Spin observables for pion photoproduction on the deuteron in the Δ(1232)-resonance region

Abstract

Spin observables for the three charge states of the pion for the pion photoproduction reaction on the deuteron, γd → πN N , with polarized photon beam and/or oriented deuteron target are predicted. For the beam-target double-spin asymmetries, it is found that only the longitudinal asymmetries T ℓ 20 and T ℓ 2±2 do not vanish, whereas all the circular and the other longitudinal asymmetries do vanish. The sensitivity of spin observables to the model deuteron wave function is investigated. It has been found that only T 21 and T 22 are sensitive to the model deuteron wave function, in particular in the case of π 0 -production above the ∆-region, and that other asymmetries are not.

Incoherent pion photoproduction on the deuteron in the first resonance region

“…The predictions from Refs. [12,13] totally contradict our results both in the form of the angular distribution and in the absolute size at 250 and 350 MeV 4 . For instance, we observe a maximum around 130 • − 140 • at 250 and 350 MeV with T 11 ≃ 0.4 in the center of the peak, whereas in Refs.…”

“…For instance, we observe a maximum around 130 • − 140 • at 250 and 350 MeV with T 11 ≃ 0.4 in the center of the peak, whereas in Refs. [12,13] the vector asymmetry is close to zero at these energies for Θ π ≥ 90 • . We have no a reasonable explanation for this disagreement.…”

“…One should mention a strange result of Refs. [12,13] consisting in the statement that Σ does not vanish at Θ π = 0 and π, as it has to be because of helicity conservation [17,18]. Recently first preliminary data on the asymmetry Σ in the π 0 and π − channels at a few energies between 265 and 330…”

Incoherent pion photoproduction on the deuteron with polarization observables. I. Formal expressions

“…But also the results for circularly polarized photons are incorrect, namely the claim in Ref. [8] that all of them vanish identically is wrong. Moreover, this statement is in contradiction to Ref.…”

“…Thus, it is obvious that the importance of polarization effects requires a more careful and thorough treatment as done in Refs. [8][9][10][11][12].…”