20 research outputs found
High statistic study of the K- -> pi0 mu- nu decay
The decay K- -> pi0 mu- nu has been studied using in-flight decays detected
with the "ISTRA+" spectrometer. About 540K events were collected for the
analysis. The lambda+ and lambda0 slope parameters of the decay form-factors
f+(t), f0(t) have been measured : lambda+ = 0.0277+-0.0013 (stat)+-0.0009
(syst), lambda0 = 0.0183+-0.0011(stat)+-0.0006(syst), and
d(lambda0)/d(lambda+)=-0.348. The limits on the possible tensor and scalar
couplings have been derived: fT/f+(0)=-0.0007 +- 0.0071, fS/f+(0)=0.0017 +-
0.0014. No visible non-linearity in the form-factors have been observed.Comment: 11 pages, 8 EPS figures, accepted by Physics Letters
High statistics study of the K- -> pi0 e- nu decay
The decay K- -> pi0 e- nu has been studied using in-flight decays detected
with the "ISTRA+" spectrometer working at the 25 GeV negative secondary beam of
the U-70 PS. About 550K events were used for the analysis. The lambda+
parameter of the vector form-factor has been measured: lambda+ = 0.0286 +-
0.0008 (stat) +- 0.0006(syst). The limits on the possible tensor and scalar
couplings have been obtained: f(T)/f+(0)=0.021 +0.064 -0.075 (stat) +-
0.026(syst) ; f(S)/f+(0)=0.002 +0.020 -0.022 (stat) +- 0.003(syst)Comment: LaTeX-2e, epsfig.sty, 10 pages, 7 figures in EPS forma
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
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 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
Observation of the Decay \bar{B0}-> Ds+ Lambda \bar{p}
We report the first observation of the decay \bar{B0} -> D_s^+ Lambda \bar{p}
with a statistical significance of 6.6 sigma. We measure Br(\bar{B0} -> Ds+
Lambda \bar{p}) = (2.9 \pm 0.7\pm 0.5 \pm 0.4)* 10^{-5}, where the first error
is statistical, the second is systematic and the third error comes fr\om the
uncertainty in Br(Ds+ -> phi pi+). The data used for this analysis was
accumulated at the Upsilon(4S) resonance, using the Belle detector at the KEKB
asymmetric-energy e+e- collider. The integrated luminosity of the data sample
is 414 fb-1, corresponding to 449*10^{6} B{\bar B} pairs.Comment: 5 pages, 2 PostScript figures, 1 tabl
Search for the decay B0 to gamma gamma
The rare decay B0 -> gamma gamma is searched for in 104 fb^-1 of data,
corresponding to 111 x 10^6 BBar pairs, collected with the Belle detector at
the KEKB asymmetric-energy e+ e- collider. No evidence for the signal is found,
and an upper limit of 6.2 x 10^-7 at 90% confidence level is set for the
corresponding branching fraction.Comment: 7 pages, 3 figures, accepted for publication by Phys. Rev.
Study of the decay mechanism for B+ to p pbar K+ and B+ to p pbar pi+
We study the characteristics of the low mass ppbar enhancements near
threshold in the three-body decays B+ to p pbar K+ and B+ to p pbar pi+. We
observe that the proton polar angle distributions in the ppbar helicity frame
in the two decays have the opposite polarity, and measure the forward-backward
asymmetries as a function of the ppbar mass for the p pbar K+ mode. We also
search for the intermediate two-body decays, B+ to pbar Delta++ and B+ to p
Delta0bar, and set upper limits on their branching fractions. These results are
obtained from a 414 fb^{-1} data sample that contains 449 times 10^6 BBbar
events collected near the Upsilon(4S) resonance with the Belle detector at the
KEKB asymmetric-energy e+ e- collider.Comment: 15 pages, 5 figures (14 figure files), revisions to Phys. Lett.
Measurement of the branching fraction for the decay Υ(4S) →Υ(1S)π+π-
We study transitions between Υ states with the emission of charged pions using 604.6fb-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured product branching fraction is B(Υ(4S)→Υ(1S)π+π-)×B(Υ(1S)→μ+μ-)=(2. 11±0.30(stat)±0.14(sys))×10-6 and the partial decay width is Γ(Υ(4S)→Υ(1S)π+π-)=(1.75±0.25(stat)±0. 24(sys))keV. © 2009 The American Physical Society