Moments of the Hadronic Invariant Mass Spectrum in B --> X_c l nu Decays at Belle

We present a measurement of the hadronic invariant mass squared (M^2_X) spectrum in charmed semileptonic B meson decays B --> X_c l nu based on 140 fb^-1 of Belle data collected near the Y(4S) resonance. We determine the first, the second central and the second non-central moments of this spectrum for lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations between these measurements are evaluated.Comment: published version of the paper (one figure added, minor changes in the text); 16 pages, 3 figures, 10 table

Time-Dependent CP Violation Effects in Partially Reconstructed B0→D∗πB^0 \to D^* \pi Decays

We report measurements of time-dependent decay rates for $B^0 \to D^{*\mp} \pi^\pm$ decays and extraction of CP violation parameters related to $\phi_3$. We use a partial reconstruction technique, whereby signal events are identified using information only from the primary pion and the charged pion from the decay of the $D^{*\mp}$. The analysis uses $140 {\rm fb}^{-1}$ of data accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We measure the CP violation parameters $S^+ = 0.035 \pm 0.041 ({\rm stat}) \pm 0.018 ({\rm syst})$ and $S^- = 0.025 \pm 0.041 ({\rm stat}) \pm 0.018 ({\rm syst})$.Comment: 15 pages, 5 figures. To appear in Physics Letters

A Search for the Rare Leptonic Decays B+ -> mu+ nu and B+ -> e+ nu

We present a search for the decays B+ -> mu+ nu_mu and B+ -> e+ nu_e in a 253 fb-1 data sample collected at the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy B factory. We find no significant evidence for a signal and set 90% confidence level upper limits of B(B+ -> mu+ nu_mu) e+ nu_e) < 9.8 x 10^{-7}.Comment: 13 pages, 10 figures, accepted to Phys. Lett.

Observation of the Decay \bar{B0}-> Ds+ Lambda \bar{p}

We report the first observation of the decay \bar{B0} -> D_s^+ Lambda \bar{p} with a statistical significance of 6.6 sigma. We measure Br(\bar{B0} -> Ds+ Lambda \bar{p}) = (2.9 \pm 0.7\pm 0.5 \pm 0.4)* 10^{-5}, where the first error is statistical, the second is systematic and the third error comes fr\om the uncertainty in Br(Ds+ -> phi pi+). The data used for this analysis was accumulated at the Upsilon(4S) resonance, using the Belle detector at the KEKB asymmetric-energy e+e- collider. The integrated luminosity of the data sample is 414 fb-1, corresponding to 449*10^{6} B{\bar B} pairs.Comment: 5 pages, 2 PostScript figures, 1 tabl

Search for the decay B0 to gamma gamma

The rare decay B0 -> gamma gamma is searched for in 104 fb^-1 of data, corresponding to 111 x 10^6 BBar pairs, collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. No evidence for the signal is found, and an upper limit of 6.2 x 10^-7 at 90% confidence level is set for the corresponding branching fraction.Comment: 7 pages, 3 figures, accepted for publication by Phys. Rev.

Measurement of gamma gamma -> p p-bar production at Belle

A high precision study of the process gamma gamma -> p p-bar has been performed using a data sample of 89/fb collected with the Belle detector at the KEKB e+e- collider. The cross section of p p-bar production has been measured at two-photon center-of-mass (c.m.) energies between 2.025 and 4.0 GeV and in the c.m. angular range of |cos(theta^*)| eta_c -> p p-bar is observed and the product of the two-photon width of the eta_c and its branching ratio to p p-bar is determined.Comment: 20 pages, 9 figures, Fig.1 added, accepted for publication in Phys. Lett.

Observation of B- -> J/psi Lambda pbar and searches for B- -> J/psi Sigma0 pbar and B0 -> J/psi p pbar Decays

We report the observation of B- -> J/psi Lambda pbar and searches for B- -> J/psi Sigma0 pbar and B0 -> J/psi p pbar decays, using a sample of 275 million BBbar pairs collected with the Belle detector at the Upsilon(4S) resonance. We observe a signal of 17.2 +/- 4.1 events with a significance of 11.1sigma and obtain a branching fraction of B(B- -> J/psi Lambda pbar) = [11.6 +/- 2.8 (stat.) +1.8 -2.3(sys.)] x 10^-6. No signal is found for either of the two decay modes, B- -> J/psi Sigma0 pbar and B0 -> J/psi p pbar, and upper limits for the branching fractions are determined to be B(B- -> J/psi Sigma0 pbar) < 1.1 x 10^{-5} and B(B0 -> J/psi p pbar) < 8.3 x 10^{-7} at 90% confidence level.Comment: 6 pages, 3 figures, submitted to PRD (RC), Lepton-Photon 2005 Conference in Uppsala, Sweden and HEP2005 Europhysics Conference in Lisboa, Portuga

Measurement of Branching Fractions for B→χc1(2)K(K∗)B\to {\chi}_{c1(2)} K (K^*) at Belle

We have measured the branching fractions for the exclusive decay modes $B\to {\chi}_{c1(2)} K(K^*)$ using a $140~{\rm fb}^{-1}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The measured branching fractions for $B^+\to {\chi}_{c1}K^+$, $B^0\to {\chi}_{c1}K^0$, $B^0\to {\chi}_{c1}K^{*0}$ and $B^+\to {\chi}_{c1}K^{*+}$ decay modes are $(4.5\pm 0.2\pm0.5)\times 10^{-4}$, $(3.5\pm 0.3\pm0.5)\times 10^{-4}$, $(3.1\pm 0.3\pm0.7)\times 10^{-4}$ and $(4.1\pm 0.6\pm0.9)\times 10^{-4}$, respectively, where the first error is statistical and the second error is systematic. We do not observe statistically significant signals for the $B\to {\chi}_{c2}K(K^*)$ decay modes and set upper limits at the 90% confidence level. We also study the helicity distribution for $B\to {\chi}_{c1} K^*$ decay mode and show that the longitudinal polarization component is dominant. {{\it Keywords:} {$B$-meson, Charmonium, Branching Fractions, Polarization}} {{\it PACS:} 13.25.Hw, 11.30.Er}Comment: 21 pages, 5 figures, 3 tables. Submitted to PL

Search for lepton flavor violating decays tau- -> l- pi0, l- eta, l- eta'

We have searched for lepton flavor violating semileptonic tau decays using a data sample of 153.8/fb accumulated with the Belle detector at the KEKB e+e- collider. For the six decay modes studied, the observed yield is compatible with the estimated background and the following upper limits are set at the 90% confidence level: B(tau- -> e- eta) mu- eta) < 1.5 x 10^-7, B(tau- -> e- pi0) mu- pi0) < 4.1 x 10^-7, B(tau- -> e- eta') mu- eta') < 4.7 x 10^-7. These results are 10 to 64 times more restrictive than previous limits.Comment: 14 pages, 13 figures, RevTex

Search for the Θ(1540)+ pentaquark using kaon secondary interactions at Belle

AbstractUsing kaon secondary interactions in the material of the Belle detector, we search for both inclusive and exclusive production of the Θ(1540)+. We set an upper limit of 2.5% at the 90% C.L. on the ratio of the Θ(1540)+ to Λ(1520) inclusive production cross sections. We also search for the Θ(1540)+ as an intermediate resonance in the charge exchange reaction K+n→pKS0. We set an upper limit of ΓΘ+<0.64 MeV at the 90% C.L. for mΘ+=1.539 MeV/c2. These results are obtained from a 397 fb−1 data sample collected with the Belle detector near the ϒ(4S) resonance, at the KEKB asymmetric energy e+e− collider