Simulation and Reconstruction

Bhabha events tagging in MC

Bhabha scattering events are flagged in SteppingAction, by assigning to E_Bh the energy of the positron if the process involved at a certain step is "eIoni" and the volume where this occurs is "Target":

    if(theParticleName == "e+"
       && thePostVolume == "/pienu/Target"
       && theProcessName == "eIoni") {
      runAction->PositronFromBhabha(postEnergy, postMomentum);
      runAction->PositronPreBhabha(preEnergy, preMomentum);  
    }

    if(theParticleName == "e-" 
       && thePostVolume == "/pienu/Target"
       && theCreatorProcessName == "eIoni"
       && theTrack->GetCurrentStepNumber()==1) {
      runAction->ElectronFromBhabha(prePosition, preEnergy, preMomentum);        
    }

The "eIoni" physics processes are implemented in module G4MollerBhabhaModel.cc from the Geant4 MC simulation package.

Events such tagged were studied to understand energy and angular distributions of the Bhabha-scattered e- and e+ and compare them with 'non-Bhabha' events.

Analysis

The first step was to validate our software by reproducing all plots done with MC from Chloe's thesis. The second step was to try to reproduce data results from Chloe's thesis with our MC (adding radiative effects, pileup etc. if necessary). We have satisfactorily achieved these steps.

Shift Schedule

Available here: http://pienu02.triumf.ca/pienu_shifts/index.php

Bhabha events tagging

In MC, this is done via a code snippet added by Chloe in SteppingAction.cc:

//Chloe's addition (in SteppingAction.cc)
    if (theParticleName == "e+" 
        && thePostVolume == "/pienu/Target" 
        && theProcessName == "eIoni") {
        runAction->SBhabha(postEnergy);
     // G4cout << postEnergy/MeV << G4endl;
    } 

Reproducing plots from Chloe's thesis

The data tree produced by MCtoData contains numerous new branches, which can be useful for this analysis. A first step is trying to identify these branches and reproduce some of the most important plots from Chloe's thesis. These PDFs contain our plots:

• Plots-2012-06-26.pdf: Plots reproducing figures 1.2, 5.1 and 5.19

The ROOT macros used to draw these plots are attached here.

PPE People

Tagging Bhabha events

... Will be documented along the way ...

Monte Carlo

MC run using recommended settings, 100k events (to check):

• Output of default MC run pienu pienu.mac : run1.root
• Output from MCtoData run1out.root run1.root : run1out.root (stdout)

PiENu

People

Currently, David Britton and DanProtopopescu are directly involved in this experiment.

Documentation

• Official website at Triumf: http://pienu.triumf.ca/
• INPC 2010 talk by Chloé Malbrunot
• PIENU Proposal

Code compilation

The MC code was obtained from svn (pienu02.triumf.ca/pienumc/trunk) and unpacked on the UI. Specific versions of CLHEP (2.0.4.2) and Geant4 (4.9.0.3.p02) were installed in the user directory in ~/packages/. Detailed download and compilation instructions for CLHEP, Geant4 and the main pienu code were provided by Aleksey Sher via email (May 2011).

PiENu

This wiki refers to the PiENu experiment at Triumf: http://pienu.triumf.ca/

-- DanProtopopescu - 2012-04-05