186 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
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
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
Spectra of prompt electrons from decays of B+ and B0 mesons and ratio of inclusive semielectronic branching fractions
We present spectra of prompt electrons from decays of neutral and charged B
mesons. The results are based on 140 /fb of data collected by the Belle
detector on the Upsilon(4S) resonance at the KEKB e+e- asymmetric collider. We
tag Upsilon(4S) -> B \bar{B} events by reconstructing a B meson in one of
several hadronic decay modes; the semileptonic decay of the other B meson is
inferred from the presence of an identified electron. We obtain for charged and
neutral B mesons the partial rates of semileptonic decay, to electrons with
momentum greater than 0.6 GeV/c in the B rest frame, and their ratio b_+/b_0 =
1.08 +- 0.05 +- 0.02, where the first and second errors are statistical and
systematic, respectively.Comment: 16 pages, 2 figure files, submitted to Phys. Lett.
Measurements of exclusive B_s^0 decays at the Y(5S) resonance
Several exclusive decays are studied using a 1.86 fb-1 data sample
collected at the Y(5S) resonance with the Belle detector at the KEKB asymmetric
energy e^+ e^- collider. In the decay mode we find 10
candidates and measure the corresponding branching fraction. Combining
the B_s^0 -> D_s^{(*)-} \pi^+, B_s^0 -> D_s^{(*)-} \rho^+, B_s^0 -> J/\psi \phi
and B_s^0 -> J/\psi \eta decay modes, a significant signal is observed.
The ratio \sigma (e^+ e^- -> B_s^* \bar{B}_s^*) / \sigma (e^+ e^- -> B_s^{(*)}
\bar{B}_s^{(*)}) = (93^{+7}_{-9} \pm 1)% is obtained at the Y(5S) energy,
indicating that meson production proceeds predominantly through the
creation of pairs. The and meson masses are
measured to be M(B_s^0)=(5370 \pm 1 \pm 3)MeV/c^2 and M(B_s^*)=(5418 \pm 1 \pm
3)MeV/c^2. Upper limits on the B_s^0 -> \gamma \gamma, B_s^0 -> \phi \gamma,
B_s^0 -> K^+ K^- and B_s^0 -> D_s^{(*)+} D_s^{(*)-} branching fractions are
also reported.Comment: 9 pages, 5 figures, published in Phys. Rev. D76, 012002 (2007
Search for Resonant Decays at Belle
We report measurements and searches for resonant decays where is a
meson or
the X(3872) particle.Comment: accepted by Physics Letters
Study of charmonia in four-meson final states produced in two-photon collisions
We report measurements of charmonia produced in two-photon collisions and
decaying to four-meson final states, where the meson is either a charged pion
or a charged kaon. The analysis is based on a 395fb^{-1} data sample
accumulated with the Belle detector at the KEKB electron-positron collider. We
observe signals for the three C-even charmonia eta_c(1S), chi_{c0}(1P) and
chi_{c2}(1P) in the pi^+pi^-pi^+pi^-, K^+K^-pi^+pi^- and K^+K^-K^+K^- decay
modes. No clear signals for eta_c(2S) production are found in these decay
modes. We have also studied resonant structures in charmonium decays to
two-body intermediate meson resonances. We report the products of the
two-photon decay width and the branching fractions, Gamma_{gamma gamma}B, for
each of the charmonium decay modes.Comment: 22 pages, 12 figure
Observation of B+ -> K+ eta gamma
We report measurements of radiative B decays with K eta gamma final states,
using a data sample of 253 /fb recorded at the Upsilon(4S) resonance with the
Belle detector at the KEKB e+e- storage ring. We observe B+ -> K+ eta gamma for
the first time with a branching fraction of (8.4 +- 1.5(stat) +1.2 -0.9(syst))
X 10^{-6} for M(Keta) K0 eta gamma.
We also search for B -> K3*(1780) gamma.Comment: 12 pages, 5 figures, accepted by Phys. Lett.
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
Improved measurement of CP-violating parameters in rho+rho- decays
We present a measurement of the CP-violating asymmetry in rho+rho- decays
using 535 million BBbar pairs collected with the Belle detector at the KEKB
e+e- collider. We measure CP-violating coefficients A = 0.16 +- 0.21(stat) +-
0.07 (syst) and S = 0.19 +- 0.30(stat) +- 0.07 (syst}. These values are used to
determine the unitarity triangle angle phi_2 using an isospin analysis; the
solution consistent with Standard Model lies in the range 53 < phi_2 < 114 deg.
at 90 C.L.Comment: 6 pages, 4 figures, presented at JPS/DPF 2006 (Added KEK, BELLE
preprint numbers, submitted to PRD(RC)
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