Inclusive cross sections of intermediate mass fragments from the reaction Ar+ ' 'Au at E/A =30 Me... more Inclusive cross sections of intermediate mass fragments from the reaction Ar+ ' 'Au at E/A =30 MeV and 220 MeV were measured with a low threshold and over a large range of angles. The integrated cross sections are about 2 b at both energies but the emission characteristics change considerably.
The European Physical Journal A - Hadrons and Nuclei, 2003
The transport properties of the 36 Ar + 58 Ni system at 95 A • MeV measured with the INDRA array,... more The transport properties of the 36 Ar + 58 Ni system at 95 A • MeV measured with the INDRA array, are studied within the BNV kinetic equation. A general protocol of comparison between the N-body experimental fragment information and the one-body distribution function is developed using global variables, with a special focus on charge density. This procedure avoids any definition of sources and any use of an afterburner in the simulation. We shall discuss the feasibility of such an approach and the distortions induced by the finite detection efficiency and the completeness requirements of the data selection. The sensitivity of the different global observables to the macroscopic parameters of the effective nuclear interaction will be studied in detail.
We analyzed the 93 N b on nat M g reaction at 30 MeV/nucleon in the aim of disentangling binary s... more We analyzed the 93 N b on nat M g reaction at 30 MeV/nucleon in the aim of disentangling binary sequential decay and multifragmentation decay close to the energy threshold, i.e. ≃ 3 MeV/nucleon. Using the backtracing technique applied to the statistical models GEMINI and SMM we reconstruct simulated charge, mass and excitation energy distributions and compare them to the experimental ones. We show that data are better described by SMM than by GEMINI in agreement with the fact that multifragmentation is responsible for fragment production at excitation energies around 3 MeV/nucleon.
Monthly Notices of the Royal Astronomical Society, 2022
The interstellar gas in spiral galaxies can constitute a significant fraction of the baryon mass ... more The interstellar gas in spiral galaxies can constitute a significant fraction of the baryon mass and it has been demonstrated that the sum of stellar and gas components correlates well with the kinematic signature of the total mass content, the widths of H i line profiles. The correlation of baryonic mass with H i line widths is used here to obtain distances for 9984 galaxies extending to ∼0.05c. The sample is H i flux limited and a correction is required to account for an H i selection bias. The absolute scale is established by 64 galaxies with known distances from studies of Cepheid variables and/or the magnitudes of stars at the tip of the red giant branch. The calibration of the baryonic relationship results in a determination of the Hubble constant of H0 = 75.5 ± 2.5 km s−1 Mpc−1. The error estimate is statistical. This material will be combined with contributions from other methodologies in a subsequent article where systematic uncertainties will be investigated.
Monthly Notices of the Royal Astronomical Society: Letters, 2019
This letter presents a new approach using the cosmic peculiar velocity field to characterize the ... more This letter presents a new approach using the cosmic peculiar velocity field to characterize the morphology and size of large-scale structures in the local Universe. The algorithm developed uses the three-dimensional peculiar velocity field to compute flow lines, or streamlines. The local Universe is then partitioned into volumes corresponding to gravitational basins, also called watersheds, among the different end points of the velocity flow lines. This new methodology is first tested on numerical cosmological simulations, used as benchmark for the method, and then applied to the Cosmic-Flows project observational data in order to pay particular attention to the nearby superclusters including ours. More extensive tests on both simulated and observational data will be discussed in an accompanying paper.
Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-... more 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 129 Xe+ nat Sn and 36 AMeV 155 Gd+ nat U central collisions. Relying thus on simulations, average freeze-out times of 200-240 fm/c are estimated The corresponding spatial distributions of fragments are more compact for the lighter system (∼3-4V 0 vs ∼8V 0 ). Sn( 129 Xe, X), E = 32 AMeV; nat U( 155 Gd, X), E = 36 AMeV, measured fragment energies, charges and yields with a 4π array, central collisions, fragment energy spectra and velocity correlations, comparison to stochastic mean-field calculation, spatial topology at
58Ni+58Ni collisions at 32 MeV/nucleon have been studied with the 4pi multidetector INDRA. The ev... more 58Ni+58Ni collisions at 32 MeV/nucleon have been studied with the 4pi multidetector INDRA. The evolution from binary (dissipative) collisions to a fusionlike process is evidenced with decreasing impact parameter throughout a set of experimental observables within a discriminant analysis. Preequilibrium effects and characteristics of a single-source emission are discussed. A coexistence (bimodality) between two decay mechanisms is pointed out and
Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-... more 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 129 Xe+ nat Sn and 36 AMeV 155 Gd+ nat U central collisions. Relying thus on simulations, average freeze-out times of 200-240 fm/c are estimated The corresponding spatial distributions of fragments are more compact for the lighter system (∼3-4V 0 vs ∼8V 0 ). Sn( 129 Xe, X), E = 32 AMeV; nat U( 155 Gd, X), E = 36 AMeV, measured fragment energies, charges and yields with a 4π array, central collisions, fragment energy spectra and velocity correlations, comparison to stochastic mean-field calculation, spatial topology at
Isospin effects on multifragmentation properties were studied thanks to nuclear collisions betwee... more Isospin effects on multifragmentation properties were studied thanks to nuclear collisions between different isotopes of xenon beams and tin targets. It is shown that, in central collisions leading to multifragmentation, the mean number of fragments and their mean kinetic energy increase with the neutron-richness of the total system. Comparisons with a stochastic transport model allow to attribute the multiplicity increase to the multifragmentation stage, before secondary decay. The total charge bound in fragments is proposed as an alternate variable to quantify preequilibrium emission and to investigate symmetry energy effects. PACS numbers: 25.70.Pq, 24.10.-i * Current address: PTB Brauncshweig,
Nuclear stopping has been investigated in central nuclear collisions at intermediate energies by ... more 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 transverse to parallel momenta (energies) reaches a minimum near the Fermi energy, saturates or slowly increases depending on the mass of the system as the beam energy increases, and then stays lower than unity, showing that significant stopping is not achieved even for the heavier systems. Close to and above the Fermi energy, experimental data show no effect of the isospin content of the interacting system. A comparison with transport model calculations reveals that the latter overestimates the stopping power at low energies.
Isotopic effects in the fragmentation of excited target residues following collisions of 12 C on ... more 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 4π detector. The measured yield ratios for light particles and fragments with atomic number Z ≤ 5 obey the exponential law of isotopic scaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. Symmetry term coefficients, deduced from these data within the statistical description of isotopic scaling, are near γ = 25 MeV for peripheral and γ < 15 MeV for central collisions. PACS numbers: 25.70.Mn, 25.70.Pq, 24.10.Pa
The same hot nuclear system (SigmaZ=18) has been studied for two different entrance channels with... more The same hot nuclear system (SigmaZ=18) has been studied for two different entrance channels with reaction products detected in a forward array of scintillators: central collisions of 24Mg on a 12C target at 25A and 35A MeV and peripheral pickup reactions of 35Cl on a 197Au target at 43A MeV. The detection-efficiency-corrected charge distributions, multiplicity of charged particles and cross
This paper introduces a new method for the selection of central singlesource events, based on cla... more This paper introduces a new method for the selection of central singlesource events, based on classical multivariate techniques. The resulting discriminating variable is shown to be valid for different hypotheses on the nuclear source deexcitation mechanism. It enables the selection of events which are representative of the whole set of single-source events. Application to the Ni+Ni at 32A MeV system measured with the indra multidetector has allowed the determination of the fusion probability as a function of the impact parameter and the evaluation of the corresponding cross-section.
Characteristics of the primary fragments produced in central collisions of 129 Xe + nat Sn from 3... more Characteristics of the primary fragments produced in central collisions of 129 Xe + nat Sn 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 LCP's.
Unstable 10 C nuclei are produced as quasi-projectiles in 12 C+ 24 Mg collisions at E/A = 53 and ... more Unstable 10 C nuclei are produced as quasi-projectiles in 12 C+ 24 Mg 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 tool to access spectroscopic information of unbound states in exotic nuclei, such as their energies and the relative importance of different sequential decay widths. Energetic heavy-ion collisions have been extensively studied to extract information about the properties of nuclear matter under extreme conditions [1].
Inclusive cross sections of intermediate mass fragments from the reaction Ar+ ' 'Au at E/A =30 Me... more Inclusive cross sections of intermediate mass fragments from the reaction Ar+ ' 'Au at E/A =30 MeV and 220 MeV were measured with a low threshold and over a large range of angles. The integrated cross sections are about 2 b at both energies but the emission characteristics change considerably.
The European Physical Journal A - Hadrons and Nuclei, 2003
The transport properties of the 36 Ar + 58 Ni system at 95 A • MeV measured with the INDRA array,... more The transport properties of the 36 Ar + 58 Ni system at 95 A • MeV measured with the INDRA array, are studied within the BNV kinetic equation. A general protocol of comparison between the N-body experimental fragment information and the one-body distribution function is developed using global variables, with a special focus on charge density. This procedure avoids any definition of sources and any use of an afterburner in the simulation. We shall discuss the feasibility of such an approach and the distortions induced by the finite detection efficiency and the completeness requirements of the data selection. The sensitivity of the different global observables to the macroscopic parameters of the effective nuclear interaction will be studied in detail.
We analyzed the 93 N b on nat M g reaction at 30 MeV/nucleon in the aim of disentangling binary s... more We analyzed the 93 N b on nat M g reaction at 30 MeV/nucleon in the aim of disentangling binary sequential decay and multifragmentation decay close to the energy threshold, i.e. ≃ 3 MeV/nucleon. Using the backtracing technique applied to the statistical models GEMINI and SMM we reconstruct simulated charge, mass and excitation energy distributions and compare them to the experimental ones. We show that data are better described by SMM than by GEMINI in agreement with the fact that multifragmentation is responsible for fragment production at excitation energies around 3 MeV/nucleon.
Monthly Notices of the Royal Astronomical Society, 2022
The interstellar gas in spiral galaxies can constitute a significant fraction of the baryon mass ... more The interstellar gas in spiral galaxies can constitute a significant fraction of the baryon mass and it has been demonstrated that the sum of stellar and gas components correlates well with the kinematic signature of the total mass content, the widths of H i line profiles. The correlation of baryonic mass with H i line widths is used here to obtain distances for 9984 galaxies extending to ∼0.05c. The sample is H i flux limited and a correction is required to account for an H i selection bias. The absolute scale is established by 64 galaxies with known distances from studies of Cepheid variables and/or the magnitudes of stars at the tip of the red giant branch. The calibration of the baryonic relationship results in a determination of the Hubble constant of H0 = 75.5 ± 2.5 km s−1 Mpc−1. The error estimate is statistical. This material will be combined with contributions from other methodologies in a subsequent article where systematic uncertainties will be investigated.
Monthly Notices of the Royal Astronomical Society: Letters, 2019
This letter presents a new approach using the cosmic peculiar velocity field to characterize the ... more This letter presents a new approach using the cosmic peculiar velocity field to characterize the morphology and size of large-scale structures in the local Universe. The algorithm developed uses the three-dimensional peculiar velocity field to compute flow lines, or streamlines. The local Universe is then partitioned into volumes corresponding to gravitational basins, also called watersheds, among the different end points of the velocity flow lines. This new methodology is first tested on numerical cosmological simulations, used as benchmark for the method, and then applied to the Cosmic-Flows project observational data in order to pay particular attention to the nearby superclusters including ours. More extensive tests on both simulated and observational data will be discussed in an accompanying paper.
Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-... more 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 129 Xe+ nat Sn and 36 AMeV 155 Gd+ nat U central collisions. Relying thus on simulations, average freeze-out times of 200-240 fm/c are estimated The corresponding spatial distributions of fragments are more compact for the lighter system (∼3-4V 0 vs ∼8V 0 ). Sn( 129 Xe, X), E = 32 AMeV; nat U( 155 Gd, X), E = 36 AMeV, measured fragment energies, charges and yields with a 4π array, central collisions, fragment energy spectra and velocity correlations, comparison to stochastic mean-field calculation, spatial topology at
58Ni+58Ni collisions at 32 MeV/nucleon have been studied with the 4pi multidetector INDRA. The ev... more 58Ni+58Ni collisions at 32 MeV/nucleon have been studied with the 4pi multidetector INDRA. The evolution from binary (dissipative) collisions to a fusionlike process is evidenced with decreasing impact parameter throughout a set of experimental observables within a discriminant analysis. Preequilibrium effects and characteristics of a single-source emission are discussed. A coexistence (bimodality) between two decay mechanisms is pointed out and
Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-... more 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 129 Xe+ nat Sn and 36 AMeV 155 Gd+ nat U central collisions. Relying thus on simulations, average freeze-out times of 200-240 fm/c are estimated The corresponding spatial distributions of fragments are more compact for the lighter system (∼3-4V 0 vs ∼8V 0 ). Sn( 129 Xe, X), E = 32 AMeV; nat U( 155 Gd, X), E = 36 AMeV, measured fragment energies, charges and yields with a 4π array, central collisions, fragment energy spectra and velocity correlations, comparison to stochastic mean-field calculation, spatial topology at
Isospin effects on multifragmentation properties were studied thanks to nuclear collisions betwee... more Isospin effects on multifragmentation properties were studied thanks to nuclear collisions between different isotopes of xenon beams and tin targets. It is shown that, in central collisions leading to multifragmentation, the mean number of fragments and their mean kinetic energy increase with the neutron-richness of the total system. Comparisons with a stochastic transport model allow to attribute the multiplicity increase to the multifragmentation stage, before secondary decay. The total charge bound in fragments is proposed as an alternate variable to quantify preequilibrium emission and to investigate symmetry energy effects. PACS numbers: 25.70.Pq, 24.10.-i * Current address: PTB Brauncshweig,
Nuclear stopping has been investigated in central nuclear collisions at intermediate energies by ... more 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 transverse to parallel momenta (energies) reaches a minimum near the Fermi energy, saturates or slowly increases depending on the mass of the system as the beam energy increases, and then stays lower than unity, showing that significant stopping is not achieved even for the heavier systems. Close to and above the Fermi energy, experimental data show no effect of the isospin content of the interacting system. A comparison with transport model calculations reveals that the latter overestimates the stopping power at low energies.
Isotopic effects in the fragmentation of excited target residues following collisions of 12 C on ... more 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 4π detector. The measured yield ratios for light particles and fragments with atomic number Z ≤ 5 obey the exponential law of isotopic scaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. Symmetry term coefficients, deduced from these data within the statistical description of isotopic scaling, are near γ = 25 MeV for peripheral and γ < 15 MeV for central collisions. PACS numbers: 25.70.Mn, 25.70.Pq, 24.10.Pa
The same hot nuclear system (SigmaZ=18) has been studied for two different entrance channels with... more The same hot nuclear system (SigmaZ=18) has been studied for two different entrance channels with reaction products detected in a forward array of scintillators: central collisions of 24Mg on a 12C target at 25A and 35A MeV and peripheral pickup reactions of 35Cl on a 197Au target at 43A MeV. The detection-efficiency-corrected charge distributions, multiplicity of charged particles and cross
This paper introduces a new method for the selection of central singlesource events, based on cla... more This paper introduces a new method for the selection of central singlesource events, based on classical multivariate techniques. The resulting discriminating variable is shown to be valid for different hypotheses on the nuclear source deexcitation mechanism. It enables the selection of events which are representative of the whole set of single-source events. Application to the Ni+Ni at 32A MeV system measured with the indra multidetector has allowed the determination of the fusion probability as a function of the impact parameter and the evaluation of the corresponding cross-section.
Characteristics of the primary fragments produced in central collisions of 129 Xe + nat Sn from 3... more Characteristics of the primary fragments produced in central collisions of 129 Xe + nat Sn 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 LCP's.
Unstable 10 C nuclei are produced as quasi-projectiles in 12 C+ 24 Mg collisions at E/A = 53 and ... more Unstable 10 C nuclei are produced as quasi-projectiles in 12 C+ 24 Mg 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 tool to access spectroscopic information of unbound states in exotic nuclei, such as their energies and the relative importance of different sequential decay widths. Energetic heavy-ion collisions have been extensively studied to extract information about the properties of nuclear matter under extreme conditions [1].
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Papers by D. Guinet