S. Cole

Measurement of the time-dependent CP-violating asymmetry in BO→KSOπOγ decays

We present a new measurement of CP-violation parameters in B(0)-->K(0)(S)pi(0)gamma decay based on a sample of 275 x 10(6) BB pairs collected at the Gamma(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. One of the B mesons is fully reconstructed in the B(0)-->K(0)(S)pi(0)gamma decay. The flavor of the accompanying B meson is identified from its decay products. CP-violation parameters are obtained from the asymmetry in the distribution of the proper time intervals between the two B decays. We obtain SK(0)(S)(pi(0)gamma) = -0.58(+0.46)(-0.38)(stat) +/- 0.11(syst) and AK(0)(S)(pi(0)gamma) = +0.03 +/- 0.34(stat) +/- 0.11(syst), for the K(0)(S)pi(0) invariant mass covering the full range up to 1.8 GeV/c2. We also measure the CP-violation parameters for the case B(0)-->K(*0)(-->K(0)(S)pi(0))gamma and obtain S(K(*0)gamma) = -0.79(+0.63)(-0.50)(stat) +/- 0.10(syst) for A(K(*0)gamma) fixed at 0.

Observation of Large CP Violation and Evidence for Direct CP Violation in B0→π+π- Decays

We report the first observation of CP violation in B0-->pi(+)pi(-) decays based on 152x10(6) gamma (4S)-->BB decays collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We reconstruct a B0-->pi(+)pi(-) CP eigenstate and identify the flavor of the accompanying B meson from its decay products. From the distribution of the time intervals between the two B meson decay points, we obtain A(pipi)=+0.58+/-0.15(stat)+/-0.07(syst) and S(pipi)=-1.00+/-0.21(stat)+/-0.07(syst). We rule out the CP-conserving case, A(pipi)=S(pipi)=0, at a level of 5.2 standard deviations. We also find evidence for direct CP violation with a significance at or greater than 3.2 standard deviations for any S(pipi) value.

Determination of /Vub/ from measurements of the inclusive charmless semileptonic partial rates of B mesons using full reconstruction tags.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element /Vub/, based on 253 fb(-1) of data collected by the Belle detector at the KEKB e+ e- asymmetric collider. Events are tagged by fully reconstructing one of the B mesons, produced in pairs from Gamma(4S). The signal for b --> u semileptonic decay is distinguished from the b --> c background using the hadronic mass Mx, the leptonic invariant mass squared q2 and the variable P+ [triple bond] Ex - /px/. The results are obtained for events with p(l)* > or = 1 GeV/c, in three kinematic regions (1) Mx < 1.7 GeV/c2, (2) Mx < 1.7 GeV/c2 combined with q2 > 8 GeV2/c2, and by (3) P+ < 0.66 GeV/c. The matrix element /Vub/ is found to be (4.09 +/- 0.19 +/- 0.20(+0.14) -0.15 +/- 0.18) x 10(-3), where the errors are statistical, systematic including Monte Carlo modeling, theoretical, and from shape function parameter determination, respectively.

Measurement of γγ → pp̄ 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.

Study of decay mechanisms in B-->Lambda(+)(c)p pi(-) decays and observation of low-mass structure in the Lambda(+)(c)p system

Using a sample of 152 million BBbar pairs accumulated with the Belle detector at the KEKB e+e- collider, we perform a Dalitz plot analysis of the three-body charmed decay B- ->Lambda_c+ p_bar pi-. The intermediate two-body decay B- ->Sigma_c(2455)0 p_bar is observed for the first time with a branching fraction of (3.67^{+0.74}_{-0.66}+-0.36+-0.95)x10^(-5) and a statistical significance of 8.4sigma. We also observe a low-mass enhancement in the (Lambda_c+ p_bar) system, which can be parameterized as a Breit-Wigner function with a mass of (3.35^{+0.01}_{-0.02}+-0.02)GeV/c^2 and a width of (0.07^{+0.04}_{-0.03}+-0.04)GeV/c^2. We measure the product of the corresponding decay branching fractions to be (3.87^{+0.77}_{-0.72}+-0.43+-1.01)x10^(-5)

Observation of the decays B0 → K+π -π0 and B0 → ρ-K +

with a statistical significance of 6.2sigma. The errors are statistical, systematic, and that of the Lambda_c^+ ->pK-pi+ decay branching fraction.

Measurement of the branching fractions for B- → D (*)+π-ℓ-v̄ℓ and B̄0 → D(*)0π+ℓ -v̄ℓ

We report the observation of B0 decays to the K+π-π0 final state using a data sample of 78 fb-1 collected by the Belle detector at the KEKB e+e- collider. With no assumptions about intermediate states in the decay, the branching fraction is measured to be (36.6-4.3+4.2±3.0)×10-6. We also search for B decays to intermediate two-body states with the same K+π-π0 final state. Significant B signals are observed in the ρ(770)-K+ and K*(892)+π- channels, with branching fractions of (15.1-3.3-1.5-2.1+3.4+1.4+2.0)×10-6 and (14.8-4.4-1.0-0.9+4.6+1.5+2.4) ×10-6, respectively. The first error is statistical, the second is systematic and the third is due to the largest possible interference. Contributions from other possible two-body states will be discussed. No CP asymmetry is found in the inclusive K+π-π0 or ρ-K+ modes, and we set 90% confidence level bounds on the asymmetry of -0.12

Measurement of the CP asymmetry in B → Xsγ

We report on a measurement of the branching fractions for B- → D(*)+π- l -vl and B0 → D (*)0π+l-vl with 275 × 106 BB events collected at the γ(4S) resonance with the Belle detector at KEKB. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We obtain B(B- → D+π- l-vl = (0.54±0.07(stat)±0.07(syst)±0.06(BR))× 10 -2, B(B- → D(*)+π- l-vl = (0.67 ±0.11(stat) ±0.09(syst) ±0.03(BR)) × 10-2, B(B0 → D0π+ l -vl) = (0.33 ±0.06(stat) ± 0.06(syst) ±0.03(BR)) × 10-2, B(B0 → D(*)0π+l -vl) = (0.65 ±0.12(stat) ± 0.08(syst) ±0.05(BR)) × 10-2, where the third error comes from the error on B → D(*)l -vl decays. Contributions from B0 → D(*)+l-vl decays are excluded in the measurement of B0 → D0π +l-vl.

Studies of CP violation in B → J/ψK* decays

Direct CP violation in the b-->sgamma process is a sensitive probe of physics beyond the standard model. We report a measurement of the CP asymmetry in B-->X(s)gamma, where the hadronic recoil system X(s) is reconstructed using a pseudoreconstruction technique. In this approach there is negligible contamination from b-->dgamma decays, which are expected to have a much larger CP asymmetry. We find A(CP)=0.002+/-0.050(stat)+/-0.030(syst) for B-->X(s)gamma events having recoil mass smaller than 2.1 GeV/c(2). The analysis is based on a data sample of 140 fb(-1) recorded at the upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring.