Study of B -> \rho \pi decays at Belle

This paper describes a study of B meson decays to the pseudoscalar-vector final state \rho\pi using 31.9\times 10^6 B\bar{B} events collected with the Belle detector at KEKB. The branching fractions B(B^+ \to \rho^0\pi^+) = (8.0^{+2.3+0.7}_{-2.0-0.7}) \times 10^{-6} and B(B^0 -> \rho^{+-} \pi^{-+}) = (20.8^{+6.0+2.8}_{-6.3-3.1}) \times 10^{-6} are obtained. In addition, a 90% confidence level upper limit of B(B^0 \to \rho^0\pi^0) < 5.3 \times 10^{-6}is reported.Comment: 14 pages, 3 figures, to be submitted to Phys. Lett.

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

Improved Measurements of Partial Rate Asymmetry in B -> h h Decays

We report improved measurements of the partial rate asymmetry (Acp) in B -> h h decays with 140fb^-1 of data collected with the Belle detector at the KEKB e+e- collider. Here h stands for a charged or neutral pion or kaon and in total five decay modes are included: K-+ pi+-, K0s pi-+, K-+ pi0, pi-+ pi0 and K0s pi0. The flavor of the last decay mode is determined from the accompanying B meson. Using a data sample 4.7 times larger than that of our previous measurement, we find Acp(K-+ pi+-) -0.088+-0.035+-0.013, 2.4 sigma from zero. Results for other decay modes are also presented.Comment: 9 pages, 1 figur

Evidence for B- -> tau- nu_bar with a Semileptonic Tagging Method

We present a measurement of the decay B- -> tau- nu_bar using a data sample containing 657 million BB_bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. A sample of BB_bar pairs are tagged by reconstructing one B meson decaying semileptonically. We detect the B- -> tau- nu_bar candidate in the recoil. We obtain a signal with a significance of 3.6 standard deviations including systematic uncertainties, and measure the branching fraction to be Br(B- -> tau- nu_bar) = [1.54+0.38-0.37(stat)+0.29-0.31(syst)]*10^-4. This result confirms the evidence for B- -> tau- nu_bar obtained in a previous Belle measurement that used a hadronic B tagging method.Comment: 7 pages, 3 figures, corrected references, to appear in PRD-R

Study of the decays B->D_s1(2536)+ anti-D(*)

We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*) is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0, B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4, (2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.Comment: 6 pages, 2 figues, submitted to PRD (RC

Search for CP violation in the decay B0->D*+-D-+

We report a search for CP-violating asymmetry in B0 -> D*+- D-+ decays. The analysis employs two methods of B0 reconstruction: full and partial. In the full reconstruction method all daughter particles of the B0 are required to be detected; the partial reconstruction technique requires a fully reconstructed D- and only a slow pion from the D*+ -> D0 pi_slow+ decay. From a fit to the distribution of the time interval corresponding to the distance between two B meson decay points we calculate the CP-violating parameters and find the significance of nonzero CP asymmetry to be 2.7 standard deviations.Comment: 4 pages, 3 figure

Studies of the Decay B+- -> D_CP K+-

We report studies of the decay B+- -> D_CP K+-, where D_CP denotes neutral D mesons that decay to CP eigenstates. The analysis is based on a 29.1/fb data sample of collected at the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e+ e- storage ring. Ratios of branching fractions of Cabibbo-suppressed to Cabibbo-favored processes involving D_CP are determined to be B(B- -> D_1 K-)/B(B- -> D_1 pi-)=0.125 +- 0.036 +- 0.010 and B(B- -> D_2 K-)/B(B- -> D_2 pi-)=0.119 +- 0.028 +- 0.006, where indices 1 and 2 represent the CP=+1 and CP=-1 eigenstates of the D0 - anti D0 system, respectively. We also extract the partial rate asymmetries for B+- -> D_CP K+-, finding A_1 = 0.29 +- 0.26 +- 0.05 and A_2 = -0.22 +- 0.24 +- 0.04.Comment: 10 pages, 2 figures, submitted to Physical Review Letter

Measurement of CP-Violating Parameters in B→η′KB\to \eta^\prime K Decays

We present measurements of CP-violating parameters in $B^0(\bar{B}{}^0) \to \eta^\prime K_S^0$ and $B^{\pm} \to \eta' K^{\pm}$ decays based on a 41.8 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. We fully reconstruct one neutral $B$ meson as a $B^0(\bar{B}{}^0) \to \eta^\prime K_S^0$ CP eigenstate and identify the flavor of the accompanying $B$ from its decay products. From the distribution of time intervals between pairs of $B$ meson decay points, we obtain the CP-violating asymmetry parameters ${\mathcal S}_{\eta^\prime K_S^0} = 0.28\pm0.55(stat)^{+0.07}_{-0.08}(syst)$, and ${\mathcal A}_{\eta^\prime K_S^0} = 0.13\pm0.32(stat)^{+0.09}_{-0.06}(syst)$. We also reconstruct charged $B^{\pm} \to \eta^\prime K^{\pm}$ decays and determine a direct-CP violating asymmetry value of ${\mathcal A}_{\eta^\prime K^\pm}=(-1.5\pm7.0(stat)\pm0.9(syst))$.Comment: Revised version: 16 pages, 3 figures, 1 table submitted to Phys. Lett.

Measurement of masses and branching ratios of Ξc+\Xi_c^+ and Ξc0\Xi_c^0 baryons

We report a measurement of the $\Xi_c^+$ and $\Xi_c^0$ baryon masses, and the branching ratios for various $\Xi_c$ decays, using $140 \mathrm{fb}^{-1}$ of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider.The mass splitting $m_{\Xi_c^0} - m_{\Xi_c^+}$ is found to be $2.9\pm 0.5 \mathrm{MeV}/c^2$; this measurement is three times as precise as the current world average. We measure the branching ratios $\Gamma (\Xi_c^+\to \Lambda K\pi\pi)/\Gamma (\Xi_c^+\to\Xi\pi\pi) = 0.32\pm 0.03 \pm 0.02$ and $\Gamma (\Xi_c^0\to p KK\pi)/\Gamma (\Xi_c^0\to\Xi\pi) = 0.33\pm 0.03 \pm 0.03$, with improved precision, and measure $\Gamma (\Xi_c^+\to p K^0_S K^0_S)/\Gamma (\Xi_c^+\to\Xi\pi\pi) = 0.087\pm 0.016 \pm 0.014$, $\Gamma (\Xi_c^0\to \Lambda K\pi)/\Gamma (\Xi_c^0\to\Xi\pi) = 1.07\pm 0.12 \pm 0.07$ and $\Gamma (\Xi_c^0\to \Lambda K^0_S)/\Gamma (\Xi_c^0\to\Xi\pi) = 0.21\pm 0.02 \pm 0.02$ for the first time. In $\Xi_c^0$ decays to the $p K^- K^- \pi^+$ final state, we find evidence for the process $\Xi_c^0 \to p K^- \bar{K}{}^\ast(892)^0$ and measure the fraction of decays via this process to be $0.51\pm 0.03 \pm 0.01$.Comment: 16 pages, 9 figures, LaTeX, submitted to Phys. Lett.

Measurement of Br(Bbar -> D+l-nubar) and Determination of |Vcb|

We present a measurement of the branching fraction for the semileptonic B decay Bbar -> D+l-nubar, where l- can be either an electron or a muon. We find Gamma(Bbar -> D+l-nubar)= (13.79+/-0.76+/-2.51) ns^{-1}, and the resulting branching fraction Br(Bbar -> D+l-nubar)= (2.13 +/- 0.12 +/- 0.39)%, where the first error is statistical and the second systematic. We also investigate the Bbar -> D+l-nubar form factor and the implications of the result for |Vcb|. From a fit to the differential decay distribution we obtain the rate normalization |Vcb|F_D(1)= (4.11+/-0.44+/-0.52)x10^{-2}. Using a theoretical calculation of F_D(1), the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|=(4.19+/-0.45+/-0.53+/-0.30)x10^{-2} is obtained, where the last error comes from the theoretical uncertainty of F_D(1). The results are based on a data sample of 10.2 fb^{-1} recorded at the Upsilon(4S)$ resonance with the Belle detector at the KEKB e+e- collider.Comment: 21pages, 5 figures, elsart.cls, to be published in PLB. In this version, the form factor comparison between B->Dlnu and D*lnu is include