123 research outputs found
Study of Exclusive B decays to Charmed Baryons
Using 29.1fb-1 of data accumulated at the Upsilon(4S) with the Belle detector
at KEKB, we have studied the decay modes B0bar->Lambda_c+ pbar pi+pi-, B- ->
Lambda_c+ pbar pi-, and B0bar ->Lambda_c+ pbar. We report branching fractions
of exclusive B decays to charmed baryons with four-, three- and two-body final
states, including intermediate Sigma_c++ and Sigma_c0 states. We observed B0bar
-> Sigma_c(2455)++pbar pi- for the first time with a branching fraction of
(2.38+0.63-0.55+-0.41+-0.62)x10-4 and observed evidence for the two-body decay
B- ->Sigma_c(2455)0 pbar with a branching fraction of
(0.45+0.26-0.19+-0.07+-0.12)x10-4. We also set improved upper limits for the
two-body decays B0bar -> Lambda_c+ pbar and B- -> Sigma_c(2520)0 pbar.Comment: accepted for publication in Phys. Rev.
Observation of Large CP Violation in the Neutral B Meson System
We present a measurement of the Standard Model CP violation parameter sin
2phi_1 based on 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.
One neutral B meson is fully reconstructed as a J/psi Ks, psi(2S) Ks, chi_c1
Ks, eta_c Ks, J/psi K_L or J/psi K^{*0} decay and the flavor of the
accompanying B meson is identified from its decay products. From the asymmetry
in the distribution of the time intervals between the two B meson decay points,
we determine sin 2phi_1 = 0.99 +- 0.14(stat) +- 0.06(syst). We conclude that we
have observed CP violation in the neutral B meson system.Comment: 4 figures, to appear in Phys. Rev. Letter
Observation of B0bar --> D(*)0 p pbar
The B meson decay modes B --> D p pbar and B --> D* p pbar have been studied
using 29.4 fb^{-1} of data collected with the Belle detector at KEKB. The B0bar
--> D0 p pbar and B0bar --> D*0 p pbar decays have been observed for the first
time with branching fractions Br(B0bar --> D0 p pbar) =(1.18\pm 0.15\pm 0.16)
10^{-4} and Br(B0bar --> D*0 p pbar) =(1.20^{+0.33}_{-0.29}\pm 0.21) 10^{-4}.
No signal has been found for the B+ --> D+ p pbar and B+ --> D*+ p pbar decay
modes, and the corresponding upper limits at 90% C.L. are presented.Comment: 6 pages, 3 figures, submited to Phys. Rev. Let
Measurement of Branching Fractions for Decays
We report measurements of branching fractions for charged and neutral decays where the meson is reconstructed in the and decay
channels. The neutral channel is a CP eigenstate and can be used to
measure the CP violation parameter . We also report the first
observation of the mode. The results are based on an
analysis of 29.1 fb of data collected by the Belle detector at KEKB.Comment: To appear in Physical Review Letter
A Measurement of Lifetime Difference in Meson Decays
We report a measurement of the - mixing parameter
using 23.4 fb of data collected near the (4S) resonance with
the Belle detector at KEKB. is measured from the lifetime difference
of mesons decaying into the state and the CP even eigenstate
. We find , where
the first error is statistical and the second systematic, corresponding to a
95% confidence interval .Comment: 10 pages, 3 figure
Observation of Ds+ K- and evidence for Ds+ pi- final states in neutral B decays
We report the first observation of a B meson decay that is not accessible by
a direct spectator process. The channel B0bar -> Ds+ K- is found in a sample of
85 timse 10^6 B Bbar events, collected with the Belle detector at KEKB, with a
branching fraction Br(B0bar -> Ds+ K-)=(4.6^{+1.2}_{-1.1} +- 1.3) times
10^{-5}. We also obtain evidence for the B0 -> Ds+ pi- decay with branching
fraction Br(B0 -> Ds+ pi-)=(2.4^{+1.0}_{-0.8} +- 0.7) times 10^{-5}. This value
may be used to extract a model-dependent value of |Vub|.Comment: Accepted to publication in Phys. Rev. Let
Measurement of B0d - B0d-bar mixing rate from the time evolution of dilepton events at the Upsilon(4S)
We report a determination of the B0d - B0d-bar mixing parameter Delta-m_d
based on the time evolution of dilepton yields in Upsilon(4S) decays. The
measurement is based on a 5.9 /fb data sample collected by the Belle detector
at KEKB. The proper-time difference distributions for same-sign and
opposite-sign dilepton events are simultaneously fitted to an expression
containing Delta-m_d as a free parameter. Using both muons and electrons, we
obtain Delta-m_d = 0.463 +- 0.008(stat.) +- 0.016(sys.) ps^{-1} This is the
first determination of Delta-m_d from time evolution measurements at the
Upsilon(4S). We also place limits on possible CPT violations.Comment: 12 pages, 2 figure
Search for Charmless Two-body Baryonic Decays of B Mesons
We report the results of a search for the rare baryonic decays , , and . The analysis
is based on a data set of events collected by the
Belle detector at the KEKB collider. No statistically significant
signals are found, and we set branching fraction upper limits , , and at the 90% confidence level.Comment: 6 pages, 4 figures and 1 table. Submitted to Phys. Rev. D Rapid
Communication
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