927 research outputs found
Search for violation in decays and observation of the Cabibbo-suppressed decay
No full textWe search for violation by measuring a -odd asymmetry in the
Cabibbo-suppressed decay, and
in the Cabibbo-favored and
decays. We use 980 of data collected by the Belle detector running at the KEKB
asymmetric-energy collider. The -violating -odd parameter
is measured to be
and
where the first
uncertainty is statistical and the second is systematic. We also report the
first observation of the Cabibbo-suppressed decay . The branching fraction is measured relative to
that of the analogous Cabibbo-favored decay :
Angular analysis of the low K+K− invariant mass enhancement in B+→K+K−π+ decays
No full textWe study the decay B+→K+K−π+ and investigate the angular distribution of K+K− pairs with invariant mass below 1.1 GeV/c2. This region exhibits both a strong enhancement in signal and very large direct CP violation. We construct a coherent sum model for the angular distribution of S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of MK+K− and the differential branching fractions in bins of MK+π−. The results are based on a data sample that contains 772×10^6 BB ̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The measured overall branching fraction and the direct CP asymmetry are (5.38±0.40±0.35)×10^−6 and −0.170±0.073±0.017, respectively, where the first uncertainties are statistical and the second are systematic
Angular analysis of the low K+ K- invariant mass enhancement in B+ →K+ K- π+ decays
No full textWe study the decay B+→K+K-π+ and investigate the angular distribution of K+K- pairs with invariant mass below 1.1 GeV/c2. This region exhibits both a strong enhancement in signal and very large direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of MK+K- and the differential branching fractions in bins of MK+π-. The results are based on a data sample that contains 772×106 BB ̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The result favors the presence of S- and D-waves in low MK+K- region to the detriment of a P-wave
Observation of and
No full textInternational audienceWe report the study of B+→pΛ¯K+K- and B+→p¯ΛK+K+ decays using a 772×106 BB¯ pair data sample recorded on the ϒ(4S) resonance with the Belle detector at KEKB. The following branching fractions are measured: B(B+→pΛ¯K+K-)=(4.10-0.43+0.45±0.50)×10-6, B(B+→p¯ΛK+K+)=(3.70-0.37+0.39±0.44)×10-6, B(ηc→pΛ¯K-+c.c.)=(2.83-0.34+0.36±0.35)×10-3 and B(B+→pΛ¯ϕ)=( 7.95±2.09±0.77)×10-7, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also find evidence for B(ηc→Λ(1520)Λ¯+c.c.)=(3.48±1.48±0.46)×10-3 and B(B+→Λ(1520)Λ¯K+)=( 2.23±0.63±0.25)×10-6. No significant signals are found for J/ψ→Λ(1520)Λ¯+c.c. and B+→Λ¯(1520)ΛK+; we set the 90% confidence level upper limits on their decay branching fractions as <1.80×10-3 and <2.08×10-6, respectively
Experimental constraints on the spin and parity of the
No full textWe perform a full amplitude analysis of anti-B0 -> psi' K- pi+ decays, with psi' -> mu+ mu- or e+ e-, to constrain the spin and parity of the Z(4430)+. The J^P = 1+ hypothesis is favored over the 0- hypothesis at the 2.9 sigma level, while all other hypotheses with J <= 2 are excluded at the level of at least 4.3 sigma. The analysis is based on a 711 fb^-1 data sample that contains 772x10^6 B B pairs, collected at the Y(4S) resonance by the Belle detector at the asymmetric-energy e+ e- collider KEKB
First observation of and search for exotic baryons in systems
No full textThe process γγ→pp¯K+K- and its intermediate processes are measured for the first time using a 980 fb-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The production of pp¯K+K- and a Λ(1520)0 (Λ¯(1520)0) signal in the pK- (p¯K+) invariant mass spectrum are clearly observed. However, no evidence for an exotic baryon near 1540 MeV/c2, denoted as Θ(1540)0 (Θ¯(1540)0) or Θ(1540)++ (Θ(1540)--), is seen in the pK- (p¯K+) or pK+ (p¯K-) invariant mass spectra. Cross sections for γγ→pp¯K+K-, Λ(1520)0p¯K++c.c. and the products σ(γγ→Θ(1540)0p¯K++c.c.)B(Θ(1540)0→pK-) and σ(γγ→Θ(1540)++p¯K-+c.c.)B(Θ(1540)++→pK+) are measured. We also determine upper limits on the products of the χc0 and χc2 two-photon decay widths and their branching fractions to pp¯K+K- at the 90% credibility level
Measurement of asymmetries in decays at Belle II
No full textWe report a measurement of decay-time dependent charge-parity () asymmetries in decays. We use pairs collected at the resonance with the Belle II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the -violating parameters and from a fit to the distribution of the decay-time difference between the two mesons. The resulting confidence region is consistent with previous measurements in and decays, and with predictions based on the standard model
Measurement of branching fraction and direct asymmetry in charmless decays at Belle
No full textWe report a study of the charmless hadronic decay of the charged meson to the three-body final state . The results are based on a data sample that contains pairs collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. The measured inclusive branching fraction and the direct asymmetry are and , respectively, where the first uncertainties are statistical and the second are systematic. The invariant mass distribution of the signal candidates shows an excess in the region below GeV/, which is consistent with the previous studies from BaBar and LHCb. In addition, strong evidence of a large direct asymmetry is found in the low-invariant-mass region
Measurement of the Resonant and Non-Resonant Branching Ratios in
No full textUsing the entire data sample of integrated luminosity collected with the Belle detector at the KEKB asymmetric-energy collider, we present an amplitude analysis measuring the branching fractions of the Cabibbo-allowed, -exchange resonant decay with a polarized and the non-resonant decay via a direct process . We present these measurements, relative to the normalization mode , and find branching ratios and which suggest that only minor cusping peaks occur in the combinatorial background of due to these decays
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