title: Improved limits on nu(e) emission from mu+ decay.
abstract: We investigated mu(+) decays at rest produced at the ISIS beam stop target. Lepton flavor (LF) conservation has been tested by searching for nu(e) via the detection reaction p(nu(e),e(+))n. No nu(e) signal from LF violating mu(+) decays was identified. We extract upper limits of the branching ratio (BR) for the LF violating decay mu(+)-->e(+)+nu(e)+nu(-) compared to the standard model (SM) mu(+)-->e(+)+nu(e)+nu(mu) decay: BR<0.9(1.7) x 10(-3) (90% C.L.) depending on the spectral distribution of nu(e) characterized by the Michel parameter rho=0.75(0.0). These results improve earlier limits by one order of magnitude and restrict extensions of the SM in which nu(e) emission from mu(+) decay is allowed with considerable strength. The decay mu(+)-->e(+)+nu(e)+nu(mu) often proposed as a potential source for the nu(e) signal observed in the LSND experiment can be excluded.
authors.affiliation: Institut für Kernphysik, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Armbruster
authors.forename: G
authors.initials: G
authors.lastname: Drexlin
authors.forename: K
authors.initials: K
authors.lastname: Eitel
authors.forename: T
authors.initials: T
authors.lastname: Jannakos
authors.forename: J
authors.initials: J
authors.lastname: Kleinfeller
authors.forename: R
authors.initials: R
authors.lastname: Maschuw
authors.forename: C
authors.initials: C
authors.lastname: Oehler
authors.forename: P
authors.initials: P
authors.lastname: Plischke
authors.forename: J
authors.initials: J
authors.lastname: Reichenbacher
authors.forename: M
authors.initials: M
authors.lastname: Steidl
authors.forename: B
authors.initials: B
authors.lastname: Zeitnitz
authors.forename: H
authors.initials: H
authors.lastname: Gemmeke
authors.forename: M
authors.initials: M
authors.lastname: Kleifges
authors.forename: C
authors.initials: C
authors.lastname: Eichner
authors.forename: C
authors.initials: C
authors.lastname: Ruf
authors.forename: B A
authors.initials: BA
authors.lastname: Bodmann
authors.forename: E
authors.initials: E
authors.lastname: Finckh
authors.forename: J
authors.initials: J
authors.lastname: Hössl
authors.forename: P
authors.initials: P
authors.lastname: Jünger
authors.forename: W
authors.initials: W
authors.lastname: Kretschmer
authors.forename: J
authors.initials: J
authors.lastname: Wolf
authors.forename: N E
authors.initials: NE
authors.lastname: Booth
authors.forename: I M
authors.initials: IM
authors.lastname: Blair
authors.forename: J A
authors.initials: JA
authors.lastname: Edgington