52 research outputs found
Precise measurement of hadronic tau-decays with an eta meson
We have studied hadronic tau decay modes involving an eta meson using 490
fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy
e+e- collider. The following branching fractions have been measured: B(tau- ->
K- eta nu)=(1.58 +- 0.05 +- 0.09)x 10^{-4}, B(tau- -> K- pi0 eta nu)=(4.6 +-
1.1 +- 0.4)x 10^{-5}, B(tau- -> pi- pi0 eta nu)=(1.35 +- 0.03 +- 0.07)x
10^{-3}, B(tau- -> pi- KS eta nu)=(4.4 +- 0.7 +- 0.2)x 10^{-5}, and B(tau- ->
K^{*-} eta nu)=(1.34 +- 0.12 +- 0.09)x 10^{-4}. These results are substantially
more precise than previous measurements. The new measurements are compared with
theoretical calculations based on the CVC hypothesis or the chiral perturbation
theory. We also set upper limits on branching fractions for tau decays into K-
KS eta nu, pi- KS pi0 eta nu, K- eta eta nu, pi- eta eta nu and non-resonant K-
pi^0 eta nu final states.Comment: 24 pages, 7 figure
Search for Resonant Decays at Belle
We report measurements and searches for resonant decays where is a
meson or
the X(3872) particle.Comment: accepted by Physics Letters
Search for B+ -> D*+ pi0 decay
We report on a search for the doubly Cabibbo suppressed decay B+ -> D*+ pi0,
based on a data sample of 657 million BBbar pairs collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider.
We find no significant signal and set an upper limit of Br(B+ -> D*+ pi0) < 3.6
x 10^-6 at the 90% confidence level. This limit can be used to constrain the
ratio between suppressed and favored B -> D* pi decay amplitudes, r < 0.051, at
the 90% confidence level.Comment: 5pages, 2figures, submitted to PRL (v1); PRL published version (v2:
minor corrections in the text
Search for the Electric Dipole Moment of the tau Lepton
We have searched for a CP violation signature arising from an electric dipole
moment (d_tau) of the tau lepton in the e+e- -> tau+tau- reaction. Using an
optimal observable method and 29.5 fb^{-1} of data collected with the Belle
detector at the KEKB collider at sqrt{s} = 10.58 GeV, we find Re(d_tau) = (1.15
+- 1.70) x 10^{-17} ecm and Im(d_tau) = (-0.83 +- 0.86) x 10^{-17} ecm and set
the 95% confidence level limits -2.2 < Re(d_tau) < 4.5 (10^{-17}ecm) and -2.5 <
Im(d_tau) < 0.8 (10^{-17}ecm).Comment: 15 pages, LaTeX, 21 figures, submitted to Phys. Lett.
Measurement of the ratio B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) and the time-integrated CP asymmetry in D0->pi+pi-pi0
We report a high-statistics measurement of the relative branching fraction
B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) using a 532 fb^{-1} data sample collected with
the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured
value of the relative branching fraction is B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) =
(10.12 +/- 0.04(stat) +/- 0.18(syst))x10^{-2} which has an accuracy comparable
to the world average. We also present a measurement of the time-integrated CP
asymmetry in D0->pi+pi-pi0 decay. The result, A_{CP} = (0.43 +/- 1.30)%, shows
no significant CP violation.Comment: 15 pages, 11 figures, submitted to Physics Letters
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
Search for B -> h(*) nu nubar Decays at Belle
We present a search for the rare decays B -> h(*) nu nubar, where h(*) stands
for a light meson. A data sample of 535 million BBbar pairs collected with the
Belle detector at the KEKB e+e- collider is used. Signal candidates are
required to have an accompanying B meson fully reconstructed in a hadronic mode
and signal-side particles consistent with a single h(*) meson. No significant
signal is observed and we set upper limits on the branching fractions at 90%
confidence level. The limits on B0 -> K*0 nu nubar and B+ -> K+ nu nubar decays
are more stringent than the previous constraints, while the first searches for
B0 -> K0 nu nubar, pi0 nu nubar, rho0 nu nubar, phi nu nubar and B+ -> K*+ nu
nubar, rho+ nu nubar are reported.Comment: 6 pages, 2 figures, submit to PR
Spectra of prompt electrons from decays of B+ and B0 mesons and ratio of inclusive semielectronic branching fractions
We present spectra of prompt electrons from decays of neutral and charged B
mesons. The results are based on 140 /fb of data collected by the Belle
detector on the Upsilon(4S) resonance at the KEKB e+e- asymmetric collider. We
tag Upsilon(4S) -> B \bar{B} events by reconstructing a B meson in one of
several hadronic decay modes; the semileptonic decay of the other B meson is
inferred from the presence of an identified electron. We obtain for charged and
neutral B mesons the partial rates of semileptonic decay, to electrons with
momentum greater than 0.6 GeV/c in the B rest frame, and their ratio b_+/b_0 =
1.08 +- 0.05 +- 0.02, where the first and second errors are statistical and
systematic, respectively.Comment: 16 pages, 2 figure files, submitted to Phys. Lett.
Observation of B+ -> K+ eta gamma
We report measurements of radiative B decays with K eta gamma final states,
using a data sample of 253 /fb recorded at the Upsilon(4S) resonance with the
Belle detector at the KEKB e+e- storage ring. We observe B+ -> K+ eta gamma for
the first time with a branching fraction of (8.4 +- 1.5(stat) +1.2 -0.9(syst))
X 10^{-6} for M(Keta) K0 eta gamma.
We also search for B -> K3*(1780) gamma.Comment: 12 pages, 5 figures, accepted by Phys. Lett.
Study of Decays
We report on a study of decays using
29.1 fb of annihilation data recorded at the
resonance with the Belle detector at the KEKB storage ring. Making no
assumptions about the intermediate mechanism, the branching fractions for
and are
determined to be and respectively. An analysis of candidates yields to the first observation of the color-suppressed
hadronic decay with the branching fraction . We measure the ratio of branching fractions
= 1.6 0.8.Comment: 13 pages, LaTex, 4 figures, submitted to Phys. Lett.
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