The PIENU experiment at TRIUMF: A sensitive probe for new physics

Chloé Malbrunot, A. A. Aguilar-Arevalo, M. Aoki, M. Blecher, D. I. Britton, D. A. Bryman, S. Chen, J. Comfort, M. Ding, J. Doornbos, L. Doria, P. Gumplinger, C. Hurst, A. Hussein, Y. Igarashi, N. Ito, S. Kettell, Y. Kuno, L. Kurchaninov, L. LittenbergT. Numao, R. Poutissou, A. Sher, T. Sullivan, D. Vavilov, K. Yamada, M. Yoshida

Research output: Contribution to journalConference articlepeer-review

4 Scopus citations


Study of rare decays is an important approach for exploring physics beyond the Standard Model (SM). The branching ratio of the helicity suppressed pion decays, R = Γ(π+ → e+ νe + π+ → e+ νe γ/ Γ(π+ → μ+ νμ + π+ → μ+ νμ γ, is one of the most accurately calculated decay process involving hadrons and has so far provided the most stringent test of the hypothesis of electron-muon universality in weak interactions. The branching ratio has been calculated in the SM to better than 0.01% accuracy to be RSM = 1.2353(1) × 10 4. The PIENU experiment at TRIUMF, which started taking physics data in September 2009, aims to reach an accuracy five times better than the previous experiments, so as to confront the theoretical calculation at the level of ±0.1%. If a deviation from the RSM is found, "new physics" beyond the SM, at potentially very high mass scales (up to 1000 TeV), could be revealed. Alternatively, sensitive constraints on hypotheses can be obtained for interactions involving pseudoscalar or scalar interactions. So far, 4 million π+ → e+ νe ue events have been accumulated by PIENU. This paper will outline the physics motivations, describe the apparatus and techniques designed to achieve high precision and present the latest results.

Original languageEnglish (US)
Article number102010
JournalJournal of Physics: Conference Series
Issue numberSECTION 10
StatePublished - 2011
EventInternational Nuclear Physics Conference 2010, INPC2010 - Vancouver, BC, Canada
Duration: Jul 4 2010Jul 9 2010

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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