Based on a sample of 1.31 × 109J / ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η'→ π + π - π 0 and η' → π 0 π 0 π 0 is performed. A significant ...P-wave contribution from η'→ ρ ± π ∓ is observed for the first time in η' → π + π - π 0 . The branching fraction is determined to be B ( η'→ ρ ± π ∓ ) = ( 7.44 ± 0.60 ± 1.26 ± 1.84 ) × 10-4, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S -wave component, there is a significant σ meson component. The branching fractions of the combined S -wave components are determined to be B ( η' → π + π - π 0 ) S = ( 37.63 ± 0.77 ± 2.22 ± 4.48 ) × 10-4 and B ( η' → π 0 π 0 π 0 ) = ( 35.22 ± 0.82 ± 2.54 ) × 10-4, respectively. Finally, the latter one is consistent with previous BESIII measurements.
Using 2.93 fb −1 of e+e− annihilation data collected at a center-of-mass energy √s = 3.773 GeV with the BESIII detector operating at the BEPCII collider, we search for the semileptonic D0(+) decays ...into a b1(1235) − (0) axial-vector meson for the first time. No significant signal is observed for either charge combination. The upper limits on the product branching fractions are BD0 → b1(1235)−e+νe Bb1(1235)− → ωπ−< 1.12 × 10−4 and BD+ → b1(1235)0e+νe⋅ Bb1(1235)0 → ωπ0< 1.75 × 10−4 at the 90% confidence level.
Using 2.93 fb−1 of e+e− collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay D+ → K+π+π−π0 is ...reported. After removing decays that contain narrow intermediate resonances, including D+ → K+η, D+ → K+ω, and D+ → K+ϕ, the branching fraction of the decay D+ → K+π+π−π0 is measured to be ( 1.13 ± 0.0 8stat ± 0.0 3syst) × 10−3. The ratio of branching fractions of D+ → K+π+π−π0 over D+ → K−π+π+π0 is found to be ( 1.81 ± 0.15 )%, which corresponds to ( 6.28 ± 0.52 ) tan4θC, where θC is the Cabibbo mixing angle. This ratio is significantly larger than the corresponding ratios for other doubly Cabibbo-suppressed decays. The asymmetry of the branching fractions of charge-conjugated decays D± → K±π±π∓π0 is also determined, and no evidence for C P violation is found. In addition, the first evidence for the D+ → K+ω decay, with a statistical significance of 3.3σ, is presented and the branching fraction is measured to be B (D+ → K+ω) = ( 5. 7−2.1 stat+2.5 ± 0.2syst ) × 10−5.
The observed cross sections for e+e− → μ+μ− at energies from 3.8 to 4.6 GeV are measured using data samples taken with the BESIII detector operated at the BEPCII collider. We measure the muonic ...widths and determine the branching fractions of the charmonium states ψ(4040), ψ(4160), and ψ(4415) decaying to μ+μ−, as well as making a first determination of the phase of the amplitudes. In addition, we observe evidence for a structure in the dimuon cross section near 4.220 GeV/c2, which we denote as S(4220). Analyzing a coherent sum of amplitudes yields eight solutions, one of which gives a mass of MS(4220) = 4216.7 ± 8.9 ± 4.1 MeV/c2, a total width of Γ tot S(4220) = 47.2 ± 22.8 ± 10.5 MeV, and a muonic width of Γ μμS(4220) = 1.53 ± 1.26 ± 0.54 keV , where the first uncertainties are statistical and the second systematic. The eight solutions give the central values of the mass, total width, muonic width to be, respectively, in the range from 4212.8 to 4219.4 MeV/c2, from 36.4 to 49.6 MeV, and from 1.09 to 1.53 keV. The statistical significance of the S(4220) signal is 3.9σ. Correcting the total dimuon cross section for radiative effects yields a statistical significance for this structure of 8.1σ.
Using a data set with an integrated luminosity of 2.93 fb−1 collected at s=3.773 GeV with the BESIII detector operating at the BEPCII storage rings, we search for the rare decay D+→D0e+νe. No ...signal events are observed. We set the upper limit on the branching fraction for D+→D0e+νe to be 1.0×10−4 at the 90% confidence level.
This Letter reports the first extraction of individual antineutrino spectra from ^{235}U and ^{239}Pu fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at ...Daya Bay. The analysis uses 3.5×10^{6} inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, ^{235}U and ^{239}Pu, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4-6 MeV, a 7% (9%) excess of events is observed for the ^{235}U (^{239}Pu) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is 4.0σ for ^{235}U spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at 5.3σ. In the energy range of 4-6 MeV, a maximal local discrepancy of 6.3σ is observed.
The cross sections of e^{+}e^{-}→π^{+}π^{-}h_{c} at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing ...Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e^{+}e^{-}→π^{+}π^{-}J/ψ and e^{+}e^{-}→π^{+}π^{-}ψ(2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e^{+}e^{-}→π^{+}π^{-}h_{c} cross sections around 4.22 and 4.39 GeV/c^{2}, which we call Y(4220) and Y(4390), respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4_{-4.5}^{+5.5}±0.9) MeV/c^{2} and a width of (66.0_{-8.3}^{+12.3}±0.4) MeV for the Y(4220), and a mass of (4391.5_{-6.8}^{+6.3}±1.0) MeV/c^{2} and a width of (139.5_{-20.6}^{+16.2}±0.6) MeV for the Y(4390), where the first uncertainties are statistical and the second ones systematic. The statistical significance of Y(4220) and Y(4390) is 10σ over one structure assumption.
Using (10.087±0.044)×109 J/ψ events collected by the Beijing Spectrum III (BESIII) detector at the Beijing Electron Positron Collider II (BEPCII) collider, we search for the hyperon semileptonic ...decay ... . No significant signal is observed and the upper limit on the branching fraction ... is set to be 2.59×10−4 at 90% confidence level. This result is one order of magnitude more strict than the previous best limit.(ProQuest: … denotes formulae omitted.)
In the present work, laminated Cu/Ni samples reinforced by graphene film with various thicknesses were produced via electrophoretic depositing graphene oxide (GO) on Cu foil by controlling deposition ...voltage, and the effect of thickness of graphene film on strengthening Cu/Ni multilayer composites were investigated in detail. Microstructural examination revealed that the fragments of graphene film were dispersed at the interface between Cu and Ni layer after hot rolling, with a range of thickness from 0.76 to 5.13 μm. The graphene film showed an excellent strengthening effect in the composites regardless of their thickness according to the tensile testing. However, the toughing effect achieved optimal as the thickness of 4.12 μm. The role of deposited graphene film played in determining the load transfer and optimizing the interface was discussed. Graphene film with appropriate thickness can effectively inhibit the severe asymmetric diffusion behavior of Cu and Ni elements, which plays an important role in strengthening and toughening clad interfaces by inhibiting the formation of Kirkendall voids. This study provides novel insights into understanding the strengthening and toughing behaviors of graphene reinforced multilayer composites, which can be developed into a technical strategy for fabricating high performance laminated metal matrix composites.
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