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Sullivan, T.; Aguilar-Arevalo, A.; Aoki, M.; Blecher, M.; Britton, D. I.; Bryman, D. A.; Bruch, D. vom; Chen, S.; Comfort, J.; Cuen-Rochin, S.; Doria, L.; Gumplinger, P.; Hussein, A.; Igarashi, Y.; Ito, S.; Kettell, S. H.; Kurchaninov, L.; Littenberg, L. S.; Malbrunot, C.; Mischke, R. E.; Numao, T.; Protopopescu, D.; Sher, A.; Vavilov, D.
Hyperfine interactions, 2017/11, Letnik: 238, Številka: 1Journal Article
The pion branching ratio, R π = Γ ( π + → e + ν e + π + → e + ν e γ ) Γ ( π + → μ + ν μ + π + → μ + ν μ γ ) , 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.
