Q2 dependence of the S11(1535) photocoupling and evidence for a P -wave resonance in η electroproduction

OpenAlex · lv

New cross sections for the reaction $\mathit{ep}\ensuremath{\rightarrow}{e}^{'}\ensuremath{\eta}p$ are reported for total center-of-mass energy $W=1.5\text{\ensuremath{-}}2.3$ GeV and invariant squared momentum transfer ${Q}^{2}=0.13\text{\ensuremath{-}}3.3$ GeV${}^{2}$. This large kinematic range allows the extraction of new information about response functions, photocouplings, and $\ensuremath{\eta}N$ coupling strengths of baryon resonances. A sharp structure is seen at $W~1.7$ GeV. The shape of the differential cross section is indicative of the presence of a $P$-wave resonance that persists to high ${Q}^{2}$. Improved values are derived for the photocoupling amplitude for the ${S}_{11}$(1535) resonance. The new data greatly expand the ${Q}^{2}$ range covered, and an interpretation of all data with a consistent parametrization is provided.