title: Precise measurement of the pi+-->pi0 e+nu branching ratio.
abstract: 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.
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, VA 22904-4714, USA. pocanic@virginia.edu
authors.forename: D
authors.initials: D
authors.lastname: Pocanić
authors.forename: E
authors.initials: E
authors.lastname: Frlez
authors.forename: V A
authors.initials: VA
authors.lastname: Baranov
authors.forename: W
authors.initials: W
authors.lastname: Bertl
authors.forename: Ch
authors.initials: Ch
authors.lastname: Brönnimann
authors.forename: M
authors.initials: M
authors.lastname: Bychkov
authors.forename: J F
authors.initials: JF
authors.lastname: Crawford
authors.forename: M
authors.initials: M
authors.lastname: Daum
authors.forename: N V
authors.initials: NV
authors.lastname: Khomutov
authors.forename: A S
authors.initials: AS
authors.lastname: Korenchenko
authors.forename: S M
authors.initials: SM
authors.lastname: Korenchenko
authors.forename: T
authors.initials: T
authors.lastname: Kozlowski
authors.forename: N P
authors.initials: NP
authors.lastname: Kravchuk
authors.forename: N A
authors.initials: NA
authors.lastname: Kuchinsky
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: R C
authors.initials: RC
authors.lastname: Minehart
authors.forename: D
authors.initials: D
authors.lastname: Mzhavia
authors.forename: B G
authors.initials: BG
authors.lastname: Ritchie
authors.forename: S
authors.initials: S
authors.lastname: Ritt
authors.forename: A M
authors.initials: AM
authors.lastname: Rozhdestvensky
authors.forename: V V
authors.initials: VV
authors.lastname: Sidorkin
authors.forename: L C
authors.initials: LC
authors.lastname: Smith
authors.forename: I
authors.initials: I
authors.lastname: Supek
authors.forename: Z
authors.initials: Z
authors.lastname: Tsamalaidze
authors.forename: B A
authors.initials: BA
authors.lastname: VanDevender
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: H-P
authors.initials: HP
authors.lastname: Wirtz
authors.forename: K O H
authors.initials: KO
authors.lastname: Ziock