4,029 research outputs found
Measurements of time-dependent CP asymmetries in decays using a partial reconstruction technique
We report results on time-dependent CP asymmetries in decays based on a data sample containing 657 {\times}
pairs collected with the Belle detector at the KEKB
asymmetric-energy collider at the resonance. We use a
partial reconstruction technique, wherein signal
events are identified using information only from the fast pion from the B
decay and the slow pion from the subsequent decay of the , where the
former (latter) corresponds to final states. We obtain CP
violation parameters and .Comment: 8 pages, 5 figures, 2 tables, submitted to Physical Review D (RC
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
Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays
We present measurements of the branching fractions for the decays B → Kμ+μ− and B → Ke+e−, and their ratio (RK), using a data sample of 711 fb−1 that contains 772 × 106BB¯ events. The data were collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The ratio RK is measured in five bins of dilepton invariant-mass-squared (q2): q2 ∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (\u3e 14.18) GeV2/c4, along with the whole q2 region. The RK value for q2 ∈ (1.0, 6.0) GeV2/c4 is 1.03−0.24+0.28 ± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for RK are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q2 bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q2 ∈ (1.0, 6.0) GeV2/c4 bin in the mode with muon final states. The measured differential branching fractions, dℬ /dq2, are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ±e∓ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10−8 for B+ → K+μ±e∓, and B0 → K0μ±e∓ modes. [Figure not available: see fulltext.
Measurement of e^+e^- to pi^+pi^-J/psi Cross Section via Initial State Radiation at Belle
The cross section for e^+e^- to pi^+pi^-J/psi between 3.8 and 5.5 GeV/c^2 is
measured using a 548 fb^{-1} data sample collected on or near the Upsilon(4S)
resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c^2,
corresponding to the so called Y(4260), is observed. In addition, there is
another cluster of events at around 4.05 GeV/c^2. A fit using two interfering
Breit-Wigner shapes describes the data better than one that uses only the
Y(4260), especially for the lower mass side of the 4.25 GeV enhancement.Comment: 11 pages, 5 figures, 2 tables; version to appear in PR
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
Observation of the D1(2420)->DPI+PI- decays
We report on the first observation of decays (where the
contribution from the dominant known decay mode is excluded)
in the decays. The observation is based on events collected with the Belle detector at the KEKB collider. We
also set 90% confidence level upper limits for the
and decays in the and
decays, respectively.Comment: 6 pages, 2 figure
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
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
Observation of B^0 \to D^{*-} \tau^+ \nu_{\tau} decay at Belle
We report an observation of the decay in a
data sample containing pairs collected with the
Belle detector at the KEKB asymmetric-energy collider. We find a
signal with a significance of 5.2 standard deviations and measure the branching
fraction . This is the first observation of an exclusive
decay with a transition.Comment: 6 pages, 3 figures, submitted to Phys. Rev. Let
Observation of , and decays
We report the first observation of the decay modes , and based on 152 10
events collected at KEKB. The branching fractions of , and are found to be , and , respectively. Charge asymmetries in the and channels are consistent with zero.Comment: 9 pages, 2 figures, KEK Preprint 2004-99, Belle Prerpint 2005-3,
submitted to PR
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