1,290 research outputs found
Observation of B+- -> omega K+- Decay
We report the first observation of the charmless two-body mode decay, and a new measurement of the branching fraction for the
decay. The measured branching fractions are
and . %and we set 90% confidence
level upper limits of %.
We also measure the partial rate asymmetry of decays
and obtain . The results are based on
a data sample of 29.4 fb collected on the resonance by
the Belle detector at the KEKB collider.Comment: 5 pages, 4 figures, resubmitted to Phys. Rev. Let
Observation of Double cc bar Production in e+ e- Annihilation at sqrt{s} ~ 10.6 GeV
We report the observation of prompt J/psi via double ccbar production from
the e+e- continuum. In this process one ccbar pair fragments into a J/psi meson
while the remaining pair either produces a bound charmonium state or fragments
into open charm. Both cases have been observed: the first by studying the mass
spectrum of the system recoiling against the J/psi, and the second by
reconstructing the J/psi together with a charmed meson. We find cross-sections
of \sigma(e+ e- -> J/psi eta_c (gamma)) * BR (eta_c -> >=4 charged) = 0.033
(+0.007 -0.006)(stat) \pm 0.009(syst)pb and \sigma(e+ e- -> J/psi D*+ X) = 0.53
(+0.19 -0.15)(stat) \pm 0.14(syst) pb, and infer \sigma(e+ e- -> J/psi c cbar)
/ \sigma(e+ e- -> J/psi X) = 0.59 (+0.15 -0.13)(stat) \pm 0.12(syst). These
results are obtained from a 46.2/fb data sample collected near the Upsilon(4S)
resonance, with the Belle detector at the KEKB asymmetric energy e+ e-
collider.Comment: 7 pages, 2 figures, to be submitted to Physical Review Letter
Observation of the decay B^0->D+D*-
We report the first observation of the decay B^0->D+-D*-+ with the Belle
detector at the KEKB e^+e^- collider operated at the Upsilon(4S) resonance. The
sum of branching fractions B(B^0->D+D*-)+B(B^0->D-D*+) is measured to be
(1.17+-0.26+0.22-0.25)x10^-3 using the full reconstruction method where both
charmed mesons from B^0 decays are reconstructed. A consistent value
((1.48+-0.38+0.28-0.31)x10^-3) is obtained using a partial reconstruction
technique that only uses the slow pion from the D*- ->bar D^0pi- decay and a
fully reconstructed D+ to reconstruct the B^0.Comment: 10 pages, 3 figure
Measurement of the CP Violation Parameter sin(2phi_1) in B^0_d Meson Decays
We present a measurement of the Standard Model CP violation parameter
sin(2phi_1) based on a 10.5 fb^{-1} data sample collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric e+e- collider. One
neutral B meson is reconstructed in the J/psi K_S, psi(2S) K_S, chi_{c1} K_S,
eta_c K_S, J/psi K_L or J/psi pi^0 CP-eigenstate decay channel and the flavor
of the accompanying B meson is identified from its charged particle decay
products. From the asymmetry in the distribution of the time interval between
the two B-meson decay points, we determine sin(2phi_1) = 0.58 +0.32-0.34 (stat)
+0.09-0.10 (syst).Comment: LaTex, 13 pages, 3 figures, submitted to P.R.
Measurement of Branching Fractions and Charge Asymmetries for Two-Body B Meson Decays with Charmonium
We report branching fractions and charge asymmetries for exclusive decays of
charged and neutral B mesons to two-body final states containing a charmonium
meson, J/psi or psi(2S). This result is based on a 29.4 fb^{-1} data sample
collected at the Upsilon(4S) resonance with the Belle detector at the KEKB
asymmetric e+e- collider.Comment: 13 pages, 5 figures, revte
Observation of Mixing-induced CP Violation in the Neutral B Meson System
This report describes an observation of mixing-induced CP violation and a
measurement of the CP violation parameter, sin(2phi_1), with the Belle detector
at the KEKB asymmetric e+e- collider. Using a data sample of 29.1 fb-1 recorded
on the Upsilon(4S) resonance that contains 31.3 million BBbar pairs, we
reconstruct decays of neutral B mesons to the following CP eigenstates: J/psi
K_S^0, psi(2S) K_S^0, chi_c1 K_S^0, eta_c K_S^0, J/psi K_L^0 and J/psi K^*0.
The flavor of the accompanying B meson is identified by combining information
from primary and secondary leptons, K+/- mesons, lambda baryons, slow and fast
pions. The proper-time interval between the two B meson decays is determined
from the distance between the two decay vertices measured with a silicon vertex
detector. The result sin(2phi_1) = 0.99 +/- 0.14(stat) +/- 0.06(syst) is
obtained by applying a maximum likelihood fit to the 1137 candidate events. We
conclude that there is large CP violation in the neutral B meson system. A zero
value for sin(2phi_1) is ruled out by more than six standard deviations.Comment: 25 pages, 16 figures, accepted for publication in Physical Review
Mesurement of the B0 - anti-B0 Mixing Parameter Delta m_d using Semileptonic B0 Decays
We present a measurement of the B^0-B^0bar mixing parameter Delta m_d using
neutral B meson pairs in a 29.1 fb^{-1} data sample collected at the
Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy
e^+e^- collider. We exclusively reconstruct one neutral B meson in the
semileptonic B^0 \to D^{*-}\ell^+\nu decay mode and identify the flavor of the
accompanying B meson from its decay products. From the distribution of the time
intervals between the two flavor-tagged B meson decay points, we obtain Delta
m_d = (0.494 +- 0.012 +- 0.015) ps^{-1}, where the first error is statistical
and the second error is systematic.Comment: 10 pages, 3 figures, Published in Phys.Rev.Lett. 89, 251803 (2002
Charmless Hadronic Two-Body B Meson Decays
We report the results of a study of two-body B meson decays to the complete
set of K pi, pi pi, and K K final states. The study is performed on a data
sample of 31.7 +/- 0.3 million B B-bar events recorded on the Upsilon(4S)
resonance by the Belle experiment at KEKB. We observe significant signals in
all K pi final states and in the pi+ pi- and pi+ pi0 final states. We set
limits on the pi0 pi0 and K K final states. A search is performed for
partial-rate asymmetries between conjugate states for flavor-specific final
states.Comment: Submitted to PR
Production of Prompt Charmonia in Annihilation at GeV
The production of prompt , , and is
studied using a data sample collected with the Belle detector at
the and 60 MeV below the resonance. The yield of prompt
mesons in the sample is compatible with that of continuum
production; we set an upper limit at the 95% confidence level, and find pb. The cross-sections for prompt
and direct are measured. The momentum spectrum, production
angle distribution and polarization are studied.Comment: submitted to Phys. Rev. Let
Measurement of the mixing rate with partial reconstruction
We report a measurement of the mixing parameter
based on a sample of resonance decays
collected by the Belle detector at the KEKB asymmetric collider. We
use events with a partially reconstructed candidate and where the flavor of the accompanying meson is
identified by the charge of the lepton from a decay. The proper-time difference between the two mesons is
determined from the distance between the two decay vertices. From a
simultaneous fit to the proper-time distributions for the same-flavor
(, ) and opposite-flavor (,
) event samples, we measure the mass difference between the two
mass eigenstates of the neutral meson to be = .Comment: 16 pages, 14 figure
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