Isospin Tracing: A Probe of Nonequilibrium in Central Heavy-Ion Collisions

Rami, F.; Leifels, Y.; Schauenburg, B. de; Gobbi, A.; Hong, B.; Alard, J. P.; Andronic, A.; Averbeck, R.; Barret, V.; Basrak, Z.; Bastid, N.; Belyaev, I.; Bendarag, A.; Berek, G.; Čaplar, R.; Cindro, N.; Crochet, P.; Devismes, A.; Dupieux, P.; Dželalija, M.; Eskef, M.; Finck, C.; Fodor, Z.; Folger, H.; Fraysse, L.; Genoux‐Lubain, A.; Grigorian, Y.; Grishkin, Y.; Herrmann, N.; Hildenbrand, K. D.; Kecskeméti, J.; Kim, Y. J.; Koczoń, P.; Kirejczyk, M.; Korolija, M.; Kötte, R.; Kowalczyk, M.; Kress, T.; Kutsche, R.; Lebedev, A.; Lee, K. S.; Manko, V.; Merlitz, Holger; Mohren, S.; Moisă, D.; Mösner, J.; Neubert, W.; Nianine, A.; Pelte, D.; Petrovici, M.; Pinkenburg, C.; Plettner, C.; Reisdorf, W.; Ritman, J.; Schüll, D.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek‐Wilczyńska, K.; Somov, A.; Stockmeier, M.; Stoicea, G.; Vasiliev, M. A.; Wagner, P.; Wiśniewski, K.; Wohlfarth, D.; Yang, Jing; Yushmanov, I. E.; Zhilin, A.

doi:10.1103/physrevlett.84.1120

Cited by 137 publications

(56 citation statements)

References 17 publications

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“…The degree of isospin equilibration can be quantified by rescaling the isospin asymmetry δ of a projectile-like residue from a specific collision according to the isospin transport ratio R i (δ) [6,9] given by ( )…”

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Isospin diffusion observables in heavy-ion reactions

et al. 2007

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Collisions of112 Sn and 124 Sn nuclei, which differ in their isospin asymmetry, provide information about the rate of isospin diffusion and equilibration. While several different probes can provide accurate diffusion measurements, the ratios of the mirror nuclei may be the simplest and most promising one. Ratios of the mass seven mirror nuclei yields are analyzed to show the rapidity, transverse momentum and impact parameter dependence of isospin diffusion. [4][5][6][7] for its determination. Recently, constraints on the density dependence of the symmetry energy were obtained from measurements of isospin diffusion in peripheral nuclear collisions [6,8]. In this paper, we identify a set of experimental observables, specifically observables constructed with yield ratios of mirror nuclei, that provide consistent measures of the isospin diffusion and extend those experimental investigations to a wider range of rapidity, transverse momentum and impact parameter.In a heavy ion collision involving a projectile and a target with different proton fractions, Z/A, the symmetry energy tends to propel the system towards isospin equilibrium so that the difference between neutron and proton densities is minimized [7].The isospin asymmetry A Z N − = δ of a projectile-like residue produced in a peripheral collision reflects the exchange of nucleons with the target; significant diffusion rates should lead to larger isospin asymmetries for collisions with neutron-rich targets and smaller isospin asymmetries for collisions with proton-rich targets [6].To isolate the isospin diffusion effects from similar effects caused by preequilibrium emission, Coulomb or sequential decays, relative comparisons involving different targets are important. In recent studies, isospin diffusion has been measured by "comparing" A+B collisions of a neutron-rich (A) nucleus and a proton-rich (B) nucleus to symmetric collisions involving two neutron-rich nuclei (A+A) and two proton-rich (B+B) nuclei under the same experimental conditions [6]. Non-isospin diffusion effects such as preequilibrium emission from a neutron-rich (A) projectile should be approximately the same for asymmetric A+B collisions as for symmetric A+A collisions. 2Similarly, non-isospin diffusion effects from a proton-rich (B) projectile in B+A collisions and B+B collisions should be the same.The degree of isospin equilibration can be quantified by rescaling the isospin asymmetry δ of a projectile-like residue from a specific collision according to the isospin transport ratio R i (δ) [6,9] given by ( )In the absence of isospin diffusion, the asymmetry B A+ δ of a residue of a neutron-rich projectile following a collision with a proton-rich target has the limiting values 1 ) (. On the other hand, if isospin equilibrum is achieved for roughly equal sized projectile and. By focusing on the differences in isospin observables between mixed and symmetric systems, R i (δ) largely removes the sensitivity to preequilibrium emission and enhances the sensitivity to isospin diffusion.Id...

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Isospin diffusion observables in heavy-ion reactions

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“…The problem is easily seen also in the case of the one-body density operator of Eq. (44). The elimination of the off-diagonal elements |φ 1 φ 2 | and |φ 2 φ 1 | does not much affect the energy conservation.…”

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confidence: 96%

Dynamics of clusters and fragments in heavy-ion collisions

Ono

2019

Progress in Particle and Nuclear Physics

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A review is given on the studies of formation of light clusters and heavier fragments in heavy-ion collisions at incident energies from several tens of MeV/nucleon to several hundred MeV/nucleon, focusing on dynamical aspects and on microscopic theoretical descriptions. Existing experimental data already clarify basic characteristics of expanding and fragmenting systems typically in central collisions, where cluster correlations cannot be ignored. Cluster correlations appear almost everywhere in excited low-density nuclear many-body systems and nuclear matter in statistical equilibrium where the properties of a cluster may be influenced by the medium. On the other hand, transport models to solve the time evolution have been developed based on the single-nucleon distribution function. Different types of transport models are reviewed putting emphasis both on theoretical features and practical performances in the description of fragmentation. A key concept to distinguish different models is how to consistently handle single-nucleon motions in the mean field, fluctuation or branching induced by two-nucleon collisions, and localization of nucleons to form fragments and clusters. Some transport codes have been extended to treat light clusters explicitly. Results indicate that cluster correlations can have strong impacts on global collision dynamics and correlations between light clusters should also be taken into account.

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“…Here, x is an isospin sensitive quantity that has to be investigated with respect to equilibration [147,3]. One can directly consider the asymmetry I = (N − Z)/A, but also other quantities, such as isoscaling coefficients, ratios of light fragment's yields, etc, can be of interest [3,4,148,126].…”

Section: Charge Equilibration In Peripheral Collision Dynamicsmentioning

confidence: 99%

Collision dynamics at medium and relativistic energies

Colonna

2020

Progress in Particle and Nuclear Physics

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Recent results connected to nuclear collision dynamics, from low up to relativistic energies, are reviewed. Heavy ion reactions offer the unique opportunity to probe the complex nuclear manybody dynamics and to explore, in laboratory experiments, transient states of nuclear matter under several conditions of density, temperature and charge asymmetry. From the theoretical point of view, transport models are an essential tool to undertake these investigations and make a connection betwen the nuclear effective interaction and sensitive observables of experimental interest. In this article, we mainly focus on the description of results of transport models for a selection of reaction mechanisms, also considering comparisons of predictions of different approaches. This analysis can help understanding the impact of the interplay between mean-field and correlation effects, as well as of in-medium effects, on reaction observables, which is an essential point also for extracting information on the nuclear Equation of State. A special emphasis will be given to the review of recent studies aimed at constraining the density behavior of the nuclear symmetry energy. For reactions at medium (Fermi) energies, we will describe light particle and fragment emission mechanisms, together with isospin transport effects. Collective effects characterizing nuclear collision dynamics, such as transverse and elliptic flows, will be discussed for relativistic heavy ion reactions, together with meson production and isotopic ratios.

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Isospin Tracing: A Probe of Nonequilibrium in Central Heavy-Ion Collisions

Cited by 137 publications

References 17 publications

Isospin diffusion observables in heavy-ion reactions

Isospin diffusion observables in heavy-ion reactions

Dynamics of clusters and fragments in heavy-ion collisions

Collision dynamics at medium and relativistic energies

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