The double gluon distribution from the single gluon distribution
  Using momentum sum rule for evolution equations for Double Parton Distribution Functions (DPDFs) in the leading logarithmic approximation, we find that the double gluon distribution function can be uniquely constrained via the single gluon distribution function. We also study numerically its evolution with a hard scale and show that an approximately factorized ansatz into the product of two single gluon distributions performs quite well at small values of $x$ but is always violated for larger values, as expected. 
Krzysztof Golec-Biernat, Emilia Lewandowska, Mirko Serino, Zachary   Snyder and Anna Stasto
hep-ph