The process of e^{+}e^{-}→ppover ¯ is studied at 22 center-of-mass energy points (sqrts) from 2.00 to 3.08 GeV, exploiting 688.5 pb^{-1} of data collected with the BESIII detector operating at the ...BEPCII collider. The Born cross section (σ_{ppover ¯}) of e^{+}e^{-}→ppover ¯ is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio (|G_{E}/G_{M}|) and the value of the effective (|G_{eff}|), electric (|G_{E}|), and magnetic (|G_{M}|) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. |G_{E}/G_{M}| and |G_{M}| are determined with high accuracy, providing uncertainties comparable to data in the spacelike region, and |G_{E}| is measured for the first time. We reach unprecedented accuracy, and precision results in the timelike region provide information to improve our understanding of the proton inner structure and to test theoretical models which depend on nonperturbative quantum chromodynamics.
Using a sample of 1.31×109J/ψ events collected with the BESIII detector, we perform a study of J/ψ→γKK¯η′. X(2370) is observed in the KK¯η′ invariant-mass distribution with a statistical significance ...of 8.3σ. Its resonance parameters are measured to be M=2341.6±6.5(stat.)±5.7(syst.)MeV/c2 and Γ=117±10(stat.)±8(syst.)MeV. The product branching fractions for J/ψ→γX(2370),X(2370)→K+K-η′ and J/ψ→γX(2370),X(2370)→KS0KS0η′ are determined to be (1.79±0.23(stat.)±0.65(syst.))×10-5 and (1.18±0.32(stat.)±0.39(syst.))×10-5, respectively. No evident signal for X(2120) is observed in the KK¯η′ invariant-mass distribution. The upper limits for the product branching fractions of B(J/ψ→γX(2120)→γK+K-η′) and B(J/ψ→γX(2120)→γKS0KS0η′) are determined to be 1.49×10-5 and 6.38×10-6 at the 90% confidence level, respectively.
Using 2.93 fb(-1) of e(+)e(-) collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D-0 -> K-1 (1270)(-)e(+)nu(e) semileptonic decay is ...presented. The statistical significance of the decay D-0 -> K-1 (1270)e(+)nu(e) is greater than 10 sigma. The branching fraction of D-0 -> K-1 (1270)(-)e(+)nu(e) is measured to be (1.09 +/- 0.13(-0.16)(+0.09) +/- 0.12) x 10(-3). Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K-1 (1270)(-) -> K-pi(+)pi(-). The fraction of longitudinal polarization in D-0 -> K-1 (1270)(-)e(+)nu(e) is determined for the first time to be 0.50 +/- 0.19(stat )+/- 0.08(syst).
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 ± 0.08stat ± 0.03syst) × 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) tan4 θC, 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 CP 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 $^{+2.5}_{–2.1 stat}$ ± 0. 2syst) × 10–5.
Based on (10087±44)×10^{6} J/ψ events collected with the BESIII detector, a partial wave analysis of the decay J/ψ→γK_{S}^{0}K_{S}^{0}η^{'} is performed. The mass and width of the X(2370) are ...measured to be 2395±11(stat)_{-94}^{+26}(syst) MeV/c^{2} and 188_{-17}^{+18}(stat)_{-33}^{+124}(syst) MeV, respectively. The corresponding product branching fraction is BJ/ψ→γX(2370)×BX(2370)→f_{0}(980)η^{'}×Bf_{0}(980)→K_{S}^{0}K_{S}^{0}=(1.31±0.22(stat)_{-0.84}^{+2.85}(syst))×10^{-5}. The statistical significance of the X(2370) is greater than 11.7σ and the spin parity is determined to be 0^{-+} for the first time. The measured mass and spin parity of the X(2370) are consistent with the predictions of the lightest pseudoscalar glueball.
We present measurements of the Born cross sections for the processes e^{+}e^{-}→ωχ_{c1} and ωχ_{c2} at center-of-mass energies sqrts from 4.308 to 4.951 GeV. The measurements are performed with data ...samples corresponding to an integrated luminosity of 11.0 fb^{-1} collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring. Assuming the e^{+}e^{-}→ωχ_{c2} signals come from a single resonance, the mass and width are determined to be M=(4413.6±9.0±0.8) MeV/c^{2} and Γ=(110.5±15.0±2.9) MeV, respectively, which is consistent with the parameters of the well-established resonance ψ(4415). In addition, we also use one single resonance to describe the e^{+}e^{-}→ωχ_{c1} line shape and determine the mass and width to be M=(4544.2±18.7±1.7) MeV/c^{2} and Γ=(116.1±33.5±1.7) MeV, respectively. The structure of this line shape, observed for the first time, requires further understanding.
We present cross sections for the reaction e^{+}e^{-}→K_{S}^{0}K_{L}^{0} at center-of-mass energies ranging from 3.51 to 4.95 GeV using data samples collected in the BESIII experiment, corresponding ...to a total integrated luminosity of 26.5 fb^{-1}. The ratio of neutral-to-charged kaon form factors at large momentum transfers (12<Q^{2}<25 GeV^{2}) is determined to be 0.21±0.01, which indicates a small but significant effect of flavor-SU(3) breaking in the kaon wave function, and, consequently, excludes the possibility that flavor-SU(3) breaking is the primary reason for the strong experimental violation of the pQCD prediction |F(π^{±})|/|F(K^{±})|=f_{π}^{2}/f_{K}^{2}, where F(π^{±}) and F(K^{±}) are the form factors, and f_{π} and f_{K} are the decay constants of charged pions and kaons, respectively. We also observe a significant signal for the charmless decay ψ(3770)→K_{S}^{0}K_{L}^{0} for the first time. Within a 1σ contour of the likelihood value, the branching fraction for ψ(3770)→K_{S}^{0}K_{L}^{0} is determined to be B=(2.63_{-1.59}^{+1.40})×10^{-5}, and the relative phase between the continuum and ψ(3770) amplitudes is ϕ=(-0.39_{-0.10}^{+0.05})π. The branching fraction is in good agreement with the S- and D-wave charmonia mixing scheme proposed in the interpretation of the "ρπ puzzle" between J/ψ and ψ(3686) decays.
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