2024/06/18 by F. Afzal, C. S. Akondi, Afzal, F. +246
Physics and Astronomy · #Atomic and Molecular Physics #FOS: Physical sciences #Nuclear Experiment (nucl-ex) #Nuclear physics research studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2406.12829
openalex publication_date 2024/06/18 · openalex created_date 2024/06/20 · openalex updated_date 2026/07/31
We measure the spin-density matrix elements (SDMEs) of the Δ++(1232) in the photoproduction reaction γp → π-Δ++(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 GeV2. 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.