Improved Measurement of the π→eν Branching Ratio.

  title={Improved Measurement of the π→eν Branching Ratio.},
  author={A. A. Aguilar-Arevalo and Masanori Aoki and Melvln Blecher and Darren Britton and Douglas Bryman and D Vom Bruch and Shao-min Chen and Joseph Comfort and M C Ding and Laura Doria and S Cuen-Rochin and P. Gumplinger and Abdirazak Hussein and Yasumasa Igarashi and Soichi Ito and Steve Kettell and L. L. Kurchaninov and Laurence S. Littenberg and C. Malbrunot and Robert. Mischke and Toshio Numao and Dan Protopopescu and Anna Sher and Todd Sullivan and D. V. Vavilov and Kiyoyasu Yamada},
  journal={Physical review letters},
  volume={115 7},
A new measurement of the branching ratio R_{e/μ}=Γ(π^{+}→e^{+}ν+π^{+}→e^{+}νγ)/Γ(π^{+}→μ^{+}ν+π^{+}→μ^{+}νγ) resulted in R_{e/μ}^{exp}=[1.2344±0.0023(stat)±0.0019(syst)]×10^{-4}. This is in agreement with the standard model prediction and improves the test of electron-muon universality to the level of 0.1%. 

3 Figures & Tables