Extraction of the intrinsic light-quark sea in the proton

The HERMES Collaboration recently reported a reevaluation of the strange-quark parton distribution, S(x), based on kaon production in semi-inclusive deep-inelastic scattering. Two distinct results on S(x) at the x>0.1 region, one with a sizable magnitude and another with a vanishing content, were reported. We show that the latter result is due to a particular assumption adopted in the analysis. The impact of the new HERMES S(x) result on the extraction of intrinsic light-quark sea in the proton is discussed. Given the large uncertainty in the kaon fragmentation function, we find that the latest HERMES data do not exclude the existence of a significant intrinsic strange-quark sea in the proton. The x dependence of the (s+s¯)/(u¯+d¯) ratio is also in qualitative agreement with the presence of intrinsic strange-quark sea.