Measurement of Azimuthal Asymmetries in Inclusive Production of Hadron Pairs in e+e- Annihilation at Belle

The Collins effect connects transverse quark spin with a measurable azimuthal dependence in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods we observe statistically significant azimuthal asymmetries for charged pion pairs in e+e- annihilation at a center-of-mass energy of 10.52 GeV, which can be attributed to a transverse polarization of the primordial quarks. The measurement was performed using a sample of 79 million hadronic events collected with the Belle detector.Comment: 6 pages, 4 figure

Observation of the decay B0→J/ψηB^0 \to J/\psi \eta

We report the first observation of $B^0 \to J/\psi \eta$ decay. These results are obtained from a data sample that contains 449 million $B\bar{B}$ pairs accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We observe a signal with a significance of 8.1$\sigma$ and obtain a branching fraction of (9.5 $\pm$ 1.7 (stat) $\pm$ 0.8 (syst))$\times 10^{-6}$.Comment: 5 pages, 2 figures, submit to PRL (8 pages, 2 figures, ICHEP'06 Conference Paper

Improved measurement of B0bar --> Ds-D+ and search for B0bar --> Ds+Ds- at Belle

We reconstruct B0bar --> Ds-D+ decays using a sample of 449 x 10^6 BBbar pairs recorded by the Belle experiment, and measure the branching fraction to be Br(B0bar --> Ds-D+)=[7.5 +- 0.2(stat) +- 0.8(syst) +- 0.8(Br's)] x 10^(-3). A search for the related decay B0bar --> Ds+Ds- is also performed. Since we observe no statistically significant signal an upper limit on the branching fraction is set at 3.6 x 10^(-5) (90% C.L.).Comment: 7 pages, 2 figures, Submitted to Physical Review D, Rapid Communication

Measurement of inclusive DsD_s, D0D^0, and J/ψJ/\psi rates and determination of the Bs(∗)Bˉs(∗)B_s^{(*)} \bar{B}_s^{(*)} production fraction in bbˉb \bar{b} events at the Y(5S) resonance

The inclusive production of $D_s$, $D^0$, and $J/\psi$ mesons is studied using a 1.86 fb$^{-1}$ data sample collected on the $\Upsilon$(5S) resonance by the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider. The number of $b\bar{b}$ events in the $\Upsilon$(5S) data sample is determined. We measure the branching fractions $B(\Upsilon({\rm 5S}) \to D_s X) / 2 = (23.6 \pm 1.2 \pm 3.6)$, $B(\Upsilon({\rm 5S}) \to D^0 X) / 2 = (53.8 \pm 2.0 \pm 3.4)$}, and $B(\Upsilon({\rm 5S}) \to J/\psi X) / 2 = (1.030 \pm 0.080 \pm 0.067)$. From the $D_s$ and $D^0$ inclusive branching fractions the ratio $f_s = (18.0 \pm 1.3 \pm 3.2)$} of $B_s^{(*)} \bar{B}_s^{(*)}$ to the total $b\bar{b}$ quark pair production at the $\Upsilon$(5S) energy is obtained in a model-dependent way.Comment: 6 pages, 4 figures, accepted by Phys. Rev. Let