Exclusive $\ddot{\mathbf{I}}{€}^0\mathbf{p}$ electroproduction off protons in the resonance region at photon virtualities 0.4~GeV${}^2$ $\le {\mathbf{Q}}^2\le 1$~GeV${}^2$

Abstract

The exclusive electroproduction process $ep\to e^{\prime }{p}^{\prime }\ddot{I}{€}^0$ was measured in the range of photon virtualities $Q^2=0.4-1.0$~GeV${}^2$ and the invariant mass range of the $p\ddot{I}{€}^0$ system of $W=1.1-1.8$~GeV. These kinematics are covered in exclusive $\ddot{I}{€}^0$ electroproduction off the proton with nearly complete angular coverage in the $p\ddot{I}{€}^0$ center-of-mass system and with high statistical accuracy. Nearly 36000 cross section points were measured, and the structure functions $\ddot{I}{ƒ}_T+\hat{I}\mu \ddot{I}{ƒ}_L$, $\ddot{I}{ƒ}_{LT}$, and $\ddot{I}{ƒ}_{TT}$, were extracted via fitting the $\ddot{I}{•}_{\ddot{I}{€}^0}$ dependence of the cross section. A Legendre polynomial expansion analysis demonstrates the sensitivity of our data to high-lying $N^{\ast }$ and $\hat{I}{”}^{\ast }$ resonances with $M>1.6$ GeV. As part of a broad effort to determine the electrocouplings of the $N^{\ast }$ and $\hat{I}{”}^{\ast }$ resonances using both single- and double-pion electroproduction, this dataset is crucial for the reliable extraction of the high-lying resonance electrocouplings from the combined isospin analysis of the $N\ddot{I}€$ and $\ddot{I}{€}^{+}\ddot{I}{€}^{-}p$ channels.

21 pages, 24 figures