Quark helicity distributions in the nucleon for up, down, and strange quarks from semi-inclusive deep-inelastic scattering

Abstract

Polarized deep-inelastic scattering data on longitudinally polarized hydrogen and deuterium targets have been used to determine double-spin asymmetries of cross sections. Inclusive and semi-inclusive asymmetries for the production of positive and negative pions from hydrogen were obtained in a reanalysis of previously published data. Inclusive and semi-inclusive asymmetries for the production of negative and positive pions and kaons were measured on a polarized deuterium target. The separate helicity densities for the up and down quarks and the anti-up, anti-down, and strange sea quarks were computed from these asymmetries in a "leading order" QCD analysis. The polarization of the up-quark is positive and that of the down-quark is negative. All extracted sea quark polarizations are consistent with zero, and the light quark sea helicity densities are flavor symmetric within the experimental uncertainties. First and second moments of the extracted quark helicity densities in the measured range are consistent with fits of inclusive data

Measurement of parity-violating spin asymmetries inW±production at midrapidity in longitudinally polarizedp+pAdare1, Makek2, Zou3 2016Phys. Rev. DSelf Cite372300View full textAdd to dashboardCite

“…Although the overall quark contribution (∆Σ = ∆q + ∆q) has been well-determined through DIS experiments (in the range 10 −3 < x < 1), the contributions from sea quarks separated by flavor (determined through SIDIS experiments) are comparatively poorly known. Data from HERMES and COMPASS [6,16] provide constraints on the contribution from the sea quarks, however, uncertainties in fragmentation functions and the low energy scales of fixed target experiments limit the accuracy with which these measurements can quantitatively deter- * PHENIX Co-Spokesperson: morrison@bnl.gov † PHENIX Co-Spokesperson: jamie.nagle@colorado.edu ‡ Deceased mine the sea quark contribution [17]. As such, an independent measurement using a different technique [18] to determine the contribution from different flavors of sea quarks is desirable.…”

“…These high Q 2 data probe the parton structure of the proton at W mass scale and provide an important addition to our understanding of the anti-quark parton helicity distribution functions at an intermediate Bjorken The determination of the contributions of partons to the spin of the proton has inspired significant theoretical and experimental effort for several decades [1][2][3][4][5][6][7][8][9][10][11][12][13]. The quark contribution to the nucleon spin has been deduced through measurements in polarized inclusive deep-inelastic scattering (DIS) and semi-inclusive deepinelastic scattering (SIDIS) experiments [6,[12][13][14][15]. Although the overall quark contribution (∆Σ = ∆q + ∆q) has been well-determined through DIS experiments (in the range 10 −3 < x < 1), the contributions from sea quarks separated by flavor (determined through SIDIS experiments) are comparatively poorly known.…”

Measurements of the Double-Spin Asymmetry A₁ on Helium-3: Toward a Precise Measurement of the Neutron A₁

“…Circles represent data from HERMES [39]; triangles pointing up show SLAC data [40]; triangles pointing up correspond to data from Hall A of Jefferson Lab [41]; and squares show CLAS data [42].…”

Hadron mass corrections in semi-inclusive deep-inelastic scattering

“…Important insights have been provided through semiinclusive deep-inelastic scattering (SIDIS) experiments on phenomena such as the SU (2) flavor asymmetry in the proton sea [3] and the ratio of strange to nonstrange quark distributions [4,5]. From experiments with polarized targets, SIDIS data have also provided fascinating glimpses of the possible flavor asymmetry in the polarized light-antiquark sea [6], while kaon production data has fueled the recent controversy concerning the sign of the polarized strange sea [7][8][9]. Furthermore, detection of forward baryons (in the center of mass frame) in the target fragmentation region of SIDIS is a potentially important avenue for extracting information on the pion cloud of the nucleon or the structure of the virtual pion itself [10][11][12][13].…”