0 1 2 -t+t$_{min}$ [GeV$^{2}$] -200 -100 0 100 200 d int  /dt [nb/GeV 2 ] 0 1 2 -t+t$_{min}$ [GeV$^{2}$] 0 1 2 -t+t$_{min}$ [GeV$^{2}$] 0 1 2 -t+t$_{min}$ [GeV$^{2}$] 1 < Q$^{2}$< 2 GeV 2 2 < Q$^{2}$< 3 GeV 2 3 < Q$^{2}$< 4 GeV 2 4 < Q$^{2}$< 11 GeV 2 0.02 < x$_{B}$ < 0.15 0.06 < x$_{B}$ < 0.23 0.11 < x$_{B}$ < 0.31 0.15 < x$_{B}$ < 0.55 21 FIG. 16: (Color online) − t + t$_{min}$ dependence of the interference cross sections dσ$_{TT}$ (dashed curves) and dσ$_{LT}$ (solid curves) at HERMES. The average values of Q 2 and x$_{B}$ used for different ( Q $^{2}$, x$_{B}$ ) bins are the same as in Figure 14. In the left panel the dash-dotted and dash-dash-dotted curves describe the contribution of the π -reggeon exchange to dσ$_{TT}$ and dσ$_{LT}$ , respectively. ready at JLAB energies. For instance, if the cross sec- tion would be dominated by the π -reggeon exchange then dσ$_{TT}$/dt would be positive (dash-dotted curves in the left panel) and dσ$_{LT}$/dt negative (dash-dash-dotted curves in the left panel). The interference between the π -trajectory and r/p -contributions change the sign of both dσ$_{TT}$/dt and dσ$_{LT}$/dt . The solid and dashed curves describe the model results for dσ$_{LT}$/dt and dσ$_{TT}$/dt , respectively. fall-off of Regge contributions as a function of − t , the meson-exchange processes are already negligible. Above − t > 1 GeV 2 the model cross section points mainly to- ward the direct coupling of the virtual photons to par- tons. Indeed, this is rather natural, since with increasing − t at fixed Q 2 smaller distances can be accessed. This is opposed to t -channel meson-exchange processes which involve peripheral production of π $^{+}$. Contrary to the two-component model of Ref. [27], in the present model there is a sizable longitudinal r/p - component which is effective in the off-forward π + pro- duction at low values of Bjorken x$_{B}$ . For instance, the dip in εdσ$_{L}$/dt , see the dash-dotted curves in Figure 14, re- sults from the interference between the meson-exchange and the r/p -contributions. In Figure 15 we show the different contributions to εdσ$_{L}$/dt for the lowest x$_{B}$ bin. The solid and dash-dotted curves in Figure 15 are the same as in Figure 14 (left panel). The contribution of the π -exchange to εdσ$_{L}$/dt is shown by the dashed curve. The latter falls exponentially down as a function of − t . The dash-dash-dotted curve describe the r/p - contribution to εdσ$_{L}$/dt . It vanishes at forward angles and by the destructive interference with the π -reggeon exchange produces a dip in εdσ$_{L}$/dt . With increasing − t the partonic component of εdσ$_{L}$/dt continues to domi- nate the longitudinal response. It has been proposed that the Q 2 dependence of l/t separated exclusive p ( γ ∗ , π $^{+}$) n cross sections may pro- vide a test of the factorization theorem [19] in the sep- aration of long-distance and short-distance physics and the extraction of GPD. The leading twist GPD scenario predicts for σ$_{L}$ ∼ 1 /Q 6 and σ$_{T}$ ∼ 1 /Q $^{8}$. An observa- tion of the Q 2 power law scaling is considered as a model independent test of QCD factorization. The Q behavior of cross sections in exclusive reaction p ( γ ∗ , π $^{+}$) n has been studied at JLAB in Ref. [3]. It was shown that while the scaling laws are reasonably consis- tent with the Q 2 dependence of the longitudinal σ$_{L}$ data, they fail to describe the Q 2 dependence of the transverse σ$_{T}$ data. The Q 2 dependence of the p ( γ ∗ , π $^{+}$) n cross sec- tion in DIS has been also studied at HERMES [57]. It was found that the Q 2 dependence of the data is in gen- eral well described by the calculations from GPD models which include the power corrections, see Ref. [57] and ref- erences therein. However, the magnitude of the theoreti- cal cross section is underestimated. The Regge model of Ref. [38] was shown to be compatible with, both, − t and Q 2 dependencies of the HERMES data. In the following In Figure 15 the dot-dot-dashed curve describes the real photon limit Q 2 = 0 of the model cross section for E$_{γ}$ = 8 GeV ( W ≃ 4 GeV). The photoproduction data are from Ref. [54]. This is the same W region as in the HERMES electroproduction data. The model is in agree- ment with both the photo- and electroproduction data. In Figure 16 we present the results for the interfer- ence cross sections at HERMES energies. dσ$_{TT}$/dt and dσ$_{LT}$/dt are sizable, and follow a behavior observed al- X. Q 2 DEPENDENCE OF THE CROSS SECTIONS