41 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
Impact of double-logarithmic electroweak radiative corrections on the non-singlet structure functions at small x
In the QCD context, the non-singlet structure functions of u and d -quarks
are identical, save the initial quark densities. Electroweak radiative
corrections, being flavor-dependent, bring further difference between the
non-singlets. This difference is calculated in the double-logarithmic
approximation and the impact of the electroweak corrections on the non-singlet
intercepts is estimated numerically.Comment: 17 pages, no figure
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
Perturbative power Q^2-corrections to the structure function g(1)
We prove that regulating infrared divergencies generates power (~1/(Q^2)^k)
corrections to the spin structure function g_1 at small x and large Q^2. At the
same time it leads to the corrections ~(Q^2)^k at small Q^2. We present the
explicit series of such terms as well as the formulae for their resummation.
These contributions are not included in the standard analysis of the
experimental data. We argue that accounting for such terms can sizably change
the impact of the other power corrections conventionally attributed to the
higher twists.Comment: Theoretical grounds for our approach are considered in much more
detailed way than in the previous version; 10 pages, 2 figure
An Analytical Expression for the Non-Singlet Structure Functions at Small in the Double Logarithmic Approximation
A simple analytic expression for the non-singlet structure function
is given. The expression is derived from the result of Ref. [1] obtained by low
resummation of the quark ladder diagrams in the double logarithmic
approximation of perturbative QCD.Comment: 5 pages, A few comments and refs are adde
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
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
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
QCD running coupling effects for the non-singlet structure function at small x
A generalization of the leading-order DGLAP evolution at small x is performed
for the non-singlet structure function by resumming the leading-order DGLAP
anomalous dimension to all orders in the QCD coupling. Explicit expressions are
obtained for the non-singlet structure function of the deep inelastic
scattering, taking into account both the double-logarithmic and the
single-logarithmic contributions, including the running alpha_s effects. It is
shown that when these contributions are included, the asymptotic small-x
behaviour is power-like, with an exponent of about 0.4.Comment: Latex, 20 pages, 7 figure