We present a new measurement of the virtual photon proton asymmetry A1p from deep inelastic scattering of polarized muons on polarized protons in the kinematic range 0.0008 < x < 0.7 and 0.2 < Q2 < 100 GeV2. With this, the statistical uncertainty of our measurement has improved by a factor of 2 compared to our previous measurements. The spin-dependent structure function g1p is determined for the data with Q2 > 1 GeV2. A perturbative QCD evolution in next-to-leading order is used to determine g1p(x) at a constant Q2. At Q2 = 10 GeV2 we find, in the measured range, View the MathML source. The value of the first moment View the MathML source of g1p depends on the approach used to describe the behaviour of g1p at low x. We find that the Ellis-Jaffe sum rule is violated. With our published result for Γ1d we confirm the Bjorken sum rule with an accuracy of ≈ 15% at the one standard deviation level.
