EA propagation: Monte Carlo

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We need a range of Monte Carlo simulations of nuclear effects on parton prpagation and fragmentation, which allow us to simulate various phsyical ideas, and produce detailed projections for the various detectors and machines designs.

There are currently 3 efforts underway:

  • modify PYTHIA as simply as possibe to include various scenarios and physics ideas
  • Adapt Q-PYTHIA to cold nuclear matter, and extend it to HT energy loss.
  • the GiBUU code, which is a full scale Monte Carlo simulation, but currently supports only one prehadron absorption model

Ideas that are currently being implemented are typed in boldface below, for the other we welcome volunteers.

PYTHIA modifications

[ Accardi, Dupre, Daniel, Majumder ]

An effort is underway to modify PYTHIA as simply as possibe to include various energy loss or prehadron absorption models, as well other physics idea. The idea is to have on a short time scale a simulation tool to play around with various ideas, and check how they affect various observables, how well these can be measured in any given detector/machine, and what we can learn out of them. For example: can one distinguish energy loss from preahdron absorption models in the pT-broadening of the eta meson compared to the pion?

  • Fermi motion, BDMPS energy loss with Lund fragmentation [ Dupre, Accardi ]
    • Table [1] of multiplicities produced by PYTHIA without modification.
    • Working note
  • Use PYTHIA as parton level generator [ Daniel, Accardi ]
    • BDMPS energy loss and fragmentation with Fragmentation Functions [2] [ Daniel ]
    • Prehadron absorption by Accardi et al. [3] or a la GiBUU [4]
    • Nuclear FF by Sassot, Strattman, Zurita [5]
    • Nuclear broadening of intrinsic kT in PDF [ Avakian ? ]
  • Implement GLV energy loss


[Ploskon, Accardi, Majumder]

The Q-Pythia Monte Carlo [6] [7] is a Monte Carlo generator implementing in-medium modified DGLAP evolution in the Quark-Gluon Plasma in a formalism that generalizes BDMPS.

We want to

  • Adapt it to cold nuclear matter geometry [ Accardi, Ploszkon ]
    • analytic formulae are ready [8]: we need to implement them in the code, which should be fairly straightforward
  • Extend it to treat HT energy loss [9] [ Majumder ]


[ Gallmeister, Mosel ]

The GiBUU code [10] is a full scale Monte Carlo simulation tested with high energy electrons and cold matter, but currently supports only one prehadron absorption model.

The questions are:

  • is it possible to implement other physics scenarios from here to November?
    • different space-time prehadron picture (e.g., Accardi et al.)?
    • struck parton energy loss, stand alone ?
    • struck parton energy loss together with prehadron absorption ?
  • How modular is GiBUU? i.e.,
    • can we use it as "parton generator" as we wish to do with Pythia?
      (advantage: a lot of nuclear physics in the initial state is already included)
    • can we use it for modified DGLAP showers the way Q-PYTHIA does?
  • To what extent can it be used to study jet physics?

CVS repository

We are collecting our working group documents and MC codes (except GiBUU) in this CVS repository:


checkout the module


Only people with a JLab account can so far access it. Please, send an e-mail to Alberto to be added to the suitable UNIX group. We'll look for different solutions if the need for easier accessibilty arises.

Resources and links