We report results of an electron-beam-dump search for neutral particles with masses in the range 1 to 15 MeV and lifetimes r between 10 ~1 4 and 10 -10 s. No evidence was found for such an object. We rule out the existence of any 1.8-MeV pseudoscalar boson with r > 8.2 x 10 ~1 5 s and an absorption cross section in matter less than 1 mb per nucleon, and exclude r> 1 x 10 ~1 4 s were its cross section to equal 50 mb per nucleon. In conjunction with measurements of the electron's anomalous magnetic moment, this experiment shows that the narrow positron peaks observed in heavy-ion collisions at the Gessellschaft fur Schwerionenforschung are not due to an elementary pseudoscalar.
The neutron longitudinal and transverse asymmetries A n 1 and A n 2 have been extracted from deep inelastic scattering of polarized electrons by a polarized 3 He target at incident energies of 19.42, 22.66 and 25.51 GeV. The measurement allows for the determination of the neutron spin structure functions g n 1 (x; Q 2 ) and g n 2 (x; Q 2 ) over the range 0:03 < x < 0:6 at an average Q 2 of 2 (GeV=c) 2 . The data are used for the evaluation of the Ellis-Ja e and Bjorken sum rules. The neutron spin structure function g n 1 (x; Q 2 ) is small and negative within the range of our measurement, yielding an integral R 0:6 0:03 g n 1 (x)dx = 0:028 0:006 (stat) 0:006 (syst). Assuming Regge behavior at low x, we extract n 1 =
The spin structure function of the neutron gr has been determined over the range 0.03 < x < 0.6 at an average Q2 of 2 (GeV/c)2 by measuring the asymmetry in deep inelastic scattering of polarized electrons from a polarized 3He target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is fo. nd to be Ji g?(x) dx =-0.022 f 0.011. Earlier reported proton results 2. .- .-_together with the Bjorken sum rule predict &r g?(x) dx =-0.059 f 0.019.
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