Recent Pythia 8 developments: Hard diffraction, Colour reconnection and $\gamma\gamma$ collisions

TL;DR

This paper reviews recent updates to Pythia 8, including models for hard diffraction, colour reconnection with beyond leading colour effects, and photon-photon collision simulations, enhancing its physics simulation capabilities.

Contribution

It introduces new models for hard diffraction, colour reconnection with beyond leading colour effects, and photon-photon collision implementation in Pythia 8.

Findings

New hard diffraction model integrated with MPI framework

Enhanced colour reconnection model including beyond leading colour effects

Implementation of photon-photon collisions with modified initial state radiation

Abstract

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) framework, is discussed. Then the new colour reconnection model, which includes beyond leading colour effects that can become important when MPI are present, is briefly reviewed. As a last topic an introduction is given to our implementation of photon-photon collisions. In particular photon PDFs, required modifications for the initial state radiation algorithm and beam remnant handling with photon beams is discussed.