27 0 0.1 0.2 0.3 0.4 -t+t$_{min}$ [GeV$^{2}$] 0 1 0 0.1 0.2 0.3 0.4 -t+t$_{min}$ [GeV$^{2}$] 0 0.1 0 1 2 T L TT LT 0 1 2 3 4 0 0.1 0.2 0.3 0.4 -t+t$_{min}$ [GeV$^{2}$] 0 0.1 0.2 0 0.1 0.2 0.3 0.4 -t+t$_{min}$ [GeV$^{2}$] 0 0.2 0.4 d /dt [ b/GeV 2 ] 0 10 20 30 d /dt [$^{µ}$ b/GeV 2 ] Q$^{2}$= 1.6 GeV 2 W = 3.0 GeV JLAB@12 GeV JLAB@12 GeV JLAB@12 GeV Q$^{2}$= 4.5 GeV 2 W = 3.28 GeV Q$^{2}$= 2.45 GeV 2 JLAB@12 GeV Q$^{2}$= 5.25 GeV 2 W = 3.20 GeV W = 3.20 GeV Q$^{2}$= 3.5 GeV 2 W = 3.1 GeV JLAB@12 GeV Q$^{2}$= 6 GeV 2 W = 3.20 GeV JLAB@12 GeV JLAB@12 GeV Q$^{2}$= 0.3 GeV 2 W = 2.2 GeV n( )p FIG. 24: (Color online) − t + t$_{min}$ dependence of l/t separated differential cross sections dσ$_{T}$/dt (solid), dσ$_{L}$/dt (dashed), dσ$_{LT}$/dt (dash-dotted) and dσ$_{TT}$/dt (dash-dash-dotted) in exclusive reaction n ( γ $^{∗}$, π$^{−}$) p in the ( Q $^{2}$, W ) kinematics at JLAB@12. duction off the neutrons is predicted to be much smaller in magnitude and very sensitive to the different scenarios concerning the structure of the a$_{1}$ (1260) meson. The Q 2 behavior of the model exclusive p ( γ ∗ , π $^{+}$) n reaction cross sections is in agreement with JLAB and deeply virtual HERMES data. are reproduced. Our principal result is that a longstand- ing problem concerning the description of the transverse and interference cross sections can be solved by the reso- nance/partonic effects in line of the DIS mechanism pro- posed in [25, 27]. However, the present model goes be- yond the two-component approach of [25, 27] and allows to treat the resonance/partonic contributions on the am- plitude level. The latter show up as a large transverse background contribution to the π quasi-elastic knockout mechanism. As in [25, 27], we find that at high values of Q 2 the resonances dominate in σ$_{T}$ . We have furthermore calculated the ratio of π − /π + cross sections which is of present interest in the dedi- cated experiments at JLAB. Model predictions for JLAB at 12 GeV are also provided. On the experimental side, the present results may be used as a guideline in the ex- perimental analysis of background contributions to the π quasi-elastic knockout mechanism. The latter is impor- tant for the extraction of the pion transition form factor to minimize systematic uncertainties. The contribution of resonances in the forward longitu- dinal response σ$_{L}$ is rather small and makes an experi- mental isolation of the pion-pole amplitude and the pion transition form factor in the region of Bjorken x$_{B}$ < 0 . 5 feasible. The interference pattern of the π -exchange and resonance contributions is sufficient to explain the sign and magnitude of the interference σ$_{TT}$ and σ$_{LT}$ cross sections measured at JLAB and DESY. The same res- onance/partonic mechanism is responsible for the posi- tive azimuthal beam SSA observed in p ( ⃗ e, e ′ π $^{+}$) n . On the contrary, the beam SSA in deep exclusive π − pro- This work was supported by DFG through the SFB/TR16. Acknowledgments