arXiv subjects
Publications and source records attributed to Belle Collaboration.
We report a search for the decay $B^0 \to J/ψϕ$, using a sample of 657 $\times 10^6$ $B\bar{B}$ pairs collected with the Belle detector at the $Υ(4S)$ resonance. No statistically significant signal is found and an upper limit for the branching fraction is determined to be $\mathcal{B}(B^0 \to J/ψϕ) < 9.4 \times 10^{-7}$ at 90% confidence level.
The Collins effect connects transverse quark spin with a measurable azimuthal asymmetry in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods we measure statistically significant azimuthal asymmetries for charged pion pairs in e+e- annihilation at center-of-mass energies of 10.52 GeV and 10.58 GeV, which can be attributed to the fragmentation of primordial quarks with transverse spin components. The measurement was performed using a dataset of 547 fb^{-1} collected by the Belle detector at KEKB improving the statistics of the previously published results by nearly a factor of 20.
We report a fully inclusive measurement of the flavor changing neutral current decay $B\to X_sγ$ in the energy range $1.7 \GeV\le E^\mathrm{c.m.s}_γ\le 2.8 \GeV$, covering 97% of the total spectrum, where c.m.s is the center of mass system. Using $605\ifb$ of data, we obtain in the rest frame of the $B$-meson ${\mathcal B}(B\to X_sγ: E^B_γ>1.7 \mathrm{GeV})= (3.31 \pm 0.19 \pm 0.37 \pm 0.01)\times 10^{-4}$, where the errors are statistical, systematic and from the boost correction needed to transform from the rest frame of the $Υ(4S)$ (c.m.s) to that of the $B$-meson, respectively. We also measure the first and second moments of the photon energy spectrum as functions of various energy thresholds, which extend down to $1.7 \GeV$. The results are preliminary.
We present an updated measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the K^0_S pi+ pi- decay of the neutral D meson produced in B+- ->D(*)K+- decays. The method exploits the interference between D^0 and Dbar^0 to extract the angle phi_3, strong phase delta and the ratio r of suppressed and allowed amplitudes. We apply this method to a 605 fb-1 data sample collected by the Belle experiment. The analysis uses two modes: B+- -> DK+-, and B+- -> D*K+- with D* -> D pi0, as well as the corresponding charge-conjugate modes. From a combined maximum likelihood fit to the two modes, we obtain phi_3=76+12-13(stat)+-4(syst)+-9(model). The statistical significance of CP violation (phi_3\neq 0) in our measurement is (1-5.5*10^{-4}), or 3.5 standard deviations. These results are preliminary.
We report measurements and searches for resonant $B^{\pm} \to K^{\pm} h \to K^{\pm} γγ$ decays where $h$ is a $η,η^{\prime},η_{c},η_{c}(2S),χ_{c0},χ_{c2},J/ψ$ meson or the X(3872) particle.
We report a precise measurement of the masses of the $Ξ_c(2645)$ and $Ξ_c(2815)$ baryons using a data sample of 414 fb$^{-1}$ collected by the Belle collaboration at the KEKB $e^+ e^-$ collider. The states $Ξ_c(2645)^{0,+}$ are observed in the $Ξ_c^{+,0}π^{-,+}$ decay modes, while the $Ξ_c(2815)^{0,+}$ are reconstructed in the $Ξ_c(2645)^{+,0}π^{-,+}$ decay modes. The following mass splittings are determined: $m_{Ξ_c(2645)^+} - m_{Ξ_c(2645)^0} = (-0.1 \pm 0.3 ({\rm stat}) \pm 0.6 {(\rm syst})) {\rm MeV}/{\rm c}^2$ and $m_{Ξ_c(2815)^+} - m_{Ξ_c(2815)^0} = (-3.4 \pm 1.9 ({\rm stat}) \pm 0.9 {(\rm syst})) {\rm MeV}/{\rm c}^2$ with a much better precision than the current world averages. We also observe a new decay mode, $Ξ_c(2980)^{0,+} \to Ξ_c(2645)^{+,0}π^{-,+}$.
We search for the radiative penguin decays B_s to phi gamma and B_s to gamma gamma 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 meson in the B_s to phi gamma mode. No significant B_s to gamma gamma signal is observed.
We report an improved measurement of the B+ -> D+ D0bar and B0 -> D0 D0bar decays based on 657 10^6 BBar events collected with the Belle detector at KEKB. We measure the branching fraction and charge asymmetry for the B+ -> D+ D0bar decay: B(B+ -> D+ D0bar)=(3.85 +- 0.31 +- 0.38) 10^{-4} and Acp(B+ -> D+ D0bar)=0.00 +- 0.08 +- 0.02, where the first error is statistical and the second is systematic. We also set the upper limit for the B0 -> D0 D0bar decay: B(B0 -> D0 D0bar)< 0.43 10^{-4}at 90% CL.
We present a measurement of the branching fraction $B(D_s^+\toμ^+ν_μ)$ 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 $DKγX$ in events of the type $e^+e^-\to D_s^\ast DKX, D_s^\ast \to D_sγ$, where $X$ represents additional pions or photons from fragmentation. The full reconstruction method provides high resolution in the neutrino momentum and thus good background separation, equivalent to that reached by experiments at the tau-charm factories. We obtain the branching fraction $B(D_s^+\toμ^+ν_μ) = (6.44 \pm 0.76({\rm stat}) \pm 0.57({\rm syst})) \cdot 10^{-3}$, implying a $D_s$ decay constant of $f_{D_s} = (275 \pm 16({\rm stat}) \pm 12({\rm syst}))$ MeV.
We report the first observation of the $ψ(4415)$ resonance in the reaction $\e^+e^-\to D^0 D^-π^+$ and a measurement of its cross section in the center-of-mass energy range $4.0\mathrm{GeV}$ to $5.0\mathrm{GeV}$ with initial state radiation. From a study of resonant structure in $ψ(4415)$ decay we conclude that the $ψ(4415)\to D^0 D^-π^+$ decay is dominated by $ψ(4415)\to D \bar D{}^{*}_2(2460)$. We obtain $\mathcal{B}(ψ(4415)\to D^0 D^-π^+_{\mathrm {non-resonant}})/\mathcal{B}(ψ(4415)\to D \bar D{}^{*}_2(2460)\to D^0 D^-π^+)<0.22$ at 90% C.L. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 673 $\mathrm{fb}^{-1}$.
We report a high-statistics measurement of the relative branching fraction B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) using a 532 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured value of the relative branching fraction is B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) = (10.12 +/- 0.04(stat) +/- 0.18(syst))x10^{-2} which has an accuracy comparable to the world average. We also present a measurement of the time-integrated CP asymmetry in D0->pi+pi-pi0 decay. The result, A_{CP} = (0.43 +/- 1.30)%, shows no significant CP violation.
We report measurements of the exclusive cross section for $e^+e^- \to D \bar D $, where $D=D^0$ or $D^+$, in the center-of-mass energy range from the $D \bar D $ threshold to $5\mathrm{GeV}/c^2$ with initial-state radiation. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 673 $\mathrm{fb}^{-1}$.
We report a measurement of the CP-violating parameters in B0->K0S K0S decays based on a data sample of 657 million BBbar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. In this study, one neutral B meson is fully reconstructed in the B0->K0S K0S 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 = -0.38 +0.69-0.77(stat) +-0.09(syst) and A = -0.38 +-0.38(stat) +-0.05(syst).
The process e+e- to K+K-J/psi is observed for the first time via initial state radiation. The cross section of e+e- to K+K-J/psi for center-of-mass energies between threshold and 6.0 GeV is measured using 673 fb^{-1} of data collected with the Belle detector on and off the Upsilon(4S) resonance. We also find evidence for e+e- to K_S K_S J/psi in the same energy region.
Recent measurements of branching fractions, form factors and decay constants of leptonic and semileptonic decays of D_(s)-mesons acquired at experiments running at the Upsilon(4S) resonance energy are reviewed.
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 4433+-4(stat)+-2(syst) MeV and Gamma = 45^+18_-13(stat) ^+30_-13 MeV. The product branching fraction is determined to be Bf(B-->KZ(4430))xBf(Z(4430)-->pi^+psi') = (4.1+-1.0(stat)+-1.4(syst))x10^{-5), where Z(4430) is used to denote the observed structure. The statistical significance of the observed peak is 6.5sigma. These results are obtained from a 605 fb-1 data sample that contains 657 million BBbar pairs collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider.
We present a study of the X(3940) state in the process e+e- -> J/psi D* Dbar. The X(3940) mass and width are measured to be (3942 +7 -6 +- 6)MeV/c^2 and Gamma=(37 + 26 - 15 +- 8 MeV. In the process e+e- -> J/psi D* D*bar we have observed another charmonium-like state, which we denote as X(4160), in the spectrum of invariant masses of D*+ D*- combinations. The X(4160) parameters are M= 4156 + 25 - 20 +- 15 MeV/c^2 and Gamma = 139 + 111 -61 +- 21 MeV. The analysis is based on a data sample with an integrated luminosity of 693 /fb recorded near the Upsilon(4S) resonance with the Belle detector at the KEKB e+ e- asymmetric-energy collider.
Using 462/fb of e+e- annihilation data recorded by the Belle detector, we report the first observation of the decay Ds1(2536)+ -> D+pi-K+. The ratio of branching fractions B(Ds1+ -> D+pi-K+)/B(Ds1+ -> D*+K0) is measured to be (3.27+-0.18+-0.37)%. We also study the angular distributions in the Ds1(2536)+ -> D*+K0S decay and measure the ratio of D- and S-wave amplitudes. The S-wave dominates, with a partial width of Gamma_S/Gamma_total=0.72+-0.05+-0.01.