4,296 research outputs found
Study of the Baryon-Antibaryon Low-Mass Enhancements in Charmless Three-body Baryonic B Decays
The angular distributions of the baryon-antibaryon low-mass enhancements seen
in the charmless three-body baryonic B decays B+ -> p pbar K+, B0 -> p pbar Ks,
and B0 -> p Lambdabar pi- are reported. A quark fragmentation interpretation is
supported, while the gluonic resonance picture is disfavored. Searches for the
Theta+ and Theta++ pentaquarks in the relevant decay modes and possible
glueball states G with 2.2 GeV/c2 < M-ppbar < 2.4 GeV/c2 in the ppbar systems
give null results. We set upper limits on the products of branching fractions,
B(B0 -> Theta+ p)\times B(Theta+ -> p Ks) Theta++
pbar) \times B(Theta++ -> p K+) G K+) \times
B(G -> p pbar) < 4.1 \times 10^{-7} at the 90% confidence level. The analysis
is based on a 140 fb^{-1} data sample recorded on the Upsilon(4S) resonance
with the Belle detector at the KEKB asymmetric-energy e+e- collider.Comment: 14 pages, 13 figure files, update of hep-ex/0409010 for journal
submisssio
Test of lepton flavor universality and search for lepton flavor violation in B â Kââ decays
We present measurements of the branching fractions for the decays B â KÎŒ+ÎŒâ and B â Ke+eâ, and their ratio (RK), using a data sample of 711 fbâ1 that contains 772 Ă 106BBÂŻ events. The data were collected at the Ï(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+eâ collider. The ratio RK is measured in five bins of dilepton invariant-mass-squared (q2): q2 â (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 â (1.0, 6.0) GeV2/c4 is 1.03â0.24+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 â (1.0, 6.0) GeV2/c4 bin in the mode with muon final states. The measured differential branching fractions, d⏠/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 â KΌ±eâ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10â8 for B+ â K+Ό±eâ, and B0 â K0Ό±eâ modes. [Figure not available: see fulltext.
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
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 B+->Lambda_c+Lambda_c-K+ and B0->Lambda_c+Lambda_c^-K0 decays
We report first measurements of the doubly charmed baryonic B decays
B->Lambda_c+Lambda_c-K. The B+->Lambda_c+Lambda_c-K+ decay is observed with a
branching fraction of (6.5+1.0-0.9+-1.1+-3.4)x10^{-4} and a statistical
significance of 15.4sigma. The B0->Lambda_c+Lambda_c-K0 decay is observed with
a branching fraction of (7.9+2.9-2.3+-1.2+-4.2)x10^{-4} and a statistical
significance of 6.6sigma. The branching fraction errors are statistical,
systematic, and the error resulting from the uncertainty of Lambda_c+->pK-pi+
decay branching fraction. The analysis is based on 357fb-1 of data accumulated
at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e+e-
collider.Comment: 10 pages, 3 figure
Study of CP Violating Effects in Time Dependent Decays
We report measurements of time dependent decay rates for decays and extraction of CP violation parameters
containing . Using fully reconstructed events from a data sample collected at the resonance, we obtain
the CP violation parameters for and decays, , where is
the ratio of the magnitudes of the doubly-Cabibbo-suppressed and
Cabibbo-favoured amplitudes, and is the strong phase
difference between them. Under the assumption of being
close to either 0 or , we obtain and .Comment: 9 pages, 3 figures, Submitted to Physical Review Letter
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
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