We determine the valence parton distribution function of the pion by performing a new analysis of data for the Drell-Yan process ${\pi }^{-}N\to {\mu }^{+}{\mu }^{-}X$. Compared to previous analyses, we include next-to-leading-logarithmic threshold resummation effects in the calculation of the Drell-Yan cross section. As a result of these, we find a considerably softer valence distribution at high momentum fractions $x$ than obtained in previous next-to-leading-order analyses, in line with expectations based on perturbative-QCD counting rules or Dyson-Schwinger equations.

• Received 15 September 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.252003