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experimental data here. 

An extension of the model to electroproduction is straightforward provided the Q $^{2}$-dependent transition form factors are defined. In Figure 4 we plot the trans- verse dσ$_{T}$/dt (left panel) and longitudinal dσ$_{L}$/dt (right panel) π + electroproduction data from JLAB and DESY (old data) scaled to the same values of Q 2 = 0 . 7 GeV 2 and W = 2 . 19 GeV [4]. The value of the momentum cut-off Λ$_{γππ}$ in the pion form factor, Eq. (14), is largely constrained by the magnitude of dσ$_{L}$/dt at forward an- gles. In the following the JLAB data are considered to be a guideline for fixing the model parameters. The dashed curves correspond to Λ 2 γππ = 0 . 46 GeV 2 and describe the contribution of the π -reggeon exchange only. The exchange of π dominates in dσ$_{L}$/dt at forward angles. However, in dσ$_{T}$/dt the π -exchange is not compatible with data and also vanishes in the forward direction. 

The dash-dotte d curves correspond to the gauged electric model with the on-shell Dirac form factor, see Eq. (15), 

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and exchange of ρ (770) /a$_{2}$ (1320) and a$_{1}$ (1260) Regge trajectories. In Eq. (42) the electric form factor G p E decreases linea rly as a function of Q 2 with respect to the magnetic f orm factor G p M with a node around Q 2 0 ≃ 8 GeV 2 [49] pr ovided µ$_{p}$G p $_{E}$/G p M = 1 − Q $^{2}$/Q2$_{0}$. On the other hand up t o ≃ 5 GeV 2 the magnetic form factor is a dipole G p M = µ$_{p}$ / (1 + Q $^{2}$/ 0 . 71GeV $^{2}$) 2 where µ$_{p}$ = 2 . 793 is the magnetic moment of the proton. 

As one can see, this model (dash-dotted curves) with the nucle on-pole (gauge invariance), vector and axial-vector me son-exchange Regge trajectories describes dσ$_{L}$/dt well an d grossly underestimates dσ$_{T}$/dt . Varia- tions of the cut -offs in the vector and axial-vector meson transition form factors do not improve the description. This preliminary comparison with data shows that being consistent with photoproduction the above simple exten- sion of the Regge model to electroproduction is not able to describe the data already at values of Q 2 as low as Q 2 ≃ 1 GeV $^{2}$. The discrepancies with data increase with increasing value of Q 2 [4]. 

Next, consider the resonance contributions using the transition form factors as defined in Eq. (31). We have two parameters at hand: the parameter β which is related to the level density of states and a parameter ξ describ- ing the average cut-off in the resonance transition form factors. All the exclusive p ( γ ∗ , π $^{+}$) n and n ( γ ∗ , π − ) p elec- troproduction data considered in this work from JLAB, DESY and Cornell to DIS region at HERMES can be well described by the choice β = 3 and ξ = 0 . 4. The formulae for the transition form factors given in (31) and (32) can be integrated and yield (for β = 3) 

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In Figure 5 we plot the Q 2 dependence of the absolute 

value of the transition form factor | F$_{s}$ ( Q $^{2}$, s ) | (dashed 

