In this paper, the spin and parity of the Zc(3900)± state are determined to be JP = 1+ with a statistical significance larger than 7σ over other quantum numbers in a partial wave analysis of the ...process e+e- → π+π-J/Ψ. We use a data sample of 1.92 fb-1 accumulated at $ \sqrt{s}=4.23 $ and 4.26 GeV with the BESIII experiment. When parametrizing the Zc(3900)± with a Flatté-like formula, we determine its pole mass Mpole = (3881.2±4.2stat ±52.7syst) MeV/c2 and pole width Γpole = (51.8± 4.6stat ± 36.0syst) MeV. Finally, we also measure cross sections for the process e+e- → Zc(3900)+π- + c.c. → J/Ψπ+π- and determine an upper limit at the 90% confidence level for the process e+e- → Zc(4020)+π- + c.c. → J/Ψ π+π-.
Here, in an analysis of a 2.92 fb–1 data sample taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be B(D0 → K–e+νe) = ...(3.505 ± 0.014 ± 0.033)% and B(D0 → π–e+νe) = (0.295 ± 0.004 ± 0.003)%. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f$ $^{K}_{+}$(0)|Vcs| = 0.7172 ± 0.0025 ± 0.0035 and $f$ $^{π}_{+}$(0)|Vcd| = 0.1435 ± 0.0018 ± 0.0009.
Using 448.0×106 ψ(3686) events collected with the BESIII detector, an amplitude analysis is performed for ψ(3686)→γχc1, χc1→ηπ+π− decays. The most dominant two-body structure observed is a0(980)±π∓; ...a0(980)±→ηπ±. The a0(980) line shape is modeled using a dispersion relation, and a significant nonzero a0(980) coupling to the η′π channel is measured. We observe χc1→a2(1700)π production for the first time, with a significance larger than 17σ. The production of mesons with exotic quantum numbers, JPC=1−+, is investigated, and upper limits for the branching fractions χc1→π1(1400)±π∓, χc1→π1(1600)±π∓, and χc1→π1(2015)±π∓, with subsequent π1(X)±→ηπ± decay, are determined.
Using a data set of 2.93 fb taken at a center-of-mass energy root s = 3.773 GeV with the BESIII detector at the BEPCII collider, we perform a search for an extra U(1) gauge boson, also denoted as a ...dark photon. We examine the initial state radiation reactions e(+)e(-) -> e(+)e(-) gamma(ISR) and e(+)e(-) -> mu(+)mu(-) gamma(ISR) for this search, where the dark photon would appear as an enhancement in the invariant mass distribution of the leptonic pairs. We observe no obvious enhancement in the mass range between 1.5 and 3.4 GeV/c(2) and set a 90% confidence level upper limit on the mixing strength of the dark photon and the Standard Model photon. We obtain a competitive limit in the tested mass range.
Using 1310.6×106 J/ψ and 447.9×106 ψ(3686) events collected with the BESIII detector at the BEPCII e+e− collider, the branching fractions and the angular distributions of J/ψ and ψ(3686) decays to ...ΛΛ¯ and Σ0Σ¯0 final states are measured. The branching fractions are determined, with much improved precision, to be 19.43±0.03±0.33, 11.64±0.04±0.23, 3.97±0.02±0.12 and 2.44±0.03±0.11 for J/ψ→ΛΛ¯, J/ψ→Σ0Σ¯0, ψ(3686)→ΛΛ¯ and ψ(3686)→Σ0Σ¯0, respectively. The polar angular distributions of ψ(3686) decays are measured for the first time, while those of J/ψ decays are measured with much improved precision. In addition, the ratios of branching fractions B(ψ(3686)→ΛΛ¯)B(J/ψ→ΛΛ¯) and B(ψ(3686)→Σ0Σ¯0)B(J/ψ→Σ0Σ¯0) are determined to test the “12% rule.”
We study the singly Cabibbo suppressed decays Λc+→pη and Λc+→pπ0 using Λc+Λ¯c− pairs produced by e+e− collisions at a center-of-mass energy of s=4.6 GeV. The data sample was collected by the BESIII ...detector at the BEPCII collider and corresponds to an integrated luminosity of 567 pb−1. We find the first evidence for the decay Λc+→pη with a statistical significance of 4.2σ and measure its branching fraction to be B(Λc+→pη)=(1.24±0.28(stat)±0.10(syst))×10−3. No significant Λc+→pπ0 signal is observed. We set an upper limit on its branching fraction B(Λc+→pπ0)<2.7×10−4 at the 90% confidence level.
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