P. Lautesse

Evidence for Spinodal Decomposition in Nuclear Multifragmentation

Multifragmentation of a fused system was observed for central collisions between 32 MeV/nucleon 129Xe and (nat)Sn. Most of the resulting charged products were well identified due to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but nonambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a fossil signal of spinodal instabilities in finite nuclear systems.

Bimodal behavior of the heaviest fragment distribution in projectile fragmentation.

The charge distribution of the heaviest fragment detected in the decay of quasiprojectiles produced in intermediate energy heavy-ion collisions has been observed to be bimodal. This feature is expected as a generic signal of phase transition in nonextensive systems. In this Letter, we present new analyses of experimental data from Au on Au collisions at 60, 80, and 100 MeV/nucleon showing that bimodality is largely independent of the data selection procedure and of entrance channel effects. An estimate of the latent heat of the transition is extracted.

Evidence for α-particle condensation in nuclei from the Hoyle state deexcitation

Abstract The fragmentation of quasi-projectiles from the nuclear reaction 40Ca + 12C at 25 MeV/nucleon was used to produce excited states candidates to α-particle condensation. Complete kinematic characterization of individual decay events, made possible by a high-granularity 4π charged particle multi-detector, reveals that 7.5 ± 4.0 % of the particle decays of the Hoyle state correspond to direct decays in three equal-energy α-particles.

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.

Long Fission Times of Super‐Heavy Compound Nuclei

The blocking technique in single crystals is a direct method to investigate the presence of long fission time components. With a lead beam impinging on a germanium single crystal, we tried to produce compound nuclei (CN) with atomic number Z = 114 at high excitation energy. Blocking patterns for reaction products are reconstructed with position sensitive detectors at 20 ° relative to the beam direction. The Z and the energies of all products are measured with DeltaE-E telescopes of the 4pi INDRA array, so that all reaction channels are unambiguously identified. With this setup, we can reach long fission times (>10−18 s) that can be associated with CN fissions. However, in contrast to previous experiments in which such long fission times could be measured for Z = 120 and 124, no hint of long lifetimes within our sensitivity limit for Z = 114 was observed, which may be due to the neutron deficiency of the formed isotopes.This paper generalizes the classification in a paper of Dimitrov and Penkov of Borel subalgebras of gl_infty. Root-reductive Lie algebras are direct limits of finite-dimensional reductive Lie algebras along inclusions preserving the root spaces with respect to nested Cartan subalgebras. A Borel subalgebra of a root-reductive Lie algebra is by definition a maximal locally solvable subalgebra. The main general result of this paper is that a Borel subalgebra of an infinite-dimensional indecomposable root-reductive Lie algebra is the simultaneous stabilizer of a certain type of generalized flag in each of the standard representations. For the three infinite-dimensional simple root-reductive Lie algebras more precise results are obtained. The map sending a maximal closed (isotropic) generalized flag in the standard representation to its stabilizer hits Borel subalgebras, yielding a bijection in the cases of sl_infty and sp_infty; in the case of so_infty the fibers are of size one and two. A description is given of a nice class of toral subalgebras contained in any Borel subalgebra. Finally, certain Borel subalgebras of a general root-reductive Lie algebra are seen to correspond bijectively with Borel subalgebras of the commutator subalgebra, which are understood in terms of the special cases.

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

Isospin diffusion in semi-peripheral collisions is probed as a function of the dissipated energy by studying two systems

Yield scaling, size hierarchy and fluctuations of observables in fragmentation of excited heavy nuclei

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

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Fragment properties of fragmenting heavy nuclei produced in central and semi-peripheral collisions

^{58}Ni

Multi-particle correlation function to study short-lived nuclei

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