105 research outputs found
The NNLO QCD analysis of the CCFR data for xF_3: is there still the room for the twist-4 terms?
The results of the more detailed NNLO QCD analysis of the CCFR data for
SF are presented. The factorization scale uncertainties are analysed.
The NNLO results for and twist-4 contributions are obtained.
Despite the fact that the amplitude of the -shape of the twist-4 factor is
consequently decreasing at the NLO and NNLO, our new QCD analysis seems to
reveal the remaining twist-4 structure at the NNLO level. The definite NLO
uncertainties are fixed using the [0/2] Pad\'e resummation technique.Comment: LaTeX, 3 pages, 1 figure; to be published in the Proceedings of DIS99
Workshop, Zeuthen, April 19-23; some technical shortcomings are fixed in the
file, 2 referencies correcte
Conformational effects in non-stoichiometric complexes of two hyperbranched molecules with a linear polyelectrolyte
We report results from Brownian dynamics computer simulations of systems comprised by two terminally charged hyperbranched molecules preferentially branched in the periphery, with an oppositely charged linear chain of varying length. Comparison of the findings from the present study to stoichiometric counterparts and to analogous dendrimer-based complexes, reveal that the presence of the second hyperbranched molecule incurs significant changes in the conformational characteristics of both components of the complex. Instead of step-like changes in the average size and shape of the hyperbranched component that were noted in the previously studied stoichiometric systems, a rather smooth change is observed upon increase of the length of the linear component. In addition, a markedly different behavior is also noticed in the conformational characteristics of the linear chain when compared to that in similar dendrimer-based systems. The above findings are consistent with the higher degree of deformability of the peripherally branched molecules which allow appropriate rearrangements in shape in order to accommodate the favorable Coulombic interactions between the two components of the complex. This behavior offers new insight towards the design of more efficient hyperbranched-based systems which can take advantage of the multifunctionality and the structural properties of the highly branched polymer components
The 16th moment of the three loop anomalous dimension of the non-singlet transversity operator in QCD
We present the result of the three loop anomalous dimension of non-singlet
transversity operator in QCD for the Mellin moment N=16. The obtained result
coincides with the prediction from arXiv:1203.1022 and can serve as a
confirmation of the correctness of the general expression for three loop
anomalous dimension of non-singlet transversity operator in QCD for the
arbitrary Mellin moment.Comment: 7 pages, 1 figure, minor changes in the tex
Decoupling of heavy quarks in HQET
Decoupling of c-quark loops in b-quark HQET is considered. The decoupling
coefficients for the HQET heavy-quark field and the heavy-light quark current
are calculated with the three-loop accuracy. The last result can be used to
improve the accuracy of extracting f_B from HQET lattice simulations (without
c-quark loops). The decoupling coefficient for the flavour-nonsinglet QCD
current with n antisymmetrized gamma-matrices is also obtained at three loops;
the result for the tensor current (n=2) is new.Comment: JHEP3 documentclass; the results in a computer-readable form can be
found at http://www-ttp.physik.uni-karlsruhe.de/Progdata/ttp06/ttp06-25/ V2:
a few typos corrected, a few minor text improvements, a few references added;
V3: several typos in formulas fixe
Next-to-Next-to-Leading Order QCD Analysis of DIS Structure Functions
It is performed for the first time a next-to-next-to-leading order analysis
of deep inelastic structure functions and using the recently
determined first moments of the non-singlet anomalous dimensions and the
corresponding Wilson coefficients. {}From a comparison to BCDMS data we found a
slight decrease in the energy scale of perturbative QCD with respect to the
next-to-leading order analysis, which brings the scale closer to the value
predicted from a scheme invariant approach.Comment: Latex 12 pages, 2 figures available on request, preprint UCI-TR/94-
Next-to-next-to-leading order prediction for the photon-to-pion transition form factor
We evaluate the next-to-next-to-leading order corrections to the
hard-scattering amplitude of the photon-to-pion transition form factor. Our
approach is based on the predictive power of the conformal operator product
expansion, which is valid for a vanishing -function in the so-called
conformal scheme. The Wilson--coefficients appearing in the non-forward
kinematics are then entirely determined from those of the polarized
deep-inelastic scattering known to next-to-next-to-leading accuracy. We propose
different schemes to include explicitly also the conformal symmetry breaking
term proportional to the -function, and discuss numerical predictions
calculated in different kinematical regions. It is demonstrated that the
photon-to-pion transition form factor can provide a fundamental testing ground
for our QCD understanding of exclusive reactions.Comment: 62 pages LaTeX, 2 figures, 9 tables; typos corrected, some references
added, to appear in Phys. Rev.
Higher twists and extractions from the NNLO QCD analysis of the CCFR data for structure function
A detailed next-to-next-to-leading order (NNLO) QCD analysis is performed for
the experimental data of the CCFR collaboration for the structure
function. Theoretical ambiguities of the results of our NNLO fits are estimated
by application of the Pad\'e resummation technique and variation of the
factorization and renormalization scales. The NNLO and NLO
-matching conditions are used. In the process of the fits we are
taking into account of twist-4 -terms. We found that the amplitude of
the -shape of the twist-4 factor is decreasing in NLO and NNLO, though some
remaining twist-4 structure seems to retain in NNLO in the case when
statistical uncertainties are taken into account. The question of the stability
of these results to the application of the [0/2] Pad\'e resummation technique
is considered. Our NNLO results for values, extracted from the
CCFR data, are provided the twist-4 contributions are fixed through the
infrared renormalon model and provided the twist-4 terms are considered as
free parameters.Comment: 33 pages LaTeX, 3 ps figures; minor misprints are eliminated, 2 new
referencies are added; accepted for publication in Nucl. Phys.
QCDMAPT: program package for Analytic approach to QCD
A program package, which facilitates computations in the framework of
Analytic approach to QCD, is developed and described in details. The package
includes the explicit expressions for relevant spectral functions calculated up
to the four-loop level and the subroutines for necessary integrals.Comment: 18 pages, 4 figures; QCDMAPT package is available from
http://cpc.cs.qub.ac.uk/summaries/AEGP_v1_0.htm
Small x behaviour of parton distributions with soft initial conditions
We present an analytical parametrization of the QCD description of the small
x behaviour of parton distribution functions in the leading twist approximation
of the Wilson operator product expansion, in the case of soft initial
conditions. The results are in very good agreement with deep inelastic
scattering experimental data from HERA.Comment: 21 pages, latex + 3 ps figure
Microwave diagnostic system of the Uragan-2М torsatron
The construction of microwave sections together with results of loss calculation in the microwave lines for different frequencies are presented. The construction of microwave lead-ins is also described. The whole system has been well-tested on the Uragan-2M torsatron in conditions of SHF and RF cleaning at a low magnetic field, and of pulse regime with a higher magnetic field up to 6 kOe. The results of testing are illustrated by temporal evolutions of plasma density and by digitalized signals from the detector.Представлено конструкції НВЧ-трактів з розрахунком втрат в лініях на різних частотах і конструкції НВЧ- введень. НВЧ-комплекс, що описано, був випробуваний на торсатроні Ураган-2М в режимах НВЧ- і ВЧ- чищення при низькій напруженості магнітного поля, а також в імпульсному режимі з магнітним полем до 6 кЕ. Результати вимірювань ілюструються часовими залежностями густини і цифровими сигналами, отриманими з детектора.Представлены конструкции СВЧ-трактов с расчетом потерь в линиях на различных частотах и конструкции СВЧ-вводов. Описанный СВЧ-комплекс испытан на торсатроне Ураган-2М в режимах СВЧ- и ВЧ- чистки при низкой напряженности магнитного поля, а также в импульсном режиме с магнитным полем до 6 кЭ. Результаты измерений иллюстрируются временными зависимостями плотности и цифровыми сигналами, полученными с детектора
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