Analysis of pion electroproduction data in terms of a pion distribution function of the proton

Abstract Experimental data on the longitudinal π + electroproduction on hydrogen have been analyzed in terms of a pion distribution function of the proton. This interpretation is based on the assumption that the pion can be considered as a parton in the nucleon for low momentum transfer Q 2 . For the kinematical conditions photon mass Q 2 2 and electron energy loss ν > 2.2 GeV the pion electroproduction in the direction of the virtual photon can be viewed upon as quasielastic e π + → e′ π + scattering. Using the impulse approximation the pion distribution function of the proton can be deduced. According to the distribution function evaluated from pion electroproduction in the infinite momentum frame, the physical proton has a 3% admixture of the n π + state and the π + in the n π + state carries 0.6% of the proton momentum.