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15 pages, 6 figures, accepted in Physics Letters BInternational audienceThe fragmentation of quasi-projectiles from the nuclear reaction $^{40}$Ca+$^{12}$C at 25 MeV per nucleon bombarding energy was used to produce $\alpha$-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, evidence in favor of $\alpha$-particle clustering from excited $^{16}O$, $^{20}Ne$ and $^{24}Mg$ is reported

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

Abstract. The goal of the FAZIA Collaboration is the design of a new-generation 4π detector array for heavy-ion collisions with radioactive beams. This article summarizes the main results of the R&D phase, devoted to the search for significant improvements of the techniques for charge and mass identification of reaction products. This was obtained by means of a systematic study of the basic detection module, consisting of two transmission-mounted silicon detectors followed by a CsI(Tl) scintillator. Significant improvements in ΔE-E and pulse-shape techniques were obtained by controlling the doping homogeneity and the cutting angles of silicon and by putting severe constraints on thickness uniformity. Purposely designed digital electronics contributed to identification quality. The issue of possible degradation related to radiation damage of silicon was also addressed. The experimental activity was accompanied by studies on the physics governing signal evolution in silicon. The good identification quality obtained with the prototypes during the R&D phase, allowed us to investigate also some aspects of isospin physics, namely isospin transport and odd-even staggering. Now, after the conclusion of the R&D period, the FAZIA Collaboration has entered the demonstrator phase, with the aim of verifying the applicability of the devised solutions for the realization of a larger-scale experimental set-up.

The prompt γ -ray emission is investigated in the 16 A MeV energy region by means of the 36,40Ar + 96,92Zr fusion reactions leading to a compound nucleus in the vicinity of 132Ce. The dynamical nature\ud of this radiation is confirmed. We show that the prompt γ radiation has an angular distribution pattern\ud consistent with a dipole oscillation along the symmetry axis of the dinuclear system. The data are\ud compared with calculations based on a collective bremsstrahlung analysis of the reaction dynamics

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High-energy γ rays and light charged particles from the 36Ar + 96Zr and 40Ar + 92Zr reactions at Elab = 16\ud and 15.1 MeV/nucleon, respectively, were measured in coincidence with evaporation residues by means of the\ud MEDEA multidetector array coupled to four parallel plate avalanche counters. The aim of this experiment was to\ud investigate the prompt γ radiation, emitted in the decay of the dynamical dipole mode, in the about 16 MeV/nucleon\ud energy range and to map its beam energy dependence, comparing the present results with our previous ones\ud obtained at lower energies. The studied reactions populate, through entrance channels having different charge\ud asymmetries, a compound nucleus in the region of Ce under the same conditions of excitation energy and spin.\ud Light charged particle energy spectra were used to pin down the average excitation energy and the average mass\ud of the system. By studying the γ -ray spectra of the charge symmetric reaction 40Ar + 92Zr, the statistical giant\ud dipole resonance (GDR) parameters and angular distribution were extracted, and a comparison of the linearized\ud 90◦γ -ray spectra of the two reactions revealed a 12% extra yield in the GDR energy region for the more charge\ud asymmetric system. The center-of-mass angular distribution data of this extra γ yield, compatible with a dipole\ud oscillating along the symmetry axis of the dinuclear system, support its dynamical nature. The experimental\ud findings are compared with theoretical predictions performed within a Boltzmann-Nordheim-Vlasov transport\ud model and based on a collective bremsstrahlung analysis of the entrance channel reaction dynamics.An interesting\ud sensitivity to the symmetry term of the equation of state and to in-medium effects on nucleon-nucleon (nn) cross\ud sections is finally discussed

40 Ca+ 40,48 Ca, 46 Ti reactions at 25 MeV/A have been studied using the 4π CHIMERA detector. An isospin effect on the competition between incomplete fusion and dissipative binary reaction mechanisms has been observed. The probability of producing a compound system is observed to be lower in the case of N≈Z colliding systems as compared to the case of reactions induced on the more neutron rich 48 Ca target. Predictions based on CoMD-II calculations show that the competition between fusion-like and dissipative reactions, for the selected centrality, can strongly constraint the parameterization of symmetry energy and its density dependence in the nuclear equation of state.Pacs: 21.65. Ef, 21.65.Mn, 25.70.Jj, 25.70.Lm Collisions between heavy ions with different neutronproton asymmetries offer a unique opportunity to study the equation of state (EOS) of asymmetric nuclear matter [1][2][3][4]. Accessing the density dependence of the symmetry energy has recently attracted the interest of the community due to its implications in both nuclear physics and astrophysics of neutron stars [2,5,6]. The isotopic composition of fragments produced in multifragmentation phenomena is being extensively studied at intermediate beam energies (E/A=20-100 MeV) bearing important information on the symmetry energy [7]. One aspect not yet fully investigated is represented by the effect of the isospin asymmetry on the fate of hot nuclear systems. The combined effects of the symmetry energy and of the repulsive Coulomb interaction can significantly affect the reaction mechanism and the rate of production of hot compound nuclei in heavy-ion reactions at low and intermediate energies [8][9]. The isospin N/Z-asymmetry can also play an important role in opening different decay channels for a hot nuclear system once this has been produced. In this respect, the limiting temperature of a nucleus is expected to depend on both its mass and its isotopic composition [10][11][12]. Experimentally, the observation of small isotopic effects on the temperatures of projectile spectators in relativistic heavy-ion collisions have been interpreted as a signal of no isospin dependence of nuclear limiting temperatures [13]. At lower beam energies, a mass and N/Z-asymmetry dependence in limiting temperatures have been explored by studying the population of the Giant Dipole Resonance (GDR) at high excitation energies [14]. A small difference in the limiting GDR excitation energy has been observed when comparing a symmetric N~Z system to a neutron rich system [15]. All these findings stimulate attempts to link N/Z effects on measured observables to the nuclear symmetry energy and its density dependence in the equation of state.In this work we explore isospin effects in heavy residue (HR) remnants produced in incomplete fusion reactions between projectile and targets with different N/Z asymmetries. The results on the competition between incomplete fusion and binary dissipative mechanisms are compared to simulations performed with a microscopic mode...