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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 . 

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 

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- 

