254 research outputs found
Moments of the Hadronic Invariant Mass Spectrum in B --> X_c l nu Decays at Belle
We present a measurement of the hadronic invariant mass squared (M^2_X)
spectrum in charmed semileptonic B meson decays B --> X_c l nu based on 140
fb^-1 of Belle data collected near the Y(4S) resonance. We determine the first,
the second central and the second non-central moments of this spectrum for
lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations
between these measurements are evaluated.Comment: published version of the paper (one figure added, minor changes in
the text); 16 pages, 3 figures, 10 table
Measurement of the gamma gamma -> pi+ pi- and gamma gamma -> K+ K- processes at energies of 2.4 - 4.1 GeV
We have measured pi+pi- and K+K- production in two-photon collisions using
87.7 /fb of data collected with the Belle detector at the asymmetric energy
e+e- collider KEKB. The cross sections are measured to high precision in the
two-photon center-of-mass energy (W) range between 2.4 GeV < W < 4.1 GeV and
angular region |cos theta^{*}| < 0.6. The cross section ratio
sigma(gammagamma->K+K-)/sigma(gammagamma->pi+pi-) is measured to be 0.89 +-
0.04(stat) +- 0.15(syst) in the range of 3.0 GeV < W < 4.1 GeV, where the ratio
is energy independent. We observe a sin^{-4} theta^{*} behavior of the cross
section in the same W range. Production of chi_{c0} and chi_{c2} mesons is
observed in both gammagamma -> pi+pi- and gammagamma -> K+K- modes.Comment: 17 pages, 5 figures, submitted to Phys. Lett. B, errors relative to
the two-photon decay width correcte
Search for tau -> e gamma decay at Belle
We have searched for the lepton-flavor-violating decay tau -> e gamma using a
data sample of 86.7/fb collected with the Belle detector at the KEKB asymmetric
e^+ e^- collider. No evidence for a signal is obtained, and we set an upper
limit for the branching fraction Br(tau -> e gamma) < 3.9 x 10^-7 at the 90%
C.L.Comment: 11 pages, 10 figures, ReVTeX4, eps
Observation of the Decays B0->K+pi-pi0 and B0->rho-K+
We report the observation of B^0 decays to the K^+pi^-pi^0 final state using
a data sample of 78 fb^-1 collected by the Belle detector at the KEKB e^+e^-
collider. With no assumptions about intermediate states in the decay, the
branching fraction is measured to be (36.6^{+4.2}_{-4.3}+- 3.0)*10^-6.We also
search for B decays to intermediate two-body states with the same K^+pi^-pi^0
final state. Significant B signals are observed in the rho(770)^- K^+ and
K^*(892)^+pi^- channels, with branching fractions of
(15.1^{+3.4+1.4+2.0}_{-3.3-1.5-2.1})* 10^-6 and
(14.8^{+4.6+1.5+2.4}_{-4.4-1.0-0.9})* 10^-6, respectively. The first error is
statistical, the second is systematic and the third is due to the largest
possible interference. Contributions from other possible two-body states will
be discussed. No CP asymmetry is found in the inclusive K^+pi^-pi^0 or rho^-K^+
modes, and we set 90% confidence level bounds on the asymmetry of
-0.12<A_{CP}<0.26 and -0.18<A_{CP}<0.64, respectively.Comment: 18 pages, 7 figure
Time-Dependent CP Violation Effects in Partially Reconstructed Decays
We report measurements of time-dependent decay rates for decays and extraction of CP violation parameters related to .
We use a partial reconstruction technique, whereby signal events are identified
using information only from the primary pion and the charged pion from the
decay of the . The analysis uses of data
accumulated at the resonance with the Belle detector at the KEKB
asymmetric-energy collider. We measure the CP violation parameters
and .Comment: 15 pages, 5 figures. To appear in Physics Letters
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings
Single W boson production in electron-positron collisions is studied with the
L3 detector at LEP. The data sample collected at a centre-of-mass energy of
\sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1.
Events with a single energetic lepton or two acoplanar hadronic jets are
selected. Within phase-space cuts, the total cross-section is measured to be
0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation.
Including our single W boson results obtained at lower \sqrt{s}, the WWgamma
gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma =
0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13
Search for an invisibly decaying Higgs boson in e^+e^- collisions at \sqrt{s} = 183 - 189 GeV
A search for a Higgs boson decaying into invisible particles is performed
using the data collected at LEP by the L3 experiment at centre-of-mass energies
of 183 GeV and 189 GeV. The integrated luminosities are respectively 55.3 pb^-1
and 176.4 pb^-1. The observed candidates are consistent with the expectations
from Standard Model processes. In the hypothesis that the production cross
section of this Higgs boson equals the Standard Model one and the branching
ratio into invisible particles is 100%, a lower mass limit of 89.2 GeV is set
at 95% confidence level
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV
A search for the lightest neutral scalar and neutral pseudoscalar Higgs
bosons in the Minimal Supersymmetric Standard Model is performed using 176.4
pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of
189 GeV. No signal is observed, and the data are consistent with the expected
Standard Model background. Lower limits on the masses of the lightest neutral
scalar and pseudoscalar Higgs bosons are given as a function of tan(beta).
Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h
> 77.1 GeV and m_A > 77.1 GeV
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
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