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M. Olivier Lopez

Chercheur CNRS

Groupe : Dynamique et thermodynamique nucléaire

lopezo in2p3.fr


Tel : +33 2 31 45 29 62



PUBLICATIONS

[hal-01582794] Isotopic identification using Pulse Shape Analysis of current signals from silicon detectors: Recent results from the FAZIA collaboration

7 septembre 2017

The FAZIA apparatus exploits Pulse Shape Analysis (PSA) to identify nuclear fragments stopped in the first layer of a Silicon-Silicon-CsI(Tl) detector telescope. In this work, for the first time, we show that the isotopes of fragments having atomic number as high as Z∼20 can be identified. Such (...)

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[in2p3-00867220] Coulomb chronometry to probe the decay mechanism of hot nuclei

13 mars 2017

In 129 Xe+ nat Sn central collisions from 8 to 25 MeV/A, the three-fragment exit channel occurs with a significant cross section. We show that these fragments arise from two successive binary splittings of a heavy composite system. The sequence of fragment production is determined. Strong (...)

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[in2p3-01348951] New semi-automatic method for reaction product charge and mass identification in heavy-ion collisions at Fermi energies

3 février 2017

This article presents a new semi-automatic method for charge and mass identification of charged nuclear fragments using either ∆E − E correlations between measured energy losses in two successive detectors or correlations between charge signal amplitude and rise time in a single silicon detector, (...)

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[hal-01438702] ParSys: a new particle system for the introduction of on-line physical behaviour to three-dimensional synthetic objects

18 janvier 2017

The incorporation of physical behaviour to synthetic objects constructed by computer is one of the main objectives of computer graphics research. In this paper we present a new interactive deformable model based on linked volumes. As such, it is straightforward and implicitly preserves the (...)

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[in2p3-01345974] Reaction and fusion cross sections for the near-symmetric system $^{129}$Xe+$^{nat}$Sn from $8$ to $35$ $AMeV$

20 octobre 2016

item[Background]Heavy-ion reactions from barrier up to Fermi energy. \item[Purpose]Reaction and fusion cross sections determination. Fusion reactions induced by $^129Xe$ projectiles on $^natSn$ targets for energies ranging from $8$ A.MeV to $35$ A.MeV were measured with the INDRA (...)

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[in2p3-01100158] Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems

6 juin 2016

We report experimental signals of Bose-Einstein condensation in the decay of hot Ca projectilelike sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4$\pi$ detector array to the forward angle VAMOS magnetic (...)

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[in2p3-01300455] Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems

11 avril 2016

We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA (...)

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[in2p3-01282609] Probing clustering in excited alpha-conjugate nuclei

30 mars 2016

The 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 (...)

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[in2p3-00013647] Transverse velocity scaling in $^{197}$Au+$^{197}$Au fragmentation

11 septembre 2015

Invariant transverse-velocity spectra of intermediate-mass fragments were measured with the 4-pi multi-detector system INDRA for collisions of Au on Au at incident energies between 40 and 150 MeV per nucleon. Their scaling properties as a function of incident energy and atomic number Z are used (...)

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[in2p3-01177619] The Billotron: a way to experimentally apprehend the subatomic world

18 juillet 2015

The Billotron is a device designed and built by the LPC Caen to illustrate the methods with which physicists are able to study the basic structure of matter, in particular the nucleus of the atom.

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[in2p3-01120218] Low-temperature technique of thin silicon ion implanted epitaxial detectors

4 juillet 2015

A new technique of large-area thin ion implanted silicon detectors has been developed within the R&D performed by the FAZIA Collaboration. The essence of the technique is the application of a lowtemperature baking process instead of high-temperature annealing. This thermal treatment is (...)

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[hal-00347268] Isospin diffusion in semi-peripheral $^{58}Ni$+$^{197}Au$ collisions at intermediate energies (I): Experimental results

3 juillet 2015

Isospin diffusion in semi-peripheral collisions is probed as a function of the dissipated energy by studying two systems $^58Ni$+$^58Ni$ and $^58Ni$+$^197Au$, over the incident energy range 52-74\AM. A close examination of the multiplicities of light products in the forward part of phase space (...)

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[hal-00112886] Bimodalities : a survey of experimental data and models

3 juillet 2015

Bimodal distributions of some chosen variables measured in nuclear collisions were recently proposed as a non ambiguous signature of a first order phase transition in nuclei. This section presents a compilation of both theoretical and experimental studies on bimodalities performed so far, in (...)

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[hal-00008225] Multifragmentation of very heavy nuclear systems (III): fragment velocity correlations and event topology at freeze-out.

3 juillet 2015

Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-field calculations, are successfully confronted with experimental data for single multifragmenting sources prepared at the same excitation energy per nucleon in 32 AMeV 129Xe+natSn and 36 AMeV (...)

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[hal-00008456] Estimate of average freeze-out volume in multifragmentation events

3 juillet 2015

An estimate of the average freeze-out volume for multifragmentation events is presented. Values of volumes are obtained by means of a simulation using the experimental charged product partitions measured by the 4pi multidetector INDRA for 129Xe central collisions on Sn at 32 AMeV incident (...)

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[hal-00004650] Bimodality as a signal of Liquid-Gas phase transition in nuclei?

3 juillet 2015

We use the HIPSE (Heavy-Ion Phase-Space Exploration) Model to discuss the origin of the bimodality in charge asymmetry observed in nuclear reactions around the Fermi energy. We show that it may be related to the important angular momentum (spin) transferred into the quasi-projectile before (...)

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[hal-00137572] New approach of fragment charge correlations in $^{129}$Xe+$^{nat}$Sn central collisions

3 juillet 2015

A previous analysis of the charge (Z) correlations in the $\Delta Z-$ plane for Xe+Sn central collisions at 32 MeV/u has shown an enhancement in the production of equally sized fragments (low $\Delta Z$) which was interpreted as an evidence for spinodal decomposition. However the signal is weak (...)

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[in2p3-01066044] In-medium effects for nuclear matter in the Fermi energy domain

3 juillet 2015

We study nuclear stopping in central collisions for heavy-ion induced reactions in the Fermi energy domain, between $15$ and $100$ A\,\textrmMeV. Using the large dataset of exclusive measurements provided by the $4\pi$ array \emphINDRA, we determine the relative degree of stopping as a function (...)

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[in2p3-00023603] Isotopic Scaling and the Symmetry Energy in Spectator Fragmentation

3 juillet 2015

Isotopic effects in the fragmentation of excited target residues following collisions of $^12$C on $^112,124$Sn at incident energies of 300 and 600 MeV per nucleon were studied with the INDRA 4$\pi$ detector. The measured yield ratios for light particles and fragments with atomic number $Z (...)

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[in2p3-00023600] Directed and elliptic flow in $^{197}$Au+$^{197}$Au at intermediate energies

3 juillet 2015

Directed and elliptic flow for the Au + Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4 pi multi-detector. For semi-central collisions, the elliptic flow of Z = 2 particles switches from in-plane to out-of-plane enhancement at around 100 MeV (...)

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[in2p3-00025576] Bimodality: a possible experimental signature of the liquid-gas phase transition of nuclear matter

3 juillet 2015

We have observed a bimodal behaviour of the distribution of the asymmetry between the charges of the two heaviest products resulting from the decay of the quasi-projectile released in binary Xe+Sn and Au+Au collisions from 60 to 100 MeV/u. Event sorting has been achieved through the transverse (...)

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[hal-00277843] Multifragmentation threshold in $^{93}Nb+${nat}Mg collisions at 30 MeV/nucleon

3 juillet 2015

We analyzed the $^93Nb$ on $^natMg$ reaction at $30$ MeV/nucleon in the aim of disentangling binary sequential decay and multifragmentation decay close to the energy threshold, i.e. $\simeq 3$ MeV/nucleon. Using the backtracing technique applied to the statistical models GEMINI and SMM we (...)

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[hal-00001474] Model-independent tracking of criticality signals in nuclear multifragmentation data

3 juillet 2015

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 (...)

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[in2p3-00171092] Yield scaling, size hierarchy and fluctuations of observables in fragmentation of excited heavy nuclei

3 juillet 2015

Multifragmentation properties measured with INDRA are studied for single sources produced in Xe+Sn reactions in the incident energy range 32-50 A MeV and quasiprojectiles from Au+Au collisions at 80 A MeV. A comparison for both types of sources is presented concerning Fisher scaling, Zipf law, (...)

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[in2p3-00023886] Neutron to proton ratios of quasiprojectile and midrapidity emission in the ${58}$Ni-${58}$Ni reaction at 52 MeV/Nucleon

3 juillet 2015

By combining data from a charged particle $^58$Ni+$^58$Ni experiment at 52 MeV/nucleon with an $^36$Ar+$^58$Ni experiment at 50 MeV/nucleon for which free neutrons have been detected, an increase in the neutron to proton ratio of the whole nuclear material at midrapidity has been experimentally (...)

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[hal-00821065] Constrained caloric curves and phase transition for hot nuclei

3 juillet 2015

Simulations based on experimental data obtained from multifragmenting quasi-fused nuclei produced in central $^129$Xe + $^nat$Sn collisions have been used to deduce event by event freeze-out properties in the thermal excitation energy range 4-12 AMeV [Nucl. Phys. A809 (2008) 111]. From these (...)

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Isospin effects and symmetry energy studies with INDRA

27 mars 2014

The equation of state of asymmetric nuclear matter is still controversial, as predictions at subsaturation as well as above normal density widely diverge. We discuss several experimental results measured in heavy-ion collisions with the INDRA array in the incident energy range 5-80AMeV. In (...)

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[in2p3-00966956] The FAZIA project in Europe: R&D phase

27 mars 2014

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 (...)

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Isospin transport in 84Kr + 112;124 Sn collisions at Fermi energies with the FAZIA detector

3 mars 2014

Isotopically resolved fragments up to Z 20 have been studied in a test experiment by the FAZIA Collaboration with a three-stage telescope. The reactions 84Kr+112Sn (n-poor) and 84Kr+124Sn (n-rich) at 35 MeV/nucleon were measured. The telescope was located near the grazing angle, so the detected (...)

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[in2p3-00951103] Energy measurement and fragment identification using digital signals from partially depleted Si detectors

24 février 2014

A study of identification properties of a Si-Si DE-E telescope exploiting an underdepleted residual-energy detector has been performed. Five different bias voltages have been used, one corresponding to full depletion, the others associated with a depleted layer ranging from 90% to 60% of the (...)

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[in2p3-00875063] Isospin effects and symmetry energy studies with INDRA

21 octobre 2013

The equation of state of asymmetric nuclear matter is still controversial, as predictions at subsaturation as well as above normal density widely diverge. We discuss several experimental results measured in heavy-ion collisions with the INDRA array in the incident energy range 5-80 MeV/nucleon. (...)

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[in2p3-00868032] N and Z odd-even staggering in Kr + Sn collisions at Fermi energies

1er octobre 2013

The odd-even staggering of the yield of final reaction products has been studied as a function of proton (Z) and neutron (N) numbers for the collisions 84 Kr+112 Sn and 84 Kr+124 Sn at 35 MeV/nucleon, in a wide range of elements (up to Z ~ 20). The experimental data show that staggering effects (...)

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Coulomb chronometry to probe the decay mechanism of hot nuclei

30 septembre 2013

In $^129$Xe+$^nat$Sn central collisions from 12 to 25 MeV/A, the three-fragment exit channel occurs with a significant cross section. We show that these fragments arise from two successive binary splittings of a heavy composite system. The sequence of fragment production is unambiguously (...)

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Coulomb chronometry to probe the decay mechanism of hot nuclei

27 septembre 2013

In $^129$Xe+$^nat$Sn central collisions from 12 to 25 MeV/A, the three-fragment exit channel occurs with a significant cross section. We show that these fragments arise from two successive binary splittings of a heavy composite system. The sequence of fragment production is unambiguously (...)

Lire la suite

Isospin transport in 84Kr+112,124Sn reactions at Fermi energies

10 septembre 2013

Isospin transport phenomena in dissipative heavy ion collisions have been investigated at Fermi energies with a beam of 84Kr at 35AMeV. A comparison of the /Z of light and medium products forward-emitted in the centre of mass frame when the beam impinges on a n-poor 112Sn and a n-rich 124Sn (...)

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The european FAZIA initiative: a high-performance digital telescope array for heavy-ion studies

6 septembre 2013

The european Fazia collaboration aims at building a new modular array for charged product identification to be employed for heavy-ion studies. The elementary module of the array is a Silicon-Silicon-CsI telescope, optimized for ion identification also via pulse shape analysis. The achievement (...)

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Nuclear stopping for heavy-ion induced reactions in the Fermi Energy range : from 1-Body to 2-Body dissipation

5 septembre 2013

We address the stopping in heavy-ion induced reactions around the Fermi energy using central collisions recorded with \emphINDRA $4\pi$ array. The stopping is minimal around the Fermi energy and corresponds to the disappearance of the Mean-Field effects and the appearance of nucleon-nucleon (...)

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Probing the statistical decay and alpha-clustering effects in 12c+12c and 14n+10b reactions

3 septembre 2013

An experimental campaign has been undertaken at INFN Laboratori Nazionali di Legnaro, Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation (...)

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Effects of irradiation of energetic heavy ions on digital pulse shape analysis with silicon detectors

29 août 2013

Detected energy, charge rise-time and pulse shape identfication capabilities of nTD silicon detectors under prolonged irradiation by energetic heavy ions have been studied. Sizeable effects on the amplitude and the risetime of the charge signal have been found for detectors irradiated with (...)

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The Fazia initiative: more powerful detectors for a more detailed investigation on the origin and the decay of charged fragments

29 août 2013

The main results of the R&D program of the FAZIA collaboration are described. The objective was to improve particle identication capabilities from solid-state telescopes made of Silicon detectors and CsI(Tl) scintillators in view of a new large acceptance apparatus to be used for heavy-ion (...)

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Constrained caloric curves and phase transition for hot nuclei

7 mai 2013

Simulations based on experimental data obtained from multifragmenting quasi-fused nuclei produced in central $^129$Xe + $^nat$Sn collisions have been used to deduce event by event freeze-out properties in the thermal excitation energy range 4-12 AMeV [Nucl. Phys. A809 (2008) 111]. From these (...)

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[in2p3-00782509] Effects of irradiation of energetic heavy ions on digital pulse shape analysis with silicon detectors

29 janvier 2013

The next generation of 4π detector arrays for heavy ion studies will largely use Pulse Shape Analysis to push the performance of silicon detectors with respect to ion identification. Energy resolution and pulse shape identification capabilities of silicon detectors under prolonged irradiation by (...)

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[in2p3-00778551] Isospin transport in 84Kr + 112,124Sn collisions at Fermi energies

21 janvier 2013

Isotopically resolved fragments with Z =20 have been studied with high resolution telescopes in a test run for the FAZIA collaboration. The fragments were produced by the collision of a 84Kr beam at 35 MeV/nucleon with a n-rich (124Sn) and a n-poor (112Sn) target. The fragments, detected close (...)

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[in2p3-00772111] A single-chip telescope for heavy-ion identification

10 janvier 2013

A ΔE-E telescope exploiting a single silicon chip for both ΔE measurement and scintillation light collection has been tested. It is a Si-CsI(Tl) telescope tailored for mass identification of light charged particles and intermediate mass fragments. A procedure based on two different shaping (...)

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[in2p3-00753651] Comparison of charged particle identification using pulse shape discrimination and ΔE−E methods between front and rear side injection in silicon detectors

22 novembre 2012

The response of silicon-silicon-CsI(Tl) telescopes, developed within the FAZIA collaboration, to fragments produced in nuclear reactions 84Kr+120-124Sn at 35 A MeV, has been used to study ion identification methods. Two techniques are considered for the identification of the nuclear products in (...)

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Neutron and charged particle identification by means of various detectors

11 septembre 2012

Identification methods for photons, neutrons and heavy ions by using scintillator and semiconductor detectors are discussed by stressing the advantages of signal digitization.

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The behaviour of constrained caloric curves as ultimate signature of a phase transition for hot nuclei

25 juillet 2012

Simulations based on experimental data obtained from multifragmenting quasifused nuclei produced in central 129Xe + natSn collisions have been used to deduce event by event freeze-out properties on the thermal excitation energy range 4-12 AMeV. From these properties and temperatures deduced (...)

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Transition from participant to spectator fragmentation in Au+Au reactions between 60A and 150A MeV

2 juillet 2012

Using the quantum molecular dynamics approach, we analyzed the results of the recent INDRA Collaboration Au+Au experiments at GSI in the energy range between 60A and 150A MeV. It turns out that in this energy region, the transition toward a participant-spectator scenario takes place. The large (...)

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Particle identification using the (DELTA)E-E technique and pulse shape discrimination with the silicon detectors of the FAZIA project

4 janvier 2012

The response of silicon-silicon-CsI(Tl) and silicon-CsI(Tl) telescopes to fragments produced in nuclear interactions has been studied. The telescopes were developed within the FAZIA collaboration. The capabilities of two methods are compared: (a) the standard ΔE-E technique and (b) the digital (...)

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[in2p3-00656422] Particle identification using the (DELTA)E-E technique and pulse shape discrimination with the silicon detectors of the FAZIA project

4 janvier 2012

The response of silicon-silicon-CsI(Tl) and silicon-CsI(Tl) telescopes to fragments produced in nuclear interactions has been studied. The telescopes were developed within the FAZIA collaboration. The capabilities of two methods are compared: (a) the standard ΔE-E technique and (b) the digital (...)

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Description of current pulses induced by heavy ions in silicon detectors (II)

20 avril 2011

Current pulses induced in a silicon detector by 10 different heavy ion species at known energies around 10 AMeV have been sampled in time at high frequency. Their individual average shapes are quite well reproduced by a fit procedure based on our recent charge carrier collection treatment which (...)

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[in2p3-00587352] Description of current pulses induced by heavy ions in silicon detectors (II)

20 avril 2011

Current pulses induced in a silicon detector by 10 different heavy ion species at known energies around 10 AMeV have been sampled in time at high frequency. Their individual average shapes are quite well reproduced by a fit procedure based on our recent charge carrier collection treatment which (...)

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Test of FAZIA prototypes at LNS.

31 janvier 2011

The response of a few silicon-silicon-CsI(Tl) and silicon-silicon telescopes with high quality detectors developed within the FAZIA collaboration [1] is tested in this work. The silicon detectors were manufactured from “random cut” wafers to avoid channeling effects and are characterized by a (...)

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[in2p3-00560905] Test of FAZIA prototypes at LNS.

31 janvier 2011

The response of a few silicon-silicon-CsI(Tl) and silicon-silicon telescopes with high quality detectors developed within the FAZIA collaboration [1] is tested in this work. The silicon detectors were manufactured from “random cut” wafers to avoid channeling effects and are characterized by a (...)

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Production of $\alpha$-particle condensate states in heavy-ion collisions

8 septembre 2010

The fragmentation of quasi-projectiles from the nuclear reaction $^40Ca$ + $^12C$ at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. The experiment was performed at LNS-Catania using the CHIMERA multidetector. Accepting the emission simultaneity (...)

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Production of $\alpha$-particle condensate states in heavy-ion collisions

8 septembre 2010

The fragmentation of quasi-projectiles from the nuclear reaction $^40Ca$ + $^12C$ at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. The experiment was performed at LNS-Catania using the CHIMERA multidetector. Accepting the emission simultaneity (...)

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Inférence statistique dans des modèles de moments conditionnels en présence de censure

24 juin 2010

Une large littérature statistique, biostatistique, économétrique, ... étudie l'inférence statistique (estimation et tests) dans des modèles semi paramétriques définis par des moments conditionnels lorsque les données sont censurées. La régression paramétrique classique ou quantile en présence d'une (...)

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Inférence statistique dans des modèles de moments conditionnels en présence de censure

24 juin 2010

Une large littérature statistique, biostatistique, économétrique, ... étudie l'inférence statistique (estimation et tests) dans des modèles semi paramétriques définis par des moments conditionnels lorsque les données sont censurées. La régression paramétrique classique ou quantile en présence d'une (...)

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Détection de rupture dans un modèle exponentiel

24 juin 2010

Nous considérons un modèle de rupture sur le paramètre d'un modèle exponentiel, qui est estimé par maximum de vraisemblance. Grâce à de nouvelles bornes exponentielles, nous obtenons des résultats à distance finie sur la qualité d'estimation de l'instant de rupture ainsi que de son (...)

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Détection de rupture dans un modèle exponentiel

24 juin 2010

Nous considérons un modèle de rupture sur le paramètre d'un modèle exponentiel, qui est estimé par maximum de vraisemblance. Grâce à de nouvelles bornes exponentielles, nous obtenons des résultats à distance finie sur la qualité d'estimation de l'instant de rupture ainsi que de son (...)

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Study of Nuclear Stopping in Central Collisions at Intermediate Energies

22 juin 2010

Nuclear stopping has been investigated in central nuclear collisions at intermediate energies by analyzing kinematically complete events recorded with the help of the 4π multidetector INDRA for a large variety of symmetric systems. It is found that the mean isotropy ratio defined as the ratio of (...)

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[in2p3-00494230] Study of Nuclear Stopping in Central Collisions at Intermediate Energies

22 juin 2010

Nuclear stopping has been investigated in central nuclear collisions at intermediate energies by analyzing kinematically complete events recorded with the help of the 4π multidetector INDRA for a large variety of symmetric systems. It is found that the mean isotropy ratio defined as the ratio of (...)

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Phase diagram of the charged lattice-gas model with two types of particles

17 juin 2010

A lattice-gas model with two types of particles, a particle-dependent short-range coupling and a long-range repulsive Coulombic interaction, is introduced. The phase diagram of an isolated finite system of 129 particles is constructed using the bimodality properties of the observables' (...)

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[in2p3-00492917] Phase diagram of the charged lattice-gas model with two types of particles

17 juin 2010

A lattice-gas model with two types of particles, a particle-dependent short-range coupling and a long-range repulsive Coulombic interaction, is introduced. The phase diagram of an isolated finite system of 129 particles is constructed using the bimodality properties of the observables' (...)

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Alpha-particle condensation in excited 12C

20 avril 2010

The fragmentation of quasi-projectiles from the nuclear reaction $^40Ca+^12C$ at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. The methodology relies on high granularity 4$\pi$ detection coupled to correlation function techniques. Under the (...)

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Alpha-particle condensation in excited 12C

20 avril 2010

The fragmentation of quasi-projectiles from the nuclear reaction $^40Ca+^12C$ at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. The methodology relies on high granularity 4$\pi$ detection coupled to correlation function techniques. Under the (...)

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A study of stopping power in nuclear reactions at intermediate energies

10 mars 2010

We show a systematic experimental study based on INDRA data of the stopping power in central symmetric nuclear reactions. Total mass of the systems goes from 80 to 400 nucleons while the incident energy range is from 12 AMeV to 100 AMeV. The role of isospin diffusion at 32 and 45 MeV/nucleon (...)

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A study of stopping power in nuclear reactions at intermediate energies

10 mars 2010

We show a systematic experimental study based on INDRA data of the stopping power in central symmetric nuclear reactions. Total mass of the systems goes from 80 to 400 nucleons while the incident energy range is from 12 AMeV to 100 AMeV. The role of isospin diffusion at 32 and 45 MeV/nucleon (...)

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Isospin diffusion in 58Ni-induced reactions at intermediate energies

4 mars 2010

Isospin diffusion is probed as a function of the dissipated energy by studying two systems $^58$Ni+$^58$Ni and $^58$Ni+$^197$Au, over the incident energy range 52-74\AM. Experimental data are compared with the results of a microscopic transport model with two different parameterizations of the (...)

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Isospin diffusion in 58Ni-induced reactions at intermediate energies

4 mars 2010

Isospin diffusion is probed as a function of the dissipated energy by studying two systems $^58$Ni+$^58$Ni and $^58$Ni+$^197$Au, over the incident energy range 52-74\AM. Experimental data are compared with the results of a microscopic transport model with two different parameterizations of the (...)

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Isoscaling as a Measure of Symmetry Energy in the Lattice Gas Model

27 novembre 2009

The energetic properties of nuclear clusters inside a low-density, finite-temperature medium are studied with a lattice gas model including isospin dependence and Coulomb forces. Important deviations are observed with respect to the Fisher approximation of an ideal gas of noninteracting (...)

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[in2p3-00378550] Isoscaling as a Measure of Symmetry Energy in the Lattice Gas Model

27 novembre 2009

The energetic properties of nuclear clusters inside a low-density, finite-temperature medium are studied with a lattice gas model including isospin dependence and Coulomb forces. Important deviations are observed with respect to the Fisher approximation of an ideal gas of noninteracting (...)

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Multifragmentation and spinodal decomposition of finite nuclear systems

28 avril 2009

A bulk effect in multifragmentation of very heavy fused systems has been experimentally evidenced. Such an effect is very well reproduced by a complete dynamical simulation of collisions in which multifragmentation occurs through the growth of density fluctuations in the unstable spinodal (...)

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Multifragmentation and spinodal decomposition of finite nuclear systems

28 avril 2009

A bulk effect in multifragmentation of very heavy fused systems has been experimentally evidenced. Such an effect is very well reproduced by a complete dynamical simulation of collisions in which multifragmentation occurs through the growth of density fluctuations in the unstable spinodal (...)

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New digital techniques applied to A and Z identification using pulse shape discrimination of silicon detector current signals

27 avril 2009

Extending pulse shape discrimination (PSD) to digitized signals is one of the most promising methods to identify particles stopped in a detector. Using the CIME accelerator in the GANIL laboratory, a measurement campaign was done to collect data corresponding to different charges, masses and (...)

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[in2p3-00363510] New digital techniques applied to A and Z identification using pulse shape discrimination of silicon detector current signals

27 avril 2009

Extending pulse shape discrimination (PSD) to digitized signals is one of the most promising methods to identify particles stopped in a detector. Using the CIME accelerator in the GANIL laboratory, a measurement campaign was done to collect data corresponding to different charges, masses and (...)

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Isospin diffusion in semi-peripheral $^{58}Ni$+$^{197}Au$ collisions at intermediate energies (I): Experimental results

15 décembre 2008

Isospin diffusion in semi-peripheral collisions is probed as a function of the dissipated energy by studying two systems $^58Ni$+$^58Ni$ and $^58Ni$+$^197Au$, over the incident energy range 52-74\AM. A close examination of the multiplicities of light products in the forward part of phase space (...)

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Isospin diffusion in semi-peripheral $^{58}Ni$+$^{197}Au$ collisions at intermediate energies (I): Experimental results

15 décembre 2008

Isospin diffusion in semi-peripheral collisions is probed as a function of the dissipated energy by studying two systems $^58Ni$+$^58Ni$ and $^58Ni$+$^197Au$, over the incident energy range 52-74\AM. A close examination of the multiplicities of light products in the forward part of phase space (...)

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Multi-particle correlation function to study short-lived nuclei

8 octobre 2008

Unstable 10C nuclei are produced as quasi-projectiles in 12C+24Mg collisions at E/A = 53 and 95 MeV. The decay of their short-lived states is studied with the INDRA multidetector array via multi-particle correlation functions. The obtained results show that heavy-ion collisions can be used as a (...)

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[in2p3-00310864] Multi-particle correlation function to study short-lived nuclei

8 octobre 2008

Unstable 10C nuclei are produced as quasi-projectiles in 12C+24Mg collisions at E/A = 53 and 95 MeV. The decay of their short-lived states is studied with the INDRA multidetector array via multi-particle correlation functions. The obtained results show that heavy-ion collisions can be used as a (...)

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Freeze-out properties of multifragmentation events

30 juin 2008

Freeze-out properties of multifragmentation events produced in central 129Xe+natSn collisions at different beam energies (32, 39, 45 and 50 AMeV) were estimated by means of a simulation based on the experimental data collected by the 4π INDRA multidetector. A rapid increase (between 32 and 45 (...)

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[in2p3-00291789] Freeze-out properties of multifragmentation events

30 juin 2008

Freeze-out properties of multifragmentation events produced in central 129Xe+natSn collisions at different beam energies (32, 39, 45 and 50 AMeV) were estimated by means of a simulation based on the experimental data collected by the 4π INDRA multidetector. A rapid increase (between 32 and 45 (...)

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Multifragmentation threshold in $^{93}Nb+${nat}Mg collisions at 30 MeV/nucleon

7 mai 2008

We analyzed the $^93Nb$ on $^natMg$ reaction at $30$ MeV/nucleon in the aim of disentangling binary sequential decay and multifragmentation decay close to the energy threshold, i.e. $\simeq 3$ MeV/nucleon. Using the backtracing technique applied to the statistical models GEMINI and SMM we (...)

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Multifragmentation threshold in $^{93}Nb+${nat}Mg collisions at 30 MeV/nucleon

7 mai 2008

We analyzed the $^93Nb$ on $^natMg$ reaction at $30$ MeV/nucleon in the aim of disentangling binary sequential decay and multifragmentation decay close to the energy threshold, i.e. $\simeq 3$ MeV/nucleon. Using the backtracing technique applied to the statistical models GEMINI and SMM we (...)

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Source shape determination with directional fragment-fragment velocity correlations

12 novembre 2007

Correlation functions, constructed from directional projections of the relative velocities of fragments, are used to determine the shape of the breakup volume in coordinate space. For central collisions of 129Xe + natSn at 50 MeV per nucleon incident energy, measured with the 4pi multi-detector (...)

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[in2p3-00186887] Source shape determination with directional fragment-fragment velocity correlations

12 novembre 2007

Correlation functions, constructed from directional projections of the relative velocities of fragments, are used to determine the shape of the breakup volume in coordinate space. For central collisions of 129Xe + natSn at 50 MeV per nucleon incident energy, measured with the 4pi multi-detector (...)

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

13 septembre 2007

Multifragmentation properties measured with INDRA are studied for single sources produced in Xe+Sn reactions in the incident energy range 32-50 A MeV and quasiprojectiles from Au+Au collisions at 80 A MeV. A comparison for both types of sources is presented concerning Fisher scaling, Zipf law, (...)

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

13 septembre 2007

Multifragmentation properties measured with INDRA are studied for single sources produced in Xe+Sn reactions in the incident energy range 32-50 A MeV and quasiprojectiles from Au+Au collisions at 80 A MeV. A comparison for both types of sources is presented concerning Fisher scaling, Zipf law, (...)

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New approach of fragment charge correlations in $^{129}$Xe+$^{nat}$Sn central collisions

20 mars 2007

A previous analysis of the charge (Z) correlations in the $\Delta Z-$ plane for Xe+Sn central collisions at 32 MeV/u has shown an enhancement in the production of equally sized fragments (low $\Delta Z$) which was interpreted as an evidence for spinodal decomposition. However the signal is weak (...)

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New approach of fragment charge correlations in $^{129}$Xe+$^{nat}$Sn central collisions

20 mars 2007

A previous analysis of the charge (Z) correlations in the $\Delta Z-$ plane for Xe+Sn central collisions at 32 MeV/u has shown an enhancement in the production of equally sized fragments (low $\Delta Z$) which was interpreted as an evidence for spinodal decomposition. However the signal is weak (...)

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Bimodality : a signature for phase transition in nuclei ; theoretical and experimental aspects.

16 janvier 2007

Nature of Phase transitions... Phase transitions reflect the self- organization of a system and are ruled by common properties such as predicted by universality classes and RG. They are therefore present in all domains of Physics : Solid, liquid and gas phases Plasma (electrons, QGP, ...) (...)

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Bimodality : a signature for phase transition in nuclei ; theoretical and experimental aspects.

16 janvier 2007

Nature of Phase transitions... Phase transitions reflect the self- organization of a system and are ruled by common properties such as predicted by universality classes and RG. They are therefore present in all domains of Physics : Solid, liquid and gas phases Plasma (electrons, QGP, ...) (...)

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Universal fluctuations: a new approach to the study of phase transitions in intermediate energy heavy ion collisions

15 janvier 2007

The universal theory of order parameter fluctuations (D-scaling laws) is applied to a wide range of intermediate energy heavy-ion collision data obtained with INDRA. This systematic study confirms that the observed fragment production is compatible with aggregation scenarios for in- or (...)

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Universal fluctuations: a new approach to the study of phase transitions in intermediate energy heavy ion collisions

15 janvier 2007

The universal theory of order parameter fluctuations (D-scaling laws) is applied to a wide range of intermediate energy heavy-ion collision data obtained with INDRA. This systematic study confirms that the observed fragment production is compatible with aggregation scenarios for in- or (...)

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Directed and elliptic flow in $^{197}$Au+$^{197}$Au at intermediate energies

5 janvier 2007

Directed and elliptic flow for the $^197$Au+$^197$Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4$\pi$ multi-detector. For semi-central collisions, the excitation function of elliptic flow shows a transition from in-plane to out-of-plane (...)

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[in2p3-00122885] Directed and elliptic flow in $^{197}$Au+$^{197}$Au at intermediate energies

5 janvier 2007

Directed and elliptic flow for the $^197$Au+$^197$Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4$\pi$ multi-detector. For semi-central collisions, the excitation function of elliptic flow shows a transition from in-plane to out-of-plane (...)

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Evolution of the fusion cross-section for light systems at intermediate energies

5 janvier 2007

Ar + Ni and Ni + Ni collisions are investigated between 32 and around 100A MeV incident energy with the 4π multidetector INDRA. Fusion cross-sections are found to decrease from ˜ 180mb at 32A MeV to zero above 50A MeV. Other experimental results, for light systems, are compared. Moreover, (...)

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[in2p3-00072508] Evolution of the fusion cross-section for light systems at intermediate energies

5 janvier 2007

Ar + Ni and Ni + Ni collisions are investigated between 32 and around 100A MeV incident energy with the 4π multidetector INDRA. Fusion cross-sections are found to decrease from ˜ 180mb at 32A MeV to zero above 50A MeV. Other experimental results, for light systems, are compared. Moreover, (...)

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Effect of the intermediate velocity emissions on the quasi-projectile properties for the Ar + Ni system at 95 A.MeV

4 janvier 2007

The quasi-projectile (QP) properties are investigated in the Ar+Ni collisions at 95 A.MeV taking into account the intermediate velocity emission. Indeed, in this reaction, between 52 and 95 A.MeV bombarding energies, the number of particles emitted in the intermediate velocity region is related (...)

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Effect of the intermediate velocity emissions on the quasi-projectile properties for the Ar + Ni system at 95 A.MeV

4 janvier 2007

The quasi-projectile (QP) properties are investigated in the Ar+Ni collisions at 95 A.MeV taking into account the intermediate velocity emission. Indeed, in this reaction, between 52 and 95 A.MeV bombarding energies, the number of particles emitted in the intermediate velocity region is related (...)

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Bimodality: a robust signature of the liquid-gas phase transition of nuclear matter?

14 novembre 2006

Bimodality is observed on the size of the heaviest released fragment for semi-peripheral heavy ion induced reactions in the intermediate energy domain. From lattice-gas calculations, this signal can sign a phase transition even if the system has not reached a complete equilibrium. It is shown (...)

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Bimodality: a robust signature of the liquid-gas phase transition of nuclear matter?

14 novembre 2006

Bimodality is observed on the size of the heaviest released fragment for semi-peripheral heavy ion induced reactions in the intermediate energy domain. From lattice-gas calculations, this signal can sign a phase transition even if the system has not reached a complete equilibrium. It is shown (...)

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Bimodality and negative heat capacity in multifragmentation

14 novembre 2006

This contribution addresses the question of the possible link between multifragmentation and the liquid-gas phase transition of nuclear matter. Bimodality seems to be a robust signal of this link in the sense that theoretical calculations indicate that it is preserved even if a sizeable (...)

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Bimodality and negative heat capacity in multifragmentation

14 novembre 2006

This contribution addresses the question of the possible link between multifragmentation and the liquid-gas phase transition of nuclear matter. Bimodality seems to be a robust signal of this link in the sense that theoretical calculations indicate that it is preserved even if a sizeable (...)

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Bimodalities : a survey of experimental data and models

10 novembre 2006

Bimodal distributions of some chosen variables measured in nuclear collisions were recently proposed as a non ambiguous signature of a first order phase transition in nuclei. This section presents a compilation of both theoretical and experimental studies on bimodalities performed so far, in (...)

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Bimodalities : a survey of experimental data and models

10 novembre 2006

Bimodal distributions of some chosen variables measured in nuclear collisions were recently proposed as a non ambiguous signature of a first order phase transition in nuclei. This section presents a compilation of both theoretical and experimental studies on bimodalities performed so far, in (...)

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Three-body correlations in Borromean halo nuclei

10 juillet 2006

Three-body correlations in the dissociation of Borromean halo nuclei are explored for the first time using a technique based on intensity interferometry and Dalitz plots. As an example, the breakup of $^14$Be into $^12$Be+n+n by Pb and C targets is analysed. The combined treatment of n-n and (...)

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Three-body correlations in Borromean halo nuclei

10 juillet 2006

Three-body correlations in the dissociation of Borromean halo nuclei are explored for the first time using a technique based on intensity interferometry and Dalitz plots. As an example, the breakup of $^14$Be into $^12$Be+n+n by Pb and C targets is analysed. The combined treatment of n-n and (...)

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Transition from participant to spectator fragmentation in Au+Au reaction between 60 AMeV and 150 AMeV

10 juillet 2006

Using the quantum molecular dynamics approach, we analyze the results of the recent INDRA Au+Au experiments at GSI in the energy range between 60 AMeV and 150 AMeV. It turns out that in this energy region the transition toward a participant-spectator scenario takes place. The large Au+Au system (...)

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[in2p3-00084674] Transition from participant to spectator fragmentation in Au+Au reactions between 60A and 150A MeV

10 juillet 2006

Using the quantum molecular dynamics approach, we analyze the results of the recent INDRA Au+Au experiments at GSI in the energy range between 60 AMeV and 150 AMeV. It turns out that in this energy region the transition toward a participant-spectator scenario takes place. The large Au+Au system (...)

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Multifragmentation of a very heavy nuclear system (I): selection of a single-source events

10 juillet 2006

A sample of `single-source' events, compatible with the multifragmentation of very heavy fused systems, are isolated among well-measured $^155$Gd+$^nat$U 36AMeV reactions by examining the evolution of the kinematics of fragments with Z>=5 as a function of the dissipated energy and loss of (...)

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Multifragmentation of a very heavy nuclear system (I): selection of a single-source events

10 juillet 2006

A sample of `single-source' events, compatible with the multifragmentation of very heavy fused systems, are isolated among well-measured $^155$Gd+$^nat$U 36AMeV reactions by examining the evolution of the kinematics of fragments with Z>=5 as a function of the dissipated energy and loss of (...)

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Multifragmentation of a very heavy nuclear system (II) bulk properties and spinodal decomposition

10 juillet 2006

The properties of fragments and light charged particles emitted in multifragmentation of single sources formed in central 36AMeV Gd+U collisions are reviewed. Most of the products are isotropically distributed in the reaction c.m. Fragment kinetic energies reveal the onset of radial collective (...)

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Multifragmentation of a very heavy nuclear system (II) bulk properties and spinodal decomposition

10 juillet 2006

The properties of fragments and light charged particles emitted in multifragmentation of single sources formed in central 36AMeV Gd+U collisions are reviewed. Most of the products are isotropically distributed in the reaction c.m. Fragment kinetic energies reveal the onset of radial collective (...)

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Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions (Part I) : recombination and $\delta$-electrons

7 juillet 2006

A simple formalism describing the light response of CsI(Tl) to heavy ions, which quantifies the luminescence and the quenching in terms of the competition between radiative transitions following the carrier trapping at the Tl activator sites and the electron-hole recombination, is proposed. The (...)

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[in2p3-00019578] Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions (Part I) : recombination and $\delta$-electrons

7 juillet 2006

A simple formalism describing the light response of CsI(Tl) to heavy ions, which quantifies the luminescence and the quenching in terms of the competition between radiative transitions following the carrier trapping at the Tl activator sites and the electron-hole recombination, is proposed. The (...)

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Bimodality: a possible experimental signature of the liquid-gas phase transition of nuclear matter

7 février 2006

We have observed a bimodal behaviour of the distribution of the asymmetry between the charges of the two heaviest products resulting from the decay of the quasi-projectile released in binary Xe+Sn and Au+Au collisions from 60 to 100 MeV/u. Event sorting has been achieved through the transverse (...)

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Liquid-Gas Coexistence Region in Central Xe+Sn Reactions

18 octobre 2005

Charge partitions and distributions of fragments emitted in multifragmentation of fused systems produced in central collisions are studied over the incident energy range 32-50 MeV per nucleon. Most of the charged products are well identified thanks to the high performances of the INDRA 4pi (...)

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Evidence for Spinodal Decomposition in Nuclear Multifragmentation

18 octobre 2005

Multifragmentation of a ``fused system\'\' was observed for central collisions between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products were well identified thanks to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments (...)

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Bimodality as a signal of Liquid-Gas phase transition in nuclei?

29 septembre 2005

We use the HIPSE (Heavy-Ion Phase-Space Exploration) Model to discuss the origin of the bimodality in charge asymmetry observed in nuclear reactions around the Fermi energy. We show that it may be related to the important angular momentum (spin) transferred into the quasi-projectile before (...)

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Estimate of average freeze-out volume in multifragmentation events

5 septembre 2005

An estimate of the average freeze-out volume for multifragmentation events is presented. Values of volumes are obtained by means of a simulation using the experimental charged product partitions measured by the 4pi multidetector INDRA for 129Xe central collisions on Sn at 32 AMeV incident (...)

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Multifragmentation of very heavy nuclear systems (III): fragment velocity correlations and event topology at freeze-out.

26 août 2005

Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-field calculations, are successfully confronted with experimental data for single multifragmenting sources prepared at the same excitation energy per nucleon in 32 AMeV 129Xe+natSn and 36 AMeV (...)

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Evolution of Fragment Distributions and Reaction Mechanisms for the Ar+Ni System from 32 to 95 A.MeV

24 juin 2005

Within the framework of flow and multifragmentation study, the 36Ar+58Ni experiment has been performed at seven incident energies from 32 to 95 A.MeV with the INDRA detector at GANIL. After a brief description of the experimental set-up, the main trends as well as the evolution of fragment (...)

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The halo of $^{14}$Be

19 avril 2005

The two-neutron halo nucleus 14Be has been investigated in a kinematically complete measurement of the fragments (12Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross-sections, neutron angular distributions and invariant mass spectra (...)

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Bimodality and negative heat capacity in multifragmentation

24 mars 2005

This contribution addresses the question of the possible link between multifragmentation and the liquid-gas phase transition of nuclear matter. Bimodality seems to be a robust signal of this link in the sense that theoretical calculations indicate that it is preserved even if a sizeable (...)

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A study of nuclear stopping in central symmetric nuclear collisions at intermediate energies

14 mars 2005

Nuclear stopping has been investigated in central symmetric nuclear collisions at intermediate energies. Firstly, it is found that the isotropy ratio, Riso, reaches a minimum near the Fermi energy and saturates or slowly increases depending on the mass of the system as the beam energy (...)

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Isotopic Scaling and the Symmetry Energy in Spectator Fragmentation

17 février 2005

Isotopic effects in the fragmentation of excited target residues following collisions of $^12$C on $^112,124$Sn at incident energies of 300 and 600 MeV per nucleon were studied with the INDRA 4$\pi$ detector. The measured yield ratios for light particles and fragments with atomic number $Z (...)

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Directed and elliptic flow in $^{197}$Au+$^{197}$Au at intermediate energies

11 février 2005

Directed and elliptic flow for the Au + Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4 pi multi-detector. For semi-central collisions, the elliptic flow of Z <= 2 particles switches from in-plane to out-of-plane enhancement at around (...)

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Model-independent tracking of criticality signals in nuclear multifragmentation data

6 septembre 2004

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 (...)

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Transverse velocity scaling in $^{197}$Au+$^{197}$Au fragmentation

25 février 2003

Invariant transverse-velocity spectra of intermediate-mass fragments were measured with the 4-pi multi-detector system INDRA for collisions of Au on Au at incident energies between 40 and 150 MeV per nucleon. Their scaling properties as a function of incident energy and atomic number Z are used (...)

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