We study the process e+e−→π+π−ψ(3686) using 5.1 fb−1 of data collected at 16 center-of-mass energy (s) points from 4.008 to 4.600 GeV by the BESIII detector operating at the BEPCII collider. The ...measured Born cross sections for e+e−→π+π−ψ(3686) are consistent with previous results, but with much improved precision. A fit to the cross section shows contributions from two structures: the first has M=4209.5±7.4±1.4 MeV/c2 and Γ=80.1±24.6±2.9 MeV, and the second has M=4383.8±4.2±0.8 MeV/c2 and Γ=84.2±12.5±2.1 MeV, where the first errors are statistical and the second systematic. The lower-mass resonance is observed in the process e+e−→π+π−ψ(3686) for the first time with a statistical significance of 5.8σ. A charged charmoniumlike structure is observed in the π±ψ(3686) invariant mass spectrum for data at s=4.416 GeV. A fit with an S-wave Breit-Wigner function yields a mass M=4032.1±2.4 MeV/c2, where the errors are statistical only. However, there are still unresolved discrepancies between the fit model and data. The width of the intermediate state varies in a wide range for different kinematic regions within the data set. Therefore, no simple interpretation of the data has been found, and a future data sample with larger statistics and more theoretical input will be required to better understand this issue.
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•Rapid softening and hardening phenomenon are found in the SLM Ti6Al4V alloy after EPT.•The changes of microhardness were attributed to the phase transformation and microstructure evolution.•EPT ...induced rapid α → β phase transformation by decreasing transformation barrier in the SLM Ti6Al4V alloy.•The improvement of metallurgical bonding of the α lamella after EPT may enhance the mechanical properties.
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Optimizing the microstructure and mechanical properties of the selective laser melted (SLM) Ti6Al4V alloy is an important issue both in the scientific and engineering interests. In this study, the rapid hardening and softening of the SLM-Ti6Al4V alloy is realized due to the obvious evolution of microstructures during the electropulsing treatment (EPT) with different discharge voltages. The microhardness of the EPT-7.5 kV sample decreased about 7% while the EPT-8 kV sample increased about 10% compared with the as-received sample. Scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) analysis were used to characterize the evolutions of α and β grains and dislocation structures which are corresponding with the microhardness changes induced by EPT. Analysis shows that EPT could reduce the thermodynamic barrier for α → β solid-state phase transformation, further arise microstructure refinement in the SLM-Ti6Al4V alloy. This research shed some new light on rapidly and efficiently improving the microstructure and mechanical properties of the additive manufactured metal components.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Using a data sample of (10087 ± 44) x 10 6 J/ψ events collected by the BESIII detector in 2009, 2012, 2018 and 2019, the electromagnetic Dalitz process J/ψ → e + e - η(1405) is observed via the decay ...η(1405) → π 0 f 0 (980), f 0 (980) → π + π - , with a significance of about 9.8σ. The branching fraction of this decay is measured to be B(J/ψ → e + e − η(1405) → e + e − π 0 f 0 (980) → J/ψ→ e + e - η(1405) → e + e - π 0 f 0 (980) → e + e - π 0 π + π - ) = (2.04 ± 0.20(stat) ± 0.08(syst)) x 10 -7 . The branching fraction ratio B(J/ψ → e + e - η(1405))/B(J/ψ → γη(1405)) is determined to be (1.36 ± 0.17(stat) ± 0.06(syst)) x 10 -2 . Furthermore, an e + e - invariant mass dependent transition form factor of J/ψ → e + e - η(1405) is presented for the first time. The obtained result provides input for different theoretical models and is valuable for the improved understanding the intrinsic structure of the η(1405) meson.
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The singly Cabibbo suppressed decay Λ + c → pη′ is measured using 4.5 fb −1 of e + e − collision data collected at center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at ...BEPCII. Evidence for Λ + c → pη′ with a statistical significance of 3.6σ is reported with a double-tag approach. The Λ + c → pη′ absolute branching fraction is determined to be (5.62 +2.46 −2.04 ±0.26)×10 −4 , where the first and second uncertainties are statistical and systematic, respectively. Our result is consistent with the branching fraction obtained by the Belle collaboration within the uncertainty of 1σ.
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Using 2.93 fb −1 of e+e− collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the absolute branching fractions of 14 hadronic ...D0(+) decays to exclusive final states with an η , e.g., D0 → K−π+η , K0Sπ0η , K+K−η , K0SK0Sη, K−π+π0η , K0Sπ+π−η , K0Sπ0π0η , and π+π−π0η ; D+ → K0Sπ+η,K0SK+η, K−π+π+η, K0Sπ+π0η, π+π+π−η , and π+π0π0η. Among these decays, the D0 → K−π+η and D+→K0Sπ+η decays have the largest branching fractions, which are B (D0 → K−π+η) = ( 1.853 ± 0.02 5 stat ± 0.03 1 syst ) % and B ( D+ → K0Sπ+η ) = ( 1.309 ± 0.03 7 stat ± 0.03 1 syst ) % , respectively. The charge-parity asymmetries for the six decays with highest event yields are determined, and no statistically significant charge-parity violation is found.
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This paper reports the study of D+s→τ+ν via τ+→π+¯ντ using a boosted decision tree method, with 7.33 fb−1 of e+e− collision data collected by the BESIII detector at center-of-mass energies between ...4.128 and 4.226 GeV. The branching fraction of D+s→τ+ντ is determined to be (5.44±0.17stat±0.13syst)%. The product of the D+s decay constant fD+s and the Cabibbo-Kobayashi-Maskawa matrix element |Vcs| is fD+s|Vcs|=(248.3±3.9stat±3.1syst±1.0input) MeV. Combining with the |Vcs| value obtained from the Standard Model global fit or the fD+s from the lattice quantum chromodynamics, we determine |Vcs|=0.993±0.015stat±0.012syst±0.004input and fD+s=(255.0±4.0stat±3.2syst±1.0input) MeV. The first uncertainty is statistical, the second one is systematic and the third one is due to the input parameters, mainly the lifetime of D+s. All results obtained in this work supersede the BESIII previous results based on 6.32 fb−1 of e+e− collision data taken at center-of-mass energies between 4.178 and 4.226 GeV.
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