Diffractive Parton Distributions from Fits with Higher Twist
  We determine diffractive parton distributions of the proton from DGLAP based fits to HERA data including the twist--4 contribution from longitudinal polarized virtual photons, which is known to be important in the region of large beta. The biggest impact of this contribution is on the diffractive gluon distribution and on the diffractive longitudinal structure function to be determined from HERA data. 
Krzysztof Golec-Biernat and Agnieszka Luszczak