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Register a new userElectroweak Results from LEP and SLC and Tests of the Standard Model
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E. Tournefier
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An update of the electroweak measurements at LEP and SLC is presented. These measurements are used to perform precise tests of the Standard Model. A constraint on the Standard Model Higgs mass is obtained when the direct measurements of $m_{top}$ and $M_W$ are included in the fit. A combination with the direct Higgs search is also shown.
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This paper is an updated version of the invited plenary talk given at the XXII Physics in Collision Conference at Stanford, (June 2002). The measurements performed at LEP and SLC have substantially improved the precision of the tests of the Minimal Standard Model. The precision is such that there is sensitivity to pure weak radiative corrections. This allows to indirectly determine the top mass (mt=178$pm$10 GeV), the W-boson mass (MW=80.368$pm$0.022 GeV), and to set an upper limit on the Higgs boson mass of 193 GeV at 95% confidence level.
We consider the error budget for the calculation of the LEP/SLC luminosity in the Monte Carlo event generator BHLUMI4.04 from the standpoint of new calculations of the exact result for the O(alpha) correction to the process e+ e- -> e+ e- + gamma in the low angle luminosity regime at SLC/LEP energies, for the double bremsstrahlung effect e+ e- -> e+ e- + gamma gamma in this regime, and for the size of the two-loop virtual correction to e+ e- -> e+ e- in this regime in context of Yennie-Frautschi-Suura exponentiation. We find that the error on the O(alpha**2) photonic correction can be reduced from the currently published value 0.1% to the value 0.027%. This leads to an over-all precision tag for the currently available program BHLUMI4.04 of 0.061%. This reduction of the precision of the calculation is important for the final LEP1 EW precision Z physics tests of the Standard Model.
Selected topics on precision tests of the Standard Model of the Electroweak and the Strong Interaction at the LEP $e^+e^-$ collider are presented, including an update of the world summary of measurements of $alpha_s$, representing the state of knowledge of summer 1999. This write-up of lecture notes consists of a reproduction of slides, pictures and tables, supplemented by a short descriptive text and a list of relevant references.
A wide array of deep-inelastic-scattering and hadron collider experiments have tested the predictions of the electroweak theory and measured its parameters, while also searching for new particles and processes. We summarise recent measurements and searches that probe the Standard Model to unprecedented precision.
Leptons, quarks and gauge bosons are assumed to be pointlike particles in the Standard Model. Stringent bounds on the radii of quarks and leptons and their weak anomalous magnetic moments can be derived from the high-precision measurements at LEP and SLC. We find a model-independent bound of $Rlsim 10^{-17}cm$ for quark and lepton radii. HERA will provide complementary information on the electromagnetic static properties of the quarks and the parameters of the charged quark currents.
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