Pocanić D, Frlez E, Baranov V A, Bertl W, Brönnimann Ch, Bychkov M, Crawford J F, Daum M, Khomutov N V, Korenchenko A S, Korenchenko S M, Kozlowski T, Kravchuk N P, Kuchinsky N A, Li W, Minehart R C, Mzhavia D, Ritchie B G, Ritt S, Rozhdestvensky A M, Sidorkin V V, Smith L C, Supek I, Tsamalaidze Z, VanDevender B A, Wang Y, Wirtz H-P, Ziock K O H
Department of Physics, University of Virginia, Charlottesville, VA 22904-4714, USA.
Phys Rev Lett. 2004 Oct 29;93(18):181803. doi: 10.1103/PhysRevLett.93.181803. Epub 2004 Oct 25.
Using a large acceptance calorimeter and a stopped pion beam we have made a precise measurement of the rare pi(+)-->pi(0)e(+)nu (pi(beta)) decay branching ratio. We have evaluated the branching ratio by normalizing the number of observed pi(beta) decays to the number of observed pi(+)-->e(+)nu (pi(e2)) decays. We find the value of Gamma(pi(+)-->pi(0)e(+)nu)/Gamma(total)=[1.036+/-0.004(stat)+/-0.004(syst)+/-0.003(pi(e2))]x10(-8), where the first uncertainty is statistical, the second systematic, and the third is the pi(e2) branching ratio uncertainty. Our result agrees well with the standard model prediction.
我们使用大型接收量热计和停止的π介子束，对罕见的π⁺→π⁰e⁺ν（π(β)）衰变分支比进行了精确测量。我们通过将观察到的π(β)衰变数量与观察到的π⁺→e⁺ν（π(e2)）衰变数量进行归一化来评估分支比。我们发现Γ(π⁺→π⁰e⁺ν)/Γ(总)=[1.036±0.004(统计)±0.004(系统)±0.003(π(e2))]×10⁻⁸，其中第一个不确定度是统计性的，第二个是系统性的，第三个是π(e2)分支比的不确定度。我们的结果与标准模型预测吻合得很好。
