Observation of two new N* resonances in the decay ψ(3686)→ppπ0.

Based on 106×10(6)ψ(3686) events collected with the BESIII detector at the BEPCII facility, a partial wave analysis of ψ(3686)→ppπ0 is performed. The branching fraction of this channel has been determined to be B(ψ(3686)→ppπ0)=(1.65±0.03±0.15)×10(-4). In this decay, 7 N* intermediate resonances are observed. Among these, two new resonances, N(2300) and N(2570) are significant, one 1/2+ resonance with a mass of 2300(-30-0)(+40+109) MeV/c2 and width of 340(-30-58)(+30+110) MeV/c2, and one 5/2- resonance with a mass of 2570(-10-10)(+19+34) MeV/c2 and width of 250(-24-21)(+14+69) MeV/c2. For the remaining 5 N* intermediate resonances [N(1440), N(1520), N(1535), N(1650) and N(1720)], the analysis yields mass and width values that are consistent with those from established resonances.

Evidence for the direct two-photon transition from ψ(3686) to J/ψ.

The two-photon transition ψ(3686)→γγJ/ψ is studied in a sample of 1.06×10(8) ψ(3686) decays collected by the BESIII detector. The branching fraction is measured to be (3.1±0.6(stat)(-1.0)(+0.8)(syst))×10(-4) using J/ψ→e(+)e(-) and J/ψ→µ(+)µ(-) decays, and its upper limit is estimated to be 4.5×10(-4) at the 90% confidence level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the ψ(3686) decay plane and the J/ψ polarization in this decay are also studied. In addition, the product branching fractions of sequential E1 transitions ψ(3686)→γχ(cJ) and χ(cJ)→γJ/ψ(J=0,1,2) are reported.

First observation of the M1 transition ψ(3686)→γη(c)(2S).

Using a sample of 106×10(6) ψ(3686) events collected with the BESIII detector at the BEPCII storage ring, we have made the first measurement of the M1 transition between the radially excited charmonium S-wave spin-triplet and the radially excited S-wave spin-singlet states: ψ(3686)→γη(c)(2S). Analyses of the processes ψ(3686)→γη(c)(2S) with η(c)(2S)→K(S)(0)K(±)π(∓) and K(+)K(-)π(0) give an η(c)(2S) signal with a statistical significance of greater than 10 standard deviations under a wide range of assumptions about the signal and background properties. The data are used to obtain measurements of the η(c)(2S) mass (M(η(c)(2S))=3637.6±2.9(stat)±1.6(syst) MeV/c(2)), width (Γ(η(c)(2S))=16.9±6.4(stat)±4.8(syst) MeV), and the product branching-fraction (B(ψ(3686)→γη(c)(2S))×B(η(c)(2S)→KKπ)=(1.30±0.20(stat)±0.30(syst))×10(-5)). Combining our result with a BABAR measurement of B(η(c)(2S)→KKπ), we find the branching fraction of the M1 transition to be B(ψ(3686)→γη(c)(2S))=(6.8±1.1(stat)±4.5(syst))×10(-4).

Confirmation of the X(1835) and observation of the resonances X(2120) and X(2370) in J/ψ→γπ+π-η'.

With a sample of (225.2±2.8)×10(6) J/ψ events registered in the BESIII detector, J/ψ→γπ(+)π(-)η(') is studied using two η(') decay modes: η(')→π(+)π(-)η and η(')→γρ(0). The X(1835), which was previously observed by BESII, is confirmed with a statistical significance that is larger than 20σ. In addition, in the π(+)π(-)η(') invariant-mass spectrum, the X(2120) and the X(2370), are observed with statistical significances larger than 7.2σ and 6.4σ, respectively. For the X(1835), the angular distribution of the radiative photon is consistent with expectations for a pseudoscalar.

Evidence for ψ' decays into γπ0 and γη.

The decays ψ'→γπ(0), γη and γη' are studied using data collected with the BESIII detector at the BEPCII e(+)e(-) collider. The processes ψ'→γπ(0) and ψ'→γη are observed for the first time with signal significances of 4.6σ and 4.3σ, respectively. The branching fractions are determined to be B(ψ'→γπ(0))=(1.58±0.40±0.13)×10(-6), B(ψ'→γη)=(1.38±0.48±0.09)×10(-6), and B(ψ'→γη')=(126±3±8)×10(-6), where the first errors are statistical and the second ones systematic.