Precision measurement of the deuteron spin structure function gd1

We report on a high-statistics measurement of'. the deuteron spin structure function g(di) at a beam energy of 29 GeV in the kinematic range 0.029 < x < 0.8 and 1 < Q2 < IO (GeV / c) (2) • The integral r(di) = f(1o) g(di) dx evaluated at fixed Q2 = 3 (GeV/c) 2 gives 0.042 ± 0.003(stat) ± 0.004(syst). Combining this result with our earlier measurement of g(di), we find r(pi) - r(nt) = 0.163 ± O.OIO(stat) ± 0.016(syst), which agrees with the prediction of the Bjorken sum rule with O(a(3x)) corrections, r(pi) - r(ni) = 0.171 ± 0.008. We find the quark contribution to the proton helicity to be liq = 0.30 ± 0.06. This work was supported by Department of Energy Contracts No. DE-AC05-84ER40150 (CEBAF), No. W-2795-Eng-48 (LLNL), No. DE-AC0376SF00515 (SLAC), No. DE-FG03-88ER40439 (Stanford), No. DE-FG05-88ER40390 and No. DEFG05-86ER4026 (Virginia), and No. DE-AC02-76ER00881 (Wisconsin); by National Science Foundation Grants No. 9114958 (American), No. 9307710 (Massachusetts), No. 9217979 (Michigan), No. 9104975 (ODU) and No. 9118137 (U. Penn.); by the Schweizersche Nationalfonds (Basel); by the Commonwealth of Virginia (Virginia); by the Centre NAtional de la Recherche Scientifique and the Commissariat a l'Energie Atomique (French groups); and by the Japanese Ministry of Education, Science and Culture (Tohoku).