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
04
The interaction region of high energy protons
I.M. Dremin🇷🇺 · S.N. White🇨🇭
The spatial view of the interaction region of colliding high energy protons (in terms of impact parameter) is considered. It is shown that the region of inelastic collisions has a very peculiar shape. It saturates for central collisions at an energy of 7 TeV. We speculate on the further evolution with energy, which is contrasted to the "black disk" picture.
↳ hep-phhep-exnucl-exnucl-th9 citations
05
A Rotation/Magnetism Analogy for the Quark-Gluon Plasma
Brett McInnes🇸🇬
In peripheral heavy ion collisions, the Quark-Gluon Plasma that may be formed often has a large angular momentum per unit energy. This angular momentum may take the form of (local) rotation. In many physical systems, rotation can have effects analogous to those produced by a magnetic field; thus, there is a risk that the effects of local rotation in the QGP might be mistaken for those of the large genuine magnetic fields which are also known to arise in these systems. Here we use the gauge-gravity duality to investigate this, and we find indeed that, with realistic parameter values, local rotation has effects on the QGP (at high values of the baryonic chemical potential) which are not only of the same kind as those produced by magnetic fields, but which can in fact be substantially larger. Furthermore, the combined effect of rotation and magnetism is to change the shape of the main quark matter phase transition line in an interesting way, reducing the magnitude of its curvature; again, local rotation contributes to this phenomenon at least as strongly as magnetism.
↳ hep-thhep-phnucl-thNPB(2016)·43 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

The interaction region of high energy protons

A Rotation/Magnetism Analogy for the Quark-Gluon Plasma

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