Showing papers by "Ascelin Gordon published in 2003"

Measurements of the $D_{sJ}$ resonance properties

Abstract: We report measurements of the properties of the D(+)(sJ)(2317) and D(+)(sJ)(2457) resonances produced in continuum e(+)e(-) annihilation near sqrt[s]=10.6 GeV. The analysis is based on an 86.9 fb(-1) data sample collected with the Belle detector at KEKB. We determine the masses to be M(D(+)(sJ)(2317))=2317.2+/-0.5(stat)+/-0.9(syst) MeV/c(2) and M(D(+)(sJ)(2457))=2456.5+/-1.3(stat)+/-1.3(syst) MeV/c(2). We observe the radiative decay mode D(+)(sJ)(2457)-->D(+)(s)gamma and the dipion decay mode D(+)(sJ)(2457)-->D(+)(s)pi(+)pi(-) and determine their branching fractions. No corresponding decays are observed for the D(sJ)(2317) state. These results are consistent with the spin-parity assignments of 0(+) for the D(sJ)(2317) and 1(+) for the D(sJ)(2457).

Observation of B ± → ρ ±ρ 0 decays

Abstract: We report the first observation of the charmless vector-vector decay process B-/+-->rho(-/+)rho(0). The measurement uses a 78 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric e(+)e(-) collider operating at the Y(4S) resonance. We obtain a branching fraction of B (B-/+-->rho(-/+)rho(0))=[31.7+/-7.1(stat)(-6.7)(+3.8)(syst)]x10(-6). An analysis of the rho helicity-angle distributions gives a longitudinal polarization fraction of Gamma(L)/Gamma=0.95+/-0.11(stat)+/-0.02(syst). We also measure the direct-CP-violating asymmetry A(CP)(B-/+-->rho(-/+)rho(0))=0.00+/-0.22(stat)+/-0.03(syst).

Observation ofB∓→ρ∓ρ0Decays

Abstract: We report the first observation of the charmless vector-vector decay process ${B}^{\ensuremath{\mp}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{\mp}}{\ensuremath{\rho}}^{0}$. The measurement uses a $78\text{ }\text{ }\mathrm{f}{\mathrm{b}}^{\mathrm{\ensuremath{-}}\mathrm{1}}$ data sample collected with the Belle detector at the KEKB asymmetric ${e}^{+}{e}^{\ensuremath{-}}$ collider operating at the $\ensuremath{\Upsilon}(4S)$ resonance. We obtain a branching fraction of $\mathcal{B}({B}^{\ensuremath{\mp}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{\mp}}{\ensuremath{\rho}}^{0})=[31.7\ifmmode\pm\else\textpm\fi{}7.1(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}{)}_{\ensuremath{-}6.7}^{+3.8}(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. An analysis of the $\ensuremath{\rho}$ helicity-angle distributions gives a longitudinal polarization fraction of ${\ensuremath{\Gamma}}_{L}/\ensuremath{\Gamma}=0.95\ifmmode\pm\else\textpm\fi{}0.11(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$. We also measure the direct-$CP$-violating asymmetry ${\mathcal{A}}_{CP}({B}^{\ensuremath{\mp}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{\mp}}{\ensuremath{\rho}}^{0})=0.00\ifmmode\pm\else\textpm\fi{}0.22(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$.

Measurement of branching fractions and charge asymmetries for two-body B meson decays with charmonium

Abstract: We report branching fractions and charge asymmetries for exclusive decays of charged and neutral B mesons to two-body final states containing a charmonium meson, J/Ψ or Ψ/(2S). This result is based on a 29.4 fb-1 data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e+e- collider. © 2003 The American Physical Society.

Study of time-dependent CP-violating asymmetries in b→sq̄q decays

Abstract: We present a measurement of CP-violation parameters in the b→sqq penguin transitions (q = s,u,d) based on a 78 fb-1 data sample collected at the Y(4S) resonance with the Belle detector at the KEKB energyasymmetric e+e- collider. One neutral B meson is reconstructed in the φKS 0, K+K -KS 0, or η′ KS 0 decay channel, and the flavor of the accompanying B meson is identified from its decay products. CP violation parameters for each of the three modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. © 2003 The American Physical Society.

Evidence for $B^0 \to \pi^0 \pi^0$

Abstract: We report evidence for the decay $B^0 \to \pi^0 \pi^0$. The analysis is based on a data sample of 152 million $B\bar{B}$ pairs collected at the $\Upsilon(4s)$ resonance with the Belle detector at the KEKB $e^+ e^-$ storage ring. We find $25.6^{+ 9.3}_{-8.4}(stat)^{+1.6}_{-1.4}(syst)$ $B^0 \to \pi^0 \pi^0$ signal events with a significance of 3.4 standard deviations. We measure the branching fraction to be ($1.7 \pm 0.6 (stat) \pm 0.2 (syst))*10^{-6}$.

Studies of the decay B+ - DcpK+

Abstract: We report studies of the Cabibbo-suppressed decay B+/- --> DCPK+/-, where D-CP denotes CP eigenstates of the D-0 - (D) over bar (0) system. The analysis is based on a 29.1 fb(-1) sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e(+)e(-) storage ring. We measure ratios of branching fractions, relative to Cabibbo-favored B+/--->D(CP)pi+/-, of B>(B- --> D1K-)/B(B- --> D(1)pi(-)) = 0.125 +/-0.036 +/- 0.010 and B(B- --> D2K-)/B(B- --> D(2)pi(-)) = 0.119 +/- 0.028 +/- 0.006; the index 1 (2) denotes the CP = +1 (-1) eigenstate. We also extract the partial rate asymmetries for B+/- --> DCPK+/-, finding A(1) = 0.29 +/- 0.26 +/- 0.05 and A(2) = -0.22 +/- 0.24 +/- 0.04.

The data acquisition system of the Belle silicon vertex detector (SVD) upgrade

Abstract: We have developed a new data acquisition system (DAQ) utilizing PC farms for the upgraded silicon vertex detector (SVD2) in the Belle experiment at the KEKB factory. The SVD upgrade will increase the number of readout channels by about 50% to 110592. The maximum trigger rate is also expected to rise to 1.0kHz due to the increasing beam intensity from KEKB. To manage the increased dataflow, we have constructed the DAQ system with twelve Linux PCs, each of which is directly connected to three flash AD converter boards through PCI data I/O boards. The advantages of using the PCs include the ease of software maintenance, market availability of hardware when replacements are needed, scalability and much improved processing speed. In order to decrease the data transfer load to the data storage system, we have developed data sparsification algorithms that calculate pedestal and noise, find particle hit channels and thus reduce the data down to 5% of the original volume. We have measured the data processing speed of the system at various read-out channel occupancy levels. The system is able to process data at a 1.3kHz trigger rate with 5% occupancy and will thus be able to handle the anticipated 1.0kHz trigger rate.

The Belle trigger system with the new silicon vertex detector SVD 2.0

Abstract: During the summer shutdown of 2003, the new silicon vertex detector SVD2 was installed in Belle at the KEKB factory and started to take data in October 2003. It provides important improvements in the tracking capabilities and adds new trigger functionality. In addition, a new hardware trigger Level 1.5 was designed and installed that takes advantage of the digitized SVD hit data. The improvement in the Belle trigger system will be important to deal with the increasing luminosity and higher beam currents of the KEKB factory.

Charmless two-body decays

Abstract: We report the latest results of a study of charmless two-body B meson decays using data recorded by the Belle experiment at KEKB. Branching fractions or upper limits are provided for the complete set of Kμ, μμ and K K final states; the B → ϱπ decays with final states ϱ0π+, ϱ±π± and ϱ0π0; we also provide a first measurement of the branching fraction of the vector-vector decay B+ → ϱ+ϱ0.