Ilkka Helenius, Jesper R. Christiansen and Christine O. Rasmussen
Recent PYTHIA 8 developments: Hard diffraction, Colour reconnection and $\gamma\gamma$ collisions


An overview of recent developments in PYTHIA 8 is given. First the new hard diffraction model, which is implemented as a part of the multiparton interactions(MPI) framwork, is discussed. Then new colour reconnection model, which includes beyond leading colour effects that can become importanct when MPI are present, is briefly reviewed. As a last topic an introduction is given to our implementation of photon-photon collisions. In particluar photon PDFs, required modifications for the initial state radiationalgorithm and beam remnant handling with photon beams is discussed.

LU TP 16-01