arXiv subjects
Publications and source records attributed to K. Abe.
We reconstruct B0bar -> D_s^-D^+ decays using a sample of 275 million BBbar pairs recorded by the Belle experiment, and we measure the branching fraction to be [7.42 +- 0.23(stat) +- 1.36(syst)] x 10^(-3). We also search for the related decay B0bar -> D_s^+D_s^-. We observe no statistically significant signal and set an upper limit on the branching fraction of 2.0 x 10^(-4) at 90% C.L.
We report improved measurements of B decays with an eta meson in the final state using 357 fb^-1 of data collected by the Belle detector at the KEKB e^+ e^- collider. We observe the decays B^+- ->eta pi^+- and B^+- -> eta K^+-; the measured branching fractions are Br(B^+- -> eta pi^+-) = (3.9 +- 0.5(stat.)+-0.2(sys.))*10^-6 and Br(B^+- -> eta K^+-) = (2.2+-0.4(stat.)+-0.1(sys.))*10^-6, respectively. Their corresponding CP-violating asymmetries are measured to be -0.10+-0.11(stat.)+-0.02(sys.) for eta pi^+- and -0.55+-0.19(stat.)+0.04-0.03(sys.) for eta K^+-. No significant signal is found for B^0-> eta K^0 decays; the upper limit on the branching fraction at the 90% confidence level is Br(B^0->eta K^0) < 1.9*10^-6.
We report a measurement of the charmless semileptonic decays $B^0 \to π^- / ρ^- \ell^{+} ν$ and $B^+ \to π^0 / ρ^0 \ell^{+} ν$, based on 253 fb$^{-1}$ of data collected with the Belle detector at the KEKB $e^+e^-$ asymmetric collider. In this analysis, the accompanying $B$ meson is reconstructed in the semileptonic mode $B \to D^{(*)} \ell ν$, enabling detection of the signal modes with high purity. We measure the branching fractions ${\cal B}(B^0 \to π^- \ell^+ ν) = (1.48\pm 0.20\pm 0.16\pm 0.04) \times 10^{-4}$, ${\cal B}(B^0 \to ρ^- \ell^+ ν) = (2.07\pm 0.47\pm 0.25\pm 0.14) \times 10^{-4}$, ${\cal B}(B^+ \to π^0 \ell^+ ν) = (0.76\pm 0.13\pm 0.08\pm 0.04) \times 10^{-4}$ and ${\cal B}(B^+ \to ρ^0 \ell^+ ν) = (1.39\pm 0.23\pm 0.17\pm 0.03) \times 10^{-4}$, where the errors are statistical, experimental systematic, and systematic due to form-factor uncertainties, respectively. For each mode we also present the partial branching fractions in three $q^2$ intervals; $q^2 < 8$, $8 \leq q^2 < 16$, and $q^2 \geq 16$ GeV$^2/c^2$. Based on these results, the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ub}$ is extracted. All of the presented results are preliminary.
We report measurements of B meson decays to two kaons using 250/fb of data collected with the Belle detector at the KEKB asymmetric energy e+ e- collider. We find evidence of signals in B+ -> K0(bar) K+ and B0 -> K0 K0(bar) with significances of 3.0 sigma and 3.5 sigma, respectively. The corresponding branching fractions are measured to be BF(B+ -> K0(bar) K+) = (1.0+-0.4+-0.1) x 10^-6 and Br(B0 -> K0 K0(bar)) = 0.8+-0.3+-0.1) x 10^-6. These decay modes are examples of hadronic b -> d transitions. No signal is observed in the decay B0 -> K+ K- and we set an upper limit of 3.7 x 10^-7 at 90% confidence level.
Using kaon secondary interactions in the material of the Belle detector, we search for both inclusive and exclusive production of the Theta(1540)+. We set an upper limit of 2.5% at the 90% C.L. on the ratio of the Theta(1540)+ to Lambda(1520) inclusive production cross sections. We also search for the Theta(1540)+ as an intermediate resonance in the charge exchange reaction K+ n -> p Ks. An upper limit of Gamma(Theta+)<0.64MeV at the 90% C.L. at m(Theta+)=1.539MeV is set. These results are obtained from a 397/fb data sample collected with the Belle detector near the Upsilon(4S) resonance, at the KEKB asymmetric energy e+e- collider.
We report an improved measurement of the branching fraction for B0bar -> DsJ*(2317)+ K- and present evidence of the B0bar -> DsJ(2460)+ K- decay. These results are obtained from a data sample containing 386 million BBbar pairs that was collected near the Y(4S) resonance, with the Belle detector at the KEKB asymmetric energy e+ e- collider.
We present a preliminary measurement of the angle phi1 of the CKM Unitarity Triangle using time-dependent analysis of D -> Ks pi+ pi- decays produced in neutral B meson decay to a neutral D meson and a light meson (B -> D h). The method allows one to directly extract the value of 2phi1. The ambiguity between 2phi1 and pi-2phi1 in the measurement of sin(2phi1) can then be resolved. We obtain phi1=16 +- 21 +- 11. The 95% CL region including systematic error is -30<phi1<62, thus ruling out the second solution from sin(2phi1)=0.726 +- 0.037 at the 97% CL.
We present measurements of CP-violation parameters in b -> s gamma transitions based on a sample of 386x10^6 BB pairs collected at the Y(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in the B0 -> Ks Pi0 gamma decay channel irrespective to the Ks Pi0 intermediate state. The flavor of the accompanying B meson is identified from its decay products. CP-violation parameters are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. We obtain the following results for the Ks Pi0 invariant mass covering the full range up to 1.8 GeV/c^2: S_{Ks Pi0 gamma} = +0.08 +-0.41(stat) +-0.10(syst), A_{Ks Pi0 gamma} = +0.12 +-0.27(stat) +-0.10(syst).
We report an improved measurement of direct CP violation in the decay B0 --> K+pi-, and a search for CP violation in the decays B+ --> K+pi0 and B+ --> pi+pi0. The measured CP violating asymmetries are Acp(K+pi-)=-0.113+-0.022(stat.)+-0.008(syst.), Acp(K+pi0)=0.04+-0.04(stat.)+-0.02(syst.) and Acp(pi+pi0)=0.02+-0.08(stat.)+-0.01(syst.), where the latter correspond to the intervals -0.03<Acp(K+pi0)<0.11 and -0.12<Acp(pi+pi0)<0.15 at 90% confidence level. These results are obtained from a data sample that contains 386 million BBbar pairs that was collected near the Y(4S) resonance, with the Belle detector at the KEKB asymmetric nergy e+e- collider. All of the results are preliminary.
We have measured the branching fraction, longitudinal polarization fraction f_L, and the CP asymmetry coefficients A and S in B0 -> rho+rho- decays. These results are obtained from a 253 fb-1 data sample containing 275 million B\bar{B} pairs collected by the Belle detector running at the KEKB e+e- collider. We obtain B = [24.4 \pm 2.2 (stat) +3.8 -4.1 (syst)] x 10-6, f_L = 0.951 +0.033 -0.039 (stat) +0.029 -0.031 (syst), A = 0.00 \pm 0.30 (stat) +0.10 -0.09 (syst), and S = 0.09 \pm 0.42 (stat) \pm 0.08 (syst). These values are used to determine the CKM phase angle phi_2 (alpha) via an isospin analysis; the central value and one sigma error are (87 \pm 17) degrees, and 59 degrees < phi_2 < 115 degrees at 90% CL.
We report on a search for the production of new resonance states in the process gamma gamma-->D Dbar. A candidate C-even charmonium state is observed in the vicinity of 3.93 GeV/c^2. The production rate and the angular distribution in the gamma gamma center-of-mass frame suggest that this state is the previously unobserved chi_{c2}', the 2 ^3P_2 charmonium state.
We present a search for the decays B -> tau nu and B -> K nu nubar in a 253 fb^-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy B factory. Combinatorial and continuum backgrounds are suppressed by selecting a sample of events with one fully reconstructed B. The decay products of the B on the other side of the event are analyzed to search for B -> tau nu and B -> K nu nubar decays. We find no significant evidence for a signal and set 90% confidence level upper limits of B(B -> tau nu) < 1.8*10^-4 and B(B -> K nu nubar) < 3.6*10^-5.
We present measurements of time-dependent CP asymmetries in B0 --> phi(1020) K0, eta' K0, Ks Ks Ks, Ks pi0, f0(980) Ks, omega Ks and K+ K- Ks decays based on a sample of 386 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. These decays are dominated by the b --> s gluonic penguin transition and are sensitive to new CP-violating phases from physics beyond the standard model. One neutral B meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters sin2phi1^eff and {\cal A} for each of the decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. We also perform an improved measurement of CP asymmetries in B0 --> J/psi K0 decays using the same data sample. The same analysis procedure mentioned above yields sin2phi1 = +0.652 +/- 0.039(stat) +/- 0.020(syst), which serves as a reference point for the standard model, and {\cal A} = +0.010 +/- 0.026(stat) +/- 0.036(syst).
We performed a search for cosmic-ray antideuterons using data collected during four BESS balloon flights from 1997 to 2000. No candidate was found. We derived, for the first time, an upper limit of 1.9E-4 (m^2 s sr GeV/nucleon)^(-1) for the differential flux of cosmic-ray antideuterons, at the 95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the atmosphere.
The interpretation of the origin of the light scattering anomalies near the transition from incommensurate (IC) to the alpha-phase of quartz by Dolino et al. (Phys. Rev. Lett. 94, 155701 (2005)) is commented. It is shown that the observed IC structure is a pure transverse acoustic (TA) modulation without any soft optic mode component. Such a modulation cannot be responsible for the observed light scattering contrary to the interpretation by Dolino et al.
WIDGET is a robotic telescope for monitoring the HETE-2 field-of-view to detect Gamma-ray Burst optical flashes or possible optical precursors. The system has 62degx62deg wide field-of-view which covers about 80% of HETE-2 one with a 2kx2k Apogee U10 CCD camera and a Canon EF 24mm f/1.4 wide-angle lens without a bandpass filter. WIDGET has been in operation since June 2004 at Akeno observing site where is about 200 km apart from Tokyo. Typical limiting magnitude with S/N=3 at the site is V=10mag for 5 seconds exposure and V=11mag for 30 seconds exposure. We had already six coincident observations with HETE-2 position alerts. It was, however, cloudy for all cases due to rainy season in Japan. Expected number of coincident observations under clear sky is about 5 events per year. We will extend the system in early 2005 for Swift era to monitor optical transients in wider field-of-view, multi-color or polarization modes.
We report evidence for the decay modes X(3872) --> gamma J/psi and X(3872)--> pi+pi-pi0 J/psip. In the latter, the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the kinematic limit of 775 MeV, suggesting that the process is dominated by the sub-threshold decay X --> omega J/psi. These results establish the charge-conjugation parity of the X(3872) as C=+1. The results are based on a study of X(3872) mesons produced via exclusive B --> K X(3872) decays in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The X(3872) --> gamma J/psi signal and the pi+pi-pi0 J/psi signal each has a statistical significance that is greater than 4 sigma.
We examine possible J^PC quantum number assignments for the X(3872). Angular correlations between final state particles in X(3872) --> pi+pi- J/psi decays are used to rule out J^PC values of 0++ and 0-+. The shape of the pi+pi- mass distribution near its upper kinematic limit favors S-wave over P-wave as the relative orbital angular momentum between the final-state dipion and J/psi, which strongly disfavors 1-+ and 2-+ assignments. The accumulated evidence strongly favors a J^PC = 1++ assignment for the X(3872), although the 2++ possibility is not ruled out by tests reported here. The analysis is based on a sample of X(3872) mesons produced via the exclusive process B --> K X(3872) in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider.