The PIENU experiment at TRIUMF (Vancouver, Canada) aims at precisely measuring the pion decay branching ratio (π+ → eν)/(π →μν). The current experimental value for this ratio is 20 times less precise than the theoretical calculation done within the SM, leaving a large window in which non-standard physics - new interactions or exotic particles - can be involved. Or, on the other hand, improved precision that would confirm the SM would set tighter constraints on new physics scenarios.

PPE People

Currently, David Britton, DanProtopopescu and Ian Skillicorn are contributing to this experiment.

Shift Schedule

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


Code compilation

The MC code was obtained from svn (pienu02.triumf.ca/pienumc/trunk) and unpacked on the UI. Specific versions of CLHEP ( and Geant4 ( 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).

Monte Carlo

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

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") {
     // G4cout << postEnergy/MeV << G4endl;
However, this only selects Bhabha scattering events happening in the target volume.

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:

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

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf PIENU_proposal.pdf r1 manage 381.7 K 2012-05-04 - 15:11 DanProtopopescu PIENU Proposal
PDFpdf Plots-2012-06-26.pdf r1 manage 1030.5 K 2012-06-27 - 11:07 DanProtopopescu Plots reproducing figures 1.2, 5.1 and 5.19
PDFpdf TalkINPC.pdf r1 manage 3132.1 K 2012-05-04 - 15:08 DanProtopopescu INPC 2010 talk by Chlo Malbrunot
Compressed Zip archivetgz macros.tgz r1 manage 4.0 K 2012-06-27 - 11:10 DanProtopopescu Analysis macros (initial versions)
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Topic revision: r8 - 2013-02-06 - DanProtopopescu
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