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

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 re--analysis 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

Evidence for a narrow |S|=1 baryon state at a mass of 1528 MeV in quasi-real photoproduction

Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel p K^0_S --> p pi^+ pi^-. A peak is observed in the p K^0_S invariant mass spectrum at 1528 +/- 2.6 (stat) +/-2.1 (syst) MeV. Depending on the background model,the naive statistical significance of the peak is 4--6 standard deviations and its width may be somewhat larger than the experimental resolution of sigma=4.3 -- 6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Theta^{+}(uuddbar(s)) pentaquark baryon. No signal for an hypothetical Theta^{++} baryon was observed in the pK^+ invariant mass distribution. The absence of such a signal indicates that an isotensor Theta is excluded and an isovector Theta is unlikely.Comment: 8 pages, 4 figure

Economic and political determinants of the effects of FDI on growth in transition and developing countries

This study investigates the role of human capital, political development in determining the magnitude of the effects of FDI on growth for a panel of 61 transition and developing countries for the period 1989 to 2013. A baseline growth model incorporating these variables is tested and then extended to include FDI interaction effects with human capital (measured using secondary school enrolment data) and political development (based upon EIU Democracy Index scores). These growth interaction effects between FDI and human capital vary according to regime type. Political development in conjunction with FDI appears to suppress the effects of FDI on growth in authoritarian countries while enhancing them in hybrid democracies. For more democratic countries, domestic investment is a more important driver of growth. The effects of FDI on growth in the ten Transition economies included in the sample dataset are found to be insignificant. Although this result might seem to differ from a priori expectations, it is in line with the findings of most earlier studies which cover the period up until 2004. The paper also provides no strong evidence that a critical threshold of human capital is required to generate beneficial spillover growth effects from inflows of FDI. The paper provides new and more detailed insights into the effects of FDI on growth with particular respect to human capital and political regime covering a large number of transition and developing countries based upon an up to date dataset covering a twenty-five year period to 2013