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تسجيل مستخدم جديدMonte-Carlo generator for e+e- annihilation into lepton and hadron pairs with precise radiative corrections
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Recently, various cross sections of e+e- annihilation into hadrons were accurately measured in the energy range from 0.37 to 1.39 GeV with the CMD-2 detector at the VEPP-2M collider. In the pi+pi- channel a systematic uncertainty of 0.6% has been achieved. A Monte-Carlo Generator Photon Jets (MCGPJ) was developed to simulate events of the Bhabha scattering as well as production of two charged pions, kaons and muons. Based on the formalism of Structure Functions, the leading logarithmic contributions related to the emission of photon jets in the collinear region are incorporated into the MC generator. Radiative corrections (RC) in the first order of alpha are accounted for exactly. The theoretical precision of the cross sections with RC is estimated to be better than 0.2%. Numerous tests of the program as well as comparison with other MC generators and CMD-2 experimental data are presented.
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We have calculated the complete electroweak O(alpha) radiative corrections to the single Higgs-boson production processes e+ e- --> nu_l anti-nu_l H (l=e,mu,tau) in the electroweak Standard Model. Initial-state radiation beyond O(alpha) is included i
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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 $alpha$ are treated exactly. Large leading logarithmic corrections coming from collinear re
gions are taken into account in all orders of $alpha$ 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 $e^+e^-$ collider VEPP-2000.
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The past ten years of physics with e+e- colliding experiments at LEP and SLAC have shown the success of these experiments on not only impressively proving the theoretical predictions of the Standard Model (SM), but also to help provide stringent boun
ds on physics beyond the SM. With this experience in mind, there appear two equally fascinating opportunities for studying fermion-pair production processes at a future Linear Collider (LC). On the one hand, performing high precision measurements to the SM, for example, when running with high luminosity at the Z boson resonance, could be a quick and feasible enterprise in order to pin down the symmetry breaking mechanism of the electroweak sector through indirectly determining the masses of a light SM or MSSM Higgs boson or supersymmetric particles via virtual corrections. On the other hand, looking for such particles in direct production or other `New Physics effects at energies between, for example, roughly 500 and 800 GeV will naturally be the main motivation to pursue the challenging endeavor of building and utilizing such a unique facility. These two scenarios for the LC shall be sketched here, with particular emphasis on the semi-analytical program ZFITTER for fermion-pair production in comparison with numerical programs like TOPAZ0, KK2f, and others.
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