Nuclear Theory·nucl-th

Thursday·April 14, 2016

5 papers—3 primary·2 cross-listed

01
Theoretical study of photoproduction of $η^{'} N$ bound state on deuteron target with forward proton emission
Takayasu Sekihara (Osaka U., Res. Ctr. Nucl. Phys.)🇯🇵 · Shuntaro Sakai (Kyoto U.)🇯🇵 · Daisuke Jido (Tokyo Metropolitan U.)🇯🇵
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 sigma model with a coupling to $η n$ , in which an $s$ -wave $η^{'} n$ bound state can be dynamically generated, and we fix the $γ p \to η p$ and $η^{'} p$ scattering amplitudes so as to reproduce the experimental cross sections with forward proton emission. By using these $γ p \to η^{(')} p$ and $η^{(')} n \to η^{(')} n$ amplitudes, we calculate cross sections of the $γ d \to η n p$ and $η^{'} n p$ 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 $η n$ invariant mass spectrum of the $γ d \to η n p$ 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.
nucl-thhep-phnucl-exPRC(2016)·4 citations
02
Nondiffractive feature of $γ N \to ρ^{\pm} N$ with $ρ$ -meson electromagnetic multipole moments
Byung-Geel Yu🇰🇷 · Kook-Jin Kong🇰🇷
We investigate photoproduction of charged $ρ$ off the nucleon using $ρ (770) + π (140)$ Regge pole exchanges by considering the $ρ$ -meson electromagnetic multipole moments. The significance of the Ward identity at the $γ ρρ$ vertex is emphasized for current conservation in the process. Given $π$ exchange with the well-known coupling constants for $γ π ρ$ and $π N N$ , we analyze the role of the $ρ$ exchange in the $γ p \to ρ^{+} n$ and $γ n \to ρ^{-} p$ processes without model-dependences except for the magnetic moment $μ_{ρ^{\pm}} = \pm 2.01$ and electric quadrupole moment $Q_{ρ^{\pm}} = \pm 0.027$ fm $^{2}$ taken from theoretical estimates. The nondiffractive feature of both cross sections is reproduced with a rapid decrease beyond the resonance region by the dominance of $π$ exchange over the $ρ$ \,. % Cross sections for differential and density matrix elements are presented to compare with existing data. The parity and photon polarization asymmetries are predicted to demonstrate the apparent roles of the $ρ$ -meson electromagnetic multipole moments.
nucl-thhep-phPLB(2017)·6 citations
03
Mean-field instabilities and cluster formation in nuclear reactions
M. Colonna🇮🇹 · P. Napolitani🇫🇷 · V. Baran🇷🇴
We review recent results on intermediate mass cluster production in heavy ion collisions at Fermi energy and in spallation reactions. Our studies are based on modern transport theories, employing effective interactions for the nuclear mean-field and incorporating two-body correlations and fluctuations. Namely we will consider the Stochastic Mean Field (SMF) approach and the recently developed Boltzmann-Langevin One Body (BLOB) model. We focus on cluster production emerging from the possible occurrence of low-density mean-field instabilities in heavy ion reactions. Within such a framework, the respective role of one and two-body effects, in the two models considered, will be carefully analysed. We will discuss, in particular, fragment production in central and semi-peripheral heavy ion collisions, which is the object of many recent experimental investigations. Moreover, in the context of spallation reactions, we will show how thermal expansion may trigger the development of mean-field instabilities, leading to a cluster formation process which competes with important re-aggregation effects.
nucl-thnucl-ex5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Theoretical study of photoproduction of η′N bound state on deuteron target with forward proton emission

Nondiffractive feature of γN→ρ±N with ρ-meson electromagnetic multipole moments

Mean-field instabilities and cluster formation in nuclear reactions

Affiliations

Theoretical study of photoproduction of $η^{'} N$ bound state on deuteron target with forward proton emission

Nondiffractive feature of $γ N \to ρ^{\pm} N$ with $ρ$ -meson electromagnetic multipole moments