69 research outputs found
Radiative Corrections for Pion Polarizability Experiments
We use the semi-analytical program RCFORGV to evaluate radiative corrections
to one-photon radiative emission in the high-energy scattering of pions in the
Coulomb field of a nucleus with atomic number Z. It is shown that radiative
corrections can simulate a pion polarizability effect. The average effect was
estimated for pion energies 40-600 GeV. We also study the range of
applicability of the equivalent photon approximation in describing one-photon
radiative emission.Comment: 11 pages (LaTex), 6 figures, 1 table. No changes in the paper. New
submission because old files are corrupted in arXi
Radiative Corrections to High Energy Lepton Bremsstrahlung on Heavy Nuclei
One-loop radiative corrections to the leptonic tensor in high energy
bremsstrahlung on heavy nuclei are calculated. Virtual and real photon
radiation is taken into account. Double bremsstrahlung is simulated by means of
Monte Carlo. Numerical results are presented for the case of muon
bremsstrahlung in conditions of the COMPASS experiment at CERN.Comment: 7 pages, 1 figur
An effective field theory approach to the electroweak corrections at LEP energies
In the framework of the effective field theory (EFT) we discuss the
electroweak (EW) corrections at LEP energies. We obtain the effective
Lagrangian in the large m_t limit, and reproduce analytically the dominant EW
corrections to the LEP2 processes e+ e- --> gamma Z and e+ e- --> Z Z. To
include effects of finite top-quark and Higgs masses, we use the effective
Lagrangian at tree level and fit LEP1/SLD observables with four arbitrary
parameters, plus alpha_s(m_Z). The EFT approach works remarkably well. Using
the effective couplings determined from the fit, and tree-level EFT formulae,
we predict the cross sections for e+ e- --> Z Z, gamma Z at a level better than
1%.Comment: 17 pages incl. 2 eps figures, REVTeX. New references added and few
misprints correcte
Radiative Corrections to Neutrino Deep Inelastic Scattering Revisited
Radiative corrections to neutrino deep inelastic scattering are revisited.
One-loop electroweak corrections are re-calculated within the automatic SANC
system. Terms with mass singularities are treated including higher order
leading logarithmic corrections. Scheme dependence of corrections due to weak
interactions is investigated. The results are implemented into the data
analysis of the NOMAD experiment. The present theoretical accuracy in
description of the process is discussed.Comment: 19 pages, two figures are added, discussion of theoretical
uncertainties is extende
CP Violation and the Width
We discuss the effect of CP-violating , and
couplings on the width . The
presence of such couplings leads in a natural way to an increase of this width
relative to the prediction of the standard model. Various strategies of a
direct search for such CP-violating couplings by using CP-odd observables are
outlined. The number of bosons required to obtain significant information
on the couplings in this way is well within the reach of present LEP
experiments.Comment: 18 pages, LaTeX, no figure
QED Radiative Corrections in Processes of Exclusive Pion Electroproduction
Formalism for radiative correction (RC) calculation in exclusive pion
electroproduction on the proton is presented. A FORTRAN code EXCLURAD is
developed for the RC procedure. The numerical analysis is done in the
kinematics of current Jefferson Lab experiments.Comment: 13 pages, 9 figures; requires RevTeX
Theoretical uncertainties for measurements of alpha_s from electroweak observables
One of the most precise measurements of the strong coupling constant
alpha_s(MZ) is obtained in the context of global analyses of precision
electroweak data. This article reviews the sensitivity of different electroweak
observables to alpha_s and describes the perturbative uncertainties related to
missing higher orders. The complete renormalisation scale dependence for the
relevant observables is calculated at next-to-next-to-leading order and a new
method is presented to determine the corresponding perturbative uncertainty for
measurements of alpha_s based on these observables.Comment: v4: Revised version with new tables and figure
Universal extra dimensions and Z->b bar-b
We study, at the one loop level, the dominant contributions from a single
universal extra dimension to the process (Z\to b\bar{b}). By resorting to the
gaugeless limit of the theory we explain why the result is expected to display
a strong dependence on the mass of the top-quark, not identified in the early
literature. A detailed calculation corroborates this expectation, giving rise
to a lower bound for the compactification scale which is comparable to that
obtained from the parameter. An estimate of the subleading corrections
is furnished, together with a qualitative discussion on the difference between
the present results and those derived previously for the non-universal case.Comment: 16 pages, 4 figures, revtex
Quantum Gravitational Corrections to the Nonrelativistic Scattering Potential of Two Masses
We treat general relativity as an effective field theory, obtaining the full
nonanalytic component of the scattering matrix potential to one-loop order. The
lowest order vertex rules for the resulting effective field theory are
presented and the one-loop diagrams which yield the leading nonrelativistic
post-Newtonian and quantum corrections to the gravitational scattering
amplitude to second order in G are calculated in detail. The Fourier
transformed amplitudes yield a nonrelativistic potential and our result is
discussed in relation to previous calculations. The definition of a potential
is discussed as well and we show how the ambiguity of the potential under
coordinate changes is resolved.Comment: 27 pages, 17 figure
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
- …