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M. Bilenky

Publications and source records attributed to M. Bilenky.

10 recordsLinked to original sources
arXiv2000

ZFITTER v.6.21 - A Semi-Analytical Program for Fermion Pair Production in e+e- Annihilation

We describe ZFITTER, a Fortran program based on a semi-analytical approach to fermion pair production in e+e- annihilation at a wide range of centre-of-mass energies, including the PETRA, TRISTAN, LEP1/SLC, and LEP2 energies. A flexible treatment of complete O(alpha) QED corrections and of some higher order contributions is made possible with three calculational chains containing different realistic sets of restrictions in the photon phase space. Numerical integrations are at most one-dimensional. Complete O(alpha) weak loop corrections supplemented by selected higher-order terms may be included. The program calculates Delta r, the Z width, differential cross-sections, total cross-sections, integrated forward-backward asymmetries, left-right asymmetries, and for tau pair production also final-state polarization effects. Various interfaces allow fits to be performed with different sets of free parameters.

hep-ph↗
arXiv1998

Analytic approach to the complete set of QED corrections to fermion pair production in e+e- annihilation

We present the convolution integral for fermion pair production in the electroweak standard theory to order O(alpha) including also soft photon exponentiation. The result is complete in the sense that it includes initial and final state radiation and their interference. From the basic result - analytic formulae for the differential cross section - we also derive the corresponding expressions for total cross section and integrated forward-backward asymmetry. The numerical importance of different contributions for the analysis of experiments at LEP/SLC energies is discussed.

hep-ph↗
arXiv1997

Electroweak Working Group Report

The report summarizes the results of the activities of the Working Group on Precision Calculations for the Z Resonance at CERN during 1994.

hep-ph↗
arXiv1996

Triple Gauge Boson Couplings

We present the results obtained by the "Triple Gauge Couplings" working group during the LEP2 Workshop (1994-1995). The report concentrates on the measurement of $WWγ$ and $WWZ$ couplings in $e^-e^+\to W^-W^+$ or, more generally, four-fermion production at LEP2. In addition the detection of new interactions in the bosonic sector via other production channels is discussed.

hep-ph↗
arXiv1995

ZFITTER -- An Analytical Program for Fermion Pair Production in e+e- Annihilation

We describe how to use ZFITTER, a program based on a semi-analytical approach to fermion pair production in e+e- annihilation and Bhabha scattering. A flexible treatment of complete ${\cal O}(α)$ QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. One includes complete ${\cal O}(α)$ weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for $τ$~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters.

hep-ph↗
arXiv1995

Off-shell $W$-pair production in $e^+ e^-$-annihilation. Initial state radiation

With a current-splitting technique, we calculate the gauge-invariant initial-state radiation to order \oalf\ with soft-photon exponentiation for on- and off-shell $W$-pair production. This result generalizes the convolution formula, which is known from the description of the $Z$ resonance, to the case of the production of two $W$-bosons. After up to eightfold analytical integrations, a sufficiently smooth integral over three invariant masses remains to be treated numerically. Including the Coulomb singularity, the largest corrections are covered. We discuss the corrections in a large energy range up to $\sqrt{s}$=1~TeV and draw numerical conclusions on their influence on the $W$-mass determination at LEP~200. Table~1 and figure~5 are revised after correcting the analytical formulae for the nonuniversal corrections.

hep-ph↗
arXiv1994

Semi-Analytical Approach to Four-Fermion Production in $e^+ e^-$ Annihilation

A study of the semi-analytical approach to four-fermion production in $e^+ e^-$ annihilation is presented. We classify all possible four-fermion final states and present results of new calculations for the `basic' processes with the $WW,ZZ$, and $ZH$ off-shell production together with some examples of `background' processes. The Initial State Radiative corrections are included for the basic processes. Several numerical examples are given in the energy range from LEP2 up to $\sqrt{s}=1$ TeV.

hep-ph↗
arXiv1993

On the Interpretation of the Electroweak Precision Data

The recent precision electroweak data on $Γ^l, \bar s^2_W$ and $M_W/M_Z$ are compared with the tree-level and the dominant-fermion-loop as well as the full one-loop standard-model predictions. While the tree-level predictions are ruled out, the dominant-fermion-loop predictions, defined by using $α(M^2_Z)\cong 1/128.9$ in the tree-level formulae, as well as the full one-loop predictions are consistent with the experimental data. Deviations from the dominant-fermion-loop predictions are quantified in terms of an effective Lagrangian containing three additional parameters which have a simple meaning in terms of $SU(2)$ symmetry violation. The effective Lagrangian yields the standard one-loop predictions for specific values of these parameters, which are determined by $m_t$ and $m_H$.

hep-ph↗
arXiv1993

The Potential of a New Linear Collider for the Measurement of the Trilinear Couplings among the Electroweak Vector Bosons

We study the accuracy to be obtained in measuring trilinear $Z^0W^+W^-$ and $γW^+W^-$ couplings in the reaction $e^+e^- \to W^+W^-$ at "New Linear Collider" energies of $500GeV$ to $1000GeV$. We derive simple scaling laws for the sensitivity in the measurement of these couplings. For most couplings the sensitivity increases as $\sqrt{L\cdot s}$, where $L$ denotes the integrated luminosity and $\sqrt s$ denotes the $e^+e^-$ center-of-mass energy. Detailed investigations based on various fits confirm these scaling laws and show that an accuracy of the order of the standard radiative corrections can be reached at the NLC for the design values of the luminosity.

hep-ph↗