27 research outputs found
Emission of Two Hard Photons in Large-Angle Bhabha Scattering
A closed expression for the differential cross section of the large-angle
Bhabha scattering which explicitly takes into account the leading and
next-to-leading contributions due to the emission of two hard photons is
presented. Both collinear and semi-collinear kinematical regions are
considered. The results are illustrated by numerical calculations.Comment: 13 pages, LaTeX, 1 PostScript figure, submitted to Nucl. Phys.
QED collinear radiation factors in the next-to-leading logarithmic approximation
The effect of the collinear photon radiation by charged particles is
considered in the second order of the perturbation theory. Double and single
photon radiation is evaluated. The corresponding radiation factors are
obtained. The QED renormalization group approach is exploited in the
next-to-leading order. The results are suited to perform a systematic treatment
of the second order next-to-leading logarithmic radiative corrections to
various processes either analytically or numerically.Comment: 8 page
O(\alpha^2 \ln(m_\mu/m_e)) Corrections to Electron Energy Spectrum in Muon Decay
O(\alpha^2 \ln(m_\mu/m_e)) corrections to electron energy spectrum in muon
decay are computed using perturbative fragmentation function approach. The
magnitude of these corrections is comparable to anticipated precision of the
TWIST experiment at TRIUMF where Michel parameters will be extracted from the
measurement of the electron energy spectrum in muon decay.Comment: 8 pages, LaTeX, revtex4.cls, 1 PostScript figur
Monte-Carlo Generator Photon Jets for the process e+e- -> gamma gamma
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 are treated exactly. Large leading logarithmic corrections coming
from collinear regions are taken into account in all orders of 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 collider VEPP-2000.Comment: 6 pages, 5 figure
Small-Angle Electron-Positron Scattering with a Per Mille Accuracy
The elastic and inelastic high--energy small--angle electron--positron
scattering is considered. All radiative corrections to the cross--section with
the relative accuracy are explicitly taken
into account. According to the generalized eikonal representation for the
elastic amplitude, in higher orders only diagrams with one exchanged photon may
be considered. Single photon emission with radiative corrections and
next--to--leading two--photon and pair production diagrams are evaluated,
together with leading three--loop corrections. All contributions have been
calculated analytically. We integrate the calculated distributions over typical
for LEP~1 experiments intervals of angles and energies. To the leading
approximation, the results are shown to be described in terms of kernels of
electron structure functions. Some numerical results are presented.
PACS numbers 12.15.Lk, 12.20.--m, 12.20.Ds, 13.40.--fComment: 46 pages, Latex file. Replacement file (Text slightly modified and
misprints corrected). To be published in Nuclear Physics B
Universal Higher Order Singlet QED Corrections to Unpolarized Lepton Scattering
We calculate the universal flavor-singlet radiative QED corrections to
unpolarized lepton scattering applicable to general differential scattering
cross sections, involving charged fermions or photons in initial or final
states. The radiators are derived to in analytic
form. Numerical illustrations are given.Comment: 31 pages, 3 figures, 1 style fil
Small-Angle Bhabha Scattering at LEP1. Analytical Results for Wide-Narrow Angular Acceptance
Analytical formulae for small-angle Bhabha scattering cross-section at LEP1
are given for the case of wide-narrow angular acceptance. Inclusive and
calorimeter event selections are considered. Numerical results are presented.Comment: 13 pages, LaTeX, submitted to Phys. Lett. B, corrected according to
referee remark
ZFITTER: a semi-analytical program for fermion pair production in e+e- annihilation, from version 6.21 to version 6.42
ZFITTER is a Fortran program for the calculation of fermion pair production
and radiative corrections at high energy e+e- colliders; it is also suitable
for other applications where electroweak radiative corrections appear. ZFITTER
is based on a semi-analytical approach to the calculation of radiative
corrections in the Standard Model. We present a summary of new features of the
ZFITTER program version 6.42 compared to version 6.21. The most important
additions are: (i) some higher-order QED corrections to fermion pair
production, (ii) electroweak one-loop corrections to atomic parity violation,
(iii) electroweak one-loop corrections to nu-e nu-e-bar production, (iv)
electroweak two-loop corrections to the W boson mass and the effective weak
mixing angle.Comment: 60 pages, latex, 3 table
Small-Angle Bhabha Scattering
We present the calculation of the elastic and inelastic high--energy
small--angle electron--positron scattering with a {\it per mille} accuracy.
PACS numbers 12.15.Lk, 12.20.--m, 12.20.Ds, 13.40.--fComment: 10 pages, Latex file epsfig.st
Hadronic contributions to of the leptons and to the effective fine structure constant
The hadronic contributions to the anomalous magnetic moments of the leptons
and to the effective fine structure constant at the Z-mass are reevaluated
using all presently available data.Comment: 36 pages, 11 Postscript figures, available at
ftp://129.129.40.58/pub/preprints/vapogm2.ps.g