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Register a new userMeasurement of the e+e- -> pi+pi- cross section using initial state radiation at BESIII
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Benedikt Kloss
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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 $(g-2)_mu$.
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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.
A precise measurement of the cross section of the process $e^+e^-topi^+pi^-(gamma)$ from threshold to an energy of 3GeV is obtained with the initial-state radiation (ISR) method using 232fb$^{-1}$ of data collected with the BaBar detector at $e^+e^-$ center-of-mass energies near 10.6GeV. The ISR luminosity is determined from a study of the leptonic process $e^+e^-tomu^+mu^-(gamma)gamma_{rm ISR}$, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process $e^+e^-topi^+pi^-(gamma)$ is obtained with a systematic uncertainty of 0.5% in the dominant $rho$ resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured $pipi$ cross section from threshold to 1.8GeV is $(514.1 pm 2.2({rm stat}) pm 3.1({rm syst}))times 10^{-10}$.
A precise measurement of the cross section of the process e+ e- to pi+ pi- (gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb^-1 of data collected with the BABAR detector at e+ e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+ e- to mu+ mu- gamma (gamma). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the pi pi cross section measured from threshold to 1.8 GeV is (514.1 +-2.2(stat} +-3.1(syst}) x 10^{-10}.
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.
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