Search for an H-dibaryon with a mass near 2mΛ in Υ(1S) and Υ(2S) decays.

We report the results of a high-statistics search for H dibaryon production in inclusive Υ(1S) and Υ(2S) decays. No indication of an H dibaryon with a mass near the M(H)=2m(Λ) threshold is seen in either the H→Λpπ(-) or ΛΛ decay channels and 90% confidence level branching-fraction upper limits are set that are between one and two orders of magnitude below the measured branching fractions for inclusive Υ(1S) and Υ(2S) decays to antideuterons. Since Υ(1S,2S) decays produce flavor-SU(3)-symmetric final states, these results put stringent constraints on H dibaryon properties. The results are based on analyses of 102 million Υ(1S) and 158 million Υ(2S) events collected with the Belle detector at the KEKB e(+)e(-) collider.

Search for CP violation in the decays D(s)+ --> KS0pi+ and D(s)+ --> KS0K+.

We have searched for CP violation in the charmed meson decays D((s))(+) --> K(S)(0)pi(+) and D((s))(+) --> K(S)(0)K(+) using 673 fb(-1) of data collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. No evidence for CP violation is observed. We report the most sensitive CP asymmetry measurements to date for these decays: A(CP)(D(+)-->K(S)(0)pi(+)) = (-0.71 +/- 0.19 +/- 0.20)%, A(CP)(D(s)(+) --> K(S)(0)pi(+)) = (+5.45 +/- 2.50 +/- 0.33)%, A(CP)(D(+) --> K(S)(0)K(+)) = (-0.16 +/- 0.58 +/- 0.25)%, and A(CP)(D(s)(+) --> K(S)(0)K(+)) = (+0.12 +/- 0.36 +/- 0.22)%, where the first uncertainties are statistical and the second are systematic.

Observation of B(s)(0) → D(s)(*-) π+ and B(s)(0) → D(s)(*-) ρ+ and measurement of the B(s)(0) → D(s)(*-) ρ+ longitudinal polarization fraction.

First observations of the B(s)(0) → D(s)(*-) π+, B(s)(0) → D(s)(-) ρ+ and B(s)(0) → D(s)(*-) ρ+ decays are reported together with measurements of their branching fractions: B(B(s)(0) → D(s)(*-) π+) = [2.4(-0.4)(+0.5)(stat) ± 0.3(syst) ± 0.4(f(s))]×10(-3), B(B(s)(0) → D(s)(-) ρ+) = [8.5(-1.2)(+1.3)(stat) ± 1.1(syst) ± 1.3(f(s))]×10(-3) and B(B(s)(0) → D(s)(*-) ρ+) = [11.9(-2.0)(+2.2)(stat) ± 1.7(syst) ± 1.8(f(s))]×10(-3) (f(s) = N(B(s)(*) B(s)(*))/N(bb)). From helicity-angle distributions, we measured the longitudinal polarization fraction in B(s)(0) → D(s)(*-) ρ+ decays to be f(L)(B(s)(0) → D(s)(*-) ρ+) = 1.05(-0.10)(+0.08)(stat)(-0.04)(+0.03)(syst). These results are based on a 23.6 fb(-1) data sample collected at the Υ(5S) resonance with the Belle detector at the KEKB e+ e- collider.

Search for a low mass particle decaying into µ+ µ- in B0 → K*0 X and B0 → ρ0 X at Belle.

We search for dimuon decays of a low mass particle in the decays B0→K*0 X and B0→ρ0 X using a data sample of 657×10(6)BB events collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. We find no evidence for such a particle in the mass range from 212 MeV/c2 to 300 MeV/c2 for lifetimes below 10(-12) s, and set upper limits on its branching fractions. In particular, we search for a particle with a mass of 214.3 MeV/c2 reported by the HyperCP experiment, and obtain upper limits on the products B(B0→K*0 X)×B(X→µ+ µ- )<2.26(2.27)×10(-8) and B(B0→ρ0 X)×B(X→µ+ µ-)<1.73(1.73)×10(-8) at 90% C.L. for a scalar (vector) X particle.

Measurement of |V{ub}| from inclusive charmless semileptonic B decays.

We present the partial branching fraction for inclusive charmless semileptonic B decays and the corresponding value of the Cabibbo-Kobayashi-Maskawa matrix element |V{ub}|, using a multivariate analysis method to access approximately 90% of the B-->X{u}lnu phase space. This approach dramatically reduces the theoretical uncertainties from the b-quark mass and nonperturbative QCD compared to all previous inclusive measurements. The results are based on a sample of 657x10{6} BB[over ] pairs collected with the Belle detector. We find that DeltaB(B-->X{u}lnu;p(l){*B}>1.0 GeV/c)=1.963x(1+/-0.088{stat}+/-0.081{syst})x10{-3}. Corresponding values of |V{ub}| are extracted using several theoretical calculations.

Measurement of inclusive radiative B-meson decays with a photon energy threshold of 1.7 GeV.

Using 605 fb(-1) of data collected at the Upsilon(4S) resonance we present a measurement of the inclusive radiative B-meson decay channel, B-->X(s)gamma. For the lower photon energy thresholds of 1.7, 1.8, 1.9, and 2.0 GeV, as defined in the rest frame of the B meson, we measure the partial branching fraction and the mean and variance of the photon energy spectrum. At the 1.7 GeV threshold we obtain the partial branching fraction BF(B-->X(s)}gamma)=(3.45+/-0.15+/-0.40)x10(-4), where the errors are statistical and systematic.

Measurement of the differential branching fraction and forward-backward asymmetry for B --> K(*)l+l-.

We study B --> K(*)l+l- decays (l = e, mu) based on a data sample of 657 x 10(6) BB pairs collected with the Belle detector at the KEKB e+e- collider. We report the differential branching fraction, isospin asymmetry, K* polarization, and the forward-backward asymmetry (A(FB)) as functions of q2 = M(ll)(2)c2. The fitted A(FB) spectrum exceeds the standard model expectation by 2.7 standard deviations. The measured branching fractions are B(B --> K*l+l-) = (10.7(-1.0)(+1.1) +/- 0.9) x 10(-7) and B(B --> Kl+l-) = (4.8(-0.4)(+0.5) +/- 0.3) x 10(-7), where the first errors are statistical and the second are systematic, with the muon to electron ratios R(K*) = 0.83 +/- 0.17 +/- 0.08 and R(K) = 1.03 +/- 0.19 +/- 0.06.

Measurement of the Decay B_(s);(0)-->D_(s);(-)pi;(+) and Evidence for B_(s);(0)-->D_(s);(-/+)K;(+/-) in e;(+)e;(-) Annihilation at sqrt[s] approximately 10.87 GeV.

We have studied B_(s);(0)-->D_(s);(-)pi;(+) and B_(s);(0)-->D_(s);(-/+)K;(+/-) decays using 23.6 fb;(-1) of data collected at the Upsilon(5S) resonance with the Belle detector at the KEKB e;(+)e;(-) collider. This highly pure B_(s);(0)-->D_(s);(-)pi;(+) sample is used to measure the branching fraction, B(B_(s);(0)-->D_(s);(-)pi;(+))=[3.67_(-0.33);(+0.35)(stat)-0.42+0.43(syst)+/-0.49(f_(s))]x10;(-3) (f_(s)=N_(B_(s);((*))B[over ]_(s);((*)))/N_(bb[over ])) and the fractions of B_(s);(0) event types at the Upsilon(5S) energy, in particular N_(B_(s);(*)B[over ]_(s);(*))/N_(B_(s);((*))B[over ]_(s);((*)))=(90.1_(-4.0);(+3.8)+/-0.2)%. We also determine the masses M(B_(s);(0))=(5364.4+/-1.3+/-0.7) MeV/c;(2) and M(B_(s);(*))=(5416.4+/-0.4+/-0.5) MeV/c;(2). In addition, we observe B_(s);(0)-->D_(s);(-/+)K;(+/-) decays with a significance of 3.5sigma and measure B(B_(s);(0)-->D_(s);(-/+)K;(+/-))=[2.4_(-1.0);(+1.2)(stat)+/-0.3(syst)+/-0.3(f_(s))]x10;(-4).

Observation of the doubly cabibbo-suppressed decay D_{s};{+}-->K;{+}K;{+}pi;{-}.

We report the first observation of the doubly Cabibbo-suppressed decay D_{s};{+}-->K;{+}K;{+}pi;{-} using 605 fb;{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e;{+}e;{-} collider. The branching ratio with respect to its Cabibbo-favored counterpart B(D_{s};{+}-->K;{+}K;{+}pi;{-})/B(D_{s};{+}-->K;{+}K;{-}pi;{+}) is (0.229+/-0.028+/-0.012)%, where the first uncertainty is statistical and the second is systematic. We also report a significantly improved measurement of the doubly Cabibbo-suppressed decay D;{+}-->K;{+}pi;{+}pi;{-}, with a branching ratio B(D;{+}-->K;{+}pi;{+}pi;{-})/B(D;{+}-->K;{-}pi;{+}pi;{+})=(0.569+/-0.018+/-0.014)%.

Time-dependent CP-violating asymmetry in B0-->rho0gamma decays.

We report the first measurement of CP-violation parameters in B0-->rho0gamma decays based on a data sample of 657x10(6)BB pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain the time-dependent and direct CP-violating parameters, Srho0gamma=-0.83+/-0.65(stat)+/-0.18(syst) and Arho0gamma=-0.44+/-0.49(stat)+/-0.14(syst), respectively.

Evidence for neutral B meson decays to omegaK*0.

We present the results of a study of the charmless vector-vector decay B0-->omegaK*0 with 657 x 10(6) BB pairs collected with the Belle detector at the KEKB e+e- collider. We measure the branching fraction to be B(B0-->omegaK*0) = [1.8+/-0.7(stat)+/-0.3(syst)]x 10(-6) with 3.0sigma significance. We also perform a helicity analysis of the omega and K*0 vector mesons, and obtain the longitudinal polarization fraction fL(B0-->omegaK*0) = 0.56+/-0.29(stat) -0.08(+0.18)(syst). Finally, we measure a large nonresonant branching fraction B[B0-->omegaK+pi(-);M Kpi in(0.755,1.250) GeV/c2] = [5.1+/-0.7(stat)+/-0.7(syst)]x 10(-6) with a significance of 9.5sigma.

Measurement of the time-dependent CP asymmetries in B0-->K(S)(0)rho(0)gamma decays.

We report the first measurement of time-dependent CP asymmetry in B(0)-->K(S)(0)rho(0)gamma decays based on 657 x 10(6) BB pairs collected with the Belle detector at the KEKB asymmetric-energy collider. We measure the CP-violating parameter S_{K_{S};{0}rho;{0}gamma}=0.11+/-0.33(stat)-0.09+0.05(syst) from a signal of 212+/-17 events. We also obtain the effective direct CP-violating parameter A{eff}=0.05+/-0.18(stat)+/-0.06(syst) for mK(S)0pi+pi- <1.8 GeV/c(2) and 0.6 GeV/c(2)

Observation of a near-threshold enhancement in the e+e- -->Lambda+_(c)Lambda-_(c) cross section using initial-state radiation.

We report a measurement of the exclusive e+ e- -->Lambda+_(c)Lambda-_(c) cross section as a function of center-of-mass energy near the Lambda+_(c)Lambda-_(c) threshold. A clear peak with a significance of 8.2sigma is observed in the Lambda+_(c)Lambda-_(c) invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=[4634 (+8)_(-7)(stat)(+5)_(-8)(syst)] MeV/c(2) and Gamma_(tot)=[92 (+40)_(-24)(stat)(+10)_(-21)(syst)] MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Upsilon(4S) resonance and nearby continuum with an integrated luminosity of 695 fb(-1) at the KEKB asymmetric-energy e+ e- collider.

Observation of the psi(4415)-->DD2*(2460) decay using initial-state radiation.

We report measurements of the exclusive cross section for e(+)e(-)-->D(0)D(-)pi(+) over the center-of-mass energy range 4.0 GeV to 5.0 GeV with initial-state radiation and the first observation of the decay psi(4415)-->D(0)D(-)pi(+). From a study of the resonant substructure in psi(4415) decay we conclude that the psi(4415)-->D(0)D(-)pi(+) decay is dominated by psi(4415)-->DD(2)(*)(2460). We obtain B(psi(4415)-->D(0)D(-)pi(nonresonant)(+))/B(psi(4415)-->DD(2)(*)(2460)-->D(0)D(-)pi(+))<0.22 at 90% C.L. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 673 fb(-1).

Search for B+-->D*+pi0 decay.

We report on a search for the doubly Cabibbo suppressed decay B+-->D*+pi0, based on a data sample of 657x10(6) BB pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We find no significant signal and set an upper limit of B(B+-->D*+pi0)<3.6x10(-6) at the 90% confidence level. This limit can be used to constrain the ratio between suppressed and favored B-->D*pi decay amplitudes, r<0.051, at the 90% confidence level.

Measurement of B(Ds{+}-->mu+nu(mu)).

We present a measurement of the branching fraction B(D{s}{+}-->mu{+}nu{mu}) using a 548 fb{-1} data sample collected by the Belle experiment at the KEKB e{+}e{-} collider. The D{s} momentum is determined by reconstruction of the system recoiling against DKgammaX in events of the type e{+}e{-}-->D{s}{*}DKX, D{s}{*}-->D{s}gamma, where X represents additional pions or photons from fragmentation. This full-reconstruction method provides high resolution in the neutrino momentum and thus good background separation, equivalent to that achieved by experiments at the tau-charm factories. We obtain the branching fraction B(D{s}{+}-->mu{+}nu{mu})=[6.44+/-0.76(stat)+/-0.57(syst)]x10{-3}, implying a D{s} decay constant of f{D{s}}=[275+/-16(stat)+/-12(syst)] MeV.

Observation of anomalous upsilon(1S)pi+pi(-) and upsilon(2S)pi+pi(-) production near the upsilon(5S) resonance.

We report the first observation of e;{+}e;{-}-->Upsilon(1S)pi;{+}pi;{-}, Upsilon(2S)pi;{+}pi;{-}, and first evidence for e;{+}e;{-}-->Upsilon(3S)pi;{+}pi;{-}, Upsilon(1S)K+K-, near the peak of the Upsilon(5S) resonance at sqrt[s] approximately 10.87 GeV. The results are based on a data sample of 21.7 fb;{-1} collected with the Belle detector at the KEKB e;{+}e;{-} collider. Attributing the signals to the Upsilon(5S) resonance, the partial widths Gamma(Upsilon(5S)-->Upsilon(1S)pi;{+}pi;{-})=0.59+/-0.04(stat)+/-0.09(syst) MeV and Gamma(Upsilon(5S)-->Upsilon(2S)pi;{+}pi;{-})=0.85+/-0.07(stat)+/-0.16(syst) MeV are obtained from the observed cross sections. These values exceed by more than 2 orders of magnitude the previously measured partial widths for dipion transitions between lower Upsilon resonances.

Measurement of time-dependent CP-violating parameters in B(0)-->K_(S)(0)K_(S)(0) decays.

We report a measurement of the CP-violating parameters in B;{0}-->K_{S}{0}K_{S}{0} decays based on a data sample of 657x10{6} BB[over ] pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e;{+}e{-} collider. In this Letter, one neutral B meson is fully reconstructed in the B;{0}-->K_{S}{0}K_{S}{0} decay mode, and the flavor of the accompanying B meson is identified by its decay products. The CP-violating parameters are measured from the asymmetry in the distributions of the proper-time interval between the two B decays: S_K_{S}{0}K_{S}{0}}=-0.38_{-0.77}{+0.69}(stat)+/-0.09(syst) and A_{K_{S}{0}K_{S}{0}}=-0.38+/-0.38(stat)+/-0.05(syst).

Observation of B_(s)(0)-->phigamma and search for B_(s)(0)-->gammagamma decays at Belle.

We search for the radiative penguin decays B_{s}{0}-->varphigamma and B_{s}{0}-->gammagamma in a 23.6 fb{-1} data sample collected at the Upsilon(5S) resonance with the Belle detector at the KEKB e{+}e{-} asymmetric-energy collider. We observe for the first time a radiative penguin decay of the B_{s}{0} meson in the B_{s}{0}-->varphigamma mode and we measure B(B_{s}{0}-->varphigamma)=(57_{-15}{+18}(stat)-11+12(syst))x10{-6}. No significant B_{s}{0}-->gammagamma signal is observed and we set a 90% confidence level upper limit of B(B_{s}{0}-->gammagamma)<8.7x10{-6}.

Observation of a resonancelike structure in the pi +- psi' mass distribution in exclusive B-->Kpi +- psi' decays.

A distinct peak is observed in the pi +/- psi' invariant mass distribution near 4.43 GeV in B-->K pi +/- psi' decays. A fit using a Breit-Wigner resonance shape yields a peak mass and width of M=4433+/-4(stat)+/-2(syst) MeV and Gamma=45-13+18(stat)-13+30(syst) MeV. The product branching fraction is determined to be B(B 0-->K -/+Z+/-(4430)) x B(Z+/-(4430)-->pi+/-psi')=(4.1+/-1.0(stat)+/-1.4(syst)) x 10(-5), where Z+/-(4430) is used to denote the observed structure. The statistical significance of the observed peak is 6.5 sigma. These results are obtained from a 605 fb(-1) data sample that contains 657 x 10(6) BB pairs collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider.