115 research outputs found
Effect of the analytic and frozen coupling constants in QCD up to NNLO from DIS data
We give a short review of our recent analysis [1] of the deep inelastic
scattering data (provided by BCDMS, SLAC, NMC) on F2 structure function in the
non-singlet approximation with up to next-to-next-to-leading-order accuracy and
analytic and frozen modifications of the strong coupling constant featuring no
unphysical singularity (the Landau pole). Improvement of agreement between
theory and experiment, with respect to the case of the standard perturbative
definition of the strong coupling constant considered recently in [2], was
observed.Comment: 28pp, 7 figs, contribution to the Proceedings of XLV PNPI Winter
School held in Roschino (Russia) on 28 feb - 5 March, 201
About QCD coupling constant at NNLO from DIS data
We give a brief review of our recent QCD analysis carried out over the deep
inelastic scattering data on F2 structure function and in the non-singlet
approximation to the accuracy up to next-to-next-to-leading-order.
Specifically, analysis was performed over high statistics deep inelastic
scattering data provided by BCDMS, SLAC, NMC and BFP collaborations. For the
coupling constant the following value alpha_s(M_Z^2) = 0.1167 \pm 0.0022 was
found.Comment: 11 pp, 2 figs, contribution to the Proceedings of XLIV PNPI Winter
School held in Roschino (Russia) on 9-14 March, 201
Analytic and "frozen" QCD coupling constants up to NNLO from DIS data
Deep inelastic scattering data on the F_2 structure function provided by the
BCDMS, SLAC and NMC collaborations are analyzed in the non-singlet
approximation with the analytic and "frozen" modifications of the strong
coupling constant featuring no unphysical singularity (the Landau pole).
Improvement of agreement between theory and experiment, with respect to the
case of the standard perturbative definition of alpha_s considered recently, is
observed and the behavior of the higher twist terms in the
next-to-next-to-leading-order is found to be confirming earlier studies on the
subject.Comment: 22 pp, 8 fig
An approach to NLO QCD analysis of the semi-inclusive DIS data with modified Jacobi polynomial expansion method
It is proposed the modification of the Jacobi polynomial expansion method
(MJEM) which is based on the application of the truncated moments instead of
the full ones. This allows to reconstruct with a high precision the local quark
helicity distributions even for the narrow accessible for measurement Bjorken
region using as an input only four first moments extracted from the data in
NLO QCD. It is also proposed the variational (extrapolation) procedure allowing
to reconstruct the distributions outside the accessible Bjorken region
using the distributions obtained with MJEM in the accessible region. The
numerical calculations encourage one that the proposed variational
(extrapolation) procedure could be applied to estimate the full first
(especially important) quark moments
On QCD -evolution of Deuteron Structure Function for
The deep-inelastic deuteron structure function (SF) in the
covariant approach in light-cone variables is considered. The and
-dependences of SF are calculated. The QCD analysis of generated data both
for non-cumulative ranges was performed. It was
shown that -evolution of SF is valid for ranges and
for the same value of QCD scale parameter . It was
found the -dependence of SF for the ranges is essentially different.Comment: LaTeX, 10 pages, 2 Postscript figure
NNLO QCD contributions to the flavor non-singlet sector of
We present the results of our QCD analysis for nonsinglet unpolarized quark
distributions and structure function . New parameterizations are
derived for the nonsinglet quark distributions for the kinematic wide range of
and . The analysis is based on the Jacobi polynomials expansion of the
structure function. The higher twist contributions of proton and deuteron
structure function are obtained in the large region. Our calculations for
nonsinglet unpolarized quark distribution functions based on the Jacobi
polynomials method are in good agreement with the other theoretical models. The
values of and are determined.Comment: 29 pages, 8 figure
Nuclear Polarization of Molecular Hydrogen Recombined on a Non-metallic Surface
The nuclear polarization of molecules formed by recombination
of nuclear polarized H atoms on the surface of a storage cell initially coated
with a silicon-based polymer has been measured by using the longitudinal
double-spin asymmetry in deep-inelastic positron-proton scattering. The
molecules are found to have a substantial nuclear polarization, which is
evidence that initially polarized atoms retain their nuclear polarization when
absorbed on this type of surfac
First Measurement of the Transverse Spin Asymmetries of the Deuteron in Semi-Inclusive Deep Inelastic Scattering
First measurements of the Collins and Sivers asymmetries of charged hadrons
produced in deep-inelastic scattering of muons on a transversely polarized
6-LiD target are presented. The data were taken in 2002 with the COMPASS
spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins
asymmetry turns out to be compatible with zero, as does the measured Sivers
asymmetry within the present statistical errors.Comment: 6 pages, 2 figure
Measurement of Angular Distributions and R= sigma_L/sigma_T in Diffractive Electroproduction of rho^0 Mesons
Production and decay angular distributions were extracted from measurements
of exclusive electroproduction of the rho^0(770) meson over a range in the
virtual photon negative four-momentum squared 0.5< Q^2 <4 GeV^2 and the
photon-nucleon invariant mass range 3.8< W <6.5 GeV. The experiment was
performed with the HERMES spectrometer, using a longitudinally polarized
positron beam and a ^3He gas target internal to the HERA e^{+-} storage ring.
The event sample combines rho^0 mesons produced incoherently off individual
nucleons and coherently off the nucleus as a whole. The distributions in one
production angle and two angles describing the rho^0 -> pi+ pi- decay yielded
measurements of eight elements of the spin-density matrix, including one that
had not been measured before. The results are consistent with the dominance of
helicity-conserving amplitudes and natural parity exchange. The improved
precision achieved at 47 GeV,
reveals evidence for an energy dependence in the ratio R of the longitudinal to
transverse cross sections at constant Q^2.Comment: 15 pages, 15 embedded figures, LaTeX for SVJour(epj) document class
Revision: Fig. 15 corrected, recent data added to Figs. 10,12,14,15; minor
changes to tex
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