Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of e+e- --> ppbar at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal (|GE|=|GM|). In addition, the ratio of electric to magnetic form factors, |GE/GM|, and |GM| are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at sqrt(s)=2232.4 and 2400.0 MeV and a combined sample at sqrt(s)=3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BABAR, improving the overall uncertainty by about 30%. The |GE/GM| ratios are close to unity and consistent with BABAR results in the same q2 region, which indicates the data are consistent with the assumption that |GE|=|GM| within uncertainties.
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|Titolo:||Measurement of the proton form factor by studying e+e- --> ppbar|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||03.1 Articolo su rivista|