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HK: Fachverband Hadronen und Kerne

HK 81: Hadron Structure and Spectroscopy II

HK 81.3: Vortrag

Freitag, 20. März 2009, 11:30–11:45, H-ZO 30

HERMES measurements of the strange parton distribution and strange quark helicity distribution — •Polina Kravchenko — PNPI, St.Petersburg, Russia

The helicity density of the strange quark sea in the proton has been extracted from measurements of polarized semi-inclusive production of charged kaons in deep inelastic scattering of positrons from a plarized deuteron target. The isoscalar nature of the deuteron target (assuming isospin symmetry) and lack of isospin for strange quarks allows the deuteron target to be used independently without relying on fragmentation models or other experimental data. In the region of measurement of x>0.02 the helicity density is zero within experimental error and the measured first moment of the density is 0.006+/-0.029(stat)+/-0.007(sys)/. The first moment of the axial charge in the measured region is substantially less than that inferred from hyperon semi-leptonc decays.