exotic nuclei structure and reaction noyaux exotiques ... - IPN - IN2P3

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difference comes from the opposite evolution of the fragment multiplicity—see below. Figure 2: Same as figure 1, for the light charged particle (Z≤2) multiplicities. All statistical errors amount to 0.04. As appears in the table, the composite system with N/Z=1.385 has been formed by three different entrance channels. It is interesting to note that, within the error bars, the measured multiplicities are the same. This confirms that the selected quasi-fusion sources have lost the entrance channel memory and reached a high degree of equilibration [1]. fragments. As already noted for total and lcp multiplicities, the fragment multiplicity is independent of the entrance channel mass asymmetry for a given composite system. Some indications of the evolution of the multiplicities with the neutron-richness of the system were already noted in [3,4] . The independence of the entrance channel for a given N/Z is however an original new result. Dynamical simulations The reaction dynamics can be followed by solving the BNV transport equation that describes the evolution of the one-body distribution function according to the nuclear mean-field and two-body collisions . The compressibility modulus is K=200 MeV, And the free nucleon-nucleon cross-section with its energy, angular and isospin dependence is used. Two different prescriptions for the symmetry energy term [5] are chosen: an asy-stiff one (linear increase of the potential symmetry term with density) or an asy-soft term roughly varying as the square root of the density. The first results, obtained for 124 Xe+ 112 Sn and 136 Xe+ 124 Sn at 45 MeV/nucleon, show the same relative increase of the fragment number at the end of the BNV calculation (i.e. before deexcitation and filter by the experimental apparatus) as observed experimentally. The asy-stiffness of the EOS does not influence the fragment multiplicity for the neutron poor system, while slightly more fragments are produced in the asy-stiff case for the neutron-rich one. References [1] F. Gagnon-Moisan et al., Proceedings of the IWM2009. [2] G. Tabacaru et al., Eur. Phys. J. A 18, 103, 2003. [3] J. F. Dempsey et al., Phys. Rev. C 54, 1710, 1996. [4] G. J. Kunde et al., Phys. Rev. Lett. 77, 2897, 1996. [4] V. Baran et al., Nucl. Phys. A703, 603, 2002. Figure 3: Same as figure 1, for the fragment (Z≥5) multiplicities. Statistical errors are 0.02. The multiplicities for fragments (Z≥5) are displayed in figure 3. Conversely to lcp multiplicities, they only slightly increase (by about 5%) with the incident energy. Indeed the systems become more fragmented at higher energies, and the charge of the products becomes smaller [2]. Thus a larger number of them have a charge smaller than 5, which is the lower limit for our “fragment” definition. The interesting point is the increase of the fragment multiplicity for neutron-rich systems. M frag increases by about 8% when N/Z sys increases from 1.27 to 1.5. This larger fragment number can be attributed to the larger quantity of available neutrons, which helps the formation of more stable 105
Radial collective energy and fragment partitions in multifragmentation of hot heavy nuclei IPNO Participation: B. Borderie, E. Galichet, M. F. Rivet Collaborations : INDRA and ALADIN LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France GANIL, CEA et CNRS/IN2P3, Caen, France IPN Lyon, Université Claude Bernard Lyon1, CNRS/IN2P3, Villeurbanne, France IRFU/SPhN, CEA/Saclay Gif-sur-Yvette, France Laboratoire de Physique Nucléaire, Université Laval, Québec, Canada Dpt de Scienze Fisiche e Sez. INFN, Università di Napoli « Federico II », Napoli, Italy NIPNE, Bucharest Magurele, Romania Institute of Nuclear Physics IFJ-PAN, Krakov, Poland The Andrzej Soltan Institute for Nuclear Studies, Warsaw, Poland Les partitions de fragments issus de la désexcitation par multifragmentation de noyaux chauds produits dans des collisions centrales et semi-périphériques ont été comparées dans le domaine en énergie d’excitation ou l’on observe la présence d’énergie collective radiale. Il est montré qu’à énergie d’excitation par nucléon fixée (thermique + collective) pour les noyaux chauds, l’énergie collective radiale moyenne fixe la multiplicité moyenne de fragments. De plus, les partitions de fragments sont complètement déterminées à multiplicité réduite de fragments donnée. Le volume de freeze-out est vraisemblablement responsable de la loi d’échelle observée. Introduction Nucleus-nucleus collisions at intermediate energies offer various possibilities to produce hot nuclei which undergo a break-up into smaller pieces, which is called multifragmentation. The measured fragment properties are expected to reveal the existence of a phase transition for hot nuclei which was earlier theoretically predicted for nuclear matter [1]. By comparing in detail the properties of fragments (Z ≥ 5) emitted by hot nuclei formed in central (quasi-fused systems, QF, from 129 Xe+ nat Sn, 25-50 AMeV) and semi-peripheral collisions (quasi-projectiles, QP, from 197 Au+ 197 Au, 80 and 100 AMeV), i.e. with different dynamical conditions for their formation, the role of radial collective energy on partitions is emphasized [2] and general properties of partitions are deduced. Radial collective energy and fragment partitions To make a meaningful comparison of fragment properties which can be related to the nuclear phase diagram, hot nuclei showing, to a certain extent, statistical emission features must be selected. For central collisions (QF events) one selects complete and compact events in velocity space (constraint of flow angle ≥ 60°). For peripheral collisions (QP subevents) the selection method applied to quasiprojectiles minimizes the contribution of dynamical emissions by imposing a compacity of fragments in velocity space.The excitation energies of the different hot nuclei produced are calculated using the calorimetry procedure (see [2] for details); they include thermal and radial energies. By comparing the properties of selected sources on the same excitation energy domain, significant differences Figure 1: Evolution of the radial collective energy with the excitation energy per nucleon for different sources. Full squares stand for QF sources. Open (full) circles correspond to QP sources produced in 80 (100) AMeV collisions. Full triangles correspond to π - + Au reactions and the open square to an estimate of the thermal part of the radial collective energy for Xe + Sn sources produced at 50 AMeV incident energy. are observed above 5 AMeV excitation energy. QF sources have larger mean fragment multiplicities, , even normalized to the sizes of the sources (which differ by about 20% for QF and QP sources), and lower values for generalized asymmetry: A Z = σ Z / ( √M frag -1). A possible explanation of those different fragment partitions is related to the different dynamical contraints applied to the hot nuclei produced: a compression-expansion cycle for central collisions and a more gentle friction-abrasion process 106
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EXOTIC NUCLEI STRUCTURE AND REACTIO
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in the spectra by analyzing their t
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were taken from ref. [5]. Concernin
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keV -ray with the particles and the
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the 605.9 keV line of the 74 Zn 2+
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Figure 2 a n d analysis. Figure 2 s
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ing particles was thus obtained by
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First p-p p collisions in the ALICE
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Quarkonia physics with ALICE IPNO P
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NA50 updated puzzle IPNO Participat
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Status of the HADES experiment (I):
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Status of the HADES experiments (II
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Status of the HADES experiment (III
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Hadron physics in pbar-p p annihila
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Hadron Electrodynamics IPNO Partici
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G0 experiment at Jefferson Lab. IPN
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GEp-III and GEp-2 at Jefferson Lab
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Exotic low mass narrow baryons from
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The PVA4 parity violation experimen
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Etude des Distributions de Partons
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Latest Results from GRAAL IPNO Part
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Persistence of the Polarization in
Page 45 and 46: The northern site of the Pierre Aug
Page 47 and 48: The Pierre Auger southern Observato
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Page 51 and 52: THEORETICAL PHYSICS Research in the
Page 53 and 54: transfer reaction, the 34 Si(d, 3 H
Page 55 and 56: Collective excitations with SKYRME
Page 57 and 58: Pairing and nuclear incompressibili
Page 59 and 60: Pairing properties in nuclei and in
Page 61 and 62: Evaporation-residue residue cross s
Page 63 and 64: Extending the VMI model: normal and
Page 65 and 66: Alpha particle condensation in nucl
Page 67 and 68: Collective Modes in Ultracold Trapp
Page 69 and 70: Exploring key unknown neutrino prop
Page 71 and 72: Relic astrophysical and cosmologica
Page 73 and 74: After a term by term Borel resummat
Page 75 and 76: Chiral expansions of the π 0 lifet
Page 77 and 78: IPNO Participation: H. Sazdjian Eff
Page 79 and 80: fer is used to extract f + (0). We
Page 81 and 82: cleon. The spectrum becomes strongl
Page 83 and 84: A pseudo Coulombian potential in D=
Page 85 and 86: The many-body problem with an energ
Page 87 and 88: The rotational spectrum and the att
Page 89 and 90: Z-identification of very heavy nucl
Page 91 and 92: The Pegase project, a new solid sur
Page 93 and 94: But at 80 keV total energy ( 200 eV
Page 95: Isospin effects on fragment and par
Page 99 and 100: Latent heat of the phase transition
Page 101 and 102: Alpha-particle particle condensatio
Page 103 and 104: Fluo X: Deexcitation time measureme
Page 105 and 106: ENERGY AND ENVIRONMENT The increasi
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Page 111 and 112: 3D coupling of Monte-Carlo neutroni
Page 113 and 114: Fission cross sections of actinides
Page 115 and 116: Studies and synthesis of specific m
Page 117 and 118: Chemistry and Electrochemistry of T
Page 119 and 120: function of temperature. The recent
Page 121 and 122: global electron number of the redox
Page 123: (D 0 /D)-1 ln complexes of Pa(V). I
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