1,354 research outputs found
On the forward-backward charge asymmetry in e+e- -annihilation into hadrons at high energies
The forward-backward asymmetry in e+ e- annihilation into a quark-antiquark
pair is considered in the double-logarithmic approximation at energies much
higher than the masses of the weak bosons. It is shown that after accounting to
all orders for the exchange of virtual photons and W, Z -bosons one is lead to
the following effect (asymmetry): quarks with positive electric charge (e.g. u,
\bar{d}) tend to move in the e+ - direction whereas quarks with negative
charges (e.g. d, \bar{u}) tend to move in the e- - direction. The value of the
asymmetry grows with increasing energy when the produced quarks are within a
cone with opening angle, in the cmf, \theta_0\sim 2M_Z/\sqrt{s} around the e+e-
-beam. Outside this cone, at \theta_0 << \theta << 1, the asymmetry is
inversely proportional to \theta .Comment: 17 Pages, 2 Tables, 4 Figures. Hadronization effects to the asymmetry
are considered with more detail
Comment on the recent COMPASS data on the spin structure function g_1
We examine the recent COMPASS data on the spin structure function g_1
singlet. We show that it is rather difficult to use the data in the present
form in order to draw conclusions on the initial parton densities. However, our
tentative estimate is that the data better agree with positive rather than
negative initial gluon densities.Comment: 8 pages, 1 figur
Intercepts of the non-singlet structure functions
Infrared evolution equations for small- behaviour of the non-singlet
structure functions and are obtained and solved in the
next-to-leading approximation, to all orders in , and including
running effects. The intercepts of these structure functions, i.e.
the exponents of the power-like small- behaviour, are calculated. A detailed
comparison with the leading logarithmic approximation (LLA) and DGLAP is made.
We explain why the LLA predictions for the small- dependence of the
structure functions may be more reliable than the prediction for the
dependence in the range of explored at HERA.Comment: 26 pages, LaTeX, 5 Postscript figure
Double-logarithmic asymptotics of the electromagnetic form factors of the electron and quark
The asymptotic behaviour of the electromagnetic form factors of the electron
and quark is obtained in the double-logarithmic approximation for Sudakov
kinematics, i.e. for the case that the value of the momentum transfer is much
greater than the mass of the particle.Comment: RevTeX, aps.sty, epsf.sty, 16 pp, 5 fig
Production of electroweak bosons in e+e- annihilation at high energies
Production of electroweak bosons in e+e- annihilation into quarks and into
leptons at energies much greater than 100 Gev is considered. We account for
double-logarithmic contributions to all orders in electroweak couplings. It is
assumed that the bosons are emitted in the multi-Regge kinematics. The explicit
expressions for the scattering amplitudes of the process are obtained. It is
shown that the cross sections of the photon and Z production have the identical
energy dependence and asymptotically their ratio depends only on the Weinberg
angle whereas the energy dependence of the cross section of the W production is
suppressed by factor s^{-0.4} compared to them.Comment: Revtex4, 16 pages, 7 figures, 2 table
Treatment of the QCD coupling in high energy processes
The treatment of the running QCD coupling in evolution equations is
discussed. It is shown that the use of the virtuality of ladder (vertical)
partons as the scale for QCD coupling in every rung of ladder graphs is an
approximation that holds for DIS at large x only. On the contrary, in the small
x region the coupling depends on the virtuality of s -channel (horizontal)
gluons. This observation leads to different results for the Regge-like
processes and DIS structure functions at small x.Comment: RevTeX 6 pages, 6 figures epsf.st
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