Combined analysis of world data on nucleon spin structure functions

Proton Spin and Chiral Dynamics

“…Therefore, antiquarks are unpolarized. Small antiquark polarizations are consistent with the most recent SMC data [1], so that we expect only small corrections if we useū ↑ =ū ↓ in the spin fractions ∆u = u ↑ − u ↓ +ū ↑ −ū ↓ , etc., i.e. ∆s = ∆s sea , ∆ū = ∆d = ∆s = 0.…”

“…Understanding the internal proton structure is one of the goals of particle physics and, over the past dozen years or more, has led to extensive studies of the spin and flavor contents of the nucleon in terms of measured deep inelastic structure functions (DIS) [1,2]. Since spin fractions ultimately must derive from and be consistent with polarized DIS proton structure functions that are integrated over Bjorken x, we have used such a general DIS formalism [3] to analyze recent chiral models that have succeded in reproducing the spin fractions of the proton.…”

Magnetic moments of baryons and strange content of the nucleon

“…which can be compared with the other strange quark spin characteristics ∆s ≃ −.1, as given by the polarized DIS data, e.g. [14]. We wish here to note the following alternative.…”

“…As is known [14], to obtain the contributions of the u-,d-, and s-flavoured quarks to the proton spin, denoted by ∆u(p), ∆d(p) and ∆s(p), the use is usually made of baryon semileptonic weak decays treated with the help of the exact SU(3)-symmetry. It has been shown earlier [15,16]…”

x-dependent polarized parton distributions

“…The distributions begin with information from the integrated distributions and impose normalization and positivity constraints (all flavors, valence and sea) to ensure that all of the spin information extracted from data is explicitly contained in the x-dependent results. We generate polarized parton distributions from the unpolarized distributions and well defined suitable assumptions, derived from the most recent polarized deep-inelastic-scattering (PDIS) data sets available [10][11][12][13][14][15].…”