Krzysztof Golec-Biernat

Saturation in diffractive deep inelastic scattering

We successfully describe the HERA-data on diffractive deep inelastic scattering using a saturation model which has been applied in our earlier analysis of the inclusive ep-scattering data. No further parameters are needed. Saturation already turned out to be essential in describing the transition from large to small values of

A Modification of the Saturation Model : DGLAP Evolution

Q^2

Generalized parton distributions of the pion in chiral quark models and their QCD evolution

in inclusive scattering. It is even more important for diffractive processes and naturally leads to a constant ratio of the diffractive versus inclusive cross sections. We present an extensive discussion of our results as well as detailed comparison with data.

Electroweak boson production in double parton scattering

We propose to modify the saturation model of Golec-Biernat and Wusthoff by including DGLAP evolution. We find considerable improvement for the total deep inelastic cross section, in particular in the large Q^2 region. The successful description of DIS diffraction is preserved.

QCD predictions for the transverse energy flow in deep-inelastic scattering in the HERA small x regime

We evaluate generalized parton distributions of the pion in two chiral quark models: the spectral quark model and the Nambu-Jona-Lasinio model with a Pauli-Villars regularization. We proceed by the evaluation of double distributions through the use of a manifestly covariant calculation based on the a representation of propagators. As a result polynomiality is incorporated automatically and calculations become simple. In addition, positivity and normalization constraints, sum rules, and soft-pion theorems are fulfilled. We obtain explicit formulas, holding at the low-energy quark-model scale. The expressions exhibit no factorization in the t-dependence. The QCD evolution of those parton distributions is carried out to experimentally or lattice accessible scales. We argue for the need of evolution by comparing the parton distribution function and the parton distribution amplitude of the pion to the available experimental and lattice data, and confirm that the quark-model scale is low, about 320 MeV.

F(L) proton structure function from the unified DGLAP/BFKL approach

We study the

Reggeon and pion contributions in semiexclusive diffractive processes at DESY HERA

W^+W^-

Twist expansion of the nucleon structure functions, F2, and FL, in the DGLAP improved saturation model

and

Testing saturation with diffractive jet production in deep inelastic scattering

Z^0Z^0

How to impose initial conditions for QCD evolution of double parton distributions

electroweak boson production in double parton scattering using QCD evolution equations for double parton distributions. In particular, we analyze the impact of splitting terms in the evolution equations on the double parton scattering cross sections. Unlike the standard terms, the splitting terms are not suppressed for large values of the relative momentum of two partons in the double parton scattering. Thus, they play an important role which we discuss in detail for the single splitting contribution to the cross sections under the study.