The cross section for e(+)e(-)-->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.
We report a measurement of the exclusive e+e- -->D(*)+/-D*-/+ cross section as a function of center-of-mass energy near the D(*)+/-D*-/+ threshold with initial-state radiation. A partial ...reconstruction technique is used to increase the efficiency and to suppress background. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 547.8 fb(-1).
We report results of a search for the invisible decay of the Upsilon(1S) via the Upsilon(3S)-->pi+ pi- Upsilon(1S) transition using a data sample of 2.9 fb-1 at the Upsilon(3S) resonance. The data ...were collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. No signal is found, and an upper limit for the branching fraction at the 90% confidence level is determined to be B(Upsilon(1S)-->invisible)<2.5 x 10(-3).
Observation of B decays to two kaons Abe, K; Aihara, H; Anipko, D ...
Physical review letters,
05/2007, Letnik:
98, Številka:
18
Journal Article
Recenzirano
Using 449x10(6) BBover pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider, we observe clear signals for B(+)-->Kover (0)K(+) and B(0)-->Kover (0)K(0) decays with ...5.3sigma and 6.0sigma significance, respectively. We measure the branching fractions B(B(+)-->Kover (0)K(+))=(1.22(-0.28-0.16)(+0.32+0.13))x10(-6) and B(B(0)-->Kover (0)K(0))=(0.87(-0.20)(+0.25)+/-0.09)x10(-6), and partial-rate asymmetries A(CP)(B(+)-->Kover (0)K(+))=0.13(-0.24)(+0.23)+/-0.02 and A(CP)(B(0)-->Kover (0)K(0))=-0.58(-0.66)(+0.73)+/-0.04. From a simultaneous fit, we also obtain B(B(+)-->K(0)pi(+))=(22.8(-0.7)(+0.8)+/-1.3)x10(-6) and A(CP)(B(+)-->K(0)pi(+))=0.03+/-0.03+/-0.01. The first and second error in the branching fractions and the partial-rate asymmetries are statistical and systematic, respectively. No signal is observed for B(0)-->K(+)K(-) decays, and for this branching fraction, we set an upper limit of 4.1x10(-7) at the 90% confidence level.
We report measurements of branching fractions for B --> K pi and B --> pi pi decays based on a data sample of 449 x 10(6) BBover pairs collected at the Upsilon(4S) resonance with the Belle detector ...at the KEKB asymmetric-energy e(+)e(-) collider. We also measure the ratios of partial widths for B-->Kpi decays, namely R(c) identical with 2Gamma(B(+) --> K(+) pi(0))/Gamma(B(+) --> K(0) pi(+)) = 1.08+/-0.06+/-0.08 and R(n) identical with Gamma(B(0) --> K(+) pi(-))/2 Gamma(B(0) --> K(0) pi(0)) = 1.08+/-0.08+/-0.08, where the first and the second errors are statistical and systematic, respectively. These ratios are sensitive to enhanced electroweak penguin contributions from new physics; the new measurements are, however, consistent with standard model expectations.
We report the 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(-0.9)(+1.0)+/-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(-2.3)(+2.9)+/-1.2+/-4.1)x10(-4) and a statistical significance of 6.6sigma. The branching fraction errors are statistical, systematic, and the error resulting from the uncertainty of the Lambda c+ --> pK- pi+ decay branching fraction. The analysis is based on 357 fb(-1) of data accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider.
Study of τ−→KSπ−ντ decay at Belle Epifanov, D.; Aihara, H.; Aulchenko, V. ...
Physics letters. B,
10/2007, Letnik:
654, Številka:
3-4
Journal Article
Recenzirano
We present a study of the decay τ−→KSπ−ντ using a 351 fb−1 data sample collected with the Belle detector. The analysis is based on 53,110 lepton-tagged signal events. The measured branching fraction ...B(τ−→KSπ−ντ)=(0.404±0.002(stat.)±0.013(syst.))% is consistent with the world average value and has better accuracy. An analysis of the KSπ− invariant mass spectrum reveals contributions from the K∗(892)− as well as other states. For the first time the K∗(892)− mass and width have been measured in τ decay: M(K∗(892)−)=(895.47±0.20(stat.)±0.44(syst.)±0.59(mod.)) MeV/c2, Γ(K∗(892)−)=(46.2±0.6(stat.)±1.0(syst.)±0.7(mod.)) MeV. The K∗(892)− mass is significantly different from the current world average value.
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