Parton distribution functions from QCD in Euclidean space

Parton distribution functions are essential inputs in extracting information from high-energy physics emperiments. However the computation for these distribution functions is a major challenge in Lattice QCD. In recent years, novel approaches have been advocated for such calculations.

  • The method of the valence heavy quark
  • This is based on the proposal by Detmold and Lin. Through the introduction of a pure valence heavy quark, one can use the heavy mass to perform the OPE in Euclidean space and obtain high moments of the parton distribution functions. This is the approach that we are currently implementing, in collaboration with the MIT group, for the pion light-cone distribution amplitude. In the near future, similar computations for various parton distribution functions will be performed.

  • The method of the position-space operator product expansion
  • This was advocated by Braun and Mueller. Using the short distance in Euclidean space in the OPE, one can extract moments of the parton distribution functions.

  • The method of the quasi parton distribution functions
  • This approach employs the large-momentum effective theory and was first studied by Ji.

  • Other approaches
  • These include the QCDSF method, and the proposal from the Kentucky group.