Precision measurement of the deuteron spin structure function g1dg^{d}_{1}

We report on a high-statistics measurement of the deuteron spin structure function g[sup d][sub 1] at a beam energy of 29 GeV in the kinematic range 0.029 < x < 0.8 and 1 < Q2 < 10 (GeV/c)2. The integral Gamma [sup d][sub 1] = (integral)[sup 1][sub 0]g[sup d][sub 1]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[sup p][sub 1], we find Gamma [sup p][sub 1]- Gamma [sup n][sub 1] = 0.163 ± 0.010(stat) ± 0.016(syst), which agrees with the prediction of the Bjorken sum rule with O( alpha [sup 3][sub s]) corrections, Gamma [sup p][sub 1]- Gamma [sup n][sub 1] = 0.171 ± 0.008. We find the quark contribution to the proton helicity to be Delta q = 0.30 ± 0.06

Measurements of R=sigma_L/sigma_T for 0.03<x<0.1 and Fit to World Data

Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5 degrees, corresponding to 0.03<x<0.1 and 1.3<Q^2<2.7 GeV^2. Values of R=sigma_L/sigma_T were extracted in this kinematic range by comparing these data to cross sections measured at a higher beam energy by the NMC collaboration. The results are in reasonable agreement with pQCD calculations and with extrapolations of the R1990 parameterization of previous data. A new fit is made including these data and other recent results.Comment: 8 pages, 4 figures, late

Next-to-Leading Order QCD Analysis of Polarized Deep Inelastic Scattering Data

We present a Next-to-Leading order perturbative QCD analysis of world data on the spin dependent structure functions $g_1^p, g_1^n$, and $g_1^d$, including the new experimental information on the $Q^2$ dependence of $g_1^n$. Careful attention is paid to the experimental and theoretical uncertainties. The data constrain the first moments of the polarized valence quark distributions, but only qualitatively constrain the polarized sea quark and gluon distributions. The NLO results are used to determine the $Q^2$ dependence of the ratio $g_1/F_1$ and evolve the experimental data to a constant $Q^2 = 5 GeV^2$. We determine the first moments of the polarized structure functions of the proton and neutron and find agreement with the Bjorken sum rule.Comment: 21 pages, 4 figures; final version to be published in Phys. Lett. B. References updated. Uses elsart.cls version 1996/04/22, 2e-1.4

Measurements of the Q2-Dependence of the Proton and Deuteron Spin Structure Functions g1p and g1d

The ratio g1/F1 has been measured over the range 0.031 (GeV/c)2. A trend is observed for g1/F1 to decrease at lower Q2. Fits to world data with and without a possible Q2-dependence in g1/F1 are in agreement with the Bjorken sum rule, but Delta_q is substantially less than the quark-parton model expectation

Precision measurement of the proton spin structure function g1pg^{p}_{1}

We have measured the ratio g[sup p][sub 1]/F[sup p][sub 1] over the range 0.029 < x < 0.8 and 1.3 < Q2 < 10 (GeV/c)2 using deep-inelastic scattering of polarized electrons from polarized ammonia. An evaluation of the integral (integral)g[sup p][sub 1](x,Q2)dx at fixed Q2 = 3 (GeV/c)2 yields 0.127 ± 0.004(stat) ± 0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160 ± 0.006. In the quark-parton model, this implies Delta q = 0.27 ± 0.10

Precision measurement of the proton spin structure function g(p1)

We have measured the ratio (gi) /F(gi) over the range 0.029 ( x ( 0.8 and 1.3 (Q+/- ( 10 (GeV/c) using deep-inelastic scattering of polarized electrons from polarized ammonia. An evaluation of the integral fo g+/_ (x, Q2) dx at fixed Q2 = 3 (GeV/c)2 yields 0.127 +/- 0.004(stat) +/- 0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160 +/- 0.006. In the quark-parton model, this implies Aq = 0.27 +/- 0.10.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)

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)

Measurements of the Proton and Deuteron Spin Structure Functions g1 and g2

SLAC-PUB-7753, February 1998Measurements are reported of the proton and deuteron spin structure functions gp1 and gd1 at beam energies of 29.1, 16.2, and 9.7 GeV, and gp2 and gd2 at a beam energy of 29.1 GeV.Work supported in part by Department of Energy contract DE-AC03-76SF00515

Measurements of the Proton and Deuteron Spin Structure Function g2 and Asymmetry A2

Submitted to Physical Review Letters. The article of record may be found at http://dx.doi.org/10.1103/PhysRevLett.76.587.We have measured proton and deuteron virtual photon-nucleon asymmetries Ap2 and Ad2 and structure functions gp2 and gd2 over the range 0.03<x<0.8 and 1.3<Q2<10(GeV/c)2 by inelastically scattering polarized electrons off polarized ammonia targets. Results for A2 are significantly smaller than the positivity limit R‾‾√ for both targets. Within experimental precision the g2 data are well described by the twist-2 contribution, gWW2. Twist-3 matrix elements have been extracted and are compared to theoretical predictions.Work supported in part by Department of Energy contract DE-AC03-76SF00515

Measurements of R = σL/σT for 0.03 < x < 0.1 and Fit to World Data

To be submitted to Physics Letters. SLAC-PUB-7927, August 1998Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5◦, corresponding to 0.03 < x < 0.1 and 1.3 < Q2 < 2.7 GeV2. Values of R = σL/σT were extracted in this kinematic range by comparing these data to cross sections measured at a higher beam energy by the NMC collaboration. The results are in reason- able agreement with pQCD calculations and with extrapolations of the R1990 parameterization of previous data. A new fit is made including these data and other recent results.Work supported by Department of Energy contract DE–AC03–76SF00515