A Model for the parton distributions in hadrons

A simple model is presented for the parton distributions in hadrons. The parton momenta in the hadron rest frame are derived from a spherically symmetric, Gaussian, distribution having a width motivated by the Heisenberg uncertainty relation applied to the hadron size. Valence quarks and gluons originate from the `bare' hadron, while sea partons arise mainly from pions in hadronic fluctuations. Starting from a low Q 2 scale, the distributions are evolved with next-to-leading order DGLAP and give the proton structure function F 2 ( x , Q 2 ) in good agreement with deep inelastic scattering data