Measurement of Proton Electromagnetic Form Factors in e+e−→pp¯<

Dynamical Properties of Baryons

“…World data of the effective FF are shown in Figure 2. The recent data from BES, using the ISR method [19] (blue squares) and the beam scan method [18] (green triangles) confirm the regular structures previously found in [20] on the BaBar data [16,21] (black circles). The data can be fitted by damped oscillations overimposed on a monotone decreasing background [22].…”

“…While the SL data (red squares in Figure 3) show a monotone decrease, the TL ones (green triangles in Figure 3) [18], show the presence of oscillations, which do not contradict the results from BaBar [21] (black circles in Figure 3), with a minimum at q 2 = (5 − 6) GeV 2 .…”

“…Few data on the FF ratio were produced by the BaBar [16] and PS170 collaborations [17]. Only very recently could the BESIII collaboration extract |G E | and |G M | separately and with a meaningful error in the near-threshold region [18]. From the integrated cross section:…”

“…This is consistent with a point-like proton, suggesting that the proton behaves as a particle without structure in the region just above threshold. [16,21] (black circles), BESIII [19] (blue squares), and [18] (green triangles). They are shown together with the six-parameter fit from [22] compared to the fit from [20] (red dashed line).…”

“…A recent experiment in the time-like region from the BESIII collaboration [18] at the e + e − collider BEPCII, determined for the first time in the TL region the moduli of the electric and magnetic FFs. At the kinematical threshold they should coincide; the precise determination of their value provides a strong constraint for models.…”