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The proton spin problem triggered by the EMC experiment and its present status are closely examined. Recent experimental and theoretical progresses and their implications are reviewed. It is pointed out that the sign of the sea-quark…
Requiring the positivity and counting rule, we propose a new parametrization of the polarized parton distribution which reproduce the data well. We found that the NLO analysis is absolutely necessary to extract the correct information on…
We numerically study the effects of high gluon density at small x on the evolution of gluon distribution function in both hadrons and nuclei. Using a newly derived, Wilson renormalization group-based evolution equation which includes n to 1…
The $Q^2$ evolution of polarised parton fragmentation functions is discussed using Altarelli-Parisi evolution equations. The first moments of both polarised quark and gluon fragmentation functions are shown to behave in a similar fashion at…
I begin with a general discussion about importance of constructing a picture of the nucleon in terms of QCD degrees of freedom, emphasizing the role of spin structure functions. I then give a short overview on the theoretical and…
This contribution to CIPANP 2012 highlights what we have learned about the asymmetric parton distributions of the nucleon over the past 20 years. These distributions include the transverse momentum dependent parton distributions describing…
The resummation of $O(\alpha_s^{l+1} \ln^{2l} x)$ terms in the evolution equation of the singlet part of $g_1(x,Q^2)$ is carried out. The corresponding singlet evolution kernels are calculated explicitely. The leading small-$x$ contribution…
We study the splitting functions for the evolution of fragmentation distributions and the coefficient functions for single-hadron production in semi-inclusive electron-positron annihilation in massless perturbative QCD for small values of…
We present generalized evolution equations and factorization in terms of the truncated Mellin moments (TMM) of the parton distributions and structure functions. We illustrate the $x$ and $Q^2$ dependence of TMM in the polarized case. Using…
We summarize recent results on the evolution of unpolarized parton densities and deep-inelastic structure functions in massless perturbative QCD. Due to last year's extension of the integer-moment calculations of the three-loop splitting…
Recent progress in the field of spin physics of high energy particle interactions is reviewed with particular emphasis on the spin structure functions as measured in polarized deep inelastic lepton-nucleon scattering (DIS). New measurements…
The current status of global QCD analysis of parton distribution functions of the nucleon is reviewed. Recent progress made in determining various features of the parton structure of the nucleon, as well as outstanding open questions are…
New experimental results on the spin dependent structure functions g_1 and g_2 which are determined from deep-inelastic scattering experiments at CERN, SLAC and DESY are reported. These results are used to evaluate the Bjorken sum rule and…
We discuss the angular dependence of the recently proposed transverse momentum dependent quark and gluon diffractive parton distributions at small-$x$. We introduce the difractive versions of the Sivers function and the elliptic gluon…
Recent measurements of unpolarised and polarised nucleon structure functions and F_2(gamma) are reviewed. The implications for QCD and the gluon momentum distribution are discussed. The status of the understanding of the total…
We perform a global leading-order QCD fit to recent polarized structure function data in order to extract a consistent set of spin-dependent parton distributions. Assuming that there is no significant intrinsic polarization of the quark…
We extract parton distribution functions (PDFs) and structure functions from recent experimental data of polarized lepton-DIS on nucleons at next-to-leading order (NLO) Quantum Chromodynamics. We apply the Jacobi polynomial method to the…
New polarized fragmentation functions are introduced and justified, in addition to those conventional ones assumed to be independent of the helicity of the parent parton. It is demonstrated that due to our present ignorance concerning these…
The proton spin dependent structure function $g_1^p$ is analysed using the unified scheme incorporating both Altarelli-Parisi evolution and the double $ln^2(1/x)$ effects at low $x$. The latter are found to be very important in the region…
A comprehensive analysis of deep inelastic scattering of polarized charged leptons on polarized nucleons is presented; weak interaction contributions, both in neutral and charged current processes, are taken into account and the parity…