3,792 research outputs found
Theoretical developments on Quartic Gauge Boson Couplings at LEP
The search for quartic anomalous gauge couplings (QAGC) at LEP requires
appropriate predictions for the radiative processes e+ e- \to \nu\bar\nu
\gamma\gamma, e+ e- \to q\bar{q}\gamma\gamma and e+ e- \to 4 fermions+\gamma.
The current knowledge on dimension-six operators giving rise to QAGC is briefly
reviewed, together with their implementation in event generators. The accuracy
of calculations based on real approximations (used up to now for the LEP
experimental analysis) is examined by comparing them with the available exact
matrix element calculations.Comment: LaTeX, JHEP style, 5 pag. Talk presented at EPS HEP2001, Budapest,
Hungary, 12 - 18 July, 200
Radiative four-fermion processes at LEP2
The production of four fermions plus a visible photon in electron-positron
collisions is analyzed, with particular emphasis on the LEP2 energy range. The
study is based on the calculation of exact matrix elements, including the
effect of fermion masses. In the light of the present measurements performed at
LEP, triple and quartic anomalous gauge couplings are taken into account. Due
to the presence of a visible photon in the final state, particular attention is
paid to the treatment of higher-order QED corrections. Explicit results for
integrated cross sections and differential distributions are shown and
commented. The features of the Monte Carlo program WRAP, used to perform the
calculation and available for experimental analysis, are described.Comment: LaTeX, 14 pages, 6 tables, 13 figures. Numerical results added,
version to appear in Eur. Phys. J.
Six-Fermion Calculation of Intermediate-mass Higgs Boson Production at Future Colliders
The production of an intermediate-mass Higgs boson in processes of the kind
fermions at the energies of future linear colliders is studied.
The recently developed and fully automatic algorithm/code ALPHA is used to
compute the tree-level scattering amplitudes for the reactions . The code has been interfaced with the Monte Carlo program HIGGSPV/WWGENPV,
properly adapted to 6-fermion production, in order to provide realistic
results, both in the form of cross sections and event samples at the partonic
level. Phenomenological results, that incorporate the effects of initial-state
radiation and beamstrahlung, are shown and commented, emphasizing the
potentials of full six-fermion calculations for precise background evaluation
as well as for detailed studies of the fundamental properties of the Higgs
particle.Comment: 31 pages, LaTeX, 15 eps low-resolution figures include
Higher-order QED corrections to single-W production in electron-positron collisions
Four-fermion processes with a particle lost in the beam pipe are studied at
LEP to perform precision tests of the electroweak theory. Leading higher-order
QED corrections to such processes are analyzed within the framework of the
Structure Functions (SF) approach. The energy scale entering the QED SF is
determined by inspection of the soft and collinear limit of the O(alpha)
radiative corrections to the four-fermion final states, paying particular
attention to the process of single-W production. Numerical predictions are
shown in realistic situations for LEP experiments and compared with existing
results. A Monte Carlo event generator, including exact tree-level matrix
elements, vacuum polarization, higher-order leading QED corrections and
anomalous trilinear gauge couplings, is presented.Comment: LaTeX (using elsart), 21 pages, 8 .ps figure
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