Display the Experiment Proposals

Experiment: S1072

Study of the Decay π → ev

by the PIENU group

Active (Stage 2)
Spokespersons:
T. Numao (TRIUMF)
D.A. Bryman (University of British Columbia)

Progress Report for EEC meeting 200912S

Table of Contents

Detailed Information

Complete/Merged PDF S1072_200912S_merged.pdf
Form data only S1072_200912S.pdf
Detailed Statement pienu_progress_2009.pdf (347.67 kB)

Beam Shift Summary

12-hr ShiftsBeam Line / channelPriority
New Beam Requests
 420 M13

PIENU is ready for extended production running needed to reach the statistical precision proposed. In addition to primary data acquisition periods, numerous runs devoted to study of systemmatic effects including line shape measurements  will be performed. We request all the available shifts in M13 during 2010.

420 M13
PIENU is ready for extended production running needed to reach the statistical precision proposed. In addition to primary data acquisition periods, numerous runs devoted to study of systemmatic effects including line shape measurements  will be performed. We request all the available shifts in M13 during 2011.
Committee Recommendations
 840 M13 H

This proposal aims to accurately measure the branching ratio for pion decay to electron and neutrino compared to decay to muon and neutrino.  The collaboration appears to be making good progress on this high priority experiment.  We recommend stage two approval for 420 shifts per year for the next two years at high priority.

Beam Shifts Used
 101 M13

Used on Schedule 117.

Beam Shifts Remaining
 1086 -

As of May 27, 2010.


Membership

T. Numao TRIUMF Research Scientist 65 % Spokesperson
D.A. Bryman University of British Columbia Professor 50 % Spokesperson
C. Hurst UBC Student (Graduate) 100 %  
C. Malbrunot UBC Student (PhD) 100 %  
D. Vavilov TRIUMF Research Associate 100 %  
K. Yamada Osaka University Student (PhD) 100 %  
L. Doria TRIUMF Research Associate 100 %  
M. Ding Tsinghua University Research Associate 100 %  
N. Ito Osaka University Student (Graduate) 100 %  
A. Sher TRIUMF Research Associate 70 %  
A. Hussein University of Northern British Columbia Professor 50 %  
J. Comfort Arizona State University Professor 50 %  
P. Gumplinger TRIUMF Staff Member 30 %  
M. Aoki Osaka University Professor 20 %  
M. Blecher VPI Professor 20 %  
R. Poutissou TRIUMF Research Scientist 20 %  
L. Kurchaninov TRIUMF Research Scientist 15 %  
L. Littenberg BNL Research Scientist 10 %  
M. Yoshida Osaka Research Associate 10 %  
S. Kettell BNL Research Scientist 10 %  
Shaomin Chen Tsinghua University Professor 10 %  
Y. Igarashi KEK Research Scientist 10 %  
Y. Kuno Osaka University Professor 10 %  
D. Britton Glasgow University Professor 0 %  

Basic Information

Date Submitted
2009-11-03 15:44:11
Date Experiment Ready
2008-09-30
Summary *

In the Standard Model (SM), electrons and muons have identical electroweak gauge interactions (a hypothesis known as lepton universality), and the only difference between them is mass. PIENU is a high precision measurement of the ratio of decay rates of the π meson to leptons : π+ → e+ ν and π+ → μ+ ν . The SM theoretical value of this ratio is the most accurately calculated SM weak interaction observable involving quarks at a precision of <0.01%; Re/μth. = (1.2353+-0.0001).10-4. The experimental value is an order of magnitude less precise. By testing lepton universality, a precise measurement of π+ → e+ ν decay compared to π+ → μ+ ν decay can constrain most non-Standard model scenarios if agreement with the SM is confirmed. However, pseudoscalar or scalar interactions induced by leptoquarks, supersymmetric particles, extra dimensions etc. can cause a measurable deviation of the branching ratio from the theoretical prediction. Experimental observation of such a deviation would be clear evidence of new physics sensitive to mass scales up to 1000 TeV, far beyond the reach of present accelerators. If new physics shows up at the LHC it will most likely impact the π+ → e+ ν branching ratio measured by PIENU.

Plain Text Summary *
The Standard Model assumes electrons and muons have identical electroweak gauge interactions. The PIENU experiment tests this hypothesis through pion decays. Experimental observation of such a deviation would be clear evidence of new physics sensitive to mass scales up to 1000 TeV, far beyond the reach of present accelerators.
Primary Beam Line
Base 1A
Secondary Channel
Base
M13
Primary / Secondary Beam
Energy (MeV)
500(MeV)
Intensity (uA)
100(uA)
Pulse Width (ns)
3(ns)
Particle Type
pi+
Energy (MeV)
20(MeV)
Spot Size (mm)
20(mm)
Intensity (pps)
100000(pps)
Special Characteristics
particle-separated beam
Production Target
Meson Target
1AT1: 1cmC
μSR Spectrometers
TRIUMF Support (Resources Needed)

Beam line group, Magnet group, Design office, Machine shop, Detector group, DAQ group, NIM Electronics

NSERC

RTI (2006, 2008), Discovery (2006,2007-2009)

Other Funding
Muon Justification
Safety Issues

Proposals and Progress Reports

200912S
200812S
200807S
200707S
200512S (Original Proposal)