2,449 research outputs found
Measurements of Branching Fractions and Polarization in B > K^* rho Decays
We present results of a study of the charmless vector-vector decays B^0 ->
K^{*0} rho^0 and B^+ ->K^{*0} rho^+. The results are based on a 140 fb^{-1}
data sample collected by the Belle detector at the KEKB asymmetric e^+e^-
collider. We obtain the branching fraction B(B^+ -> K^{*0} rho^+)=(6.6 +-
2.2(stat.) +- 0.8 (syst.)) x 10^{-6}, and set upper limits on the branching
fractions B(B^0 -> K^{*0} rho^0) f_0(980)
K^{*0})<5.2 x 10^{-6}. We also perform a helicity analysis of the rho and K^*
vector mesons in the decay B^+ -> K^{*0} rho^+, and obtain the longitudinal
polarization fraction R_0(B^+ -> K^{*0} rho^+)=0.50 +-
0.19(stat.)+0.05-0.07}(syst.).Comment: 11 pages, 4 figures, submitted to ICHEP04, Beijing, Chin
Measurement of the branching fractions for B- --> D(*)+ pi- l- nu-bar and B0bar --> D(*)0 pi+ l- nu-bar
We report on a measurement of the branching fractions for B- --> D(*)+ pi- l-
nu-bar and B0bar --> D(*)0 pi+ l- nu-bar with 275 million BBbar events
collected at the Upsilon(4S) resonance with the Belle detector at KEKB. Events
are tagged by fully reconstructing one of the B mesons in hadronic modes. We
obtain Br(B- --> D+ pi- l- nu-bar) = (0.54 +/- 0.07(stat) +/- 0.07(syst) +/-
0.06(BR)) x 10^-2, Br(B- --> D*+ pi- l- nu-bar) = (0.67 +/- 0.11(stat) +/-
0.09(syst) +/- 0.03(BR)) x 10^-2, Br(B0bar --> D0 pi+ l- nu-bar) = (0.33 +/-
0.06(stat) +/- 0.06(syst) +/- 0.03(BR)) x 10^-2, Br(B0bar --> D*0 pi+ l-
nu-bar) = (0.65 +/- 0.12(stat) +/- 0.08(syst) +/- 0.05(BR)) x 10^-2, where the
third error comes from the error on Bbar --> D(*) l- nu-bar decays.
Contributions from B0bar --> D*+ l- nu-bar decays are excluded in the
measurement of B0bar --> D0 pi+ l- nu-bar.Comment: 6 pages, 10 figures, submitted to Physical Review D (Rapid
Communication), the Lepton-Photon 2005 Conference (Uppsala, Sweden) and the
HEP2005 Europhysics Conference (Lisboa, Portugal
Observation of B+->Lambda_c+Lambda_c-K+ and B0->Lambda_c+Lambda_c^-K0 decays
We report first measurements of the doubly charmed baryonic B decays
B->Lambda_c+Lambda_c-K. The B+->Lambda_c+Lambda_c-K+ decay is observed with a
branching fraction of (6.5+1.0-0.9+-1.1+-3.4)x10^{-4} and a statistical
significance of 15.4sigma. The B0->Lambda_c+Lambda_c-K0 decay is observed with
a branching fraction of (7.9+2.9-2.3+-1.2+-4.2)x10^{-4} and a statistical
significance of 6.6sigma. The branching fraction errors are statistical,
systematic, and the error resulting from the uncertainty of Lambda_c+->pK-pi+
decay branching fraction. The analysis is based on 357fb-1 of data accumulated
at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e+e-
collider.Comment: 10 pages, 3 figure
Measurement of Time-Dependent CP-Violating Asymmetries in Decay
We present a measurement of CP-violation parameters in the B0 -> KsKsKs decay
based on a sample of 275 x 10^6 BBbar pairs collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider.
One neutral B meson is fully reconstructed in the decay B0 -> KsKsKs, and the
flavor of the accompanying B meson is identified from its decay products.
CP-violation parameters are obtained from the asymmetry in the distributions of
the proper-time interval between the two B decays: S = +1.26 +/- 0.68(stat) +/-
0.20(syst) and A = +0.54 +/- 0.34(stat) +/- 0.09(syst).Comment: 10 pages, 2 figures 10 pages, 2 figure
Determination of |V_ub| from Measurements of the Inclusive Charmless Semileptonic Partial Rates of B Mesons using Full Reconstruction Tags
We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element
|V_ub|, based on 253 fb^-1 of data collected by the Belle detector at the KEKB
e^+e^- asymmetric collider. Events are tagged by fully reconstructing one of
the B mesons, produced in pairs from Upsilon(4S). The signal for b->u
semileptonic decay is distinguished from the b->c background using the hadronic
mass M_X, the leptonic invariant mass squared q^2 and the variable P_+ =
E_X-|\vec{p}_X|. The results are obtained for events with the prompt-lepton
momentum, p_l^* >= 1GeV/c, in three kinematic regions (1) M_X < 1.7 Gev/c^2,
(2) M_X 8 GeV^2/c^2, and by (3) P_+ < 0.66
GeV/c, allowing for a comparison of the three methods. The matrix element
|V_ub| is found to be (4.09+-0.19+-0.20(+0.14-0.15)+-0.18), where the errors
are statistical, systematic including Monte Carlo modeling, theoretical, and
from shape function parameter determination, respectively.Comment: 6 pages, 3 figures, 3 tables. Version as it appears in PRL. Changes
from v1: |V_ub| recalculated using mb(SF)=4.60+-0.04 and
mu_pi^2(SF)=0.20+-0.04. Title and text changed to reflect the calculation of
partial rate instead of partial Br. Fig. 3 changed. Explicit dependence of
the result on mb(SF) is give
Study of J/psi to p pbar, Lambda Lambdabar and observation of eta_c to Lambda Lambdabar at Belle
We study the baryonic charmonium decays of B mesons, B+ to etac K+ and B+ to
J/psi K+, where the etac and J/psi subsequently decay into a p pbar or Lambda
Lambdabar pair. We measure the J/psi to p pbar, Lambda Lambdabar anisotropy
parameters, alpha_B = -0.60 +- 0.13 +-0.14 (p pbar), -0.44 +- 0.51 +- 0.31
(Lambda Lambdabar) and compare to results from e+e- to J/psi formation
experiments. We also report the first observation of etac to Lambda Lambdabar.
The measured branching fraction is B(etac to Lambda Lambdabar) = (0.87 +0.24
-0.21(stat) +0.09 -0.14(syst) +- 0.27 (PDG)) x 10^-3. This study is based on a
357 fb^-1 data sample recorded on the Upsilon(4S) resonance with the Belle
detector at the KEKB asymmetric-energy e+e- collider.Comment: 8 pages, two figures (4 figure files), an update of hep-ex/0509020
for journal submissio
Observation of -> DsJ*(2317)+ K- decay
The decays and
are studied for the first time. A significant signal is observed in the
decay channel with . No signals are observed in
the ,
and decay modes, and upper limits are
obtained. The analysis is based on a dataset of 140 fb collected by the
Belle experiment at the asymmetric collider KEKB.Comment: 9 pages, 2 figures, submitted to PR
Study of B0 -> rho+-pi-+ Time-dependent CP Violation at Belle
We present a time-dependent analysis of CP violation in B0 -> rho pi decays
based on a 140 1/fb data sample collected at the Y(4S) resonance with the Belle
detector at the KEKB asymmetric-energy e+e- collider. We fully reconstruct one
neutral B meson in the rho+-pi-+ final state and identify the flavor of the
accompanying B meson from its decay products. We obtain the charge asymmetry
ACP = -0.16+-0.10(stat)+-0.02(syst). An unbinned maximum likelihood fit to the
proper-time distributions yields C = 0.25+-0.17(stat)+0.02-0.06(syst), DC =
0.38+-0.18(stat)+0.02-0.04(syst), S = -0.28+-0.23(stat)+0.10-0.08(syst), and DS
= -0.30+-0.24(stat)+-0.09(syst). The direct CP violation parameters for B ->
rho+pi- and B -> rho-pi+ decays are A+- = -0.02+-0.16(stat)+0.05-0.02(syst) and
A-+ = -0.53+-0.29(stat)+0.09-0.04(syst).Comment: 10 pages, 3 figures, submitted to Phys. Rev. Let
Observation of a near-threshold omega-J/psi mass enhancement in exclusive B-->K omega J/psi decays
We report the observation of a near-threshold enhancement in the omega-J/psi
invariant mass distribution for exclusive B-->K omega J/psi decays. The results
are obtained from a 253 fb-1 data sample that contains 275 million BB-bar meson
pairs that were collected near the Upsilon(4S) resonance with the Belle
detector at the KEKB asymmetric energy e+e- collider. The statistical
significance of the omega-J/psi mass enhancement is estimated to be greater
than 8 sigma.Comment: 12 pages, 4 figures, submitted to Physical Review Letter
Observation of B+ -> proton Lambdabar gamma
We report the first observation of the radiative hyperonic B decay B+ ->
proton Lambdabar gamma, using a 140 fb-1 data sample recorded on the
Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy
e+e- collider. The measured branching fraction is B(B+ -> proton Lambdabar
gamma) = (2.16 ^{+0.58}_{-0.53} +- 0.20) times 10^{-6}. A search for B+ ->
proton Sigmabar gamma yields no significant signal, so we set a 90%
confidence-level upper limit on the branching fraction of B(B+ -> proton
Sigmabar gamma) < 3.3 times 10^{-6}.Comment: 12 pages, 4 figures, submitted to ICHEP2004, Beijing, Chin
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