Abstract
We present an overview of the options for diffraction implemented in the general-purpose event generator Pythia 8 [1]. We review the existing model for soft diffraction and present a new model for hard diffraction. Both models use the Pomeron approach pioneered by Ingelman and Schlein, factorising the diffractive cross section into a Pomeron flux and a Pomeron PDF, with several choices for both implemented in Pythia 8. The model of hard diffraction is implemented as a part of the multiparton interactions (MPI) framework, thus introducing a dynamical gap survival probability that explicitly breaks factorisation.
Highlights
Despite the great success of QCD many soft phenomena still remain as mysteries because of their nonperturbative origin
In this paper we focus on the SD processes, being the simplest possible configuration and the one with the largest cross section
We have presented the two frameworks for diffraction present in the general-purpose event generator Pythia 8
Summary
Despite the great success of QCD many soft phenomena still remain as mysteries because of their nonperturbative origin. Amongst these lies soft hadron collisions, in which one or both of the hadrons survive the collision. Ingelman and Schlein proposed a model [2] in which the P can be viewed as a hadronic state with partonic content This opened up the possibility for P parton distribution functions (PDFs) to be combined with the probability of extracting a P from the colliding hadron, denoted the P flux. A model for diffractive systems should be able to describe all aspects of these collisions, such as differential cross sections, one-particle distributions and global event characteristics. We introduce the concept of rapidity gap survival probability (RGSP) (cite Bjorken), a concept unique to hadron-hadron collisions, given credibility by the lower observed rate for diffraction at the Tevatron as expected from HERA flux and PDF determinations
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