Thursday, May 26, 2016 3:00pm EST

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Meeting Information

BlueJeans Call Information

URL: [1]

Phone Number: 1-800-240-2560

Meeting ID: 624029893


  • Discuss the purpose of this working group.
  • Identify the task required to develop a pion background detector.


Attendees: Kurtis, Wouter, Rakitha, Yuxiang, David

Scribe: Kurtis

As a reminder, Wouter put together some of the important issues that will be the focus of this working group in his recent collaboration talk. Linked below:


  • Currently in remoll, the Wiser code is the only Pion generator presently in the master version of remoll
  • Rakitha: Should check the pion distributions at the detectors to see what the Wiser code is already predicting.
  • Rakitha: From working on remoll_solid, they see many low momentum pions at 11 GeV incident beam energies. David: Are you interested in the cross-section weighted acceptance(rate) or the kinematic acceptance. David thinks it should match the electron kinematics. Are there plots presently of this? Has this been studied?
  • David: What is this Hall D pion generator? Rakitha, it is a photo production pion generator for use by Hall D for determining their pion background. It is based on data and for higher momentum on (Pythia?). Rakitha then implemented an electro-production. The Hall D code then creates a paw file that is then used by the simulation to generate pions.
  • Rakitha has a personal version of the code. He implemented in the remoll_solid and it used (lund files?). Can be ported over to remoll. Should be as simple as copying over a single class.
  • Wouter: The Hall D files are under SVN control, but need to setup the entire environment to be able to compile the code base.

David suggests to take a snapshot and just port the fortan code over now.

  • Rakitha, did several benchmarks of this code and it seems to agree well. Does have a few troubles. Plans to post these so that we can have access to them.
  • David: A WM student code could take this on over the summer. Should get away from using the Wiser code.
  • David: Back to the acceptance question, is it about which kinematic variables compare with the Wiser code. Make scatter plots of scattering angle vs momentum.
  • Rakitha: Geant4 base and the Hall D code agree to about 20%.
  • Wouter suggest using a more recent version of (Pythia 8?)
  • Rakitha will post the talks and resources he has compiled on the subject to the MOLLER document database.
  • Rakitha: Still haven't figured out the asymmetries properly yet. Interested in hypron decays vs electro-production asymmtries. Generators just produce unpolarized cross-section. First attempt a simple estimate of the asymmetries.
  • David: Do the interactions/vertexes tell you where the interaction comes from? Rakitha, currently not yet. It isn't currently outputed.
  • Wiser model is just a fit to the pion, kayons, protons, neutrons data from SLAC (9-11 GeV photon-beam).
  • David: Pion detector design, assuming reasonable generator the location and dimension of the detector can start to be explored. Suggests putting in some sensitive volumes to represent the GEMS, then layers of lead, and then a sensitive volume to represent the pion detector.
  • Need to answer:
    • Does the pion cover detector all 7 septants?
    • Does the pion detector cover only one sector?
    • Run in both tracking and current mode?
    • Cost?
  • Yuxiang, reminded us that the systematics background study completed this past year assumed that the pion background was measured in all rings.
  • David: Did we assume that we can make measurements in the open, closed, and transition sectors? Yuxiang, YES.
  • David: Then a large acceptance detector will be required.
  • David: There are large transverse asymmetries, we will have to measure in all sector types.
  • David: Need to speak with Paul and KK about the transverse pion contributions.
  • Action Items:
    • Check outputs of current generators.
    • Port the Hall D generator over to remoll and compare with Wiser.
    • As for asymmetries we need to look further into this.

Next meeting June 9th