2000 character limit reached
Measurement of the $\mathrm e^+\mathrm e^-\rightarrow\mathrmπ^+\mathrmπ^-$ Cross Section between 600 and 900 MeV Using Initial State Radiation (1507.08188v3)
Published 29 Jul 2015 in hep-ex
Abstract: We extract the $e+e-\rightarrow \pi+\pi-$ cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. 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 is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor $|F_\pi|2$ as well as the contribution of the measured cross section to the leading order hadronic vacuum polarization contribution to $(g-2)\mu$. We find this value to be $a\mu{\pi\pi,\rm LO}(600-900\;\rm MeV) = (368.2 \pm 2.5_{\rm stat} \pm 3.3_{\rm sys})\cdot 10{-10}$.