We calculate the single spin asymmetry for the ep→eΔ(1232) process, for an electron beam polarized normal to the scattering plane. Such single spin asymmetries vanish in the one-photon exchange approximation and are directly proportional to the absorptive part of a two-photon exchange amplitude. As the intermediate state in such a two-photon exchange process is on its mass shell, the asymmetry allows one to access for the first time the on-shell Δ→Δ as well as N∗→Δ electromagnetic transitions. We present the general formalism to describe the ep→eΔ beam normal spin asymmetry, and we provide a numerical estimate of its value using the nucleon, Δ(1232), S11(1535), and D13(1520) intermediate states. We compare our results with the first data from the Qweak@JLab experiment and give predictions for the A4@MAMI experiment.
Beam normal spin asymmetry for the ep âe Î (1232) process
Pasquini, BarbaraMembro del Collaboration Group
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2017-01-01
Abstract
We calculate the single spin asymmetry for the ep→eΔ(1232) process, for an electron beam polarized normal to the scattering plane. Such single spin asymmetries vanish in the one-photon exchange approximation and are directly proportional to the absorptive part of a two-photon exchange amplitude. As the intermediate state in such a two-photon exchange process is on its mass shell, the asymmetry allows one to access for the first time the on-shell Δ→Δ as well as N∗→Δ electromagnetic transitions. We present the general formalism to describe the ep→eΔ beam normal spin asymmetry, and we provide a numerical estimate of its value using the nucleon, Δ(1232), S11(1535), and D13(1520) intermediate states. We compare our results with the first data from the Qweak@JLab experiment and give predictions for the A4@MAMI experiment.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
