arXiv subjects

E. De Filippo

Publications and source records attributed to E. De Filippo.

At least 19 recordsLinked to original sources

arXiv2025

Evaluation of SiC detector performances for energy and timing measurements

The development of new detectors based on Silicon Carbide (SiC) is currently a topic of interest within the scientific community. The significant features of SiC make it highly promising for detecting charged particles, neutrons, and $γ$/X radiation. In this framework, within the SAMOTHRACE (Sicilian Micro and Nano Technology Research and Innovation Center) ecosystem, an array of new-generation SiC detectors is under development, specifically designed for nuclear and medical investigations using radioactive ion beams. This paper describes the results obtained in the characterization of SiC prototypes regarding energy and timing measurements. A new method, based on coincidence data analysis, is employed to evaluate the timing performances of SiC detectors. The obtained results have been compared with tests performed using a micro-channel plate as a start detector reference for timing measurements.

physics.ins-det↗

arXiv2024

Decay study of $^{11}$Be with an Optical TPC detector

The $β$ decay of one-neutron halo nucleus $^{11}$Be was investigated using the Warsaw Optical Time Projection Chamber (OTPC) detector to measure $β$-delayed charged particles. The results of two experiments are reported. In the first one, carried out in LNS Catania, the absolute branching ratio for $β$-delayed $α$ emission was measured by counting incoming $^{11}$Be ions stopped in the detector and the observed decays with the emission of $α$ particle. The result of 3.27(46)\% is in good agreement with the literature value. In the second experiment, performed at the HIE-ISOLDE facility at CERN, bunches containing several hundreds of $^{11}$Be ions were implanted into the OTPC detector followed by the detection of decays with the emission of charged particles. The energy spectrum of $β$-delayed $α$ particles was determined in the full energy range. It was analysed in the R-matrix framework and was found to be consistent with the literature. The best description of the spectrum was obtained assuming that the two $3/2^+$ and one $1/2^+$ states in $^{11}$B are involved in the transition. The search for $β$-delayed emission of protons was undertaken. Only the upper limit for the branching ratio for this process of $(2.2 \pm 0.6_{\rm stat} \pm 0.6_{\rm sys}) \times 10^{-6}$ could be determined. This value is in conflict with the result published in [Ayyad et al. Phys. Rev. Lett. 123, 082501 (2019)] but does agree with the limit reported in [Riisager et al., Eur. Phys. J. A (2020) 56:100]

nucl-ex↗

arXiv2023

Studies of the equation-of-state of nuclear matter by heavy-ion collisions at intermediate energy in the multi-messenger era

The study of the equation-of-state (EoS) describing the properties of nuclear matter away from the normal conditions is a relevant and intriguing topic of modern nuclear physics. The last decades have witnessed a substantial experimental progress in derivation of the symmetric matter term of the EoS and of the so-called symmetry energy for the asymmetric matter, especially at densities below the saturation point. But it is only in recent years that the opening of the multi-messenger astronomy era, triggered by detection of gravitational waves due to the neutron star mergers, has renewed and enlarged the interest in high-density EoS, being the main ingredient for determining the structure and properties of neutron stars. In this paper we review our knowledge obtained from heavy-ion collisions up to the 1 GeV/nucleon regime, on the EoS above nuclear saturation density. Special emphasis is given on the still few results on symmetry energy at high densities and their interconnections with multi-messenger astronomy findings.

nucl-ex↗

arXiv2022

Comprehensive investigation of fission yields by using spallation- and (p,2p)-induced fission reactions in inverse kinematics

In the last decades, measurements of spallation, fragmentation and Coulex induced fission reactions in inverse kinematics have provided valuable data to accurately investigate the fission dynamics and nuclear structure at large deformations of a large variety of stable and non-stable heavy nuclei. To go a step further, we propose now to induce fission by the use of quasi-free (p,2p) scattering reactions in inverse kinematics, which allows us to reconstruct the excitation energy of the compound fissioning system by using the four-momenta of the two outgoing protons. Therefore, this new approach might permit to correlate the excitation energy with the charge and mass distributions of the fission fragments and with the fission probabilities, given for the first time direct access to the simultaneous measurement of the fission yield dependence on temperature and fission barrier heights of exotic heavy nuclei, respectively. The first experiment based on this methodology was realized recently at the GSI/FAIR facility and a detailed description of the experimental setup is given here.

nucl-ex↗

arXiv2021

Electron-loss-to-continuum cusp in collisions of U$^{89+}$ with N$_{2}$ and Xe

We study the electron-loss-to-continuum (ELC) cusp experimentally and theoretically by comparing the ionization of U$^{89+}$ projectiles in collisions with N$_2$ and Xe targets, at a beam energy of 75.91 MeV/u. The coincidence measurement between the singly ionized projectile and the energy of the emitted electron is used to compare the shape of the ELC cusp at weak and strong perturbations. A significant energy shift for the centroid of the electron cusp is observed for the heavy target of Xe as compared to the light target of N$_2$. Our results provide a stringent test for fully relativistic calculations of double-differential cross sections performed in the first-order approximation and in the continuum-distorted-wave approach.

physics.atom-ph↗

arXiv2021

Symmetry energy at high densities from neutron/proton flow excitation functions

Determination of the high density behavior of the symmetry energy through the simultaneous measurement of elliptic flow excitation functions of neutrons, protons and light clusters is proposed. The elliptic flow developed in relativistic heavy ion collisions has been proven theoretically and experimentally to have a unique sensitivity and robustness in probing the symmetry energy up to around $2 ρ_{o}$. The knowledge of the density dependence of the symmetry energy in a broad range of densities will provide a missing link for astrophysical predictions of the neutron star mass--radius relation. In particular, the data colud provide tighter constraints on the slope parameter L and entirely new limits on $K_{sym}$, the currently poorly constrained symmetry energy curvature parameter.

nucl-ex↗

arXiv2019

Experimental nuclear astrophysics in Italy

Nuclear astrophysics, the union of nuclear physics and astronomy, went through an impressive expansion during the last twenty years. This could be achieved thanks to milestone improvements in astronomical observations, cross section measurements, powerful computer simulations and much refined stellar models. Italian groups are giving quite important contributions to every domain of nuclear astrophysics, sometimes being the leaders of worldwide unique experiments. In this paper we will discuss the astrophysical scenarios where nuclear astrophysics plays a key role and we will provide detailed descriptions of the present and future of the experiments on nuclear astrophysics which belong to the scientific programme of INFN (the National Institute for Nuclear Physics in Italy).

nucl-ex↗

arXiv2018

Isospin influence on dynamical production of Intermediate Mass Fragments at Fermi Energies

The Intermediate Mass Fragments emission probability from Projectile-Like Fragment break-up in semi-peripheral reactions has been measured in collisions of $^{124}$Xe projectiles with two different targets of $^{64}$Ni and $^{64}$Zn at the laboratory energy of 35 \amev. The two colliding systems differ only for the target atomic number Z and, consequently, for the Isospin $N/Z$ ratio. An enhancement of Intermediate Mass Fragments production for the neutron rich $^{64}$Ni target, with respect to the $^{64}$Zn, is found. In the case of one Intermediate Mass Fragment emission, the contributions of the dynamical and statistical emissions have been evaluated, showing that the increase of the effect above is due to an enhancement of the dynamical emission probability, especially for heavy IMFs (Z$\gtrsim$ 7). This proves an influence of the target Isospin on inducing the dynamical fragment production from Projectile-Like Fragment break-up. In addition, a comparison of the Xe+Ni,Zn results with the previously studied $^{112,124}Sn+^{58,64}Ni$ systems is discussed in order to investigate the influence of the projectile Isospin alone and to disentangle between Isospin effects against system-size effects on the emission probability. These comparisons suggest that the prompt-dynamical emission is mainly ruled by the $N/Z$ content of, both, projectile and target; for the cases here investigated, the influence of the system size on the dynamical emission probability can be excluded.

nucl-ex↗

arXiv2016

Results of the ASY-EOS experiment at GSI: The symmetry energy at suprasaturation density

Directed and elliptic flows of neutrons and light charged particles were measured for the reaction 197Au+197Au at 400 MeV/nucleon incident energy within the ASY-EOS experimental campaign at the GSI laboratory. The detection system consisted of the Large Area Neutron Detector LAND, combined with parts of the CHIMERA multidetector, of the ALADIN Time-of-flight Wall, and of the Washington-University Microball detector. The latter three arrays were used for the event characterization and reaction-plane reconstruction. In addition, an array of triple telescopes, KRATTA, was used for complementary measurements of the isotopic composition and flows of light charged particles. From the comparison of the elliptic flow ratio of neutrons with respect to charged particles with UrQMD predictions, a value γ= 0.72 \pm 0.19 is obtained for the power-law coefficient describing the density dependence of the potential part in the parametrization of the symmetry energy. It represents a new and more stringent constraint for the regime of supra-saturation density and confirms, with a considerably smaller uncertainty, the moderately soft to linear density dependence deduced from the earlier FOPI-LAND data. The densities probed are shown to reach beyond twice saturation.

nucl-ex↗

arXiv2016

Probing clustering in excited alpha-conjugate buclei

The fragmentation of quasi-projectiles from the nuclear reaction $^{40}$Ca+$^{12}$C at 25 MeV per nucleon bombarding energy was used to produce $α$-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 $α$-particle clustering from excited $^{16}O$, $^{20}Ne$ and $^{24}Mg$ is reported.

nucl-ex↗

arXiv2016

Alpha-particle clustering in excited expanding self-conjugate nuclei

The fragmentation of quasi-projectiles from the nuclear reaction 40Ca + 12C at 25 MeV/nucleon 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, strong indications in favour of $α$-particle clustering in excited 16O, 20Ne and 24}Mg are reported.

nucl-ex↗

arXiv2015

Freeze-out configuration properties in the 197Au + 197Au reaction at 23 AMeV

Data from the experiment on the 197Au + 197Au reaction at 23 AMeV are analyzed with an aim to find signatures of exotic nuclear configurations such as toroid-shaped objects. The experimental data are compared with predictions of the ETNA code dedicated to look for such configurations and with the QMD model. A novel criterion of selecting events possibly resulting from the formation of exotic freeze-out configurations, "the efficiency factor", is tested. Comparison between experimental data and model predictions may indicate for the formation of flat/toroidal nuclear systems.

nucl-ex↗

arXiv2015

Dipolar degrees of freedom and Isospin equilibration processes in Heavy Ion collisions

Background: In heavy ion collision at the Fermi energies Isospin equilibration processes occur- ring when nuclei with different charge/mass asymmetries interacts have been investigated to get information on the nucleon-nucleon Iso-vectorial effective interaction. Purpose: In this paper, for the system 48Ca +27 Al at 40 MeV/nucleon, we investigate on this process by means of an observable tightly linked to isospin equilibration processes and sensitive in exclusive way to the dynamical stage of the collision. From the comparison with dynamical model calculations we want also to obtain information on the Iso-vectorial effective microscopic interaction. Method: The average time derivative of the total dipole associated to the relative motion of all emitted charged particles and fragments has been determined from the measured charges and velocities by using the 4? multi-detector CHIMERA. The average has been determined for semi- peripheral collisions and for different charges Zb of the biggest produced fragment. Experimental evidences collected for the systems 27Al+48Ca and 27Al+40Ca at 40 MeV/nucleon used to support this novel method of investigation are also discussed.

nucl-ex↗

arXiv2014

Evidence for a Novel Reaction Mechanism of a Prompt Shock-Induced Fission Following the Fusion of 78Kr and 40Ca Nuclei at E/A =10 MeV

An analysis of experimental data from the inverse-kinematics ISODEC experiment on 78Kr+40Ca reaction at a bombarding energy of 10 AMeV has revealed signatures of a hitherto unknown reaction mechanism, intermediate between the classical damped binary collisions and fusion-fission, but also substantially different from what is being termed in the literature as fast fission or quasi fission. These signatures point to a scenario where the system fuses transiently while virtually equilibrating mass asymmetry and energy and, yet, keeping part of the energy stored in a collective shock-imparted and, possibly, angular momentum bearing form of excitation. Subsequently the system fissions dynamically along the collision or shock axis with the emerging fragments featuring a broad mass spectrum centered around symmetric fission, relative velocities somewhat higher along the fission axis than in transverse direction, and virtually no intrinsic spin. The class of massasymmetric fission events shows a distinct preference for the more massive fragments to proceed along the beam direction, a characteristic reminiscent of that reported earlier for dynamic fragmentation of projectile-like fragments alone and pointing to the memory of the initial mass and velocity distribution.

nucl-ex↗

arXiv2013

Experimental effects on dynamics and thermodynamics in nuclear reactions on the symmetry energy as seen by the CHIMERA 4$π$ detector

Heavy ion collisions have been widely used in the last decade to constraint the parameterizations of the symmetry energy term of nuclear equation of state (EOS) for asymmetric nuclear matter as a function of baryonic density. In the Fermi energy domain one is faced with variations of the density within a narrow range of values around the saturation density $ρ_0$=0.16 fm$^{-3}$ down towards sub-saturation densities. The experimental observables which are sensitive to the symmetry energy are constructed starting from the detected light particles, clusters and heavy fragments that, in heavy ion collisions, are generally produced by different emission mechanisms at different stages and time scales of the reaction. In this review the effects of dynamics and thermodynamics on the symmetry energy in nuclear reactions are discussed and characterized using an overview of the data taken so far with the CHIMERA multi-detector array.

nucl-ex↗

arXiv2012

Kinematical coincidence method in transfer reactions

A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematic is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of 10Be+p-->9Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained.

nucl-ex↗

arXiv2012

Correlations between isospin dynamics and Intermediate Mass Fragments emission time scales: a probe for the symmetry energy in asymmetric nuclear matter

We show new data from the $^{64}$Ni+$^{124}$Sn and $^{58}$Ni+$^{112}$Sn reactions studied in direct kinematics with the CHIMERA detector at INFN-LNS and compared with the reverse kinematics reactions at the same incident beam energy (35 A MeV). Analyzing the data with the method of relative velocity correlations, fragments coming from statistical decay of an excited projectile-like (PLF) or target-like (TLF) fragments are discriminated from the ones coming from dynamical emission in the early stages of the reaction. By comparing data of the reverse kinematics experiment with a stochastic mean field (SMF) + GEMINI calculations our results show that observables from neck fragmentation mechanism add valuable constraints on the density dependence of symmetry energy. An indication is found for a moderately stiff symmetry energy potential term of EOS.

nucl-ex↗

arXiv2012

The ASY-EOS experiment at GSI: investigating the symmetry energy at supra-saturation densities

The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich heavy-ions systems at intermediate energies has been proposed as an observable sensitive to the strength of the symmetry term in the nuclear Equation Of State (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011.

nucl-ex↗