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 $(s+\overline{s})/(\overline{u}+\overline{d})$ ratio is also in qualitative agreement with the presence of intrinsic strange-quark sea.

• Received 19 May 2015

DOI:https://doi.org/10.1103/PhysRevD.92.054020