共查询到20条相似文献,搜索用时 15 毫秒
1.
We present a new analysis of the helicity parton distributions of the nucleon. The analysis takes into account the available data from inclusive and semi-inclusive polarized deep inelastic scattering, as well as from polarized proton-proton (p-p) scattering at RHIC. For the first time, all theoretical calculations are performed fully at next-to-leading order (NLO) of perturbative QCD, using a method that allows incorporation of the NLO corrections in a very fast and efficient way in the analysis. We find evidence for a rather small gluon polarization in the nucleon, over a limited region of momentum fraction, and for interesting flavor patterns in the polarized sea. 相似文献
2.
O. Yu. Shevchenko R. R. Akhunzyanov V. Yu. Lavrentyev 《The European Physical Journal C - Particles and Fields》2011,71(8):1713
The first moments of the polarized valence parton distribution functions (PDFs) truncated to the wide Bjorken x region 0.004<x<0.7 are directly (without any fitting procedure) extracted in the next to leading order (NLO) QCD from both COMPASS and HERMES
data on pion production in polarized semi-inclusive DIS (SIDIS) experiments. The COMPASS and HERMES data are combined in two
ways and two scenarios for the fragmentation functions (FFs) are considered. Two procedures are proposed for an estimation
of light sea quark contributions to the proton spin. Both lead to the conclusion that these contributions are compatible with
zero within the errors. 相似文献
3.
4.
We study the transverse momentum dependent factorization for single spin asymmetries in Drell-Yan and semi-inclusive deep inelastic scattering processes at one-loop order. The next-to-leading order hard factors are calculated in the Ji-Ma-Yuan factorization scheme. We further derive the QCD resummation formalisms for these observables following the Collins-Soper-Sterman method. The results are expressed in terms of the collinear correlation functions from initial and/or final state hadrons coupled with the Sudakov form factor containing all order soft-gluon resummation effects. The scheme-independent coefficients are calculated up to one-loop order. 相似文献
5.
We perform a detailed study of the consistency between different sets of polarized deep inelastic scattering data and theory,
from the standpoint of a next to leading order QCD global analysis, and following the criteria proposed by Collins and Pumplin.
In face of recent suggestions that challenge the usual assumption about parent parton spin independence of unpolarized fragmentation
functions, we specially focus on polarized semi-inclusive data.
Received: 2 December 2002 / Revised version: 6 February 2003 / Published online: 31 March 2003
RID="a"
ID="a" e-mail: sassot@df.uba.ar * Partially supported by Conicet and Fundación Antorchas 相似文献
6.
The first moments of polarized valence parton distribution functions truncated to the wide Bjorken x region 0.004 < x < 0.7 are directly (without any fitting procedure) extracted in the NLO QCD from combined semi-inclusive DIS data of COMPASS and HERMES collaborations. Two scenarios for fragmentation functions are considered. Applying the proposed original procedure to these results we estimate the contributions of sea u and d quarks to the proton spin, which turn out to be simply zero within the errors. 相似文献
7.
We present a summary of QCD formulae describing the effects of scaling violation in leptonhadron processes, with the inclusion of recently derived higher order corrections. Deep inelastic leptoproduction, one-hadron inclusive distributions in leptoproduction and ine + e ? annihilation and Drell-Yan processes are discussed in detail. Higher order corrections to parton densities, fragmentation functions and to lepton-parton cross-sections in the above processes are presented in a common factorization scheme, so that a comparative analysis of various processes as well as an independent analysis of each of them is possible. A discussion of the various scheme dependences at next-to-leading level is also included. 相似文献
8.
The next-to-leading logarithmic corrections to cross-sections for semi-inclusive deep inelastic scattering from a polarized target are worked out. Predictions for pion asymmetries and pion charge ratios are given. 相似文献
9.
The transverse, longitudinal and asymmetric components of the fragmentation function are measured from the inclusive charged
particles produced in collisions at LEP. As in deep inelastic scattering, these data are important for tests of QCD. The transverse and longitudinal components of the total hadronic cross section are evaluated from the measured fragmentation functions. They are found to be and respectively. The strong coupling constant is calculated from in next-to-leading order of perturbative QCD, giving Including non-perturbative power corrections leads to The measured transverse and longitudinal components of the fragmentation function are used to estimate the mean charged multiplicity,
The fragmentation functions and multiplicities in and light quark events are compared. The measured transverse and longitudinal components of the fragmentation function allow
the gluon fragmentation function to be evaluated.
Received: 12 September 1997 / Published online: 19 October 1998 相似文献
10.
We present a new next-to-leading order (NLO) QCD analysis of the world data on inclusive polarized deep inelastic scattering. A new set of polarized parton densities is extracted from the data and the sensitivity of the results to the newly incorporated SLAC/E155 proton data is discussed. 相似文献
11.
The global fit analysis of all published data on DIS and semi-inclusive DIS (SIDIS) asymmetries is performed in the next to leading (NLO) QCD order. The respective parameterization on polarized PDFs is constructed. The especial attention is paid to the impact of novel SIDIS data on the polarized distributions of light sea and strange quarks as well as on the polarized gluon distributions. The first moments of these distributions entering the nucleon spin are found to be surprisingly small quantities. The alternative direct (free of any fitting procedure) method of NLO QCD analysis is elaborated. Method is especially important for analysis of SIDIS data because it allows to avoid the problems arising in the conventional fitting procedure: functional arbitrariness at initial scale and ambiguities in the error band calculation. Within the alternative method the central values and uncertainties of the measured asymmetries directly propagate to the central values and uncertainties of the polarized PDFs we are interested in. The method is applied to all existing SIDIS data on pion production for an estimation in NLO QCD of the valence and sea quark contributions to the proton spin. As a result one arrives at the conclusion that, contrary to the valence contributions, the sea contributions to the proton spin are compatible with zero within the errors. 相似文献
12.
O. Yu. Shevchenko R. R. Akhunzyanov V. Yu. Lavrentyev 《Physics of Particles and Nuclei》2013,44(3):490-493
The first moments of polarized valence PDFs, responsible for the respective contributions to the nucleon spin, are extracted in NLO QCD from the data of COMPASS and HERMES collaborations on the semi-inclusive difference asymmetries. To this end the new method of QCD analysis (alternative to the usual global fit analysis) is applied. Using the obtained results on valence PDFs the first moments of polarized sea PDFs are reconstructed. They turn out surprisingly small: compatible with zeros within the errors. 相似文献
13.
We examine the possibility of using direct photon production at HERA as a means of obtaining information about the photon structure and fragmentation functions. Estimates of the cross section for inclusive prompt photon production at theep collider HERA are made completely in next-to-leading order QCD. Using parton distributions for the photon evolved in next-to-leading order QCD for the first time, we show that theO(
s
) corrections to the processes involving these functions are significant in the regions where they dominate. This can have important consequences for the possibility of measuring the gluon content of the photon using these processes at HERA. Moreover, we show that it may not be straightforward to separate the various contributions to the cross section in theep lab frame. 相似文献
14.
A. Méndez 《Nuclear Physics B》1978,145(1):199-220
We give analytic predictions for angular distributions of hadrons in semi-inclusive and inclusive leptoproduction deduced from first-order calculations in QCD. The predictions allow tests of QCD and give information about gluon fragmentation functions. 相似文献
15.
We study the inclusive photoproduction of neutral and charged pions and at HERA, via the resolved photon mechanism, in QCD to next-to-leading order. We present various distributions of phenomenological interest and study the theoretical uncertainties due to the mass scales, and to photon and proton sets of structure functions. A new set of fragmentation functions for charged pions is also presented. 相似文献
16.
A. Sissakian O. Shevchenko O. Ivanov 《The European Physical Journal C - Particles and Fields》2010,65(3-4):413-421
The combined analysis of polarized DIS and SIDIS data is performed in NLO QCD. The new parametrization on polarized PDFs is constructed. The uncertainties on PDFs and their first moments are estimated applying the modified Hessian method. Special attention is paid to the impact of novel SIDIS data on the polarized distributions of light sea and strange quarks. In particular, the important question of polarized sea symmetry is studied in comparison with the latest results on this subject. 相似文献
17.
M. Botje 《The European Physical Journal C - Particles and Fields》2000,14(2):285-297
The parton momentum density distributions of the proton are determined from a next-to-leading order QCD analysis of structure
functions measured at HERA and by fixed target experiments. Also included are data on the difference of the up and down anti-quark
distributions. The uncertainties in the parton densities, structure functions and related cross sections are estimated from
the experimental errors and those on the input parameters of the fit. Several QCD predictions based on the parton densities
obtained from this analysis are calculated and compared to data.
Received: 21 December 1999 / Published online: 6 April 2000 相似文献
18.
E. Leader A.V. Sidorov D.B. Stamenov 《The European Physical Journal C - Particles and Fields》2002,23(3):479-485
We present a new leading and next-to-leading QCD analysis of the world data on inclusive polarized deep inelastic scattering.
A new set of polarized parton densities is extracted from the data and the sensitivity of the results to the newly incorporated
SLAC/E155 proton data is discussed.
Received: 23 November 2001 / Revised version: 10 January 2002 Published online: 22 February 2002 相似文献
19.
P. Allen J. Blietschau H. Grässler D. Lanske R. Schulte H.H. Seyfert C. Geich-Gimbel T. Kokott B. Nellen R. Pech H. Saarikko P.C. Bosetti D.C. Cundy A. Grant P.O. Hulth D.R.O. Morrison L. Pape B. Saitta 《Nuclear Physics B》1980,176(2):333-345
In a neutrino-proton experiment performed with the bubble chamber BEBC, which was exposed to the wide-band neutrino beam of the CERN SPS, the semi-inclusive reaction νp→μ?h± + X is studied where h± is a hadron of a chosen type. Non-factorization of the semi-inclusive cross section is investigated in terms of double moments with respect to Bjorken-x and the energy fraction z and comparisons are made with predictions of perturbative QCD in next-to-leading order. 相似文献
20.
We discuss relative merits and shortcomings of various methods used in analyses of deep inelastic scattering data within the framework of leading twist QCD perturbation expansion. We advocate the use of Jacobi polynomials method as by far the simples, fastest and simultaneously very accurate way of analysing theQ 2-evolution of nucleon structure functions. Detailed comparison with the numerical solution of the corresponding evolution equation to the next-to-leading order is presented. 相似文献