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Roman Pasechnik

Senior lecturer

Typical working day..

Dynamic color screening in diffractive deep inelastic scattering


  • Gunnar Ingelman
  • Roman Pasechnik
  • Dominik Werder

Summary, in English

We present a novel Monte Carlo implementation of dynamic color screening via multiple exchanges of semisoft gluons as a basic QCD mechanism to understand diffractive electron-proton scattering at the HERA collider. Based on the kinematics of individual events in the standard QCD description of deep inelastic scattering at the parton level, which at low x is dominantly gluon initiated, the probability is evaluated for additional exchanges of softer gluons resulting in an overall color singlet exchange leading to a forward proton and a rapidity gap as the characteristic observables for diffractive scattering. The probability depends on the impact parameter of the soft exchanges and varies with the transverse size of the hard scattering subsystem and is therefore influenced by different QCD effects. We account for matrix elements and parton shower evolution either via conventional DGLAP logQ2 evolution with collinear factorization or CCFM small x evolution with k factorization and discuss the sensitivity to the gluon density distribution in the proton and the importance of large log x contributions. The overall result is, with only two model parameters which have theoretically motivated values, a satisfactory description of the observed diffractive cross section at HERA obtained in a wide kinematical range.


  • Department of Astronomy and Theoretical Physics - Undergoing reorganization

Publishing year





Physical Review D (Particles, Fields, Gravitation and Cosmology)





Document type

Journal article


American Physical Society


  • Subatomic Physics




  • ISSN: 1550-7998