4,777 research outputs found

    Project {\tt SANC} (former {\tt CalcPHEP}): Support of Analytic and Numeric calculations for experiments at Colliders

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    The project, aimed at the theoretical support of experiments at modern and future accelerators -- TEVATRON, LHC, electron Linear Colliders (TESLA, NLC, CLIC) and muon factories, is presented. Within this project a four-level computer system is being created, which must automatically calculate, at the one-loop precision level the pseudo- and realistic observables (decay rates and event distributions) for more and more complicated processes of elementary particle interaction, using the principle of knowledge storing. It was already used for a recalculation of the EW radiative corrections for Atomic Parity Violation [1] and complete one-loop corrections for the process e+ettˉe^+ e^-\to t\bar{t} [2-4]; for the latter an, agreement up to 11 digits with FeynArts and the other results is found. The version of {\tt SANC} that we describe here is capable of automatically computing the decay rates and the distributions for the decays Z(H,W)ffˉZ(H,W)\to f\bar{f} in the one-loop approximation.Comment: 3 Latex, Presented at ICHEP2002, Amsterdam, July 24-30, 2000; Submitted to Proceeding

    The Character of Z-pole Data Constraints on Standard Model Parameters

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    Despite the impressive precision of the Z-pole measurements made at LEP and SLC, the allowed region for the principle Standard Model parameters responsible for radiative corrections (the mass of the Higgs, the mass of the top and alpha(Mz)) is still large enough to encompass significant non-linearities. The nature of the experimental constraints therefore depends in an interesting way on the "accidental" relationships among the various measurements. In particular, the fact that the Z-pole measurements favor values of the Higgs mass excluded by direct searches leads us to examine the effects of external Higgsstrahlung, a process ignored by the usual precision electroweak calculations.Comment: 9 pages, 6 figures, REVTeX format; added reference in section IV; added paragraph on widths and a few cosmetic changes to correspond to published versio

    An electroweak library for the calculation of EWRC to e+ e- --> f fbar within the CalcPHEP project

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    We present a description of calculations of the electroweak amplitude for e+ e- --> f fbar process. The calculations are done within the OMS (on-mass-shell) renormalization scheme in two gauges: in Rxi, which allows an explicit control of gauge invariance by examining cancellation of gauge parameters and search for gauge-invariant subsets of diagrams, and in the unitary gauge as a cross-check. The formulae we derived are realized in a FORTRAN code eeffLib, which is being created within the framework of the project CalcPHEP. We present a comprehensive comparison between eeffLib results for the light top with corresponding results of the well-known program ZFITTER for the u ubar channel, as well as a preliminary comparison with results existing in the world literature.Comment: Revised version, 47 Latex, including 14 figures (2 eps figures), 5 table

    J_AW,WA functions in Passarino-Veltman reduction

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    In this paper we continue to study a special class of Passarino-Veltman functions J arising at the reduction of infrared divergent box diagrams. We describe a procedure of separation of two types of singularities, infrared and mass singularities, which are absorbed in simple C0 functions. The infrared divergences of C0's can be regularized then by any method: photon mass, dimensionally or by the width of an unstable particle. Functions J, in turn, are represented as certain linear combinations of the standard D0 and C0 Passarino-Veltman functions. The former are free of both types of singularities and are expressed as explicit and compact linear combinations of logarithms and dilogarithm functions. We present extensive comparisons of numerical results with those obtained with the aid of the LoopTools package

    Matched wideband low-noise amplifiers for radio astronomy

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    Two packaged low noise amplifiers for the 0.3–4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300–4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<−10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range

    Finite-width effects in the near-threshold ZZZ and ZWW production at ILC

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    We calculate the cross-section of the near-threshold off-shell ZZZZZZ and ZW+WZW^+W^- production at the International Linear Collider taking into account their instability and the principal part of NLO corrections. The calculations are performed in the framework of the model of unstable particles with smeared mass-shell. We show that the contribution of the finite Z/WZ/W and HH widths (their instability) is large in the Higgs resonance range and should be taken into account in the Higgs boson searches at future colliders.Comment: 5 pages, 6 figure

    Dispersion-theoretical analysis of the nucleon electromagnetic form factors: Inclusion of time-like data

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    We update a recent dispersion--theoretical fit to the nucleon electromagnetic form factors by including the existing data in the time--like region. We show that while the time--like data for the proton can be described consistently with the existing world space--like data, this is not the case for the neutron. Another measurement of the process e+enˉne^+ e^- \to \bar n n is called for. We furthermore sharpen the previous estimate of the separation between the perturbative and the non--perturbative regime, which is characterized by a scale parameter Λ210\Lambda^2 \simeq 10\,GeV2^2.Comment: 7 pp, LaTeX, uses epsf, 2 figures in separate file, four data points changed, slight changes in the fits, conclusions unchange

    Organising invention through technical mentality: Simondon’s challenge to the ‘civilisation of productivity’

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    This is an Accepted Manuscript of an article published by Taylor & Francis in Culture and Organization on 13/10/2016, available online: https://www.tandfonline.com/doi/full/10.1080/14759551.2016.1240400.According to Simondon, it is through the implementation of a ‘technical mentality’ that a technocratic system grounded on a communitarian ‘ethics of productivity’ can be transformed into a system of metastable functioning as a value. Simondon’s overall project is twofold, aiming both at a unified paradigm for the social sciences, and at a pedagogy of technics, inspired by the concept of the technical mentality. The goal of this article is to provide a conjoint and consistent analysis of Simondon’s paradigm by connecting the concepts of ‘organising amplification’ and ‘technical mentality’
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