Final-state NN-rescattering in spin asymmetries of reaction

Abstract

The role of the final-state N N -rescattering (N N -FSI) in the polarization observables of the inclusive reaction d(γ, π − )pp, involving polarization of the photon beam and/or the deuteron target, is investigated. Various single-and double-spin asymmetries are studied with respect to the influence of such interaction effect and numerical predictions are given for forthcoming experiments. It has been found that the effect of N N -FSI is quite important for the single-spin asymmetries Σ, T 20 , T 21 and T 22 and the double-spin asymmetry T ℓ 20 , whereas it is much less important for the vector target asymmetry T 11 and other beam-target double-polarization asymmetries. Furthermore, we found that the inclusion of the N N -FSI improves the description of the LEGS data for the linear photon asymmetry.

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

“…[13], which is different in case of pion production [see Eq. (12)] because of the additional pion degree of freedom in the final state, in particular its pseudovector character. In terms of the small t matrices as defined in Eq.…”

“…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].…”

“…Subsequently, various polarization asymmetries of the semi-exclusive differential cross section d( γ, π)N N were studied theoretically in a series of papers [8,9,10,11,12]. Unfortunately, many of the results presented there are based on incorrect expressions for polarization observables, because the formal expressions for them were taken in analogy from the corresponding expressions of deuteron photodisintegration [13].…”

“…Moreover, this statement is in contradiction to [10], where a non-vanishing differential spin asymmetry for circularly polarized photons is reported, because this asymmetry is proportional to the beam-target asymmetry T c 10 for circularly polarized photons and a vector polarized deuteron, which means that the latter does not vanish. Thus, it is obvious that the importance of polarization effects requires a more careful and thorough treatment as done in [8,9,10,11,12].…”

Beam-Target Spin Asymmetries in Exclusive Pion Photoproduction of Deuteron

“…Single-and double-spin asymmetries for pion photoproduction from the deuteron have been predicted in Ref. [7][8][9] without any kind of FSI effects. Arenhoevel and Fix [4] as well as Levchuk et al [5] have been studied the same reaction with particular emphasis to the extension to higher energies.…”