共查询到20条相似文献,搜索用时 15 毫秒
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M.N. Achasov S.E. Baru A.V. Bozhenok A.D. Bukin D.A. Bukin S.V. Burdin T.V. Dimova S.I. Dolinsky V.P. Druzhinin M.S. Dubrovin I.A. Gaponenko V.B. Golubev V.N. Ivanchenko A.A. Korol S.V. Koshuba A.P. Lysenko I.N. Nesterenko E.V. Pakhtusova S.I. Serednyakov V.V. Shary Yu.M. Shatunov V.A. Sidorov Z.K. Silagadze Yu.V. Usov 《The European Physical Journal C - Particles and Fields》2000,12(3):369-374
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We study the interference of resonant Higgs boson exchange in neutralino production in
m+ m-\mu^ + \mu^-
annihilation with longitudinally polarized beams. We use the energy distribution of the decay lepton in the process
[(c)\tilde]0j ? l± [(l)\tilde]-±\tilde{\chi}^0_j \to \ell^{\pm} \tilde{\ell}^\mp
to determine the polarization of the neutralinos. In the CP-conserving minimal supersymmetric standard model a non-vanishing asymmetry in the lepton energy spectrum is caused by the interference of Higgs boson exchange channels with different CP-eigenvalues. The contribution of this interference is large if the heavy neutral bosons H and A are nearly degenerate. We show that the asymmetry can be used to determine the couplings of the neutral Higgs bosons to the neutralinos. In particular, the asymmetry allows one to determine the relative phase of the couplings. We find large asymmetries and cross sections for a set of reference scenarios with nearly degenerate neutral Higgs bosons. 相似文献
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The creation of a pair of scalar fermion partners accompanying the annihilation of arbitrarily polarized electrons and positrons is studied in the gauge models SU(2)× U(l), SU(2)L× SU(2)R× U(1), and SU(3)× U(1). Different electroweak asymmetries are found and analyzed in detail (right-left asymmetry arl, P-even transversal spin asymmetry a1 and P-odd asymmetry A2) for the e–e+-beam energies s=40–360 GeV and the Weinberg parameter values 0.21 sin2W0.27. The computations show that the presence of weak neutral currents also leads to noticeable electroweak asymmetries, which are sensible to the choice of the gauge model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 78–82, May, 1989. 相似文献
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Y. Kiyo J. Kodaira K. Morii 《The European Physical Journal C - Particles and Fields》2000,18(2):327-332
We discuss top quark production and its subsequent decay as used for searching new physics at lepton colliders. The angular
dependence of the decay leptons is calculated including both QCD corrections and anomalous couplings. The off-diagonal spin basis for the top and anti-top quarks is shown to be useful to probe the anomalous couplings.
Received: 11 August 2000 / Published online: 27 November 2000 相似文献
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Existence of discrepancies between experimental data and Monte Carlo predictions for angular distributions in four-jet production
via annihilation has been known for some time at LEP1. As such QCD processes constitute significant backgrounds to -jet production at LEP2, we consider the possibility that an erroneous modelling of the helicity structure of the final-state
partons could affect the accuracy of experimental measurements of the boson parameters.
Received: 21 September 1998 / Revised version: 20 January 1999 / Published online: 22 March 1999 相似文献
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F. Gangemi G. Montagna M. Moretti O. Nicrosini F. Piccinini 《The European Physical Journal C - Particles and Fields》1999,9(1):31-41
The six-fermion production processes , with all the lepton flavours and , relevant to the study of the intermediate-mass Higgs boson at future linear colliders are analysed. A Monte Carlo program, taking into account the whole set of tree-level scattering amplitudes
and the relevant radiative effects, is developed to provide integrated cross-sections and generation of unweighted events.
The complete calculation is compared with the available results of real Higgs production, and the opportunities of precision
studies with event generation are discussed, demonstrating the relevance of a full six-fermion calculation. Numerical results
for integrated cross-sections with various kinematical cuts and including radiative effects are given and commented. In the
analysis of event samples, several distributions are studied and found to be sensitive to the presence and to the properties
of the Higgs boson.
Received: 20 December 1998 / Published online: 27 April 1999 相似文献
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S. R. Gevorkyan M. H. Misheva 《The European Physical Journal C - Particles and Fields》2014,74(5):1-5
The rare $K^\pm \rightarrow \pi ^\pm \pi ^0 e^+e^-$ decay, currently under analysis by the NA62 Collaboration, is considered. We have followed two theoretical approaches to calculate the differential decay width—in the kaon rest frame, where we use Cabibbo–Maksymowicz variables, and in the center-of-mass system of the lepton pair. The latter essentially simplifies the computations. A comparison between the two approaches has been performed. We have also found the dependencies of the differential decay rate as a function of the virtual photon and dipion system masses. 相似文献
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S. Fajfer P. Singer J. Zupan 《The European Physical Journal C - Particles and Fields》2003,27(2):201-218
We present a calculation of the rare decay modes and in the framework of the standard model. For the short distance part we have derived QCD corrections to the Wilson coefficients
involved, including C9. The latter is found to be strongly suppressed by the corrections, leading to diminished values for the branching ratios in the 10-10 range. Within SM the exclusive decays are dominated by long distance effects. Non-resonant contributions are estimated using
heavy quark and chiral symmetries to be at the level of , compared to the contributions arising from , with . The total SM branching ratio is predicted to be in the range (1-. We also consider contributions coming from MSSM with and without R parity conservation. The effects from MSSM are significant only for the R parity violating case. Such contributions enhance the branching ratio to , based on appropriately allowed values for C9 and C10. This selects as a possible probe of new physics.
Received: 25 October 2002 / Published online: 24 January 2003 相似文献
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