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H Kakuno

Publications and source records attributed to H Kakuno.

17 recordsLinked to original sources
PubMed2006

Measurement of D0-->pilnu(Klnu) form factors and absolute branching fractions.

Using a 282 fb-1 data sample collected by the Belle experiment at the KEKB e+e- collider, we study D0 decays to K-l+nu and pi-l+nu final states. The D0 flavor and momentum are tagged through a full reconstruction of the recoiling charm meson and additional mesons from fragmentation. The reconstruction method provides very good resolution in neutrino momentum and in q2=(pl+pnu)2. Normalizing to the total number of D0 tags, we measure the absolute branching fractions to be B(D0-->Klnu)=(3.45+/-0.07stat+/-0.20syst)% and B(D0-->pilnu)=(0.255+/-0.019stat+/-0.016syst)% and the semileptonic form factors (within the modified pole model) f+K(0)=0.695+/-0.007stat+/-0.022syst and f+pi(0)=0.624+/-0.020stat+/-0.030syst.

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PubMed2005

Improved evidence for direct CP violation in B0-->pi+pi- decays and model-independent constraints on phi2.

We present a new measurement of the time-dependent CP-violating parameters in B(0)--> pi(+)pi(-) decays with 275 x 10(6) BB pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider operating at the Gamma(4S) resonance. We find 666 +/- 43 B(0) --> pi(+)pi(-) events and measure the CP-violating parameters: S(pipi) = -0.67 +/- 0.16(stat) +/- 0.06(syst) and A(pipi) = +0.56 +/- 0.12(stat) +/- 0.06(syst). We find evidence for large direct CP violation with a significance greater than 4 standard deviations for any S(pipi) value. Using isospin relations, we obtain 95.4% confidence intervals for the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle phi(2) of 0 degree < phiv(2) < 19 degrees and 71 degrees < phi(2) < 180 degrees.

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PubMed2005

Study of B0-->rho+/- pi-/+ time-dependent CP violation at Belle.

We present a time-dependent analysis of CP violation in B0-->rho(+/-)pi(-/+) decays based on a 140 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at KEKB. We obtain the charge asymmetry A(rhopi)(CP)=-0.16+/-0.10(stat)+/-0.02(syst). An unbinned maximum-likelihood fit to the Deltat distributions yields C(rhopi)=0.25+/-0.17(stat)+0.02-0.06(syst), DeltaC(rhopi)=0.38+/-0.18(stat)+0.02-0.04(syst), S(rhopi)=-0.28+/-0.23(stat)+0.10-0.08(syst), and DeltaS(rhopi)=-0.30+/-0.24(stat)+/-0.09(syst). The direct CP violation parameters for B-->rho(+)pi(-) and B-->rho(-)pi(+) decays are A(+-)(rhopi)=-0.02+/-0.16(stat)+0.05-0.02(syst) and A(-+)(rhopi)=-0.53+/-0.29(stat)+0.09-0.04(syst).

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PubMed2004

Observation of large CP violation and evidence for direct CP violation in B0-->pi(+)pi(-) 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.

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PubMed2004

Measurement of /V(ub)/ using inclusive B-->X(u)lnu decays with a novel X(u)-reconstruction method.

We report the measurement of an inclusive partial branching fraction for charmless semileptonic B decay and the extraction of /V(ub)/. Candidates for B-->X(u)lnu are identified with a novel X(u) reconstruction method based on neutrino reconstruction via missing 4-momentum and a technique called "simulated annealing." Based on 86.9 fb(-1) of data taken with the Belle detector, we obtain DeltaB(B-->X(u)lnu;M(X)<1.7 GeV/c2,q2>8.0 GeV2/c2)=[7.37+/-0.89(stat)+/-1.12(syst)+/-0.55(b-->c)+/-0.24(b-->u)]x10(-4) and determine |V(ub)|=[4.66+/-0.28(stat)+/-0.35(syst)+/-0.17(b-->c)+/-0.08(b-->u)+/-0.58(theory)]x10(-3).

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PubMed2003

Evidence for B0-->pi0pi0.

We report evidence for the decay B0-->pi(0)pi(0). The analysis is based on a data sample of 152x10(6) BBmacr; pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. We detect a signal for B0-->pi(0)pi(0) with a significance of 3.4 standard deviations, and measure the branching fraction to be [1.7+/-0.6(stat)+/-0.2(syst)]x10(-6).

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PubMed2002

Measurement of the B(0)-B(0) mixing parameter Deltam(d) using semileptonic B0 decays.

We present a measurement of the B0-Bmacr;(0) mixing parameter Deltam(d) using neutral B meson pairs in a 29.1 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We exclusively reconstruct one neutral B meson in the semileptonic B0-->D(*-)l(+)nu decay mode and identify the flavor of the accompanying B meson from its decay products. From the distribution of the time intervals between the two flavor-tagged B meson decay points, we obtain Deltam(d)=(0.494+/-0.012+/-0.015) ps(-1), where the first error is statistical and the second error is systematic.

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PubMed2002

Observation of the color-suppressed decay B( 0)-->D(0)pi(0).

We report the first observation of color-suppressed B( 0)-->D(0)pi(0), D(*0)pi(0), D0eta, and D0omega decays, and evidence for B( 0)-->D(*0)eta and D(*0)omega. The branching fractions are B(B( 0)-->D0pi(0)) = (3.1 +/- 0.4 +/- 0.5)x10(-4), B(B( 0) -->D(*0)pi(0)) = (2.7(+0.8+0.5)(-0.7-0.6))x10(-4), B(B( 0) --> D0eta) = (1.4(+0.5)(-0.4) +/- 0.3)x10(-4), B(B( 0) --> D0omega) = (1.8 +/- 0.5(+0.4)(-0.3))x10(-4), and we set 90% confidence level upper limits of B(B( 0) --> D(*0)eta)<4.6 x 10(-4) and B(B( 0)-->D(*0)omega)<7.9 x 10(-4). The analysis is based on a data sample of 21.3 fb(-1) collected at the Upsilon(4S) resonance by the Belle detector at the KEKB e(+)e(-) collider.

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PubMed2001

Observation of the decay B --> Kl+l-.

We report a search for the flavor-changing neutral current decay B-->K(*)l+l- using a 29.1 fb(-1) data sample accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- storage ring. We observe the decay process B-->Kl+l-(l = e, mu), for the first time, with a branching fraction of B(B-->Kl+l-) = (0.75(+0.25)(-0.21)+/-0.09)x10(-6).

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PubMed2001

Observation of B --> J/psi K(1)(1270).

We report the first observation of the exclusive decay process B-->J/psi K(1)(1270) using a sample of 11.2M BB macro meson pairs collected in the Belle detector at the KEKB asymmetric energy e(+)e(-) collider. We measure branching fractions of B[B(0)-->J/psi K(0)(1)(1270)] = (1.30+/-0.34+/-0.32) x 10(-3) and B[B(+)-->J/psi K(+)(1)(1270)] = (1.80+/-0.34+/-0.39) x 10(-3), where the first error is statistical and the second is systematic. These modes constitute approximately 15% of the total number of B-->J/psi X decays. No evidence is seen for B-->J/psi K(1)(1400) and we set an upper limit for this branching fraction.

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PubMed2001

Observation of Cabibbo suppressed B --> D(*)K- decays at Belle.

We report observations of the Cabibbo suppressed decays B-->D((*))K- using a 10.4 fb(-1) data sample accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. We find that the ratios of Cabibbo suppressed to Cabibbo favored branching fractions are B(B--->D0K-)/B(B--->D0pi(-)) = 0.079+/-0.009+/-0.006, B(B(0)-->D+K-)/B(B(0)-->D+pi(-)) = 0.068+/-0.015+/-0.007, B(B--->D(*0)K-)/B(B--->D(*0)pi(-)) = 0.078+/-0.019+/-0.009, and B(B(0)-->D(*+)K-)/B(B(0)-->D(*+)pi(-)) = 0.074+/-0.015+/-0.006. These are the first observations of the B-->D+K-, D(*0)K-, and D(*+)K- decay processes.

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PubMed2001

Observation of large CP violation in the neutral B meson system.

We present a measurement of the standard model CP violation parameter sin2 phi(1) based on a 29.1 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. One neutral B meson is fully reconstructed as a J/psi K(S), psi(2S)K(S), chi(c1)K(S), eta(c)K(S), J/psi K(L), or J/psi K(*0) decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin2 phi(1) = 0.99+/-0.14(stat)+/-0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.

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PubMed2001

Measurement of B(0)(d)-B_(0)(d) mixing rate from the time evolution of dilepton events at the upsilon(4S).

We report a determination of the B(0)(d)-&B_(0)(d) mixing parameter Deltam(d) based on the time evolution of dilepton yields in Upsilon(4S) decays. The measurement is based on a 5.9 fb(-1) data sample collected by the Belle detector at KEKB. The proper-time difference distributions for same-sign and opposite-sign dilepton events are simultaneously fitted to an expression containing Deltam(d) as a free parameter. Using both muons and electrons, we obtain Deltam(d) = 0.463+/-0.008 (stat)+/-0.016 (syst) ps(-1). This is the first determination of Deltam(d) from time evolution measurements at the Upsilon(4S). We also place limits on possible CPT violations.

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PubMed2001

Measurement of the CP violation parameter sin2 phi(1) in B(0)(d) meson decays.

We present a measurement of the standard model CP violation parameter sin2 phi(1) (also known as sin2beta) based on a 10.5 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e(+)e(-) collider. One neutral B meson is reconstructed in the J/psiK(S), psi(2S)K(S), chi(c1)K(S), eta(c)K(S), J/psiK(L), or J/psipi(0) CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its charged particle decay products. From the asymmetry in the distribution of the time interval between the two B-meson decay points, we determine sin2 phi(1) = 0.58(+0.32)(-0.34)(stat)+0.09-0.10(syst).

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PubMed1999

Critical behavior of a random diode network.

We study the percolation properties of a random diode network (RDN) which contains two kinds of directed bonds on a square lattice. This network is a special case of the random insulation-resistor-diode network. Both Monte Carlo simulations and series expansion for the percolation probability show that an estimated critical exponent, beta=0.1794+/-0.008, is different from known values for a conventional insulation-resistor-diode network. RDN belongs to neither the isotropic percolation universality class nor to the directed percolation universality, which we attribute to a difference of symmetry breakdown around the critical point.

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