Theoretical study of photoproduction of anη′Nbound state on a deuteron target with forward proton emission

Abstract

Possibilities of observing a signal of an η n bound state are investigated by considering photoproductions of the η and η mesons on a deuteron target with forward proton emission. For this purpose, we take the η n interaction from the linear σ model with a coupling to ηn, in which an s-wave η n bound state can be dynamically generated, and we fix the γp → ηp and η p scattering amplitudes so as to reproduce the experimental cross sections with forward proton emission. By using these γp → η ( ) p and η ( ) n → η ( ) n amplitudes, we calculate cross sections of the γ d → ηnp and η np reactions with forward proton emission in single and η ( ) -exchange double-scattering processes. As a result, we find that the signal of the η n bound state can be seen below the η n threshold in the ηn invariant mass spectrum of the γ d → ηnp reaction and is comparable with the contribution from the quasifree η production above the η n threshold. We also discuss the behavior of the signal of the η n bound state in several experimental conditions and model parameters.

Possible η′d bound state and its s -channel formation in the γd→ηd reaction

“…according to Ref. [32]. These values reproduce the experimental cross sections with forward proton emission above the η ′ p threshold [41,42].…”

“…This resembles the case of photoproduction of the η ′ n bound state in the γd → ηnp reaction, as discussed in Ref. [32]. The reaction diagrams in Fig.…”

“…Experimentally, the existence of an η ′ N bound state is implied by near-threshold behavior of the total cross section of the π − p → η ′ n reaction [31]. It has been also pointed out that η ′ n bound state, if exists, can be observed in incoherent photoproduction off a deuteron target γd → ηnp [32].…”

“…Here we take the same approach taken in Ref. [32] to determine the γp → η ′ p amplitude. Namely, we calculate the scattering amplitude T γp→η ′ p as a function of E lab γ with the formula…”

Effect of the final state interaction of η′N on the η′ photoproduction off the nucleon

“…In such situations, we consider it very important to know the basic interactions of relevant mesons and nucleons, which is investigated theoretically in Refs. [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61]. To this end, in the present paper we investigate the η ′ photoproduction off a free nucleon with the finalstate interaction (FSI) between the η ′ meson and nucleon, which is the simplest process for the η ′ N interaction.…”