We report a search for a dark vector gauge boson U' that couples to quarks in the decay chain D*+→ D0π+, D0 → K$0\atop{S}$η, η → U'γ, U' → π+π-. No signal is found and we set a mass-dependent limit ...on the baryonic fine structure constant of 10-3 - 10-2 in the U0 mass range of 290 to 520 MeV/c2. This analysis is based on a data sample of 976 fb-1 collected by the Belle experiment at the KEKB asymmetric energy e+e- collider
With data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider, we measure the energy dependence of the e+e- → hb ( nP ) π+π- ( n=1 , 2) cross sections from thresholds up to ...11.02 GeV. We find clear Υ ( 10860 ) and Υ ( 11020 ) peaks with little or no continuum contribution. We study the resonant substructure of the Υ ( 11020 ) → hb ( nP ) π+π- transitions and find evidence that they proceed entirely via the intermediate isovector states Zb ( 10610 ) and Zb ( 10650 ) . The relative fraction of these states is loosely constrained by the current data: The hypothesis that only Zb ( 10610 ) is produced is excluded at the level of 3.3 standard deviations, while the hypothesis that only Zb ( 10650 ) is produced is not excluded at a significant state.
Here, we show a measurement of the CP -violation parameter φ1 obtained in a time-dependent analysis of B0 → D ¯ ( * ) 0h0 decays followed by D ¯ 0 → KS0π+π- decay. A model-independent measurement is ...performed using the binned Dalitz plot technique. The measured value is φ1=11.7°±7.8° ( stat ) ±2.1° ( syst ) . Treating sin2φ1 and cos2φ1 as independent parameters, we obtain sin2φ1=0.43±0.27 ( stat ) ±0.08 ( syst ) and cos2φ1=1.06±0.33 ( stat ) -0.15+0.21 ( syst ) . The findings are obtained with a full data sample of 772×106B B ¯ pairs collected near the Υ ( 4S ) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
In this report, we discuss the discovery of Ξ c ( 3055 ) 0 , observed by its decay into the final-state Λ D0 , and present the first observation and evidence of the decays of Ξ c ( 3055 ) + and Ξ c ( ...3080 ) + into Λ D+ . Furthermore, we perform a combined analysis of the Λ D+ with the Σ c++K- and Σ c*++K- decay modes to measure the ratios of branching fractions, masses and widths with improved accuracy. We measure the ratios of branching fractions B ( Ξ c ( 3055 ) + → Λ D+ ) / B ( Ξ c ( 3055 ) + → Σ c++K- ) =5.09±1.01±0.76 , B ( Ξ c ( 3080 ) + → Λ D+ ) / B ( Ξ c ( 3080 ) + → Σ c++K- ) = 1.29±0.30±0.15 , and B ( Ξ c ( 3080 ) + → Σ c*++K- ) / B ( Ξ c ( 3080 ) + → Σ c++K- ) =1.07±0.27±0.04 , where the uncertainties are statistical and systematic. The analysis is performed using a 980fb-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider.
We detail the analysis of the three-body e+e- → B B ¯ π± , B B ¯ *π± , and B* B ¯ *π± processes, including the first observations of the Zb± ( 10610 ) → B B ¯ *+ c . c . ± and Zb± ( 10650 ) → B* B ...¯ * ± transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of σ ( e+e- → B B ¯ *+ c . c . ±π∓ ) = 17.4±1.6 ( stat ) ±1.9 ( syst ) pb and σ ( e+e- → B* B ¯ * ±π∓ ) = 8.75±1.15 ( stat ) ±1.04 ( syst ) pb and set a 90% C.L. upper limit of σ ( e+e- → B B ¯ ±π∓ ) <2.9 pb . The results are based on a 121.4 fb-1 data sample collected with the Belle detector at a center-of-mass energy near the Υ ( 10860 ) peak.
The branching fractions of the Υ ( 1S ) inclusive decays into final states with a J / ψ or a ψ ( 2S ) are measured with higher precision to be B ( Υ ( 1S ) → J / ψ+anything ) = ( 5.25±0.13 ( stat ) ...±0.25 ( syst ) ) ×10-4 and B ( Υ ( 1S ) → ψ ( 2S ) +anything ) = ( 1.23±0.17 ( stat ) ±0.11 ( syst ) ) ×10-4 . The first search for Υ ( 1S ) decays into XYZ states that decay into a J / ψ or a ψ ( 2S ) plus one or two charged tracks yields no significant signals for XYZ states in any of the examined decay modes, and upper limits on their production rates in Υ ( 1S ) inclusive decays are determined.
In this work, we report new measurements of the total cross sections for e+e- → Υ ( n S ) π+π- ( n=1 , 2, 3) and e+e- → b b ¯ from a high-luminosity fine scan of the region s=10.63–11.05 GeV with the ...Belle detector. We observe that the Υ ( n S ) π+π- spectra have little or no nonresonant component and extract from them the masses and widths of Υ ( 10860 ) and Υ ( 11020 ) and their relative phase. We find M10860= ( 10891.1±3.2-1.7+0.6 ) MeV / c2 and Γ 10860= ( 53.7-5.6 -5.4+7.1 +1.3 ) MeV and report first measurements M11020= ( 10987.5-2.5 -2.1+6.4 +9.0 ) MeV / c2 , Γ 11020= ( 61-19 -20+9 +2 ) MeV , and Φ11020-Φ10860= ( -1.0±0.4-0.1+1.4 ) rad .
We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP ...eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results correspond to the first observation of CP violation in B0->D(*)CP h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.
The dark photon A' and the dark Higgs boson h' are hypothetical constituents featured in a number of recently proposed dark sector models. Assuming prompt decays of both dark particles, we search for ...their production in the so-called Higgstrahlung channel e+e- → A'h' , with h' → A'A' . We investigate ten exclusive final states with A' → e+e- , μ+μ- , or π+π- in the mass ranges 0.1GeV/c2<mA'< 3.5GeV/c2 and 0.2GeV/c2<mh'<10.5GeV/c2 . We also investigate three inclusive final states 2 ( e+e- ) X , 2 ( μ+μ- ) X , and ( e+e- ) ( μ+μ- ) X , where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1GeV/c2<mA'<3.5GeV/c2 and 2.2GeV/c2<mh'<10.5GeV/c2 . Using the entire 977fb-1 data set collected by Belle, we determine no significant signal. Here, we obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, B ×σBorn , on the Born cross section σBorn , and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, αD×ε2 . These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states 3 ( π+π- ) and 2 ( e+e- ) X are the first placed by any experiment. For αD equal to 1/137 , mh'<8GeV/c2 , and mA'<1GeV/c2 , we exclude values of the mixing parameter ε above ~ 8×10-4.
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