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K. Abe

Publications and source records attributed to K. Abe.

At least 343 records · Page 19Linked to original sources
arXiv2005

Improved Evidence for Direct CP Violation in B0 --> pi+ pi- Decays and Model-Independent Constraints on phi_2

We present a new measurement of the time-dependent CP-violating parameters in B0 --> pi+ pi- decays with 275 x 10^6 BB-bar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider operating at the Upsilon(4S) resonance. We find 666 +/- 43 B0 --> 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 CKM angle phi_2 of 0 deg. < phi_2 < 19 deg. and 71 deg. < phi_2 < 180 deg.

hep-ex↗
arXiv2005

Measurement of the branching ratios of the Z0 into heavy quarks

We measure the hadronic branching ratios of the Z0 boson into heavy quarks: Rb=Gamma(Z0->bb)/Gamma(Z0->hadrons) and Rc=Gamma(Z0->cc/Gamma(Z0->hadrons) using a multi-tag technique. The measurement was performed using about 400,000 hadronic Z0 events recorded in the SLD experiment at SLAC between 1996 and 1998. The small and stable SLC beam spot and the CCD-based vertex detector were used to reconstruct bottom and charm hadron decay vertices with high efficiency and purity, which enables us to measure most efficiencies from data. We obtain, Rb=0.21604 +- 0.00098(stat.) +- 0.00073(syst.) -+ 0.00012(Rc) and, Rc= 0.1744 +- 0.0031(stat.) +- 0.0020(syst.) -+ 0.0006(Rb)

hep-ex↗
arXiv2005

Improved Measurement of CP-Violation Parameters sin(2phi1) and |lambda|, B Meson Lifetimes, and B0-B0bar Mixing Parameter Delta m_d

We present a precise measurement of the standard model CP-violation parameter sin(2phi1), the direct CP violation parameter |lambda|, the lifetimes of charged and neutral B mesons and their ratio, and the B0-B0bar mixing parameter Delta m_d based on a sample of 152 x 10^6 BB-bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One of two B mesons is fully reconstructed in a CP-eigenstate or a flavor-eigenstate decay channel. The flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time interval between the two B meson decay points, we obtain sin(2phi1) = 0.728 +/- 0.056(stat) +/- 0.023(syst), |lambda| = 1.007 +/- 0.041(stat) +/- 0.033(syst), tau_B0 = 1.534 +/- 0.008(stat) +/- 0.010(syst) ps, tau_B+ = 1.635 +/- 0.011(stat) +/- 0.011(syst) ps, tau_B+/tau_B0 = 1.066 +/- 0.008(stat) +/- 0.008(syst) and Delta m_d = 0.511 +/- 0.005(stat) +/- 0.006(syst) ps-1. The results for sin(2phi1) and |lambda| are the most precise measurements performed so far, and are consistent with the standard model expectations. The significance of the observed deviation from unity in the lifetime ratio exceeds five standard deviations.

hep-ex↗
arXiv2005

Measurement of phi_3 with Dalitz Plot Analysis of B+- -> D K*+- Decay

We present a measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the three-body decay of the neutral D meson from the B+- -> D K*+- process. Using a 253 fb-1 data sample collected by the Belle experiment, we obtain 56 signal candidates for B+- -> D K*+-, where the neutral D meson decays into K_S pi+ pi-. From a maximum likelihood fit we obtain phi_3=112+-35(stat)+-9(syst)+-11(model)+-8(nonresonant B -> D K_S pi).

hep-ex↗
arXiv2005

Comment on the Debye-Waller factors for incommensurate structures

We show that the method of calculations of the Debye-Waller factors for IC structures by J.D. Axe, Phys. Rev. (1971), B 21, 4181, is not applicable for such calculations. The set of variables, which should be used for such calculations, is the phase $ϕ$ and the amplitude of the IC modulation, but not the real and imaginary parts of the complex IC modulation function.

cond-mat.mtrl-sci↗
arXiv2005

Direct Measurements of A_b and A_c using Vertex/Kaon Charge Tags at SLD

Exploiting the manipulation of the SLC electron-beam polarization, we present precise direct measurements of the parity violation parameters A_c and A_b in the Z boson - c quark and Z boson - b quark coupling. Quark/antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLD CCD vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-98 sample of 400,000 Z decays, produced with an average beam polarization of 73.4%, we find A_c = 0.673 +/- 0.029 (stat.) +/- 0.023 (syst.) and A_b = 0.919 +/- 0.018 (stat.) +/- 0.017 (syst.).

hep-ex↗
arXiv2004

Study of B0 -> \bar{D}(*)0 pi+ pi- decays

We report the results of a study of neutral B decays to the $D^0 π^+ π^-$ and $D^{*0} π^+ π^-$ final states using complete $D^{(*)0}$ reconstruction. The contributions from two-body $B\to D^{**} π$ with narrow ($j_q=3/2$) $D^{**}$ states and $B\to D^{(*)}ρ, D^{(*)} f_2, D^{(*)}σ$ decays have been determined. All results are preliminary, and are based on a large data sample collected in the Belle experiment at the KEKB $e^+e^-$ collider.

hep-ex↗
arXiv2004

New Measurements of Time-Dependent CP-Violating Asymmetries in B0 -> KsKsKs and Ks pi0 gamma Decays at Belle

We present new measurements of CP-violation parameters in B0 -> KsKsKs and Ks pi0 gamma decays based on a sample of 275 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. 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 are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. We obtain S_{KsKsKs} = +1.26 +/- 0.68(stat) +/- 0.18(syst), A_{KsKsKs} = +0.54 +/- 0.34(stat) +/- 0.08(syst), S_{Ks pi0 gamma} = -0.58 +0.46/-0.38(stat) +/- 0.11(syst), A_{Ks pi0 gamma} = +0.03 +/- 0.34(stat) +/- 0.11(syst). All results are preliminary.

hep-ex↗
arXiv2004

Measurement of phi_3 with Dalitz Plot Analysis of B->D(*)K Decay at Belle

We present a measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the three-body decay of the neutral D meson from the B->D(*)K process. Using a 253 fb-1 data sample collected by the Belle experiment, we obtain 276 signal candidates for B->DK and 69 candidates for B->D*K, where the neutral D meson decays into K_Spi+pi-. From a combined maximum likelihood fit to the B->DK and B->D*K modes, we obtain phi_3=68+14-15(stat)+-13(syst)+-11(model). The corresponding two standard deviation interval is 22<phi_3<113.

hep-ex↗
arXiv2004

Studies of CP violation in $B^0 \to J/ψK^{*0}$ decays

An angular analysis for B decays into two vector mesons gives parameters sensitive to new physics. They are the decay amplitudes of the three helicity states, the asymmetry in triple product, and the CP violating phase. The measurements of these quantities are performed for $B^0 \to J/ψK^{*0}$ decays in a data sample with 253 fb$^{-1}$ taken by the Belle detector in the KEKB asymmetric $e^+e^-$ collider. With the time-integrated angular analysis, the decay amplitudes' moduli and phase angles are measured to be $|A_0|^2=0.585\pm 0.012 \pm 0.09$, $|A_{\parallel}|^2=0.233\pm 0.013\pm 0.008$, $|A_\perp|^2=0.181\pm 0.012\pm 0.008$, $\arg(A_\parallel)=2.888\pm 0.090\pm 0.008$ radians, and $\arg(A_\perp)=0.239\pm 0.064\pm 0.010$ radians. The difference between $\arg(A_\parallel)$ and $\arg(A_\perp)$ is $2.649\pm0.110$ radians, which is shifted from $π$ by more than $4σ$; this can be interpreted as evidence for the existence of the final state interaction. The amplitude values are used in triple product correlations to obtainasymmetries of $A_T^{(1)}=0.101\pm 0.033\pm 0.007$ and $A_T^{(2)}=-0.102\pm 0.032\pm 0.003$ for $B^0$ meson decays, and $\bar{A}_T^{(1)}=0.056\pm 0.030\pm 0.006$ and $\bar{A}_T^{(2)} = -0.091\pm 0.028\pm 0.003$ for $\bar{B^0}$ meson decays. The time dependent angular analysis gives the measurements of CP violating parameters $\sin 2ϕ_1$ and $\cos 2ϕ_1$ to be $0.30 \pm 0.32 \pm 0.02$ and $-0.31 \pm 0.91 \pm 0.10$, respectively. The value of $\cos 2ϕ_1$ is $-0.56 \pm 0.86 \pm 0.11$ if $\sin 2ϕ_1$ is fixed at the world average value (0.731).

hep-ex↗
arXiv2004

New Measurements of Time-Dependent CP-Violating Asymmetries in b --> s Transitions at Belle

We present new measurements of CP-violation parameters in B0 --> phi K0, K+ K- Ks, f0(980) Ks, eta' Ks, omega Ks, Ks pi0, and K*0 gamma (K*0 --> Ks pi0) decays based on a sample of 275 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. 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 for each of the decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. All results are preliminary.

hep-ex↗
arXiv2004

Moments of the Electron Energy Spectrum in Semileptonic B Decays at Belle

We report a measurement of the inclusive electron energy spectrum for semileptonic decays of B mesons in a 140 fb^-1 data sample collected near the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric energy e^+ e^- collider. We determine the first and second moments of the spectrum for threshold values of the electron energy between 0.6 and 1.5 GeV.

hep-ex↗
arXiv2004

Study of the Baryon-Antibaryon Low-Mass Enhancements in Charmless Three-body Baryonic B Decays

The angular distributions of the baryon-antibaryon low-mass enhancements seen in the charmless three-body baryonic B decays B^+ \to p pbar K^+, B^0 \to p pbar K_S^0, and B^0 \to p Lambdabar pi^- are reported. Searches for the pentaquarks Theta^+ and Theta^{++} in the relevant decay modes and possible glueball states in the p pbar systems are presented. The analysis is based on a 140 fb^{-1} data sample recorded on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider.

hep-ex↗
arXiv2004

CP violation in B-$\bar{B}$ mixing with dilepton events

We report a measurement of the charge asymmetry for same-sign dileptons in $B^0$-$\bar B^0$ mixing. The data were collected with the Belle detector at KEKB. Using a data sample of 78 fb^{-1} recorded at the $Υ(4S)$ resonance and 9 fb^{-1} recorded at an energy 60 MeV below the resonance, we measure $\Asl = (-0.13 \pm 0.60(\text{stat}) \pm 0.56(\text{sys}))%$.

hep-ex↗
arXiv2004

Observation of B+ -> proton Lambdabar gamma

We report the first observation of the radiative hyperonic B decay B+ -> proton Lambdabar gamma, using a 140 fb-1 data sample recorded on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. The measured branching fraction is B(B+ -> proton Lambdabar gamma) = (2.16 ^{+0.58}_{-0.53} +- 0.20) times 10^{-6}. A search for B+ -> proton Sigmabar gamma yields no significant signal, so we set a 90% confidence-level upper limit on the branching fraction of B(B+ -> proton Sigmabar gamma) < 3.3 times 10^{-6}.

hep-ex↗
arXiv2004

Properties of the X(3872) at Belle

We report recent results on the properties of the X(3872) produced via the B+ --> K+ X(3872) decay process. We observe X -->pi+pi-pi0 J/psi decays where the 3pi invariant masses cluster near the upper kinematic boundary suggesting that they originate from sub-threshold decays to virtual omega(782) mesons. This is consistent with expectations for a DD*-bar bound state interpretation for the X(3872). In addition, we constrain the possible charmonium-state assignments for this particles. Results are obtained from a 253/fb data sample that contains 274 million BB-barr pairs that was collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider.

hep-ex↗
arXiv2004

Improved Measurements of Color-Suppressed Decays B0bar -> D0 pi0, D0 eta and D0 omega

We present preliminary improved measurements of the branching fractions of the color-suppressed decays B0bar -> D0 h0, where h0 represents the three light neutral mesons pi0, eta and omega. The measurements are based on a data sample of 140fb-1 collected at the Upsilon(4S) with the Belle detector at the KEKB energy-asymmetric e+e- collider, corresponding to seven times the luminosity of the previous Belle measurements.

hep-ex↗