Measurement of Spin-Density Matrix Elements in Delta⁺⁺(1232) photoproduction
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We measure the spin-density matrix elements (SDMEs) of the $\Delta^{++}(1232)$ in the photoproduction reaction $\gamma p \to \pi^-\Delta^{++}(1232)$ with the GlueX experiment in Hall D at Jefferson Lab. The measurement uses a linearly--polarized photon beam with energies from $8.2$ to $8.8$~GeV and the statistical precision of the SDMEs exceeds the previous measurement by three orders of magnitude for the momentum transfer squared region below $1.4$ GeV$^2$. The data are sensitive to the previously undetermined relative sign between couplings in existing Regge-exchange models. Linear combinations of the extracted SDMEs allow for a decomposition into natural and unnatural--exchange amplitudes. We find that the unnatural exchange plays an important role in the low momentum transfer region.
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Cited by 2 Pith papers
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First determination of vector and tensor couplings from polarized $\pi\Delta$ photoproduction
First extraction of complete NΔ vector and tensor couplings to ρ, b1, a2 from polarized πΔ photoproduction using a Regge model on GlueX data.
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Mechanisms of high energy polarized photoproduction of $\pi^{-}\Delta^{++}$
Regge amplitude fit to high-energy polarized pi- Delta++ photoproduction confirms pion dominance at small t and extracts pi N Delta coupling consistent with Delta decay plus first values for rho, b1, and a2 N Delta couplings.
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