123 research outputs found
Search for CP Violation in the Decays
We have searched for CP violation in the decays
where denotes a neutral pseudo-scalar meson which is either a ,
, or using KEKB asymmetric-energy collision data
corresponding to an integrated luminosity of 791 fb collected with the
Belle detector. No evidence of significant CP violation is observed. We report
the most precise CP asymmetry measurement in the decay to date: . We also report the first measurements of
CP asymmetries in the decays and : and , respectively
Search for Decays at Belle
We present a search for the B-> pi e^+ e^- and B-> pi \mu^+ \mu^- decays,
with a data sample of 657 million BBbar pairs collected with the Belle detector
at the KEKB collider. Signal events are reconstructed from a charged
or a neutral pion candidate and a pair of oppositely charged electrons or
muons. No significant signal is observed and we set the upper limit on the
isospin-averaged branching fraction BF(B -> \pi \ell^+\ell^-) < 6.2x10^-8 at
the 90% confidence level.Comment: 8 pages, 3 figures, accepted by PRD(RC
Search for CP violation in the decays and
We have searched for CP violation in the charmed meson decays and using 673 fb of data
collected with the Belle detector at the KEKB asymmetric-energy
collider. No evidence for CP violation is observed. We report the most
sensitive CP asymmetry measurements to date for these decays: , , , and , where the first uncertainties are statistical and
the second are systematic
Dalitz analysis of B --> K pi psi' decays and the Z(4430)+
From a Dalitz plot analysis of B --> K pi psi' decays, we find a signal for
Z(4430)+ --> pi+ psi' with a mass M= (4443(+15-12)(+19-13))MeV/c^2, width
Gamma= (107(+86-43)(+74-56))MeV, product branching fraction BR(B0 --> K-
Z(4430)+) x BR(Z(4430)+ --> pi+ psi')= (3.2(+1.8-0.9)(+5.3-1.6)) x 10^{-5}, and
significance of 6.4sigma that agrees with previous Belle measurements based on
the same data sample. In addition, we determine the branching fraction BR(B^0
--> K*(892)^0 psi')= (5.52(+0.35-0.32)(+0.53-0.58)) x 10^{-4} and the fraction
of K*(892)^0 mesons that are longitudinally polarized f_L=
44.8(+4.0-2.7)(+4.0-5.3)%. These results are obtained from a 605fb^{-1} data
sample that contains 657 million B-anti-B pairs collected near the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric energy e+e- collider.Comment: Final version published in PRD(RC
Measurements of Charmless Hadronic b->s Penguin Decays in the pi+pi-K+pi- Final State and First Observation of B0 -> rho0K+pi-
We report measurements of charmless hadronic B^0 decays into the pi+pi-K+pi+
final state. The analysis uses a sample of 657x10^6 BBbar pairs collected with
the Belle detector at the KEKB asymmetric-energy e+e- collider at the Y(4S)
resonance. The decay B^0 -> rho0 Kpi is observed for the first time; the
significance is 5.0sigma and the corresponding partial branching fraction for
M_Kpi in (0.75,1.20) GeV/c^2 is [2.8 +- 0.5(stat) +-0.5(syst)] x 10^{-6}. We
also obtain the first evidence for B^0 -> f0Kpi with 3.5sigma significance and
for B^0 -> pi+pi-K*0 with 4.5sigma significance. For the two-body decays B^0 ->
rho0K*0 and B^0 -> f0K*0, the significances are 2.7sigma and 2.5sigma,
respectively, and the upper limits on the branching fractions are 3.4x10^{-6}
and 2.2x10^{-6} at 90% confidence level.Comment: 6 pages, 3 figures. accepted by PRD(RC
Measurement of Time-Dependent CP-Violating Parameters in B0 -> K0S K0S decays
We report a measurement of the CP-violating parameters in B0->K0S K0S decays
based on a data sample of 657 million BBbar pairs collected at the Y(4S)
resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
In this study, one neutral B meson is fully reconstructed in the B0->K0S K0S
decay mode, and the flavor of the accompanying B meson is identified by its
decay products. The CP-violating parameters are measured from the asymmetry in
the distributions of the proper-time interval between the two B decays: S =
-0.38 +0.69-0.77(stat) +-0.09(syst) and A = -0.38 +-0.38(stat) +-0.05(syst).Comment: 5pages, 2figures, submitted to PR
First Measurement of Inclusive B -> X_s eta Decays
We report a first measurement of inclusive B -> X_s eta decays, where X_s is
a charmless state with unit strangeness. The measurement is based on a
pseudo-inclusive reconstruction technique and uses a sample of 657 x 10^6
BB-bar pairs accumulated with the Belle detector at the KEKB e^+e^- collider.
For M_{X_s} < 2.6 GeV/c^2, we measure a branching fraction of (26.1 +/- 3.0
(stat) +1.9 -2.1 (syst) +4.0 -7.1 (model)) x 10^-5 and a direct CP asymmetry of
A_{CP} = -0.13 +/- 0.04 +0.02 -0.03. Over half of the signal occurs in the
range M_{X_s} > 1.8 GeV/c^2.Comment: 6 pages, 1 figure, 1 table, submitted to Physical Review Letter
Measurement Of |V_ub| From Inclusive Charmless Semileptonic B Decays
We present the partial branching fraction for inclusive charmless
semileptonic B decays and the corresponding value of the CKM matrix element
|Vub|, using a multivariate analysis method to access ~90% of the B -> Xu l nu
phase space. This approach dramatically reduces the theoretical uncertainties
from the b-quark mass and non-perturbative QCD compared to all previous
inclusive measurements. The results are based on a sample of 657 million B
-Bbar pairs collected with the Belle detector. We find that Delta BR(B -> Xu l
nu; p^*B_l>1.0 GeV/c=1.963 x (1 +/- 0.088(stat.) +/- 0.081(sys.)) x 10^-3.
Corresponding values of |Vub| are extracted using several theoretical
calculations.Comment: 9 pages, 1 figure, 2 tables. Published in PR
Search for Lepton Flavor and Lepton Number Violating tau Decays into a Lepton and Two Charged Mesons
We search for lepton flavor and lepton number violating tau decays into a
lepton (ell = electron or muon) and two charged mesons (h,h' = pi^\pm or
K^\pm), tau- -> ell-h+h'- and tau- -> ell+h-h'-, using 671 fb^{-1} of data
collected with the Belle detector at the KEKB asymmetric-energy e+e- collider.
We obtain 90% C.L. upper limits on the branching fractions in the range
(4.4-8.8)x10^{-8} for tau -> ehh', and (3.3-16)x10^{-8} for tau -> muhh'
processes. These results improve upon previously published upper limits by
factors between 1.6 to 8.8.Comment: 15 page, 7 figures, submitted to Phys. Lett.
Study of the decays B->D_s1(2536)+ anti-D(*)
We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*)
is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at
the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy
e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0,
B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of
D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4,
(2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.Comment: 6 pages, 2 figues, submitted to PRD (RC
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