398 research outputs found

    Measurement of the Branching Fraction of the Decay B+π+π+ν\boldsymbol{B^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_\ell} in Fully Reconstructed Events at Belle

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    We present an analysis of the exclusive B+π+π+νB^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_{\ell} decay, where \ell represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The analysis uses the full Υ(4S)\Upsilon(4S) data sample collected by the Belle detector, corresponding to 711 fb1^{-1} of integrated luminosity. We select the events by fully reconstructing one BB meson in hadronic decay modes, subsequently determining the properties of the other BB meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of B(B+π+π+ν)=[22.71.6+1.9(stat)±3.5(syst)]×105{{\cal B}(B^{+}\to \pi^{+}\pi^{-}\ell^{+}\nu_{\ell})= [22.7 ^{+1.9}_{-1.6} (\mathrm{stat}) \pm 3.5(\mathrm{syst}) ]\times 10^{-5}}, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.Comment: 23 pages, 19 figure

    Evidence for a vector charmonium-like state in e+eDs+Ds2(2573)+c.c.e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c.

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    We report the measurement of e+eDs+Ds2(2573)+c.c.e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c. via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb1^{-1} collected with the Belle detector at the Υ(4S)\Upsilon(4S) and nearby. We find evidence for an enhancement with a 3.4σ\sigma significance in the invariant mass of Ds+Ds2(2573)+c.c.D^+_sD^*_{s2}(2573)^- +c.c. The measured mass and width are (4619.88.0+8.9(stat.)±2.3(syst.)) MeV/c2(4619.8^{+8.9}_{-8.0}({\rm stat.})\pm2.3({\rm syst.}))~{\rm MeV}/c^{2} and (47.014.8+31.3(stat.)±4.6(syst.)) MeV(47.0^{+31.3}_{-14.8}({\rm stat.})\pm4.6({\rm syst.}))~{\rm MeV}, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/c2c^2 recently reported by Belle in e+eDs+Ds1(2536)+c.c.e^+e^-\to D^+_sD_{s1}(2536)^-+c.c. The product of the e+eDs+Ds2(2573)+c.c.e^+e^-\to D^+_sD^*_{s2}(2573)^-+c.c. cross section and the branching fraction of Ds2(2573)Dˉ0KD^*_{s2}(2573)^-\to{\bar D}^0K^- is measured from Ds+Ds2(2573)D^+_sD^*_{s2}(2573)^- threshold to 5.6 GeV.Comment: 9 pages, 4 figure

    Measurement of the CKM Matrix Element Vcb|V_{cb}| from B0D+νB^{0} \to D^{*-} \ell^+ \nu_\ell at Belle

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    We present a new measurement of the CKM matrix element Vcb|V_{cb}| from B0D+νB^{0} \to D^{*-} \ell^+ \nu_\ell decays, reconstructed with the full Belle data set of 711fb1711 \, \rm fb^{-1} integrated luminosity. Two form factor parameterizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)ηEWVcb\mathcal{F}(1)\eta_{\rm EW}|V_{cb}| and the decay form factors, where F(1)\mathcal{F}(1) is the normalization factor and ηEW\eta_{\rm EW} is a small electroweak correction. In the CLN parameterization we find F(1)ηEWVcb=(35.06±0.15±0.56)×103\mathcal{F}(1)\eta_{\rm EW}|V_{cb}| = (35.06 \pm 0.15 \pm 0.56) \times 10^{-3}, ρ2=1.106±0.031±0.007\rho^{2}=1.106 \pm 0.031 \pm 0.007, R1(1)=1.229±0.028±0.009R_{1}(1)=1.229 \pm 0.028 \pm 0.009, R2(1)=0.852±0.021±0.006R_{2}(1)=0.852 \pm 0.021 \pm 0.006. For the BGL parameterization we obtain F(1)ηEWVcb=(34.93±0.23±0.59)×103\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|= (34.93 \pm 0.23 \pm 0.59)\times 10^{-3}, which is consistent with the World Average when correcting for F(1)ηEW\mathcal{F}(1)\eta_{\rm EW}. The branching fraction of B0D+νB^{0} \to D^{*-} \ell^+ \nu_\ell is measured to be B(B0D+ν)=(4.90±0.02±0.16)%\mathcal{B}(B^{0}\rightarrow D^{*-}\ell^{+}\nu_{\ell}) = (4.90 \pm 0.02 \pm 0.16)\%. We also present a new test of lepton flavor universality violation in semileptonic BB decays, B(B0De+ν)B(B0Dμ+ν)=1.01±0.01±0.03 \frac{{\cal B }(B^0 \to D^{*-} e^+ \nu)}{{\cal B }(B^0 \to D^{*-} \mu^+ \nu)} = 1.01 \pm 0.01 \pm 0.03~. The errors correspond to the statistical and systematic uncertainties respectively. This is the most precise measurement of F(1)ηEWVcb\mathcal{F}(1)\eta_{\rm EW}|V_{cb}| and form factors to date and the first experimental study of the BGL form factor parameterization in an experimental measurement

    Measurement of the branching fraction of Ξc0Λc+π\Xi_{c}^{0}\to \Lambda_{c}^{+}\pi^{-} at Belle

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    Based on a data sample of 983 fb1^{-1} collected with the Belle detector at the KEKB asymmetric-energy e+ee^+e^- collider, we present the study of the heavy-flavor-conserving decay Ξc0Λc+π\Xi_{c}^{0}\to \Lambda_{c}^{+}\pi^{-} with Λc+\Lambda_{c}^{+} reconstructed via its pKπ+pK^{-} \pi^{+} decay mode. The branching fraction ratio B(Ξc0Λc+π)/B(Ξc0Ξπ+)\mathcal{B}(\Xi_{c}^{0}\to \Lambda_{c}^{+}\pi^{-})/\mathcal{B}(\Xi_{c}^{0}\to \Xi^{-}\pi^{+}) is measured to be 0.38±0.04±0.040.38 \pm 0.04 \pm 0.04. Combing with the world average value of B(Ξc0Ξπ+)\mathcal{B}(\Xi_{c}^{0}\to \Xi^{-}\pi^{+}), the branching fraction B(Ξc0Λc+π)\mathcal{B}(\Xi_{c}^{0}\to \Lambda_{c}^{+}\pi^{-}) is deduced to be (0.54±0.05±0.05±0.12)%(0.54 \pm 0.05 \pm 0.05 \pm 0.12)\%. Here, the uncertainties above are statistical, systematic, and from B(Ξc0Ξπ+)\mathcal{B}(\Xi_c^{0} \to \Xi^{-}\pi^{+}), respectively.Comment: 5 pages, 4 figure

    Search for B0^{0} decays to invisible final states ( +γ) at Belle

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    We report searches for B0invisibleB^0\to\rm{invisible} and B0invisible+γB^0\to\rm{invisible}+\gamma decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a 711fb1711\,{\rm fb}^{-1} data sample that contains 772×106BBˉ772 \times 10^6 B\bar{B} pairs and was collected near the Υ(4S)\Upsilon\,(4S) resonance with the Belle detector at the KEKB e+ee^+ e^- collider. We observe no significant signal for either decay and set upper limits on their branching fractions at 90%90\% confidence level of B(B0invisible)<7.8×105\mathcal{B}\,(B^0\to\rm{invisible}) < 7.8\times10^{-5} and B(B0invisible+γ)<1.6×105\mathcal{B}\,(B^0\to\rm{invisible}+\gamma) < 1.6\times10^{-5}

    Measurement of Angular Coefficients of BˉDνˉ\bar{B} \to D^* \ell \bar{\nu}_\ell: Implications for Vcb|V_{cb}| and Tests of Lepton Flavor Universality

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    We measure the complete set of angular coefficients JiJ_i for exclusive BˉDνˉ\bar{B} \to D^* \ell \bar{\nu}_\ell decays (=e,μ\ell = e, \mu). Our analysis uses the full 711fb1711\,\mathrm{fb}^{-1} Belle data set with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the BDB \to D^* transition and the Cabibbo-Kobayashi-Maskawa matrix element Vcb|V_{\rm cb}|. Using recent lattice QCD calculations for the hadronic form factors, we find Vcb=(41.0±0.7)×103|V_{\rm cb}| = (41.0 \pm 0.7) \times 10^3 using the BGL parameterization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter ww, and investigate the differences of the electron and muon angular distributions. We find no deviation from Standard Model expectations

    Search for a doubly charged DDK bound state in Υ(1S, 2S) inclusive decays and via direct production in e⁺e⁻ collisions at √s = 10.520, 10.580, and 10.867 GeV

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    First determination of the spin and parity of the charmed-strange baryon Ξc_{c}(2970)+^{+}

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    Search for a doubly charged DDK bound state in Υ(1S, 2S) inclusive decays and via direct production in e⁺e⁻ collisions at √s = 10.520, 10.580, and 10.867 GeV

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    We report the results of a first search for a doubly-charged DDKDDK bound state, denoted the R++R^{++}, in Υ(1S)\Upsilon(1S) and Υ(2S)\Upsilon(2S) inclusive decays and via direct production in e+ee^+e^- collisions at s\sqrt{s} = 10.520, 10.580, and 10.867 GeV. The search uses data accumulated with the Belle detector at the KEKB asymmetric-energy e+ee^+e^- collider. No significant signals are observed in the D+Ds+D^{+}D_{s}^{*+} invariant-mass spectra of all studied modes. The 90\% credibility level upper limits on their product branching fractions in Υ(1S)\Upsilon(1S) and Υ(2S)\Upsilon(2S) inclusive decays (B(Υ(1S,2S)R+++{\cal B}(\Upsilon(1S,2S) \to R^{++} + anything)×B(R++D+Ds+)) \times {\cal B}(R^{++} \to D^{+} D_{s}^{*+})), and the product values of Born cross section and branching fraction in e+ee^+e^- collisions (σ(e+eR+++\sigma(e^+e^- \to R^{++} + anything)×B(R++D+Ds+)) \times {\cal B}(R^{++} \to D^{+} D_{s}^{*+})) at s\sqrt{s} = 10.520, 10.580, and 10.867 GeV under different assumptions of R++R^{++} masses varying from 4.13 to 4.17 GeV/c2c^2, and widths varying from 0 to 5 MeV are obtained
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