Processes of heavy quark pair (lepton pair) and two gluon (two photon) production in the high energy quark (electron) proton peripheral collisions

We considered the three jet production processes in the region of the incident lepton, photon, quark or gluon fragmentation. The fourth jet is created by the recoil proton. The kinematics of jet production is discussed in jets production in the fragmentation region. The non-trivial relation between the momenta of the recoil proton and the polar angle of its emission was derived. Based on this formalism the differential cross sections of QCD processes $gp \to (ggg) p; \,\,\,qp \to (q \bar{Q} Q) p; \,\,\, gp \to (g Q \bar{Q})p$ were obtained, including the distribution on transverse momentum component of jets fragments. It was shown that the role of the contribution of "non-Abelian" nature may become dominant in a particular kinematics of the final particles. The kinematics, in which the initial particle changes the direction of movement to the opposite one, was considered in the case of heavy quark-antiquark pair production. Different distributions, including spectral, azimuthal and polar angle distribution on the fragments of jets can be arranged using our results. We present besides the behavior of the ratio of non-Abelian contribution to the cross section to the total contribution. We show that it dominates for large values of the transverse momenta of jets component (gluons or quarks). Some historical introduction to the cross-sections of peripheral processes, including 2$\gamma$ creation mechanism production, including the result Brodsky-Kinoshita-Terazawa, is given.Comment: 25 pages, 4 figures, 5 table

Nonlinear effects in Compton scattering at photon colliders

The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e->gamma conversion the density of laser photons in the conversion region should be so high that simultaneous interaction of one electron with several laser photons is possible (nonlinear Compton effect). In this paper a detailed consideration of energy spectra, helicities of final photons and electrons in nonlinear backward Compton scattering of circularly polarized laser photons is given. Distributions of gamma-gamma luminosities with total helicities 0 and 2 are investigated. Very high intensity of laser wave leads to broadening of the energy (luminosity) spectra and shift to lower energies (invariant masses). Beside complicated exact formulae, approximate formulae for energy spectrum and polarization of backscattered photons are given for relatively small nonlinear parameter xi^2 (first order correction). All this is necessary for optimization of the conversion region at photon colliders and study of physics processes where a sharp edge of the luminosity spectrum and monochromaticity of collisions are important.Comment: 21 pages, Latex, 6 figures(.ps), Talk at International Workshop on High Energy Photon Colliders; June 14-17, 2000, DESY, Hamburg, Germany; to be published in Nucl. Instr. and Methods

Single-Spin Asymmetries for Small-Angle Pion Production in High-Energy Hadron Collisions

Within the framework of a simple model, we study single-spin asymmetries for pion production in hadron-hadron collisions at high-energies with one hadron polarised. The asymmetries are generated via a mechanism of final (initial) state interactions. For peripheral kinematics, when the pion belongs to the fragmentation region of the polarised proton, we find non-zero asymmetries in the high-energy limit. Numerical results and comparision with existing experimental data are presented. We also discuss the relationship with odderon exchange phenomenology.Comment: LaTeX2e, 12 pages, 4 figure files (2 TeX and 2 eps), uses axodraw, and cite packages; submitted to Eur. Phys. J

Quadratic electroweak corrections for polarized Moller scattering

The paper discusses the two-loop (NNLO) electroweak radiative corrections to the parity violating electron-electron scattering asymmetry induced by squaring one-loop diagrams. The calculations are relevant for the ultra-precise 11 GeV MOLLER experiment planned at Jefferson Laboratory and experiments at high-energy future electron colliders. The imaginary parts of the amplitudes are taken into consideration consistently in both the infrared-finite and divergent terms. The size of the obtained partial correction is significant, which indicates a need for a complete study of the two-loop electroweak radiative corrections in order to meet the precision goals of future experiments

Near threshold radiative 3π\pi production in e+e−e^+e^- annihilation

We consider the $\pi^+\pi^-\pi_0\gamma$ final state in electron-positron annihilation at cms energies not far from the threshold. Both initial and final state radiations of the hard photon is considered but without interference between them. The amplitude for the final state radiation is obtained by using the effective Wess-Zumino-Witten Lagrangian for pion-photon interactions valid for low energies. In real experiments energies are never such small that $\rho$ and $\omega$ mesons would have negligible effect. So a phenomenological Breit-Wigner factor is introduced in the final state radiation amplitude to account for the vector mesons influence. Using radiative 3$\pi$ production amplitudes, a Monte Carlo event generator was developed which could be useful in experimental studies.Comment: 15 pages, Latex, 6 figures. Misprints corrected. Version to be published in JHE

QED Corrections to Deep Inelastic Scattering with Tagged Photons at HERA

We calculate the QED corrections to deep inelastic scattering with tagged photons at HERA in the leading logarithmic approximation. Due to the special experimental setup, two large scales appear in the calculation that lead to two large logarithms of comparable size. The relation of our formalism to the conventional structure function formalism is outlined. We present some numerical results and compare with previous calculations.Comment: 7 pages, REVTeX, 2 figures; published versio

Signs of Intermediate Range Hadronic Forces

We consider high energy hadron-hadron scattering. We show the presence in the amplitude of terms of the form is(q 2 =m 4 ) ln(\Gammaq 2 =m 2 ) for transferred momentum squared m 2 hadr ?? \Gammaq 2 2 QCD and p s AE m. We relate such terms to a novel interaction at impact distances ae ?? 1=m hadr with a potential of the form V (ae) ¸ ae \Gamma4 . In the particular cases of photon-photon and pion-pion elastic scattering it appears that higher orders of perturbation theory do modify the lowest order result by a function of ff s ß ln s m 2 ln m 2 \Gammaq 2 . The relation with the structure of the diffractive cone at very small transferred momentum and some possible ways to detect these intermediate range effects are briefly discussed. Introduction It is well known since long time that, for the description of the high energy peripheral scattering and differently from the hard scattering, it is natural to use the impact factor representation [1, 2]. According..