17 0 0.2 0.4 0.6 0.8 1 -t [GeV$^{2}$] 0 0.2 0.4 0.6 0.8 1 1.2 1.4 [d 2 /dt d [d 2 /dt d photoproduction DESY 0 0.2 0.4 0.6 0.8 1 1.2 -t [GeV$^{2}$] Q$^{2 }$= 0.70 GeV 2 Q$^{2 }$= 1.35 GeV 2 W = 2.19 GeV  = 0.84 120 deg <   < 240 deg 120 deg <   < 240 deg  = 0.86 W = 2.19 GeV DESY DESY FIG. 11: (Color online) − t dependence of the π $^{−}$/π + ratio of double differential cross sections dσ $^{2}$/dtdφ for the value of W = 2 . 19 GeV and at values of Q 2 = 0 . 7 GeV $^{2}$, ε = 0 . 86 (left panel) and Q 2 = 1 . 35 GeV $^{2}$, ε = 0 . 84 (right panel). The experimental data are from Ref. [16]. The cross sections are integrated in the range of 120 ◦ < φ < 240 ◦ out-of-plane angles. The solid curves are the model results. The dash-dotted curves describe the results without the resonance contributions. In the left panel the dashed curve is the results without the exchange of the ρ (770) /a$_{2}$ (1320)-trajectory. The squares are the compilation of experimental data for the ratio of π $^{−}$/π + in photoproduction [55]. The dot-dot-dashed curve corresponds to the ratio of cross sections in photoproduction at Q 2 = 0 and E$_{γ}$ = 16 GeV. The ratio of transverse cross sections at value of Q 2 = 0 . 7 GeV 2 is given by the dash-dash-dotted curve. tions in essentially the same ( Q $^{2}$, W ) region as at JLAB. For the proper comparison with data some differences in the conventions used by the two different groups [13–16] and [12] have to be taken into account. The φ conven- tion used here follows Refs. [13–16]. In [12] the azimuthal angle is related to that in [13–16] by φ → π − φ . The lat- ter results in different signs of the measured interference cross section dσ$_{LT}$/dt . p ( γ ∗ , π $^{+}$) n data only, this agreement with data for the ratio p ( γ ∗ , π $^{+}$) n/n ( γ ∗ , π − ) p of cross sections is indeed remarkable, see the discussion around Eq. (46). In Fig- ure 11 (left panel) the dashed curves are the results with- out the exchange of the ρ (770) /a$_{2}$ (1320)-Regge trajec- tory. It is seen that the π − /π + ratio is indeed sensi- tive to the ρ -exchange amplitude. In the left panel we also show the compilation of experimental data for the ratio of π − /π + photoproduction cross sections at high energies [55]. For comparison we also show the ratio of only the transverse cross sections in electroproduction at Q 2 = 0 . 7 GeV 2 (dash-dash-dotted curve). The dot-dot-dashed curve in Figure 11 (left panel) cor- responds to our results for the ratio of photoproduction ( Q 2 = 0) cross sections at E$_{γ}$ = 16 GeV in the laboratory. The π − /π + asymmetry seen in the photoproduction re- sults mainly from the contribution of the ρ -Regge tra- In Figure 11 we show the results and the experimental data [16] for the ratio of exclusive π − /π + double dif- ferential cross sections dσ $^{2}$/dtdφ at the average value of W = 2 . 19 GeV and for the average values of Q 2 = 0 . 7 GeV $^{2}$, ε = 0 . 86 (left panel) and Q 2 = 1 . 35 GeV $^{2}$, ε = 0 . 84 (right panel). The cross sections are integrated in the 120 ◦ < φ < 240 ◦ azimuthal degree range [16]. The solid curves are the model results. Since, the pa- rameters of the model are constrained using the JLAB