First Monte Carlo global QCD analysis of pion parton distributions

In this work, we determined the parton distribution function (PDF) of the pion. Previously, its PDF has been determined only by Drell-Yan (DY) experiments such as E615 and NA10 which only constrain the high momentum fraction region and the valence distribution. In the DY process, two hadrons collide, with one donating a quark and the other donating an antiquark, producing a dimuon pair. For lower momentum fractions, data was included from leading neutron (LN) electroproduction experiments such as H1 and Zeus done at HERA. An electron strikes a target proton, which transforms into a neutron. This process is dominated by the one-pion exchange. These data provide previously unseen constraints on sea quark and gluon PDFs. The PDFs we obtain reveal that at the input scale, the gluon carries a significant fraction of the pion momentum ∼30%, higher than predicted with only the DY data, and the sea carries ∼15% of the momentum fraction of the pion. We can also describe the dbar-ubar asymmetry in the proton using this pion PDF.