Resonance dynamics in the coherent η meson production in the (p,p′) reaction on the spin–isospin saturated nucleus

Abstract

For the forward going proton and η meson, the coherent η meson production in the (p, p ′ ) reaction on the spin-isospin saturated nucleus occurs only due to the η meson exchange interaction between the beam proton and nucleus. In this process, the nucleon in the nucleus can be excited to resonances N * and the η meson in the final state can arise due to N * → N η. We investigate the dynamics of resonances, including nucleon Born terms, and their interferences in the coherently added cross section of this reaction. We discuss the importance of N (1520) resonance and show the sensitivity of the cross section to the hadron nucleus interaction.Keywords: η meson exchange interaction, N * propagation PACS number(s): 25.40e, 13.30.Eg, 13.60.LeThe coherent meson production in the nuclear reaction is a potential tool to investigate the resonance dynamics in the nucleus, as well as the meson nucleus interaction in the final state. Since the branching ratio of ∆(1232) → Nπ is ≃ 100% [1], the coherent pion production process has been used extensively to investigate the ∆ dynamics in the nucleus [2, 3]. This process in (γ, π) and (e, eπ) reactions is used to study the transverse N → ∆ excitation in the nucleus, where the coherent pion is produced away from the forward direction [4]. The forward emission of coherent pion is a probe for the longitudinal ∆ excitation which occur in the pion nuclear reaction [5].The coherent pion production is also studied in the proton and ion induced nuclear reaction [6,7]. The issue of ∆-peak shift in the nucleus [8] is resolved, as it occurs because of the coherent pion production [6, 7] which is not possible for proton target. The coherent pion production in the (p, n) [6] and ( 3 He, t) [7] reactions on the nucleus is shown to have one to one correspondence with that in the π + meson nucleus scattering [9,10]. For the forward going protons, the coherent pion production in the (p, p ′ ) reaction can be used to produce π 0 beam [11] which is analogous to tagged photon beam.The coherent η meson production in the nuclear reaction is another process which can be used to study the resonance dynamics in the nucleus. Amongst the resonances, N(1535) has large decay branching ratio (42%) in the Nη channel, i.e., Γ N (1535)→N η (m = 1535 MeV) 1 email: swapand@barc.gov.in

Hadron interferences in the proton-induced coherentη-meson-production reaction on a scalar-isovector nucleus

“…It is also shown in Ref. [17] that the contribution of N(1535) resonance to the considered reaction is the largest at low energy, i.e., ∼ 1 GeV, provided f ηN N (1520) is taken equal to 6.72. In multi-GeV region, the distinctly dominant contribution to the reaction (quoted above) arises due to N(1520) resonance.…”

“…In addition, this reaction can also be used to investigate the dynamics of Born terms and nucleonic resonances, similar to those presented in Ref. [17].…”

“…The importance of N(1520) resonance in the η meson production reaction is discussed in Ref. [17]. The earlier value of the coupling constant f ηN N (1520) was 6.72 where as the latest value of it is 9.98.…”

Forward coherent ω and ϕ mesons production in the photonuclear reaction on nuclei

“…The importance of the t-channel ω meson-exchange interaction in this reaction is elucidated in [9,10]. The contributions of the hadronic resonances to the coherently produced η meson in the proton nucleus collision have been explored [11], which reveal the dominant contribution to the coherent η meson production results from the decay of N(1520), specifically, at high energy. In search of η-mesic nucleus, the importance of N(1535) resonance is mentioned in the coherent η meson photoproduction from 3 He nucleus [12].…”