Experimental signals of phase transition

d'Agostino, Marco; Bruno, Matteo; Gulminelli, F.; Bougault, R.; Cannata, F.; CHOMAZ, P; Gramegna, F.; LENEIDRE, N; Moroni, Anna; Vannini, G.

doi:10.1016/s0375-9474(04)90334-x

Cited by 3 publications

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“…Similar to the other fluctuation observables, configurational energy fluctuations show a well pronounced peak at an excitation energy around 5 A.MeV. This general feature is apparent in Multics [40], Indra [43], Isis [45] and Nimrod [37] data. The only exception is EOS data [46] where this fluctuation appears monotonically decreasing.…”

Section: The Freeze Out Volume V F O Which Determines the Totalsupporting

confidence: 63%

“…The resulting fluctuation of E I σ 2 I = σ 2 k is shown for different Multics data in figure 6. The temperature has been estimated alternatively using isotopic thermometers or solving the kinetic equation of state and comes out to be in good agreement [40] with the general temperature systematics [44] (around 4.5 MeV in the fragmentation region). Similar to the other fluctuation observables, configurational energy fluctuations show a well pronounced peak at an excitation energy around 5 A.MeV.…”

Section: The Freeze Out Volume V F O Which Determines the Totalmentioning

confidence: 69%

“…One of the most interesting aspects of studying fluctuation observables, is their possible connection with a susceptibility or a heat capacity via eq.(9). Configurational energy fluctuations have been studied at length by the Multics collaboration [38,39,40] and by the Indra collaboration [39,41,42,43] on Au sources. The observable used in these studies is an estimation of the energy stored in the configurational degrees of freedom at the time of fragment formation, defined as follows…”

Section: Configurational Energy Fluctuationsmentioning

confidence: 99%

“…The evaluation of systematic errors in fluctuation measurements is necessary to achieve a quantitative estimation of fluctuations: some first encouraging results in this direction have been presented in ref. [40]. The confirma- tion (or infirmation) of the fluctuation enhancement is certainly one of the most important challenges of the field in the next years with third generations multidetectors.…”

Section: The Freeze Out Volume V F O Which Determines the Totalmentioning

confidence: 99%

“…Configurational energy fluctuations are especially interesting because of their possible connection with a heat capacity measurement. The methodology to extract such fluctuations from fragmentation data is presently under debate, in particular a careful analysis of systematic errors is presently undertaken [40]. From a more conceptual point of view, the influence of the different time scales in the reaction dynamics has to be clarified.…”

Section: Conclusion and Outlooksmentioning

confidence: 99%

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Fluctuations of fragment observables

Gulminelli

D’Agostino

2006

Eur. Phys. J. A

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This contribution presents a review of our present theoretical as well as experimental knowledge of different fluctuation observables relevant to nuclear multifragmentation. The possible connection between the presence of a fluctuation peak and the occurrence of a phase transition or a critical phenomenon is critically analyzed. Many different phenomena can lead both to the creation and to the suppression of a fluctuation peak. In particular, the role of constraints due to conservation laws and to data sorting is shown to be essential. From the experimental point of view, a comparison of the available fragmentation data reveals that there is a good agreement between different data sets of basic fluctuation observables, if the fragmenting source is of comparable size. This compatibility suggests that the fragmentation process is largely independent of the reaction mechanism (central versus peripheral collisions, symmetric versus asymmetric systems, light ions versus heavy ion induced reactions). Configurational energy fluctuations, that may give important information on the heat capacity of the fragmenting system at the freeze out stage, are not fully compatible among different data sets and require further analysis to properly account for Coulomb effects and secondary decays. Some basic theoretical questions, concerning the interplay between the dynamics of the collision and the fragmentation process, and the cluster definition in dense and hot media, are still open and are addressed at the end of the paper. A comparison with realistic models and/or a quantitative analysis of the fluctuation properties will be needed to clarify in the next future the nature of the transition observed from compound nucleus evaporation to multi-fragment production.

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Section: The Freeze Out Volume V F O Which Determines the Totalsupporting

confidence: 63%

Section: The Freeze Out Volume V F O Which Determines the Totalmentioning

confidence: 69%

Section: Configurational Energy Fluctuationsmentioning

confidence: 99%

Section: The Freeze Out Volume V F O Which Determines the Totalmentioning

confidence: 99%

Section: Conclusion and Outlooksmentioning

confidence: 99%

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Fluctuations of fragment observables

Gulminelli

D’Agostino

2006

Eur. Phys. J. A

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Fluctuations of fragment observables

Gulminelli

D’Agostino

Dynamics and Thermodynamics With Nuclear Degrees of Freedom

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Abstract. This contribution presents a review of our present theoretical as well as experimental knowledge of different fluctuation observables relevant to nuclear multifragmentation. The possible connection between the presence of a fluctuation peak and the occurrence of a phase transition or a critical phenomenon is critically analyzed. Many different phenomena can lead both to the creation and to the suppression of a fluctuation peak. In particular, the role of constraints due to conservation laws and to data sorting is shown to be essential. From the experimental point of view, a comparison of the available fragmentation data reveals that there is a good agreement between different data sets of basic fluctuation observables, if the fragmenting source is of comparable size. This compatibility suggests that the fragmentation process is largely independent of the reaction mechanism (central versus peripheral collisions, symmetric versus asymmetric systems, light ions versus heavy ion induced reactions). Configurational energy fluctuations, that may give important information on the heat capacity of the fragmenting system at the freeze out stage, are not fully compatible among different data sets and require further analysis to properly account for Coulomb effects and secondary decays. Some basic theoretical questions, concerning the interplay between the dynamics of the collision and the fragmentation process, and the cluster definition in dense and hot media, are still open and are addressed at the end of the paper. A comparison with realistic models and/or a quantitative analysis of the fluctuation properties will be needed to clarify in the next future the nature of the transition observed from compound nucleus evaporation to multi-fragment production. Fluctuations and phase transitionsSince the first inclusive heavy ion experiments, multifragmentation has been tentatively associated to a phase transition or a critical phenomenon. This expectation was triggered by the first pioneering theoretical studies of the nuclear phase diagram [1] which contains a coexistence region delimited, at each temperature below an upper critical value, by two critical points at different asymmetries [2,3].Even more important, the first exclusive multifragmentation studies have shown that multifragmentation is a threshold process occurring at a relatively well defined deposited energy [4,5,6,7]. The wide variation of possible fragment partitions naturally leads to important fluctuations of the associated partition sizes and energies.Different observables have been proposed to measure such fluctuations. Using the general definition of the n−th moment asthe variance of the charge distribution is measured by the second moment M 2 or by the normalized quantity[8]:The root mean square fluctuation per particleof the distribution of the largest fragment Z m detected in each event completes the information. We will also consider the total fluctuationand the fluctuationof the configurational energy per particle associated to each fragme...

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Progress of quantum molecular dynamics model and its applications in heavy ion collisions

Zhang

Wang

et al. 2020

Front. Phys.

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In this review article, we first briefly introduce the transport theory and quantum molecular dynamics model applied in the study of the heavy ion collisions from low to intermediate energies.The developments of improved quantum molecular dynamics model (ImQMD) and ultra-relativistic quantum molecular dynamics model (UrQMD), are reviewed. The reaction mechanism and phenomena related to the fusion, multinucleon transfer, fragmentation, collective flow and particle production are reviewed and discussed within the framework of the two models. The constraints on the isospin asymmetric nuclear equation of state and in-medium nucleon-nucleon cross sections by comparing the heavy ion collision data with transport models calculations in last decades are also discussed, and the uncertainties of these constraints are analyzed as well. Finally, we discuss the future direction of the development of the transport models for improving the understanding of the reaction mechanism, the descriptions of various observables, the constraint on the nuclear equation of state, as well as for the constraint on in-medium nucleon-nucleon cross sections.

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Experimental signals of phase transition

Cited by 3 publications

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Fluctuations of fragment observables

Fluctuations of fragment observables

Fluctuations of fragment observables

Progress of quantum molecular dynamics model and its applications in heavy ion collisions

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