L. Manduci

Characteristics of the fragments produced in central collisions of129Xe+natSnfrom 32Ato 50AMeV

Characteristics of the primary fragments produced in central collisions of 129Xe + natSn from 32 to 50 AMeV have been obtained. By using the correlation technique for the relative velocity between light charged particles (LCP) and fragments, we were able to extract the multiplicities and average kinetic energy of secondary evaporated LCP. We then reconstructed the size and excitation energy of the primary fragments. For each bombarding energy a constant value of the excitation energy per nucleon over the whole range of fragment charge has been found. This value saturates at 3 AMeV for beam energies 39 AMeV and above. The corresponding secondary evaporated LCP represent less than 40% of all produced particles and decreases down to 23% for 50 AMeV. The experimental characteristics of the primary fragments are compared to the predictions of statistical multifragmentation model (SMM) calculations. Reasonable agreement between the data and the calculation has been found for any given incident energy. However SMM fails to reproduce the trend of the excitation function of the primary fragment excitation energy and the amount of secondary evaporated LCPs.

Fragment charge correlations and spinodal decomposition in finite nuclear systems

Abstract.Enhanced production of events with almost equal-sized fragments is experimentally revealed by charge correlations in the multifragmentation of a finite nuclear system selected in 129Xe central collisions on natSn. The evolution of their weight with the incident energy: 32, 39, 45, 50 AMeV, is measured. Dynamical stochastic mean-field simulations performed at 32 AMeV, in which spinodal instabilities are responsible for multifragmentation, exhibit a similar enhancement of this kind of events. The above experimental observation evidences the spinodal decomposition of hot finite nuclear matter as the origin of multifragmentation in the Fermi energy regime.

Model-independent tracking of criticality signals in nuclear multifragmentation data

We look for signals of criticality in multifragment production in heavy-ion collisions using model-independent universal fluctuations theory. The phenomenon is studied as a function of system size, bombarding energy, and impact parameter in a wide range of INDRA data. For very central collisions (b/b_max<0.1) we find evidence that the largest fragment in each event, Z_max, plays the role of an order parameter, defining two different regimes at low and high incident energy, respectively, according to the scaling properties of its fluctuations. Data for a wide range of system masses and incident energies collapse on to an approximately universal scaling function in each regime for the most central collisions. The forms of the scaling functions for the two regimes are established, and their dependence on the total mass and the bombarding energy is mapped out. Data suggest that these regimes are linked to the disappearance of heavy residues in central collisions.

Multifragmentation process for different mass asymmetry in the entrance channel around the Fermi energy

Abstract The influence of the entrance channel mass asymmetry upon the fragmentation process is addressed by studying heavy-ion induced reactions around the Fermi energy. The data have been recorded with the INDRA 4 π array. An event selection method called the Principal Component Analysis is presented and discussed. It is applied for the selection of central events and furthermore to multifragmentation of single source events. The selected subsets of data are compared to the Statistical Multifragmentation Model (SMM) to check the equilibrium hypothesis and get the source characteristics. Experimental comparisons show the evidence of a decoupling between thermal and compressional (radial flow) component of the excitation energy stored in such nuclear systems.

In-medium effects for nuclear matter in the Fermi-energy domain

We study nuclear stopping in central collisions for heavy-ion induced reactions in the Fermi energy domain, between

Isospin diffusion in 58Ni-induced reactions at intermediate energies. I. Experimental results

15

New isospin effects in central heavy-ion collisions at Fermi energies

and

Nuclear multifragmentation time-scale and fluctuations of largest fragment size

100

Coulomb chronometry to probe the decay mechanism of hot nuclei

A\,\textrm{MeV}. Using the large dataset of exclusive measurements provided by the

Multifragmentation threshold in

4\pi