No Arabic abstract
The cross section of the process $e^+e^-topi^+pi^-pi^0$ is measured with a precision of 1.6% to 25% in the energy range between $0.7$ and 3.0 GeV using the Initial State Radiation method. A data set with an integrated luminosity of $2.93$fb$^{-1}$ taken at the center-of-mass energy of $sqrt{s}=3.773$GeV with the BESIII detector at the BEPCII collider is used. The product branching fractions for $omega$, $phi$, $omega(1420)$, and $omega(1650)$ are measured to be $mathcal{B}(omegato e^+e^-) times mathcal{B}(omega to pi^+pi^-pi^0)=(6.94pm0.08pm0.16) times 10^{-5}$, $mathcal{B}(phito e^+e^-) times mathcal{B}(phitopi^+pi^-pi^0) = (4.20pm0.08pm0.19) times 10^{-5}$, $mathcal{B}(omega(1420)to e^+e^-) times mathcal{B}(omega(1420) to pi^+pi^-pi^0) = (0.84pm0.09pm0.09) times 10^{-6}$, and $mathcal{B}(omega(1650) to e^+e^) times mathcal{B}(omega(1650)to pi^+pi^-pi^0) = (1.14pm0.15pm0.15)times10^{-6}$, respectively. The branching fraction $mathcal{B}(J/psito pi^+pi^-pi^0)$ is measured to be $(2.188 pm 0.024 pm 0.024 pm0.040 (Gamma_{ee}^{J/psi}))%$, where $Gamma_{ee}^{J/psi}$ is the dileptonic width of $J/psi$. The first errors are of statistical, the second and third ones of systematic nature.
We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260,000 signal events. We use these data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.
The cross section for e^+e^- to pi^+pi^-J/psi between 3.8 and 5.5 GeV/c^2 is measured using a 548 fb^{-1} data sample collected on or near the Upsilon(4S) resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c^2, corresponding to the so called Y(4260), is observed. In addition, there is another cluster of events at around 4.05 GeV/c^2. A fit using two interfering Breit-Wigner shapes describes the data better than one that uses only the Y(4260), especially for the lower mass side of the 4.25 GeV enhancement.
Using a data set with an integrated luminosity of 2.93 fb$^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider, we extract the $e^+e^-rightarrow pi^+pi^-$ cross section and the pion form factor $|F_pi|^2$ in the energy range between 600 and 900 MeV. We exploit the method of initial state radiation for this measurement, yielding a systematic uncertainty of 0.9%. We calculate the contribution of the measured cross section to the leading-order hadronic vacuum polarization contribution to $(g-2)_mu$.
Using data samples with a total integrated luminosity of $20.1~rm fb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the cross section of the process $e^+e^- rightarrow pi^+pi^-psi(3686)$ is measured at center-of-mass energies between 4.0076 and 4.6984 GeV. The measured cross section is consistent with previous results, but with much improved precision. A fit to the measured energy-dependent cross section, which includes three Breit-Wigner functions and a non-resonant contribution, confirms the existence of the charmonium-like states $Y(4220)$, $Y(4390)$, and $Y(4660)$. This is the first observation of the $Y(4660)$ at the BESIII experiment.
The process $e^+e^- to pi^+pi^-pi^0eta$ is studied in the center-of-mass energy region below 2 GeV with the SND detector at the VEPP-2000 $e^+e^-$ collider. The four intermediate states contribute to this process: $omegaeta$, $phieta$, $a_0(980)rho$, and a structureless $pi^+pi^-pi^0eta$ state. We measure the total $e^+e^- to pi^+pi^-pi^0eta$ cross section and the cross sections for its components: $omegaeta$, $phieta$, and a sum of $a_0(980)rho$ and the structureless state. Our results are in agreement with previous measurements and have comparable or better accuracies.