42 research outputs found

    Measurement of the Lifetime of the Tau Lepton

    Get PDF
    The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in tau_tau = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this result with the muon lifetime supports lepton universality of the weak charged current at the level of six per mille. Assuming lepton universality, the value of the strong coupling constant, alpha_s is found to be alpha_s(m_tau^2) = 0.319 +/- 0.015(exp.) +/- 0.014 (theory)

    Measurement of the Tau Branching Fractions into Leptons

    Get PDF
    Using data collected with the L3 detector near the Z resonance, corresponding to an integrated luminosity of 150pb-1, the branching fractions of the tau lepton into electron and muon are measured to be B(tau->e nu nu) = (17.806 +- 0.104 (stat.) +- 0.076 (syst.)) %, B(tau->mu nu nu) = (17.342 +- 0.110 (stat.) +- 0.067 (syst.)) %. From these results the ratio of the charged current coupling constants of the muon and the electron is determined to be g_mu/g_e = 1.0007 +- 0.0051. Assuming electron-muon universality, the Fermi constant is measured in tau lepton decays as G_F = (1.1616 +- 0.0058) 10^{-5} GeV^{-2}. Furthermore, the coupling constant of the strong interaction at the tau mass scale is obtained as alpha_s(m_tau^2) = 0.322 +- 0.009 (exp.) +- 0.015 (theory)

    4th ECFA / DESY Workshop on Physics and Detectors for a 90-GeV to 800-GeV Linear e+ee^{+}e^{-} Collider

    No full text

    Evidence for the rare decay B+→Ds+π0

    Get PDF
    We have searched for the rare decay B+ -> D-s(+) pi(0). The analysis is based on a sample of 232 X 10(6) Y(4S) -> B (B) over bar decays collected with the BABAR detector at the SLAC PEP-II e(+)e(-) storage ring. We find 19.6 signal events, corresponding to a significance of 4.7 sigma. The extracted signal yield including statistical and systematic uncertainties is 20.1(-6.0-1.5)(+6.8+0.4) and we measure B(B+ -> D-s(+) pi(0)) = (1.5(-0.4)(+0.5) +/- 0.1 +/- 0.2) X x 10(-5), where the first uncertainty is statistical, the second is systematic, and the last is due to the uncertainty on the D-s(+) decay and its daughter decay branching fractions

    Measurements of CP-violating asymmetries in B0→a1±(1260)π∓ Decays

    Get PDF
    We present measurements of CP-violating asymmetries in the decay B-0 -> a(1)(+/-)(1260)pi(-/+) with a(1)(+/-)(1260)->pi(-/+)pi(+/-)pi(+/-). The data sample corresponds to 384x10(6) B(b) over bar pairs collected with the BABAR detector at the PEP-II asymmetric B factory at SLAC. We measure the CP-violating asymmetry A(CP)(a1 pi)=-0.07 +/- 0.07 +/- 0.02, the mixing-induced CP violation parameter S-a1 pi=0.37 +/- 0.21 +/- 0.07, the direct CP violation parameter C-a1 pi=-0.10 +/- 0.15 +/- 0.09, and the parameters Delta C-a1 pi=0.26 +/- 0.15 +/- 0.07 and Delta S-a1 pi=-0.14 +/- 0.21 +/- 0.06. From these measured quantities we determine the angle alpha(eff)=78.6 degrees +/- 7.3 degrees

    Branching fraction and CP-violation charge asymmetry measurements for B-meson decays to ηK±, ηπ±, η′K, η′π±, ωK, and ωπ±

    Get PDF
    We present measurements of the branching fractions for B-0-meson decays to eta'K-0 and omega K-0, and of the branching fractions and CP-violation charge asymmetries for B+-meson decays to eta pi(+), eta K+, eta'pi(+), eta'K+, omega pi(+), and omega K+. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 383x10(6) B (B) over bar pairs produced in e(+)e(-) annihilation. The measurements agree with previous results; we find no evidence for direct CP violation

    Improved limits on the lepton-flavor violating decays tau(-) -> l(-)l(+)l(-)

    Get PDF
    A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376 fb(-1) of data collected at an e(+)e(-) center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC PEP-II storage rings. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (4-8)x10(-8) at 90% confidence level

    Production and decay of Ωc0

    Get PDF
    We present an analysis of inclusive Omega(0)(c) baryon production and decays in 230.5 fb(-1) of data recorded with the BABAR detector. Omega(0)(c) baryons are reconstructed in four final states (Omega(-)pi(+), Omega(-)pi(+)pi(0), Omega(-)pi(+)pi(+)pi(-), Xi K--(-)pi(+)pi(+)) and the corresponding ratios of branching fractions are measured. We also measure the momentum spectrum in the e(+)e(-) center-of-mass frame. From the spectrum, we observe Omega(0)(c) production from B decays and in c (c) over bar events, and extract the two rates of production

    Amplitude analysis of the decay D0→K-K+π0

    Get PDF
    Using 385 fb(-1) of e(+)e(-) collisions, we study the amplitudes of the singly Cabibbo-suppressed decay D-0 -> K-K+pi(0). We measure the strong phase difference between the (D) over bar (0) and D-0 decays to K-*(892)K-+(-) to be -35.5 degrees +/- 1.9 degrees(stat)+/- 2.2 degrees(syst), and their amplitude ratio to be 0.599 +/- 0.013(stat)+/- 0.011(syst). We observe contributions from the K pi and K-K+ scalar and vector amplitudes, and analyze their angular moments. We find no evidence for charged kappa, nor for higher spin states. We also perform a partial-wave analysis of the K-K+ system in a limited mass range
    corecore