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Author(s)
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Sullivan, T (British Columbia U.) ; Aguilar-Arevalo, A (Mexico U., ICN) ; Aoki, M (Osaka U.) ; Blecher, M (Virginia Tech.) ; Britton, D I (Glasgow U.) ; Bryman, D A (British Columbia U.) ; Bruch, D vom (Mainz U.) ; Chen, S (Tsinghua U., Beijing) ; Comfort, J (Arizona State U.) ; Cuen-Rochin, S (British Columbia U.) ; Doria, L (TRIUMF) ; Gumplinger, P (TRIUMF) ; Hussein, A (Northern British Columbia U.) ; Igarashi, Y (KEK, Tsukuba) ; Ito, S (Osaka U.) ; Kettell, S H (Brookhaven) ; Kurchaninov, L (TRIUMF) ; Littenberg, L S (Brookhaven) ; Malbrunot, C (CERN) ; Mischke, R E (TRIUMF) ; Numao, T (TRIUMF) ; Protopopescu, D (Glasgow U.) ; Sher, A (TRIUMF) ; Vavilov, D (TRIUMF) |
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Abstract
| The pion branching ratio, $R_{\pi } = \frac { {\Gamma }(\pi ^{+} \rightarrow e^{+} \nu _{e} + \pi ^{+}\rightarrow e^{+} \nu _{e} \gamma )}{\Gamma (\pi ^{+} \rightarrow \mu ^{+} \nu _{\mu } + \pi ^{+} \rightarrow \mu ^{+} \nu _{\mu } \gamma )}$ , provides a sensitive test of lepton universality and constraints on many new physics scenarios. The theoretical uncertainty on the Standard Model prediction of R$_{π}$ is 0.02 %, a factor of twenty smaller than the experimental uncertainty. The analysis of a subset of data taken by the PIENU experiment will be presented. The result, R$_{π}$ = (1.2344 ± 0.0023(s t a t) ± 0.0019(s y s t)) ⋅ 10$^{−4}$ [1], is consistent with the Standard Model prediction and represents a 0.1 % constraint on lepton non-universality. |