Determination of the freeze-out temperature by the isospin thermometer

Abstract

The high-resolution spectrometer FRS at GSI, Darmstadt, provides the full isotopic and kinematical identification of fragmentation residues in relativistic heavy-ion collisions. Recent measurements of the isotopic distribution of heavy projectile fragments led to a very surprising new physical finding: the residue production does not lose the memory of the N/Z of the projectile ending up in a universal de-excitation corridor; an ordering of the residues in relation to the neutron excess of the projectile has been observed. These unexpected features can be interpreted as a new manifestation of multifragmentation. We have found that at the last stage of the reaction the temperature of the big clusters subjected to evaporation is limited to a universal value. The thermometer to measure this limiting temperature is the neutron excess of the residues.

Pairing-energy coefficients of neutron-rich fragments in spallation reactions

“…The fragments in the reactions analyzed above have neutron excesses of more than 20. In the 0.2A GeV 136 Xe +p [45], 0.5A GeV 136 Xe +p [46], 136 Xe + d [47], and 1A GeV 136 Xe +p [48] spallation reactions, fragments with I = 10 to 24 have been measured depicted in Fig. 4.…”

Mean-Field Instabilities and Cluster Formation in Nuclear Reactions

“…The simulation, relying on the BLOB model, 60 is compared to several experimental data measured at FRS (Darmstadt) for fragments produced in proton/deuteron-induced spallation and for fragments emitted by spectator sectors in relativistic peripheral ion-ion collisions. [61][62][63][64][65] clustering, counterbalanced by mean-field resilience effects, in hot (but not initially diluted) sources, such as the nuclear systems formed in spallation reactions. From these results it clearly emerges the important role of many-body correlations even in describing processes which are driven by mean-field instabilities.…”

“…10 for the isotopic component of the nuclide production in p+ 124 Xe, 136 Xe, 208 Pb at 1AGeV. [61][62][63][64][65] In particular, it is shown that the isotopic content of the lightest IMFs evolves in time from approximately the value of the target to a value which approaches but does not reach the residue corridor. 66 This effect 67 and the collapsing of all datasets on the same ridge for a given isotopic content is a well known signature of the presence of a limiting temperature in the disassembling of the system, in connection with the liquid-gas phase transition of nuclear matter.…”

“…Fig.10.Study of the evolution in time of the isotopic content of fragments produced in three spallation systems at relativistic energy. The simulation, relying on the BLOB model,60 is compared to several experimental data measured at FRS (Darmstadt) for fragments produced in proton/deuteron-induced spallation and for fragments emitted by spectator sectors in relativistic peripheral ion-ion collisions [61][62][63][64][65]. …”

Production of hydrogen isotopes and charged pions in p (3.5 GeV) + Nb reactions

“…Thus, subsequent experimental [21] and theoretical [22,23] investigations were undertaken for these purposes. Furthermore, the emission of other products in spallation reactions, like pions [24], as well as complex heavy nuclei, were studied both experimentally [25][26][27] and theoretically [28][29][30][31]. In spite of these efforts, there remain problems which are not satisfactorily explained by existing models [32,33].…”