We study the process e+ e- →(D* D*)± π∓ at a center-of-mass energy of 4.26 GeV using a 827  pb(-1) data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be (137±9±15)  pb. We observe a structure near the (D* D*)± threshold in the π∓ recoil mass spectrum, which we denote as the Zc±(4025). The measured mass and width of the structure are (4026.3±2.6±3.7)  MeV/c2 and (24.8±5.6±7.7)  MeV, respectively. Its production ratio σ(e+ e- → Zc±(4025)π∓ → (D* D*)± π∓)/σ(e+ e- → (D* D*)± π∓) is determined to be 0.65±0.09±0.06. The first uncertainties are statistical and the second are systematic.

Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of e þ e − → pp 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 ðjG E j ¼ jG M jÞ. In addition, the ratio of electric to magnetic form factors, jG E =G M j, and jG M j are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at ffiffi ffi s p ¼ 2232.4 and 2400.0 MeV and a combined sample at ffiffi ffi s p ¼ 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 jG E =G M j ratios are close to unity and consistent with BABAR results in the same q 2 region, which indicates the data are consistent with the assumption that jG E j ¼ jG M j within uncertainties.

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