Workshop on the modeling of photon-induced processes

OC218 (IPPP)




The focus of the workshop is on the modeling of the photon-induced processes in p-p collisions at the LHC, focusing on cases when protons are not explicitly tagged with forward detectors.

List of topics:

  • Interface with Parton Shower

Interfacing photon-induced generators with Pythia is currently done through a set of parameters developed by generator authors and is available only for Pythia. Especially in the case of diffractive events, the way it’s done tends to be rather “ad-hoc” and very sensitive to Pythia variations version by version. In practice we also found the final state observables can be very sensitive to the tuning of these parameters (more on this in the tuning topic below).

We would like to explore a robust way to interface photon-induced generators with parton shower programs, building upon the experience we had so far. What is needed from the generator side and what methods the interface with parton shower can offer (e.g. parameters tuning vs user-hooks, etc …).

  • Experimental context

Historically, most of the attention has been given (both from the theory as well as experimental side) to photon-induced processes where the final state protons are detected by dedicated forward detectors. We’d like to summarize the state-of-art techniques for identifying photon-induced processes in p-p collisions using the central-detector information, summarizing and brainstorming about advantages, limitations and complementarity with the more traditional identification of forward protons. 

  • Custom yy-generators (LPair, gamma-UPC, SuperChic, MadGraph, Pythia, Sherpa)

The current implementation of specific photon-photon generators into a complete set of tools usable by large experiments require custom patches to the code to be applied and, from our experience, has been fragile with respect to changes of versions. Identifying potential developments to address the stability and generality of these programs can ensure the long-term sustainability and larger-base adoption of this interesting physics.

  • Tuning

Modelling of diffractive processes is certainly a non-trivial task. While historically a lot of attention has been given to the elastic contribution of photon-induced processes, we’d like to focus on a more inclusive approach and brainstorm of what data is available and what measurements can be done to improve our understanding of the non-elastic component of photon-induced processes.

  • Miscellaneous 

Other topics could be potentially very interesting, but we have omitted to keep the workshop more focused. These included extending the discussion to synergies with forward detectors, as well as in heavy ion collisions, photon PDFs, leptons in PDFs, etc..
However, we’re still very open to suggestions of topics that you think might fit well within the scope of this workshop and/or are high-priority for the field.

Workshop on the modeling of the photon-induced processes
  • Aleksandra Dimitrievska
  • Christos Anastopoulos
  • David d'Enterria
  • Ferhat Öztürk
  • Filip Nechansky
  • Giancarlo Panizzo
  • Ilkka Helenius
  • Jose Luis Hernando Ariza
  • Josh Puddefoot
  • Karolos Potamianos
  • Laurent Forthomme
  • Lorenzo Primomo
  • Lucian Harland-Lang
  • Lydia Beresford
  • Malik Aliev
  • Oldrich Kepka
  • Peter Meinzinger
  • Philip Sommer
  • Savannah Clawson
  • Simone Pagan Griso
  • Valery Khoze
  • +4
    • Welcome and Introduction
    • Experimental context
    • 12:30 PM
      Lunck Break
    • 1
      Speaker: Simon Plätzer (IPPP)
    • 2
      Speaker: Ilkka Helenius (University of Jyväskylä)
    • 3
      Speaker: Peter Meinzinger (IPPP)
    • 4:15 PM
      Coffee Break
    • Hands-on Sessions: Hands-on

      Planning and Hackathon-style work on specific topics

    • 4
      Speaker: Lucian Harland-Lang (University College London)
    • 5
      Speaker: Dr Laurent Forthomme
    • 10:30 AM
      Coffee Break
    • 6
      Speaker: Dr David d'Enterria (CERN)
    • 12:30 PM
      Lunck Break
    • Hands-on Sessions: Hands-on

      Planning and Hackathon-style work on specific topics

    • 3:30 PM
      Coffee Break
    • Hands-on Sessions: Hands-onn

      Planning and Hackathon-style work on specific topics

    • Workshop Dinner
    • Hands-on Sessions: Hands-on

      Planning and Hackathon-style work on specific topics

    • 10:30 AM
      Coffee Break
    • Misc
    • 12:30 PM
      Lunck Break