Coherent photoproduction of η-mesons on three-nucleon systems

Abstract

A microscopic few-body description of near-threshold coherent photoproduction of the η meson on tritium and 3 He targets is given. The photoproduction cross-section is calculated using the Finite Rank Approximation (FRA) of the nuclear Hamiltonian. The results indicate a strong final state interaction of the η meson with the residual nucleus. Sensitivity of the results to the choice of the ηN T -matrix is investigated. The importance of obeying the two-body unitarity condition in the ηN system is demonstrated.

Coherent photoproduction of η-mesons off 3He – search for η-mesic nuclei

“…Shevchenko and collaborators [66] have also calculated coherent η-production off the three-nucleon system in a microscopic few-body description. They find a strong dependence of the result on the elastic ηN rescattering, which is not sufficiently constrained by experiment.…”

Photoproduction of mesons off nuclei

“…Previous data from Pfeiffer et al [96]. Theory curves: (blue) dotted and dashed from Shevchenko et al [181] for two different versions of elastic ηN scattering, (red) solid (dash-dotted): Fix and Arenhövel [182] full model (plane wave), (black) long dash-dotted: Tiator et al [183]. Right hand side: excitation functions of π 0 −p back-to-back pairs for different ranges of the opening angle Ψπp after removal of the overall energy dependence ∝ E The left hand side of the figure shows the total cross section for the coherent γ 3 He → η 3 He reaction extracted from the two-photon and three-pion decays of the η-meson.…”

“…The model of Fix and Arenhövel, including final state interactions, reproduces a very steep slope at threshold, but does not agree with the magnitude of the cross section in that region. Also the models by Shevchenko et al [181] for two different versions of elastic ηN re-scattering show a steep rise at threshold; but can reproduce neither energy dependence nor magnitude of the data over a larger energy range. The differential cross section data (not shown), confirm also the previous finding.…”

η-PHOTOPRODUCTION OFF 3He: SEARCH FOR η-MESIC NUCLEI

“…A microscopic few-body description of near-threshold coherent photoproduction of the η meson o 3 He is given by N. Shevchenko [36]. The photoproduction cross section is calculated using the Finite Rank Approximation.…”

“…The problem of constructing the T-matrix t ηη corresponding to an η -N potential has no unique solution since the only experimental information consists of the S 11 resonance pole position and the η -N scattering length a ηN . The work of Shevchenko et al [36] uses two dierent versions of t ηη .…”