A precision measurement of the spin structure functions g(p/1) and g(d/1)

In Experiment E155 at the Stanford Linear Accelerator Center, the spin dependent structure function g1(x, Q 2) was measured for both the proton and deuteron. This was accomplished by scattering 48.3 GeV highly polarized electrons (0.813 +/- 0.020) off polarized 15NH3 (proton) and 6LiD (deuteron) targets. Data were collected in March and April of 1997 using three fixed angle, momentum analyzing spectrometers centered at 2.75°, 5.5°, and 10.5°. This enabled a kinematic coverage of 0.01 < x < 0.9 and 1 GeV2 < Q2 < 40 GeV2. At an average Q2 of 5 GeV2, the integrals in the measured region were &smallint;0.0140.9 g1 (x)dx = 0.119 +/- 0.002(stat.) +/- 0.009(syst.) for the proton and 0.043 +/- 0.003(stat.) +/- 0.003(syst.) for the deuteron. Using a perturbative QCD analysis which included a global data set, the results were found to be consistent with the Bjorken Sum Rule. Asymmetry measurements also were made using photoproduced hadrons. Data were collected concurrently with the g1 data. For the proton, the asymmetries were small and non-zero. The deuteron measurements were consistent with zero.