[en] We calculated the color-octet contribution to the double spin asymmetry of J/ψ hadroproduction with nonzero transverse momenta at fixed target energies √ s ≅ 40 GeV. It is shown that color-octet contribution is dominant in the asymmetries. The expected asymmetries and statistical errors in a future option of HERA with longitudinally polarized protons at √ s = 39 GeV (HERA-N polarized) should allow one to distinguish between different parametrizations for polarized gluon distribution in proton

[en] We review the next-to-leading-order cross-sections of the heavy quark-antiquark pair production in linearly polarized photon-photon collision. Implications for the signal of Higgs particles are discussed

[en] We discuss the double spin asymmetries in P-wave charmonium hadroproduction with non-zero transverse momenta at fixed target energies, √(s)≅40 GeV, within the framework of the factorization approach. The size of the asymmetries and the projected statistical errors in a future option of HERA with longitudinally polarized protons scattering off a polarized target (HERA-vectorN) are calculated. Measurements of the χ_c1 and χ_c2 decays into dilepton plus photon should allow to distinguish between different parametrizations for the polarized gluon distribution in the proton. At higher energies (√(s)=200 GeV) the situation appears less favourable with the presently envisaged integrated luminosities of the polarized RHIC collider. (orig.)

[en] Reactions of neutral gauge and Higgs boson pair production in photon-photon collisions are considered on the basis of complete one-loop Standard Model (SM) calculations. (orig.)

[en] We present the cross sections of the heavy quark-antiquark pair production in polarized photon photon collision for the general case of photon polarizations. The numerical results for top-antitop production cross sections together with production asymmetries are obtained for linearly polarized photon-photon collisions, including QCD radiative corrections. (orig.)

[en] We calculate the color-octet contribution to the double spin asymmetry of J/ψ hadroproduction with nonzero transverse momenta at fixed target energies √ (s) ≅40GeV. It is shown that the color-octet contribution is dominant in the asymmetries. The expected asymmetries and statistical errors in a future option of DESY HERA with longitudinally polarized protons at HERA-rvec N should allow one to distinguish between different parametrizations for the polarized gluon distribution in the proton. copyright 1997 The American Physical Society

[en] The semileptonic decays of B_c mesons in the framework of QCD are considered with use of the spectra of the excited state masses of participating mesons. The obtained results are in good agreement with other calculations carried out within QCD sum rules. The reasons for the discrepancy observed between the QCD sum-rule data and the quark models are discussed. It is shown how to eliminate these discrepancies using higher QCD corrections

[en] Perturbative QCD one-loop corrections to the cross sections of the b anti b (c anti c ) quark pair production in polarized photon-photon collisions, as well as cross sections of the radiative processes γγ→b anti b g, c anti c g leading to two- and three-jet final states are calculated. It is shown that the signal from the intermediate mass Higgs boson is observable and precise measurements of the Higgs boson two-photon width are possible at a photon-photon collider, although the statistical significance is substantially reduced with respect to the tree level calculations. We demonstrate that virtual corrections are of the same order or larger than the Born contribution in the J_z=0 channel at high energy for small values of the cut-off y_cut, separating two-jet from three-jet topologies. The nature of these large corrections is elucidated. For b anti b pair production at √s_γγ ∼ 100 GeV and for small values of y_cut≤0.04 the higher order resummation of double logarithmic terms O(α_sm_b²/s 1n² (s/m_b²)) is needed. 29 refs., 9 figs., 1 tab

[en] We present production rates of the two- and three-jet final states for the processes of massive cc/bb quark production in circularly polarized photon-photon collisions, including QCD radiative corrections. Lowest-order cross section, one-loop virtual correction, and gluon emission correction are shown to be of the same order of magnitude for bb quark production at s_γγ similar 100 GeV. It is shown that the signal from an intermediate mass Higgs boson is observable at a photon-photon collider, though the statistical significance is substantially reduced with respect to the tree-level calculation. ((orig.))

[en] Perturbative QCD one-loop corrections to the cross sections of the b bar b(c bar c) quark pair production in polarized photon-photon collisions, as well as cross sections of the radiative processes γγ→b bar bg, c bar cg, leading to two- and three-jet final states are calculated. It is shown that the signal from the intermediate-mass Higgs boson is observable and precise measurements of the Higgs boson two-photon width are possible at a photon-photon collider, although the statistical significance is substantially reduced with respect to the tree-level calculations. We demonstrate that virtual corrections are of the same order as or larger than the Born contribution in the J_z=0 channel at high energy for small values of the cutoff y_cut separating two-jet from three-jet topologies. The nature of these large corrections is elucidated. For b bar b pair production at √s_γγ∼100 GeV and for small values of y_cut≤0.04 the higher-order resummation of double logarithmic terms O(α_sm²_b/sln²(s/m²_b)) is needed. copyright 1996 The American Physical Society