Slag E155 -: A precision measurement of polarized structure function g1 of proton and deuteron

The E155 experiment at the Stanford Linear Accelerator Center (SLAC) has performed a precision measurement of the proton and deuteron spin structure function gl using deep inelastic scattering of polarized electrons on polarized (NH3)-N-15 and (LiD)-Li-6. For the kinematic range 0.014 < x < 0.9 and 1 GeV2 < Q(2) < 17 GeV2, the resulting integrals yield integral(0.014)(0.9) g(1)(p)(x)dx = 0.114 +/- 0.002(stat) +/- 0.011(syst) and integral(0.014)(0.9) g(1)(d)(x)dx = 0.034 +/- 0.002(stat) +/- 0.005(syst) at an average Q(2) = 5 GeV2. These preliminary results are in reasonably good agreement with previous data. A large range of extrapolations can accomodate the singular behaviour of the structure functional low x calling into question the usual methods to extrapolate to x = 0. The softer behaviour of the Bjorken sum rule allows us to test it.