Measurement of target and double-spin asymmetries for the ep→eπ+(n) reaction in the nucleon resonance region at low Q2

Le résumé fourni par la source

We report measurements of target- and double-spin asymmetries for the exclusive channel $\stackrel{P\vec}{e}\stackrel{P\vec}{p}\ensuremath{\rightarrow}e{\ensuremath{\pi}}^{+}(n)$ in the nucleon resonance region at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). These asymmetries were extracted from data obtained using a longitudinally polarized ${\mathrm{NH}}_{3}$ target and a longitudinally polarized electron beam with energies 1.1, 1.3, 2.0, 2.3, and 3.0 GeV. The new results are consistent with previous CLAS publications but are extended to a low ${Q}^{2}$ range from 0.0065 to $0.35\phantom{\rule{4pt}{0ex}}{(\mathrm{GeV}/c)}^{2}$. The ${Q}^{2}$ access was made possible by a custom-built Cherenkov detector that allowed the detection of electrons for scattering angles as low as ${6}^{\ensuremath{\circ}}$. These results are compared with the unitary isobar models JANR and MAID, the partial-wave analysis prediction from SAID, and the dynamic model DMT. In many kinematic regions our results, in particular results on the target asymmetry, help to constrain the polarization-dependent components of these models.

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