27 research outputs found
Study of B meson decays to three-body charmless hadronic final states
We report results of a study of charmless B meson decays to three-body KPiPi,
KKPi and KKK final states. Measurements of branching fractions for B decays to
K+0Pi+Pi-, K+K+K-, K0K+K-, KsKsK+ and KsKsKs final states are presented. The
decays B0=>K0K+K-, B+=>KsKsK+ and B0=>KsKsKs are observed for the first time.
We also report evidence for B+=>K+K-Pi+ decay. For the three-body final states
K0K+K-, KsKsPi+, K+K+Pi- and K-Pi+Pi+ 90% confidence level upper limits are
reported. Finally, we discuss the possibility of using the three-body
B0=>KsK+K- decay for CP violation studies. The results are obtained with a 78
fb^-1 data sample collected at the Y(4S) resonance by the Belle detector
operating at the KEKB asymmetric energy e+e- collider.Comment: 15 pages, 6 figures. To be submitted to PR
Improved Measurement of the Partial-Rate CP Asymmetry in B+ -> K0pi+ and B- -> K0bar pi- Decays
We report an improved measurement of the partial-rate CP asymmetry in B+ =>
K0pi+ and B- => K0bar pi- decays. The analysis is based on a data sample of 85
million BBbar pairs collected at the Upsilon(4S) resonance with the Belle
detector at the KEKB e+ e- storage ring. We measure Acp(K0pi+-) = 0.07^{+0.09
+0.01}_{-0.08 -0.03}, where the first and second errors are statistical and
systematic, respectively; the corresponding 90% confidence-level interval is
-0.10 < Acp(K0pi+-) < 0.22 .Comment: 7 pages, 8 figures, submitted to Phys. Rev.
Evidence for CP-Violating Asymmetries in B0->pi+pi- Decays and Constraints on the CKM Angle phi2
We present an improved measurement of CP-violating asymmetries in B0 -> pi+
pi- decays based on a 78 fb^-1 data sample collected at the Y(4S) resonance
with the Belle detector at the KEKB asymmetric-energy e+e- collider. We
reconstruct one neutral B meson as a B0 -> pi+ pi- CP eigenstate and identify
the flavor of the accompanying B meson from inclusive properties of its decay
products. We apply an unbinned maximum likelihood fit to the distribution of
the time intervals between the two B meson decay points. The fit yields the
CP-violating asymmetry amplitudes Apipi = +0.77+/-0.27(stat)+/-0.08(syst) and
Spipi = -1.23+/-0.41(stat)+0.08/-0.07(syst), where the statistical
uncertainties are determined from Monte Carlo pseudo-experiments. We obtain
confidence intervals for CP-violating asymmetry parameters Apipi and Spipi
based on a frequentist approach. We rule out the CP-conserving case,
Apipi=Spipi=0, at the 99.93% confidence level. We discuss how these results
constrain the value of the CKM angle phi2.Comment: 26 pages, 13 figures, submitted to Phys. Rev.
An Upper Bound on the Decay tau -> mu gamma from Belle
We have performed a search for the lepton-flavor-violating decay tau -> mu
gamma using a data sample of 86.3fb^{-1} accumulated by the Belle detector at
KEK. No evidence for a signal is seen, and we set an upper limit for the
branching fraction of B(tau -> mu gamma) < 3.1 x 10^{-7} at the 90% confidence
level.Comment: 6 pages, 4 figuresm, submitted to Phys. Rev. Let
Improved Measurements of Branching Fractions for B->Kpi, pipi and KK Decays
We report improved measurements of branching fractions for ,
, and decays based on a data sample of 85.0
million pairs collected at the resonance with the
Belle detector at the KEKB storage ring. This data sample is almost
three times larger than the sample previously used. We observe clear signals
for , and decays and set upper limits on
decays. The results can be used to give model-dependent
constraints on the CKM angle , as well as limits on the hadronic
uncertainty in the time-dependent analysis of the angle .Comment: 10 pages, 1 figure, 4 tables. Submitted to Phys. Rev. D Rapid
Communications. Several corrections were mad
Measurement of the B --> K^* gamma Branching Fractions and Asymmetries
We report measurements of the radiative decay B --> K^*\gamma. The analysis
is based on a data sample containing 85.0*10^6 B meson pairs collected by the
Belle detector at the KEKB storage ring. We measure branching fractions of
Br(B^0 --> K^{*0}\gamma) = (4.01 \pm 0.21 \pm 0.17)*10^{-5} and Br(B^+ -->
K^{*+}\gamma) = (4.25 \pm 0.31 \pm 0.24)*10^{-5}, where the first and second
errors are statistical and systematic, respectively. The isospin asymmetry
between B^0 and B^+ decay widths is measured to be \Delta_{0+} = +0.012 \pm
0.044 \pm 0.026. We search for a partial rate asymmetry between CP conjugate
modes, and find A_{cp}(B --> K^*\gamma) = =0.015 \pm 0.044 \pm 0.012.Comment: 10 pages, 5 figures, submitted to Phys. Rev.
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
Observation of the Decays B0->K+pi-pi0 and B0->rho-K+
We report the observation of B^0 decays to the K^+pi^-pi^0 final state using
a data sample of 78 fb^-1 collected by the Belle detector at the KEKB e^+e^-
collider. With no assumptions about intermediate states in the decay, the
branching fraction is measured to be (36.6^{+4.2}_{-4.3}+- 3.0)*10^-6.We also
search for B decays to intermediate two-body states with the same K^+pi^-pi^0
final state. Significant B signals are observed in the rho(770)^- K^+ and
K^*(892)^+pi^- channels, with branching fractions of
(15.1^{+3.4+1.4+2.0}_{-3.3-1.5-2.1})* 10^-6 and
(14.8^{+4.6+1.5+2.4}_{-4.4-1.0-0.9})* 10^-6, respectively. The first error is
statistical, the second is systematic and the third is due to the largest
possible interference. Contributions from other possible two-body states will
be discussed. No CP asymmetry is found in the inclusive K^+pi^-pi^0 or rho^-K^+
modes, and we set 90% confidence level bounds on the asymmetry of
-0.12<A_{CP}<0.26 and -0.18<A_{CP}<0.64, respectively.Comment: 18 pages, 7 figure
Search for neutrinoless decays tau -> 3l
We have searched for neutrinoless tau lepton decays into three charged
leptons using an 87.1 fb^{-1} data sample collected with the Belle detector at
the KEKB e^+e^- collider. Since the number of signal candidate events is
compatible with that expected from the background, we set 90% confidence level
upper limits on the branching fractions in the range (1.9-3.5) x 10^{-7} for
various decay modes tau -> l l l where l represents e or mu.Comment: 12 pages, 4figure
Measurement of Branching Fraction and Direct CP Asymmetry in B0-->rho0 pi0 Decays
We report a measurement of the decay B0 --> rho0 pi0, using 386 x 10^6 BB-bar
pairs collected at the Upsilon(4S) resonance with the Belle detector at the
KEKB asymmetric-energy e+e- collider. We detect 51^{+14}_{-13} signal events
with a significance of 4.2 standard deviations, including systematic
uncertainties, and measure the branching fraction to be B(B0 --> rho0 pi0) =
(3.12^{+0.88}_{-0.82} (stat) +/- 0.33 (syst) ^{+0.50}_{-0.68} (model)) x
10^{-6}. We also perform the first measurement of direct CP violating asymmetry
in this mode.Comment: 5 pages, 2 figures, accepted in Physical Review