Abstract Using a sample of (10.09 ± 0.04) × 109 J/ψ decays collected with the BESIII detector, partial wave analyses of the decay J / ψ → γ K S 0 K S 0 π 0 $$ J/\psi \to \gamma {K}_S^0{K}_S^0{\pi}^0 ...$$ are performed within the K S 0 K S 0 π 0 $$ {K}_S^0{K}_S^0{\pi}^0 $$ invariant mass region below 1.6 GeV/c 2. The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the K S 0 K S 0 π 0 $$ {K}_S^0{K}_S^0{\pi}^0 $$ invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, i.e., the η(1405) with a mass of 1391.7 ± 0.7 − 0.3 + 11.3 $$ 1391.7\pm {0.7}_{-0.3}^{+11.3} $$ MeV/c 2 and a width of 60.8 ± 1.2 − 12.0 + 5.5 $$ 60.8\pm {1.2}_{-12.0}^{+5.5} $$ MeV, and the η(1475) with a mass of 1507.6 ± 1.6 − 32.2 + 15.5 $$ 1507.6\pm {1.6}_{-32.2}^{+15.5} $$ MeV/c 2 and a width of 115.8 ± 2.4 − 10.9 + 14.8 $$ 115.8\pm {2.4}_{-10.9}^{+14.8} $$ MeV. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the K S 0 K S 0 π 0 $$ {K}_S^0{K}_S^0{\pi}^0 $$ invariant mass spectrum deteriorates significantly.
Abstract Using a data sample corresponding to an integrated luminosity of 11.3 fb −1 collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we observe the process e + e ...− → π 0 π 0 ψ 2(3823) for the first time with a statistical significance of 6.0 standard deviations. The ratio of average cross sections for e + e − → π 0 π 0 ψ 2(3823) and π + π − ψ 2(3823) is determined to be R = σ e + e − → π 0 π 0 ψ 2 3823 σ e + e − → π + π − ψ 2 3823 = 0.57 ± 0.14 ± 0.05 $$ \mathcal{R}=\frac{\sigma \left{e}^{+}{e}^{-}\to {\pi}^0{\pi}^0{\psi}_2(3823)\right}{\sigma \left{e}^{+}{e}^{-}\to {\pi}^{+}{\pi}^{-}{\psi}_2(3823)\right}=0.57\pm 0.14\pm 0.05 $$ , which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the ψ 2(3823) is measured to be Mψ 2(3823) = 3824.5 ± 2.4 ± 1.0 MeV/c 2. Due to the limited data sample, an upper limit of 18.8 MeV at 90% confidence level is set on the intrinsic width of ψ 2(3823).
Abstract A partial wave analysis on the process e + e − → ωπ + π − is performed using 647 pb −1 of data sample collected by using the BESIII detector operating at the BEPCII storage ring at ...center-of-mass (c.m.) energies from 2.000 GeV to 3.080 GeV. The Born cross section of the e + e − → ωπ + π − process is measured, with precision improved by a factor of 3 compared to that of previous studies. A structure near 2.25 GeV is observed in the energy-dependent cross sections of e + e − → ωπ + π − and ωπ 0 π 0 with a statistical significance of 7.6σ, and its determined mass and width are 2232 ± 19 ± 27 MeV/c 2 and 93 ± 53 ± 20 MeV, respectively, where the first and second uncertainties are statistical and systematic, respectively. By analyzing the cross sections of subprocesses e + e − → ωf 0(500), ωf 0(980), ωf 0(1370), ωf 2(1270), and b 1(1235)π, a structure, with mass M = 2200 ± 11 ± 17 MeV/c 2 and width Γ = 74 ± 20 ± 24 MeV, is observed with a combined statistical significance of 7.9σ. The measured resonance parameters will help to reveal the nature of vector states around 2.25 GeV.
Abstract Using data samples with an integrated luminosity of 6.4 fb −1 collected by the BESIII detector operating at the BEPCII storage ring, the process of e + e − → γϕJ/ψ is studied. The processes ...of e + e − → ϕχ c1, c2, χ c1, c2 → γJ/ψ are observed with a significance of more than 10σ. The s $$ \sqrt{s} $$ -dependent cross section of e + e − → ϕχ c1, c2 is measured between 4.600 and 4.951 GeV, and evidence of a resonance structure is found for the first time in the ϕχ c2 process. We also search for the processes of e + e − → γX(4140), γX(4274) and γX(4500) via the γϕJ/ψ final state, but no obvious structures are found. The upper limits on the production cross section times the branching fraction for these processes at the 90% confidence level are reported.
Abstract Based on e + e − collision samples corresponding to an integrated luminosity of 4.4 fb −1 collected with the BESIII detector at center-of-mass energies between 4.6 GeV and 4.7 GeV, a partial ...wave analysis of the charmed baryon hadronic decay Λ c + $$ {\Lambda}_c^{+} $$ → Λπ + π 0 is performed, and the decays Λ c + $$ {\Lambda}_c^{+} $$ → Λρ(770)+ and Λ c + $$ {\Lambda}_c^{+} $$ → Σ(1385)π are studied for the first time. Making use of the world-average branching fraction B Λ c + → Λ π + π 0 $$ \mathcal{B}\left({\Lambda}_c^{+}\to \Lambda {\pi}^{+}{\pi}^0\right) $$ , their branching fractions are determined to be B Λ c + → Λ ρ 770 + = 4.06 ± 0.30 ± 0.35 ± 0.23 × 10 − 2 , B Λ c + → Σ 1385 + π 0 = 5.86 ± 0.49 ± 0.52 ± 0.35 × 10 − 3 , B Λ c + → Σ 1385 0 π + = 6.47 ± 0.59 ± 0.66 ± 0.38 × 10 − 3 , $$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Lambda}_c^{+}\to \Lambda \rho {(770)}^{+}\right)=\left(4.06\pm 0.30\pm 0.35\pm 0.23\right)\times {10}^{-2},\\ {}\mathcal{B}\left({\Lambda}_c^{+}\to \varSigma {(1385)}^{+}{\pi}^0\right)=\left(5.86\pm 0.49\pm 0.52\pm 0.35\right)\times {10}^{-3},\\ {}\mathcal{B}\left({\Lambda}_c^{+}\to \varSigma {(1385)}^0{\pi}^{+}\right)=\left(6.47\pm 0.59\pm 0.66\pm 0.38\right)\times {10}^{-3},\end{array}} $$ where the first uncertainties are statistical, the second are systematic, and the third are from the uncertainties of the branching fractions B Λ c + → Λ π + π 0 $$ \mathcal{B}\left({\Lambda}_c^{+}\to \varLambda {\pi}^{+}{\pi}^0\right) $$ and B Σ 1385 → Λ π $$ \mathcal{B}\left(\Sigma (1385)\to \Lambda \pi \right) $$ . In addition, the decay asymmetry parameters are measured to be α Λρ(770)+ = − 0.763 ± 0.053 ± 0.045, α Σ 1385 + π 0 = − 0.917 ± 0.069 ± 0.056 $$ {\alpha}_{\Sigma (1385)+{\pi}^0}=-0.917\pm 0.069\pm 0.056 $$ , and α Σ 1385 0 π + = − 0.789 ± 0.098 ± 0.056 $$ {\alpha}_{\Sigma {(1385)}^0{\pi}^{+}}=-0.789\pm 0.098\pm 0.056 $$ .
Abstract The decay $$D \rightarrow K^-\pi ^+$$ D → K - π + is studied in a sample of quantum-correlated $$D{\bar{D}}$$ D D ¯ pairs, based on a data set corresponding to an integrated luminosity of ...2.93 fb $$^{-1}$$ - 1 collected at the $$\psi (3770)$$ ψ ( 3770 ) resonance by the BESIII experiment. The asymmetry between $$C\!P$$ C P -odd and $$C\!P$$ C P -even eigenstate decays into $$K^-\pi ^+$$ K - π + is determined to be $${{\mathcal {A}}}_{K\pi } = 0.132 \pm 0.011 \pm 0.007$$ A K π = 0.132 ± 0.011 ± 0.007 , where the first uncertainty is statistical and the second is systematic. This measurement is an update of an earlier study exploiting additional tagging modes, including several decay modes involving a $$K^0_L$$ K L 0 meson. The branching fractions of the $$K^0_L$$ K L 0 modes are determined as input to the analysis in a manner that is independent of any strong phase uncertainty. Using the predominantly $$C\!P$$ C P -even tag $$D\rightarrow \pi ^+\pi ^-\pi ^0$$ D → π + π - π 0 and the ensemble of $$C\!P$$ C P -odd eigenstate tags, the observable $${{\mathcal {A}}}_{K\pi }^{\pi \pi \pi ^0}$$ A K π π π π 0 is measured to be $$0.130 \pm 0.012 \pm 0.008$$ 0.130 ± 0.012 ± 0.008 . The two asymmetries are sensitive to $$r_D^{K\pi }\cos \delta _D^{K\pi }$$ r D K π cos δ D K π , where $$r_D^{K\pi }$$ r D K π and $$\delta _D^{K\pi }$$ δ D K π are the ratio of amplitudes and phase difference, respectively, between the doubly Cabibbo-suppressed and Cabibbo-favoured decays. In addition, events containing $$D \rightarrow K^-\pi ^+$$ D → K - π + tagged by $$D \rightarrow K^0_{S,L} \pi ^+\pi ^-$$ D → K S , L 0 π + π - are studied in bins of phase space of the three-body decays. This analysis has sensitivity to both $$r_D^{K\pi }\cos \delta _D^{K\pi }$$ r D K π cos δ D K π and $$r_D^{K\pi }\sin \delta _D^{K\pi }$$ r D K π sin δ D K π . A fit to $${{\mathcal {A}}}_{K\pi }$$ A K π , $${{\mathcal {A}}}_{K\pi }^{\pi \pi \pi ^0}$$ A K π π π π 0 and the phase-space distribution of the $$D \rightarrow K^0_{S,L} \pi ^+\pi ^-$$ D → K S , L 0 π + π - tags yields $$\delta _D^{K\pi }= \left( 187.6 {^{+8.9}_{-9.7}}{^{+5.4}_{-6.4}} \right) ^{\circ }$$ δ D K π = 187.6 - 9.7 + 8.9 - 6.4 + 5.4 ∘ , where external constraints are applied for $$r_D^{K\pi }$$ r D K π and other relevant parameters. This is the most precise measurement of $$\delta _D^{K\pi }$$ δ D K π in quantum-correlated $$D{\bar{D}}$$ D D ¯ decays.
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