Surveying the nuclear caloric curve

Abstract

International audienceThe 4π array INDRA was used to detect nearly all charged products emitted in Ar + Ni collisions between 52 and 95 MeV/u. The charge, mass and excitation energy E∗ of the quasi-projectiles have been reconstructed event by event. Excitation energies up to 25 MeV per nucleon are reached

Thermal bremsstrahlung photons probing the nuclear caloric curve

“…Our caloric curve disagrees, on the other hand, with the one obtained by the INDRA collaboration using kinetic temperatures [10], which follows closely the ǫ ⋆ ∼ T 2 trend. The kinetic T 's are systematically higher by about 1-2 MeV most likely due to the fact that the slope parameters of p and α kinetic energy spectra are influenced by preequilibrium and mid-rapidity emissions [33], and/or nucleon Fermi motion effects.…”

“…In the region ǫ ⋆ ≈ 3A -8A MeV, however, the curve flattens [1] suggesting a phase transition (the width of the "plateau" indicating the latent heat related to the phase change). Although such thermodynamical behaviour has also been observed in other microscopic systems such as metallic [8] and hydrogen [9] clusters, the empirical determination (and the theoretical interpretation) of the nuclear caloric curve has been a much debated issue the last years [1][2][3][4]10,11]. As a matter of fact, the three experimental methods employed so far to measure the temperatures attained in a reaction do not yield fully equivalent caloric curves.…”

Liquid-Gas Phase Transition in Nuclear Multifragmentation

“…In the past year, some of the caloric curves have been revised [67] and others including the original "caloric curve" data are being reanalyzed [10,105]. With more attention paid to the experimental problems associated with determining these curves, some of the discrepancies might be resolved in the near future.…”

Application of Information Theory in Nuclear Liquid Gas Phase Transition

“…However, due to the changing mass of Au spectators with excitation energy and the side-feeding effect to measured He-Li isotopic temperature, this conclusion is questionable [7]. Nuclear caloric curves were also surveyed by several groups [8]. However, unfortunately, the sharp signature of liquid gas phase transition in macroscopic systems may be smoothed and blurred due to the small numbers of nucleons in nuclei, and/or the difficulty to perform a direct comparison between the measured "apparent" temperature and the "real" temperature interferes obtaining the real nuclear caloric curve.…”