Cross section measurement of the exclusive single pion electroproduction for $Q^2<5$ GeV$^2$ from CLAS

The study of nucleon excitations is the key to our understanding of the effective degrees of freedom at different distance scales where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance takes place. The exclusive meson electroproduction off protons is a powerful tool to probe these effective degrees of freedom in excited nucleon states. During the last decade, a broad experimental program has been executed with the CLAS detector in Hall B at Jefferson Lab, to study the excited states of the proton using polarized electron beams and (un)polarized proton targets. In this talk, results of our latest analysis work will be presented for the reaction of $ep\to e^{\prime}n\pi^+$ at W=1.6-2.0GeV, and Q2=1.8-4.0GeV2. A preliminary extraction of the helicity amplitudes, A(1/2), A(3/2), and S(1/2) will be also presented for the N(1680)5/2+ and the N(1720)3/2+ states, in particular. Result of this new analysis as well as ongoing work on the $p\pi^0$ and $p\pi^+\pi^-$ channels in similar kinematics, will allow for the determination of electro-couplings of several high-lying excited proton states (W$>$1.6GeV) at distances where quark degrees of freedom become increasingly important and eventually dominant as photon virtuality increase.