11,201 research outputs found
NLO QCD method of the polarized SIDIS data analysis
Method of polarized semi-inclusive deep inelastic scattering (SIDIS) data
analysis in the next to leading order (NLO) QCD is developed. Within the method
one first directly extracts in NLO few first truncated (available to
measurement) Mellin moments of the quark helicity distributions. Second, using
these moments as an input to the proposed modification of the Jacobi polynomial
expansion method (MJEM), one eventually reconstructs the local quark helicity
distributions themselves. All numerical tests demonstrate that MJEM allows us
to reproduce with the high precision the input local distributions even inside
the narrow Bjorken region accessible for experiment. It is of importance
that only four first input moments are sufficient to achieve a good quality of
reconstruction. The application of the method to the simulated SIDIS data on
the pion production is considered. The obtained results encourage one that the
proposed NLO method can be successfully applied to the SIDIS data analysis. The
analysis of HERMES data on pion production is performed. To this end the pion
difference asymmetries are constructed from the measured by HERMES standard
semi-inclusive spin asymmetries. The LO results of the valence distribution
reconstruction are in a good accordance with the respective leading order SMC
and HERMES results, while the NLO results are in agreement with the existing
NLO parametrizations on these quantities
Magnetic phase diagram of a frustrated ferrimagnetic ladder: Relation to the one-dimensional boson Hubbard model
We study the magnetic phase diagram of two coupled mixed-spin
Heisenberg chains as a function of the frustration parameter related to
diagonal exchange couplings. The analysis is performed by using spin-wave
series and exact numerical diagonalization techniques. The obtained phase
diagram--containing the Luttinger liquid phase, the plateau phase with a
magnetization per rung , and the fully polarized phase--is closely
related to the generic phase diagram of the one-dimensional boson
Hubbard model.Comment: 4 pages, 2 figure
Isospin breaking in pion-nucleon scattering at threshold by radiative processes
We investigate the dispersive contribution by radiative processes such as
(pi- proton to neutron gamma) and (pi- proton to Delta gamma) to the
pion-nucleon scattering lengths of charged pions in the heavy baryon limit.
They give a large isospin violating contribution in the corresponding isoscalar
scattering length, but only a small violation in the isovector one. These terms
contribute 6.3(3)% to the 1s level shift of pionic hydrogen and give a chiral
constant F_pi^2f_1=-25.8(8) MeV.Comment: 9 pages with 1 figur
NLO QCD procedure of the semi-inclusive deep inelastic scattering data analysis with respect to the light quark polarized sea
The semi-inclusive deep inelastic scattering (SIDIS) process is considered. A
theoretical procedure is proposed allowing the direct extraction from the SIDIS
data of the first moments of the polarized valence distributions and of the
first moment difference of the light sea quark polarized distributions in the
next to leading QCD order. The validity of the procedure is confirmed by the
respective simulations
Direct extraction of transversity and its accompanying T-odd distribution from the unpolarized and single-polarized Drell-Yan processes
The Drell-Yan (DY) processes with unpolarized colliding hadrons and with the
single transversally polarized hadron are considered. The possibility of direct
(without any model assumptions) extraction of both transversity and its
accompanying T-odd parton distribution functions (PDF) is discussed. For DY
processes measurements planned at GSI the preliminary estimations demonstrate
that it is quite real to extract both transversity and its accompanying T-odd
PDF in the PAX conditions
The effect of Al2O3-MgO additives on the microstructure of spark plasma sintered silicon nitride
It was shown that spark plasma sintered silicon nitride with a high content of Al2O3 and MgO consists of α and β silicon nitride, the main phase being α silicon nitride. The increase in the sintering temperature did not lead to significant changes in the phase composition as occurs in silicon nitride added with Al2O3-Y2O3. It was found that increasing in SPS temperature above 1650 ° C leads to an insignificant increase in the density. A complex shaped equiaxed grain microstructure was shown in both case
Ferrimagnetic mixed-spin ladders in weak and strong coupling limits
We study two similar spin ladder systems with the ferromagnetic leg coupling.
First model includes two sorts of spins, s= 1/2 and s= 1, and the second model
comprises only s=1/2 legs coupled by a "triangular" rung exchange. The
antiferromagnetic (AF) rung coupling destroys the long-range order and
eventually makes the systems equivalent to the AF s=1/2 Heisenberg chain. We
investigate the situation by different methods in weak and strong rung coupling
limits. Particularly we compare the spin-wave theory and the bosonization
method in the weak coupling regime of the second model. We analyze the spectra
and correlations, and discuss the order parameter of these ladder systems.Comment: 12 pages, 4 figure
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
- …