Top Quark Pair Production in e+e- Annihilation Near Threshold

Recent progress in calculations of the total cross section for top quark pair production near threshold is reviewed. Different top quark mass definitions adequate for threshold studies are discussed. A relation between the potential subtracted mass and the IS mass is studied. The potential subtracted IS mass is defined which incorporates attractive features of both schemes

Radiative Corrections to the top quark width

Calculations of radiative corrections to the top quark width are reviewed. QCD effects are discussed for $t-\bar t$ systems produced in $e^+e^-$ annihilation near the energy threshold.}Comment: Karlsruhe Univ. preprint TTP 93-21, 6p., 2 figures not included (Talk presented by M. Je\.zabek at the Workshop on Physics and Experiments at Linear $e^+e^-$ Colliders, Waikoloa, Hawaii, April 1993

One-Loop QCD Corrected Distribution in B\rightarrow Xe{\overline {|nu } e}

We give an analytic formula for the double distribution of hadronic invariant mass and charged lepton energy to one-loop order of the perturbative QCD. Although infrared singular, this quantity is closely related to physical observables th a t can be obtained thereof through proper convolution

Perturbative QCD corrections to inclusive lepton distributions from semileptonic b ---> c anti-tau-neutrino (tau) decays

Perturbative corrections of the order of a , to inclusive double differential lepton distribution from b quark decay are considered. A perturbative correction to the charged lepton energy spectrum has been calculated for an arbitrary charged lepton mass. The perturbative contribution suppresses the partial rate but almost does not change the shape of energy distribution. Applications of our result to semileptonic B meson decays are briefly discussed

Longitudinal Top Quark Polarization

Longitudinal polarization of the top quark, averaged over the production angle, is discussed for the top quark produced in e+e- annihilation near its production threshold. It is demonstrated that Coulomb type corrections and rescattering corrections are important. They change considerably measurable quantities and should be taken into account in phenomenological analysis

The Gluon Exchange Model in proton-nucleus collisions

We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton-nucleus reactions involving N>1 proton-nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea-sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number of proton-nucleon collisions in the nucleus. As such, the nuclear stopping power appears to be governed by the emergence of new color configurations as a function of N rather than by the energy loss of the original valence diquark. The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, and a set of predictions for the N-dependence of the baryon stopping process, are included in the letter.Comment: 15 pages, 4 figure

Polarization of tau leptons in semileptonic B decays

Analytic formulae for the one-loop order QCD corrections to the differential width of the semileptonic b decay are given with the tau polarization taken into account. Thence the polarization of tau is expressed by its energy and the invariant mass of the tau + antineutrino system. The non-perturbative corrections by Falk et al. are incorporated in the calculation.Comment: one footnote and one reference have been added; the paper is going to be published in Nucl. Phys.

Special volume of Acta Physica Polonica B commemorating Martinus Veltman

This memorial volume of Acta Physica Polonica B is a special tribute to the Nobel Laureate Martinus Veltman. Professor Veltman was a member of the APPB International Editorial Council, lecturer at the Cracow School of Theoretical Physics in 1977 and 1994, and the author of two the most cited articles ever published in our journal: «Second Threshold in Weak Interactions» [Acta Phys. Pol. B 8, 475 (1977)] and «The Infrared–Ultraviolet Connection» [Acta Phys. Pol. B 12, 437 (1981)]