Modern Technique for Real Photon Radiative Correction Calculations

The problem of the bremsstrahlung contribution calculation as a part of the radiative corrections in the case of single gauge boson production was discussed. It was shown that the hard photon bremsstrahlung contribution can be divided into the finite and divergent terms. The exact calculation of soft photon bremsstrahlung and infrared part of hard photon bremsstrahlung was presented in frame of the dimensional regularization scheme. Numerical analysis of radiative corrections to the cross sections of single gauge boson production was performed.

About the polarized τ-lepton radiative decay

The polarization effects in the one-meson radiative decay of the polarized [Formula: see text] lepton, [Formula: see text], have been investigated. We present the analytical results for the [Formula: see text]-distribution of the partial differential widths, which are responsible for different polarization phenomena, in the case of the photon energy cut: [Formula: see text]. These quantities depend on the invariant mass squared [Formula: see text] of the pseudoscalar meson and photon and the photon energy cut [Formula: see text] Our analytical formulae, in terms of the weak vector and axial-vector form factors, describing the structure-dependent part of the decay amplitude, are valid also for the decay [Formula: see text] after trivial substitutions of the corresponding constants. We demonstrate the essential decrease of the inner bremsstrahlung contribution in comparison with the structural one with increase of the photon cut energy. In numerical calculations, the vector and axial-vector form factors are determined using the chiral effective theory with resonances (R[Formula: see text]T).

Differential distributions in rare four-leptonic B-decays.

The branching ratios and differential distributions for the fourleptonic decays B- → μ+μ- νe e-, B- → e+e- νμ μ- and B- → μ+ νμ μ-μ- are calculated within the Standard Model. The contributions of the virtual photon emission from the b- and u- quarks and the bremsstrahlung contribution were taken into account. The resonances contributions were calculated using the vector dominance model. In this paper we present the differential distributions for the B- → μ+μ- νe e- decay obtained by two methods. Testing the lepton universality in rare multileptonic decays of charged and neutral B mesons are discussed.

Bremsstrahlung Contribution in Compton Scattering from Heavy Metals

Theoretical estimates of the spectral distribution and total intensity of the bremsstrahlung (BS) relative to the Compton yield have been determined for photoelectrons liberated in scattering experiments on heavy metals with 60 keV radiation. Whereas the total-intensity calculations are based on the approach of Alexandropoulos et al., the spectral distribution has been computed using the Born approximation along with the Elwert and form factor corrections. These results are compared with another calculation based on the approach of Lee et al. Typical results for Mo, Ta, and W are presented. It is found that the relative contribution of BS from a W target is not trivially small, although K-shell photo-ionisation is not possible at these energies.

THE DOMINANT PART OF HIGHER ORDER CORRECTIONS IN PERTURBATIVE QCD

It is shown that in processes involving structure functions and/or fragmentation functions initiated by 2→2 parton subprocesses, there is a gauge invariant part that dominates higher order corrections over a sizeable kinematic domain. The gluon Bremsstrahlung contribution to this part arises from collinear and soft gluon configurations. This Bremsstrahlung contribution (and more generally the contribution to this part from 2→3 parton subprocesses) is shown to arise from expressions remarkably simple and general.