A new combined next to leading order QCD analysis of the polarized inclusive and semi-inclusive deep inelastic lepton-hadron scattering (DIS) data is presented. In contrast previous analyses, $1/{Q}^{2}$ terms (kinematic---target mass corrections, dynamic---higher twist corrections) in expression for nucleon spin structure function ${g}_{1}$ are taken into account. The COMPASS included analysis. impact on parton densities (PDFs) higher corrections discussed. results PDFs compared our...

It is shown that if standard methods are used to apply the Regge-pole theory relativistic problems in which external particles have nonzero spin, then there exist constraint equations enforce relationships between residue and trajectory functions of participating poles region $t\ensuremath{\sim}0$. The follow directly from general quantum-mechanical principles it therefore essential satisfy them. Moreover, number increases roughly as fourth power spin particles. structure also differs...

The Mandelstam representation is used to derive fixed-angle dispersion relations for the twelve scalar amplitudes describing process $\ensuremath{\gamma}+N\ensuremath{\rightarrow}\ensuremath{\gamma}+N$. electromagnetic interaction calculated order ${e}^{2}$. strong interactions are estimated by including one- and two-pion exchange on left-hand cut. These depend ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ decay lifetime $T=0$ $\ensuremath{\pi}\ensuremath{\pi}$ phase...

We have reanalyzed the world data on inclusive polarized DIS, in both NLO and LO QCD, including new HERMES COMPASS data. The updated densities are given $\overline{\mathrm{MS}}$ JET schemes. impact of results is discussed.

The high energy and large ${p}_{T}$ inclusive polarized process, $(A,{S}_{A})+(B,{S}_{B})\ensuremath{\rightarrow}C+X$, is considered under the assumption of a generalized QCD factorization scheme. For first time all transverse motions, partons in hadrons fragmenting partons, are explicitly taken into account; elementary interactions computed at leading order with noncollinear exact kinematics, which introduces many phases expressions their helicity amplitudes. Several new spin...

We have reanalyzed the world data on inclusive polarized deep inelastic scattering (DIS) including very precise CLAS proton and deuteron data, as well latest COMPASS asymmetry ${A}_{1}^{d}$, studied impact of these parton densities higher twist effects. demonstrate that low ${Q}^{2}$ improve essentially our knowledge corrections to spin structure function ${g}_{1}$, while large influence mainly strange quark density. In new analysis we find a negative gluon density, or one changes sign $x$,...

The numerical results of a dispersive theory for nucleon-nucleon scattering developed in previous papers are presented $d$ and higher waves. Phase parameters as function the energy given up to 400 MeV. ingredients theory---which evaluates $2\ensuremath{\pi}$ exchanges---are amplitudes that obtained from theoretical analyses simpler processes ($\ensuremath{\pi}\ensuremath{-}N$ scattering, nuclear electromagnetic form factors, etc.). Of these ingredients, those which describe low-wave ($s$...

We present a study of the tensorial structure hadronic matrix elements angular momentum operators $\mathbit{J}$. Well known results in literature are shown to be incorrect, and we have taken pains derive correct expressions three different ways, two involving explicit physical wave packets third, totally independent, based upon rotational properties state vectors. Surprisingly it turns out that very sensitive type relativistic spin used describe motion particle, i.e., whether canonical...

Abstract

Beautiful interference phenomena should be seen in many spin-dependent observables for the collision of spin-half hadrons. The occur both charged particles and neutral with particles. Of most direct interest are reactions $\mathrm{pp}\ensuremath{\rightarrow}\mathrm{pp}$, $\mathrm{np}\ensuremath{\rightarrow}\mathrm{np}$, $\ensuremath{\Lambda}p\ensuremath{\rightarrow}\ensuremath{\Lambda}p$. Much information about phases helicity-flip amplitudes near forward direction can obtained from...

A major controversy has arisen in QCD as to how split the total angular momentum into separate quark and gluon contributions, whether can itself be split, a gauge invariant way, spin orbital part. Several authors have proposed various answers these questions offered variety of different expressions for relevant operators. I argue that none is acceptable suggest canonical expression operators correct physically meaningful one. It then an inescapable fact operator cannot, general, way However,...

The much debated issue of the transverse single spin asymmetry ${A}_{N}$ observed in inclusive large ${P}_{T}$ production a hadron $pp$ interactions, ${p}^{\ensuremath{\uparrow}}p\ensuremath{\rightarrow}\ensuremath{\pi}X$, is considered momentum dependent factorization scheme. A previous result [M. Anselmino et al., Phys. Rev. D 71, 014002 (2005), M. 73, 014020 (2006)] stating that maximum contribution Collins effect strongly suppressed, revisited, correcting numerical error. New estimates...

The fact that analyses of semi-inclusive deep inelastic scattering suggest the polarized strange quark density $\mathrm{\ensuremath{\Delta}}s(x)+\mathrm{\ensuremath{\Delta}}\overline{s}(x)$ is positive in measured region Bjorken $x$, whereas all inclusive yield significantly negative values this quantity, known as ``strange polarization puzzle.'' We have analyzed world data on scattering, including COMPASS 2010 proton spin asymmetries, and for first time, new extremely precise JLab CLAS...

The claim some years ago, contrary to all textbooks, that the angular momentum of a photon (and gluon) can be split in gauge-invariant way into an orbital and spin term, sparked major controversy Particle Physics community. A further cause upset was realization gluon polarization nucleon, supposedly physically meaningful quantity, corresponds only gauge-variant derived from Noether's theorem, evaluated particular gauge. On contrary, Laser Physicists have, for decades, been happily measuring...