2008 / 09 23 5 Testing lepton universality , the π → eν / π → μ ν branching ratio


Determinations of Re/μ are based on observing final states with positrons emerging from a stopped π beam. Decays π → eν(γ) result in positrons appearing with the pion lifetime (26 ns) and with an energy distribution peaking at Ee+ = mπc/2. Decays π → μν(γ) result in positrons too, through the subsequent decay μ → eνν. The latter process leads to a time… (More)


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