Search

ibidem

Neutron-proton elliptic flow difference and ratio have been shown to be promising observables in the attempt to constrain the density dependence of the symmetry energy above the saturation point from heavy-ion collision data. Their dependence on model parameters like microscopic nucleon-nucleon cross-sections, compressibility of nuclear matter, optical potential, and symmetry energy parametrization is thoroughly studied. By using a parametrization of the symmetry energy derived from the momentum dependent Gogny force in conjunction with the T\"{u}bingen QMD model and comparing with the experimental FOPI/LAND data for 197Au+197Au collisions at 400 MeV/nucleon, a moderately stiff, x=-1.35 +/- 1.25, symmetry energy is extracted, a result that agrees with that of a similar study that employed the UrQMD transport model and a momentum independent power-law parametrization of the symmetry energy. This contrasts with diverging results extracted from the FOPI $\pi^{-}/\pi^{+}$ ratio available in the literature., Comment: 18 pages, 3 figures, accepted for publication in Phys. Rev. C

We investigated the merits of different event parameters in the identification of Light Charged Particles (LCPs) with CsI(Tl) scintillators read out by photodiodes at high incident energy (400 MeV/u). This investigation is made possible by digital signal processing the output signals. As in the conventional analogue case, the digitized signals allow the discrimination of light charged particles by computing the fast and slow components. In addition other identification parameters as the rise time of the output pulses of the CsI(Tl) come out nearly for free. Aim of this paper is the investigation of novel identification plots and the probe of their merits, in particular at relativistic energies. When the energies of the light charged particles exceed those corresponding to their ranges in CsI(Tl), the points related to the punching-through particles gather in the corresponding scatter plots giving rise to a cusp. The punch-through energies provide a complete set of data for the energy calibration of the reaction products stopped in the CsI(Tl). The obtained results suggest that at relativistic beam energies the energy vs. rise time computation provide an efficient figure for the discrimination in charge and mass of LCPs.

A new detection system KRATTA, Krak\'ow Triple Telescope Array, is presented. This versatile, low threshold, broad energy range system has been built to measure the energy, emission angle, and isotopic composition of light charged reaction products. It consists of 38 independent modules which can be arranged in an arbitrary configuration. A single module, covering actively about 4.5 msr of the solid angle at the optimal distance of 40 cm from the target, consists of three identical, 0.500 mm thick, large area photodiodes, used also for direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5 cm length, respectively. All the signals are digitally processed. The lower identification threshold, due to the thickness of the first photodiode, has been reduced to about 2.5 MeV for protons (~0.065 mm of Si equivalent) by applying a pulse shape analysis. The pulse shape analysis allowed also to decompose the complex signals from the middle photodiode into their ionization and scintillation components and to obtain a satisfactory isotopic resolution with a single readout channel. The upper energy limit for protons is about 260 MeV. The whole setup is easily portable. It performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are described using the results of Au+Au collisions at 400 MeV/nucleon obtained in this experiment., Comment: 10 pages, 18 figures, accepted by Nucl. Instr. and Meth. A

Multifragment decays of heavy nuclei have been studied at the ALADIN spectrometer system at beam energies between 100 and 1000 MeV per nucleon. The observed fragment distributions signal a universality of spectator decays at bombarding energies E A ≥ 400 MeV . The role of the radial flow for the fragmentation process is explored by comparing fragment distributions measured for Au+Au collisions at E A = 100 MeV in central collisions and at E A = 1000 MeV in more peripheral reactions. At both energies the maximum multiplicity of intermediate mass fragments (IMFs) normalized to the size of the decaying system is about one IMF per 30 nucleons but the element distributions show significant differences. Within a coalescence picture the suppression of heavy fragments in central collisions at E A = 100 MeV may be related to a reduction of the density in momentum space which is caused by a large collective expansion velocity component.

Fragment distributions have been measured for Au+Au collisions at [ital E]/[ital A]=100 and 1000 MeV. A high detection efficiency for fragments was obtained by combining the ALADIN spectrometer and the MSU-Miniball/WU-Miniwall array. At both energies the maximum multiplicity of intermediate mass fragments (IMF) normalized to the size of the decaying system is about one IMF per 30 nucleons but the element distributions show significant differences. Within a coalescence picture the suppression of heavy fragments in central collisions at [ital E]/[ital A]=100 MeV may be related to a reduction of the density in momentum space which is caused by the collective expansion.

Fragments produced in binary splits of an excited projectile-like fragment (PLF${}^{*}$) formed in the reactions ${}^{124}$Xe $+$ ${}^{112,124}$Sn at an incident energy of 50 MeV/$A$ are examined. The dependence of the isotopic composition of light fragments ($4\ensuremath{\leqslant}{Z}_{L}\ensuremath{\leqslant}8$) on rotation angle allows one to explore changes in $N/Z$ on the time scale of the rotational period of the PLF${}^{*}$. Changes in the $N/Z$ of the fragments persist for times as long as 2--3 zs (600--900 fm/$c$). The two-component nature of the time dependence of $\ensuremath{\langle}N\ensuremath{\rangle}/Z$ for ${Z}_{L}=4$ and the $Z$ dependence are related to differences in the initial configurations and subsequent decay of the PLF${}^{*}$.

The performance of the LAND neutron detector is studied. Using an event-mixing technique based on one-neutron data obtained in the S107 experiment at the GSI laboratory, we test the efficiency of various analytic tools used to determine the multiplicity and kinematic properties of detected neutrons. A new algorithm developed recently for recognizing neutron showers from spectator decays in the ALADIN experiment S254 is described in detail. Its performance is assessed in comparison with other methods. The properties of the observed neutron events are used to estimate the detection efficiency of LAND in this experiment., 16 pages, 8 figures

ECT Workshop on Strange Hadronic Matter -- SEP 26-30, 2011 -- Trento, ITALY, WOS: 000304238700020, The HypHI Phase 0 experiment with Li-6 projectiles at 2 A GeV on a carbon target has been performed at GS' in order to demonstrate the feasibility of precise hypernuclear spectroscopy with peripheral heavy ion collisions. Current data analyses have preliminary shown peaks in invariant mass distributions of p + pi(-) for Lambda, He-3 + pi(-) for H-3(Lambda) and He-4 + pi(-) for H-4(Lambda). Lifetime values for the corresponding peaks have been also deduced, which is in good agreement with the former known values. (C) 2012 Elsevier B.V. All rights reserved., Helmholtz Int Ctr FAIR, Japan Soc Promot Sci (JSPS), Integrating Activ Seventh Framework Program EU (Hadron Phys 2)

The elliptic flow in collisions of neutron-rich heavy-ion systems at intermediate energies emerges as an observable sensitive to the strength of the symmetry energy at supra-saturation densities. First results obtained by comparing ratios or differences of neutron and hydrogen flows with predictions of transport models favor a moderately soft to linear density dependence, consistent with ab-initio nuclear-matter theories. Comprehensive data sets of high accuracy can be expected to improve our knowledge of the equation of state of asymmetric nuclear matter., Comment: 16 pages, 8 figures, to appear as a review article in International Journal of Modern Physics E

The relationship between observed intermediate mass fragment and total charged particle multiplicities has been measured for [sup 84]Kr + [sup 197]Au collisions at energies between [ital E]/[ital A]=35 and 400 MeV. Fragment multiplicities are greatest for central or near-central collisions. For these collisions, fragment production increases up to [ital E]/[ital A][approx]100 MeV, and then decreases at higher energies.

The updated ultrarelativistic quantum molecular dynamics (UrQMD) model, a microscopic transport model, is used to study the directed and elliptic collective flows and the nuclear stopping in Au$+$Au collisions at incident energies covered by INDRA and lower-energy FOPI experiments. It is seen clearly that these observables are sensitive to both the potential terms (including isoscalar and isovector parts as well as the momentum dependent term) in the equation of state (EoS) and the collision term [including the Pauli blocking and the medium-modified nucleon-nucleon elastic cross section (NNECS)]. The momentum modifications of both, the mean-field potentials and the density dependent NNECS, are found to affect the collectivity of heavy-ion collisions. At INDRA energies ($\ensuremath{\leqslant}$$150$ MeV/nucleon) the dynamic transport with a soft EoS with momentum dependence and with the momentum-modified density-dependent NNECS describes the directed flow exhibited by hydrogen isotopes ($Z=1$) emitted at midrapidity fairly well.

The N/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at the GSI Schwerionen Synchrotron (SIS). Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. For the interpretation of the data, calculations with the statistical multifragmentation model for a properly chosen ensemble of excited sources were performed. The parameters of the ensemble, representing the variety of excited spectator nuclei expected in a participant-spectator scenario, are determined empirically by searching for an optimum reproduction of the measured fragment-charge distributions and correlations. An overall very good agreement is obtained. The possible modification of the liquid-drop parameters of the fragment description in the hot freeze-out environment is studied, and a significant reduction of the symmetry-term coefficient is found necessary to reproduce the mean neutron-to-proton ratios /Z and the isoscaling parameters of Z, 23 pages, 29 figures, published in Physical Review C

We report the results obtained by applying digital pulse shape acquisition and digital signal processing to the signals from CsI(Tl) scintillators read out by photodiodes at high incident energy (400 MeV/u). The digitized signals allows the discrimination of light charged particles by computing the Fast and Slow components and the Rise Time of the output pulses of the CsI(Tl). When the energies of the light charged particles exceed those corresponding to their ranges in CsI(Tl), the points related to the punching-through particles gather in the corresponding scatter plots giving rise to a cusp. The punching-through points are used as energy calibration points for the reaction products stopped in the CsI(Tl). The obtained results suggest that at relativistic beam energies it is possible to perform efficient discrimination in charge and mass of light charged particles by using the energy vs. rise time computation. © 2011 IEEE.

The elliptic-flow ratio of neutrons with respect to protons or light complex particles in reactions of neutron-rich systems at relativistic energies is proposed as an observable sensitive to the strength of the symmetry term in the equation of state at supra-normal densities. The results obtained from the existing FOPI/LAND data for 197Au + 197Au collisions at 400 MeV/nucleon in comparison with the UrQMD model favor a moderately soft symmetry term with a density dependence of the potential term proportional to rho/rho_0^gamma with gamma = 0.9 +- 0.4., Comment: 13 pages, 5 figures, submitted to Phys. Lett. B

The element yield distributionsσ(Z) of intermediate mass fragments from proton, helium, and heavy-ion induced reactions exhibit a universal behaviour as a function of the bombarding energy. The power law parameterτ, obtained from fits withσ(Z)∝σ -τ, falls monotonically with increasing projectile energy Elab and reaches a saturation valueτ≃2.0 atE lab≃2GeV. It is suggested that the behaviour at low bombarding energies is caused by a dynamical hindrance of the fragment emission at low angular momentum.

Multifragmentation has been measured for [sup 197]Au+[sup 197]Au collisions at [ital E]/[ital A]=100, 250, and 400 MeV. The mean fragment multiplicity increases monotonically with the charged particle multiplicity at [ital E]/[ital A]=100 MeV, but decreases for central collisions with incident energy, consistent with the onset of nuclear vaporization. Molecular dynamics calculations follow some trends but underpredict the observed fragment multiplicities. Including the statistical decay of excited residues improves the agreement for peripheral collisions but worsens it for central collisions.

Inclusive cross sections of intermediate mass fragments from the reaction84Kr+197Au atE/A=35 MeV were measured over the range 8°≦Θlab≦70° with a low detection threshold. A moving-source parameterization was used to fit the double-differential cross sections. The integrated cross section for fragment production exceeds the total reaction cross section thus indicating a large probability for multi-fragment processes. The deduced large temperature parameters can be explained by assuming emission from a rotating source. From the comparison to reactions with12C and40Ar projectiles at E/A=30 MeV a systematics of inclusive fragment production as a function of the projectile mass is obtained.

Proton-proton correlations at small relative momenta were measured for [sup 40]Ar+[sup 197]Au reactions at [ital E]/[ital A]=200 MeV. Comparing the correlation functions to predictions based on single-particle phase space distributions from microscopic Boltzmann-Uehling-Uhlenbeck and quantum-molecular-dynamics (QMD) simulations, no satisfactory agreement could be established. Calculations utilizing two-particle emission probabilities predicted by the QMD model differ significantly from the single-particle calculations and are much closer to the experimental observations at [ital E]/[ital A]=200 MeV, potentially signaling the importance of the two-particle density for the proton-proton correlation function.

We have studied the fragmentation of Au projectiles interacting with targets of C, Al, Cu and Pb at an incident energy of E/A = 600 MeV. The experiment was performed with the ALADiN forward spectrometer at SIS. The employed inverse kinemantics allowed nearly complete detection of projectile fragments with charge Z ≥ 2. In addition, the number of light particles for each collision was measured. We compare different observables characterizing the event and investigate the impact parameter dependence of the fragmentation process. It is found that the correlation between the mean multiplicity of intermediate mass fragments 〈Mimf〉 and Zbound, the sum charges of all projectile fragments with Z≥2, is independent of the target nucleus. This universal behavior is consistent with an - at least partial - equilibration of the projectile fragment prior to its decay. Finally we compare to two classes of statistical models, the sequential decay code GEMINI and statistical multifragmentation models.

The HypHI experiment for precise hypernuclear spectroscopy with induced reactions of stable heavy ion beams and rare isotope beams is currently under preparation at GSI. The main goal of the HypHI project is to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments at GSI and FAIR. In the first HypHI experiment (Phase 0) planned in 2009, the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π- decay channels of [Formula: see text], [Formula: see text] and [Formula: see text] with 6 Li projectiles at 2 A GeV impinging on a 12 C target. An overview of the HypHI project and the details of the Phase 0 experiment will be discussed.

WOS: 000282530300034, The first experiment of the HypHI project, Phase 0, at GSI-Darmstadt performs the feasibility study of precise hypernuclear spectroscopy with heavy ion induced reactions by using the collision of Li-6 at 2 A GeV on a C-12 target. In preparation of the Phase 0 experiment, simulation studies have been performed with a dedicated event reconstruction procedure. Details of this procedure will be discussed in this paper as well as the physics motivation of the Phase 0 and the experimental setup used during simulations. Expected results of the experiment will also be discussed. (C) 2010 Elsevier B.V. All rights reserved., Helmholtz association as Helmholtz-University Young Investigators Group [VH-NG-239]; German Research Foundation (DFG) [SA 1696/1-1]; EU, The HypHI project is funded by the Helmholtz association as Helmholtz-University Young Investigators Group VH-NG-239 at GSI. And it is also funded by German Research Foundation (DFG) with a Contract number SA 1696/1-1. It is also supported by EU FP7 HadronPhysics2 SPHERE.

Aligned fragment emission associated with peripheral and midperipheral dissipative collisions of {sup 124}Xe+{sup 124}Sn at E/A=50 MeV is examined. Binary decay of the excited projectile-like fragment (PLF*) is correlated with significant velocity damping from the projectile velocity. Both a forward emission component, attributed to standard statistical emission, and a backward component are observed. The backward component arises from both statistical and dynamical decay processes. This backward component manifests a strong alignment with the direction of the PLF* velocity and is found to depend sensitively on the atomic number of the light fragment, Z{sub L}, and the velocity of the PLF{sup *}. The yield of the backward component is significantly enhanced relative to the forward component. The composition of fragments emitted in the backward direction reveals that a correlation between alignment and neutron excess exists for fragments with Z

The mean multiplicity of intermediate mass fragments (IMF) {l angle}{ital M}{sub IMF}{r angle} produced by fragmentation of Au projectiles interacting with targets of C, Al, Cu, and Pb at an incident energy of {ital E}/{ital A}=600 MeV is compared to predictions of statistical multifragmentation and sequential evaporation models. The initial conditions for the calculations were provided by Boltzmann-Uehling-Uhlenbeck simulations. In the high excitation energy regime where the IMF multiplicity reaches its maximum the observed universal correlation between {l angle}{ital M}{sub IMF}{r angle} and the total charge {ital Z}{sub bound} of projectile fragments with charges {ital Z}{ge}2 cannot be reproduced by a sequential evaporation code. In this regime the data are better described by statistical decay calculations which assume the formation of an expanded nuclear system and a rather fast breakup.

We have studied the transition from the evaporation to the vaporization regime in 197Au induced reactions on C, Al, and Cu targets at a beam energy of 600 MeV per nucleon. The experiment was performed with the ALADIN forward spectrometer at SIS. We find that with increasing violence of the collision the mean multiplicity of intermediate mass fragments first increases to a maximum ⋍ 3.5 and then decreases again. Calculations using the BUU model suggest that the fragmentation is governed by the energy Edep deposited into the Au nucleus and that the maximum of is reached around Edep = 8 MeV/nucleon.

Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of $^{124}\mathrm{Xe}$ projectiles with $^{112}\mathrm{Sn}$ nuclei at $E/A=50$ MeV is examined. Charge correlations reveal that symmetric breakups occur with significant probability. By selecting on the parallel velocity of the heaviest fragment we minimize the entrance channel dynamics. Calculations with the statistical decay code GEMINI failed to reproduce the experimental charge correlations for any suitable combination of excitation energy and spin considered. A statistical multifragmentation model (SMM) in which breakup of low-density nuclear matter is assumed was able to reproduce the observed charge correlations. The $\ensuremath{\langle}N\ensuremath{\rangle}/Z$ and isotope distributions of fragments were compared to the results of the SMM calculations. Describing the $\ensuremath{\langle}N\ensuremath{\rangle}/Z$ of heavy fragments ($Zg6$) within SMM suggests that a reduction of the symmetry energy parameter from $\ensuremath{\gamma}=25$ to $14$ MeV is necessary. We observe that the yield of neutron-rich isotopes of heavy fragments is particularly sensitive to the symmetry energy.

The elliptic flow (squeeze-out) of neutrons, protons and light complex particles in reactions of neutron-rich systems at relativistic energies is proposed as an observable sensitive to the strength of the symmetry term in the equation of state at supra-normal densities. Preliminary results from a study of the existing FOPI/LAND data for 197Au + 197Au collisions at 400 A MeV with the UrQMD model favor a moderately soft symmetry term with a density dependence of the potential term proportional to (rho/rho_0)^gamma with gamma = 0.6+-0.3., 2 pages, 1 figure, contribution to proceedings of International School of Nuclear Physics, 30th Course, Heavy-Ion Collisions from the Coulomb Barrier to the Quark-Gluon Plasma, Erice-Sicily: 16 - 24 September 2008

WOS: 000270326800009, The construction and properties of three sets of two-dimensional scintillating fiber detector arrays for tracking of charged particles used in the HypHI Phase 0 experiment at GSI will be reported in this paper. The position resolutions and the detection efficiency of detectors have been obtained for each layer of detectors by using Li-6 primary beams and particles with Z = 1 produced by fragment reactions of Xe-136 projectiles on the hydrogen target. Besides, the response of energy deposition of charged particles in the first detector set placed right behind the target has been studied by using light projectile fragments with Z = 1, 2 and 3 produced by Ni-58 and C-12 beams. Extracted resolutions for energy deposition and position as well as the detection efficiency fulfill the requirements of the HypHl Phase 0 experiment. (C) 2009 Elsevier B.V. All rights reserved., Helmholtz association as Helmholtz-University Young Investigators Group [VH-NG-239]; German Research Foundation (DFG) [SA 1696/1-1]; Ministry of Education, Science and Culture of Japan [18042008]; EU FP7 HadronPhysic2 SPHERE, We would like to thank the accelerator department at GSI for providing us beams with excellent conditions. We would also thank H. lwase, R. Pleskac and D. Schardt to help us during the experiment in cave A at GSI. We would like to show our appreciation to the FOPI and SPALADIN collaboration to provide us beams behind their experimental setups. We would also like to show our gratitude to the Detector Laboratory at GSI, Electronics Department of the Institute for Nuclear Physics of Mainz University, the Experimental Electronics Department at GSI and the Target Laboratory at GSI for their supports for the development. The HypHI project is funded by the Helmholtz association as Helmholtz-University Young Investigators Group VH-NG-239 at GSI, and German Research Foundation (DFG) with a contract number SA 1696/1-1. The authors acknowledge financial support by the Ministry of Education, Science and Culture of Japan, Grantin-Aid for Scientific Research on Priority Areas 449. This work is also supported by the Ministry of Education, Science and Culture of Japan, Grant-in-Aids for Scientific Research 18042008 and EU FP7 HadronPhysic2 SPHERE.

It has been shown that the symmetry energy and the surface energy of hot fragments at the low‐density freeze‐out can be considerably modified. The influence of these changes on fragment yields and isotope distributions is discussed by analyzing recent ALADIN experimental data on spectator fragmentation at incident energy 600 A MeV.

Recently, is has been observed that events with the {\it same} total transverse energy of light charged particles (LCP) in the quasi target region, $E_{\perp 12}^{QT}$, show two quite distinct reaction scenarios in the projectile domain: multifragmentation and residue production. This phenomenon has been dubbed "bimodality". Using Quantum Molecular Dynamics calculations we demonstrate that this observation is very general. It appears in collisions of all symmetric systems larger than Ca and at beam energies between 50 A.MeV and 600 A.MeV and is due to large fluctuations of the impact parameter for a given $E_{\perp 12}^{QT}$. Investigating in detail the $E_{\perp 12}^{QT}$ bin in which both scenarios are present, we find that neither the average fragment momenta nor the average transverse and longitudinal energies of fragments show the behavior expected from a system in statistical equilibrium, in experiment as well as in QMD simulations. On the contrary, the experimental as well as the theoretical results point towards a fast process. This observation questions the conjecture that the observed bimodality is due to the coexistence of 2 phases at a given temperature in finite systems., Comment: accepted PRC

Apparent emission temperatures of 4 He and 5 Li fragments were deduced for the reaction 40 Ar+ 197 Au at E / A =200 MeV from the relative population of excited states. Compared to previous measurements at E / A =60 MeV, the average emission temperatures increases by less than 2 MeV to a value of about 6 MeV. QMD calculations indicate that the momentum distribution of the nucleons forming a fragment is determined at a point where the system is still close to normal nuclear density and that they do not reflect the local momentum distribution of the surrounding nucleons. The simulations suggest that the observed low emission temperatures are a consequence of the dynamics of the fragment formation process.

We investigate the onset of multifragmentation employing an improved version of the {ital N}-body quantum'' molecular-dynamics approach. We study in detail the reaction {sup 18}O+{sup 197}Au at 84 MeV/nucleon and find good agreement between the calculated results and the data for the double-differential proton cross section, the mass yield, the multiplicity, the kinetic energy of the fragments, and even for the kinematic correlations between intermediate mass fragments (IMF's), which have been measured in this experiment for the first time. We observe a strong correlation between the impact parameter and both the size of the target remnant as well as the average proton multiplicity. Hence both observables can be used to determine the impact parameter experimentally. The IMF's come from the most central collisions. The calculations confirm the experimental result that they are not emitted from an equilibrated system. Although the inclusive energy spectra look thermal, we cannot identify an impact parameter-independent isotropically emitting source. Even in central collisions global equilibrium is not observed. We find that multifragment emission at this bombarding energy is caused by a process very similar to that proposed in the macroscopic cold multifragmentation model. Thus it has a different origin than at beam energies around 1more » GeV/nucleon, although the mass yield has an almost identical slope.« less

Inclusive cross sections of intermediate mass fragments from the reaction {sup 40}Ar+{sup 197}Au at {ital E}/{ital A}=30 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 increased isotropy of the angular distributions and the strongly reduced Coulomb repulsion at the higher bombarding energy suggest that the emission process evolves towards fragmentation of excited spectator matter in central ion-ion collisions.

We have studied the fragmentation of Au projectiles interacting with targets of C, Al and Cu at an incident energy ofE/A=600 MeV. The employed inverse kinematics allowed a nearly complete detection of projectile fragments with chargeZ≧2. The recorded fragmentation events were sorted according to three observables, the multiplicityMlp of light charged particles, the largest atomic numberZmax within an event, and a new observable,Zbound, representing the sum of the atomic numbersZ of all fragments withZ≧2. Using these observables, the impact parameter dependence of the fragmentation process was investigated. For all three targets, a maximum mean multiplicity of 3 to 4 intermediate mass fragments (IMFs) is observed. The corresponding impact parameters range from central collisions for theC target to increasingly peripheral collisions for the heavier targets. It is found that the correlation between the IMF multiplicity andZbound, extending from evaporation type processes (largeZbound) to the total disassembly of the projectile (smallZbound), is independent of the target nucleus. This universal behaviour may suggest an — at least partial — equilibration of the projectile fragment prior to its decay.

R. BASSINI5), , C. BOIANO5), A.S. BOTVINA2), A. BOUDARD6), J. BRZYCHCZYK4), A. CHBIHI1), J. CIBOR8), B. CZECH8), J.-E. DUCRET6), H. EMLING2), J. FRANKLAND7), M. HELLSTROM2), D. HENZLOVA1), K. KEZZAR2), G. IMME1), I. IORI5), H. JOHANSSON2), A. LAFRIAKH3), , E. LE GENTIL6), Y. LEIFELS2) , W.G. LYNCH9), J. LUHNING2), , U. LYNEN2), Z. MAJKA4), M. MOCKO9), W.F.J. MULLER2), A. MYKULYAK10), H. ORTH2), A.N. OTTE2), R. PALIT2), P. PAW LOWSKI8) , A. PULLIA5), G. RACITI1), E. RAPISARDA1), H. SANN2), C. SCHWARZ2), H. SIMON2), K. SUMMERER2), M.B. TSANG9), C. VOLANT6), M. WALLACE9), H. WEICK2), J. WIECHULA2), A. WIELOCH4) and B. ZWIEGLINSKI10) 1) Dipartimento di Fisica, Universita degli studi di Catania and LNS-INFN, 64, Via S. Sofia, I-95123 Catania, Italy 2) Gesellschaft fur Schwerionenforchung, D-64291 Darmstadt, Germany 3) Institut de Physique Nucleaire, IN2P3-CNRS et Universite, F-91406 Orsay, France 4) M. Smoluchowski Institute of Physics, Jagiellonian Univ., Pl-30059 Krakow, Poland 5) Istituto di Scienze Fisiche, Universita degli Studi and INFN, I-20133 Milano, Italy 6) DAPNIA/SPhN, CEA/Saclay, F-91191 Gif-sur-Yvette, France 7) GANIL, CEA et IN2P3-CNRS, F-14076 Caen, France; 8) H. Niewodniczanski Institute of Nuclear Physics, Pl-31342 Krakow,Poland 9) Department of Physics and Astronomy and NSCL, MSU, East Lansing, MI 48824, USA; 10) A. So ltan Institute for Nuclear Studies, Pl-00681 Warsaw, Poland

The spallation of Fe-56 in collisions with hydrogen at 1A GeV has been studied in inverse kinematics with the large-aperture setup SPALADIN at GSI. Coincidences of residues with low-center-of-mass kinetic energy light particles and fragments have been measured allowing the decomposition of the total reaction cross section into the different possible deexcitation channels. Detailed information on the evolution of these deexcitation channels with excitation energy has also been obtained. The comparison of the data with predictions of several deexcitation models coupled to the INCL4 intranuclear cascade model shows that only GEMINI can reasonably account for the bulk of collected results, indicating that in a light system with no compression and little angular momentum, multifragmentation might not be necessary to explain the data.

The HypHI collaboration aims to perform a precise hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and fAIR in order to study hypernuclei at extreme isospin, especially neutron rich hypernuclei to look insight hyperon-nucleon interactions in the neutron rich medium, and hypernuclear magnetic moments to investigate baryon properties in the nuclei. We are currently preparing for the first experiment with $^6$Li and $^{12}$C beams at 2 AGeV to demonstrate the feasibility of a precise hypernuclear spectroscopy by identifying $^{3}_{\Lambda}$H, $^{4}_{\Lambda}$H and $^{5}_{\Lambda}$He. The first physics experiment on these hypernuclei is planned for 2009. In the present document, an overview of the HypHI project and the details of this first experiment will be discussed., Comment: 5 pages, 2 figures, French-Japanese symposium 2008, Paris (France)

The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around 124La and 107Sn were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable 124Sn projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods., Comment: 6 pages, 7 eps figures, elsart, submitted to Nucl. Instr. and Meth. A

Peripheral {sup 40}Ar+{sup 232}Th collisions at a bombarding energy {ital E}/{ital A}=30 MeV were studied by measuring coincidences of fission fragments with projectile fragments detected near the grazing angle. It is found that the sequential fission of the highly excited target residue nuclei is severely hindered if their excitation energies, determined from the measured recoil momenta, exceed a value of abour 50--75 MeV. A transient time of fission of the order of 10{sup {minus}20} s is deduced.

The backward-angle yield from 12 C + 24 Mg has been studied with the technique of inverse kinematics, using 24 Mg beams with energies from 90 to 126 MeV. In the different exit channels with 5 ⩽ Z ejectile ⩽9 the Q -integrated differential cross sections d σ d θ are consistent with isotropy at 130° ⩽ θ c.m. ⩽ 165°, which is taken as signature of orbiting. The most probable exit energies in the strongly predominant even- Z channels as a function of bombarding energy give evidence for complete damping at angular momenta close to the critical ones for fusion. The results for the weakly populated odd- Z channels suggest that the conditions of damping are affected by the large negative ground-state Q -values. Structures are observed in the Q -value spectra and in the excitation functions at given Q . The former are identified with high-spin states close to the yrast lines, which are shown to be selectively populated due to the matching conditions for deep-inelastic reactions in light heavy-ion systems. An additional selectivity for natural-parity transitions gives evidence for the conservation of the dinuclear parentage. Narrow fluctuations observed in the excitation functions for fixed narrow Q -windows are attributed to the overlapping of unbound states of the intermediate complex. In the Q -integrated excitation functions these fluctuations cancel, but weak gross structure of a few MeV width remains visible. A statistical analysis of the narrow fluctuations yields coherence widths around 400 keV, corresponding to lifetimes of the intermediate dinucleus around 2 × 10 −21 s.

The spallation of 56Fe in collisions with hydrogen at 1A GeV has been studied in inverse kinematics with the large-aperture setup SPALADIN at GSI. Coincidences of residues with low-center-of-mass kinetic energy light particles and fragments have been measured allowing the decomposition of the total reaction cross section into the different possible deexcitation channels. Detailed information on the evolution of these deexcitation channels with excitation energy has also been obtained. The comparison of the data with predictions of several deexcitation models coupled to the INCL4 intranuclear cascade model shows that only GEMINI can reasonably account for the bulk of collected results, indicating that in a light system with no compression and little angular momentum, multifragmentation might not be necessary to explain the data.

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 Au+Au system displays, in the simulations as in the experiment, simultaneously dynamical and statistical behavior, which we analyze in detail. The composition of fragments close to midrapidity follows statistical laws, and the system shows bimodality, i.e., a sudden transition between different fragmentation patterns, as a function of centrality, as expected for a phase transition. The fragment spectra at small and large rapidities, on the other hand, are determined by dynamics, and the system as a whole does not come to equilibrium--an observation that is confirmed by FOPI Collaboration experiments for the same system.

The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of \Delta A/A \approx 1.5%, lighter isotopes with atomic numbers Z \le 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations., Comment: 11 pages, 5 figures, Proceedings of International Workshop on Nuclear Dynamics in Heavy-Ion Reactions and Neutron Stars, Beijing, July 10-14, 2007, to appear in International Journal of Modern Physics E

The SPALADIN experiment using the inverse-kinematics technique where the heavy-ion beam is sent onto a liquid-hydrogen target has been carried out at GSI (Darmstadt, Germany) in order to study the spallation of 56 Fe. On an event-by-event basis, spallation residues, light-charged fragments and neutrons have been detected in coincidence. The set-up is based on a large aperture magnet (ALADiN) equipped with a time-projection chamber (TPC), a hodoscope and a high-efficiency neutron detector. The combination of the inverse kinematics and of the acceptance of the set-up focuses the measurement on the low centre-of-mass energy fragments of the reaction essentially originating from the de-excitation of the prefragment formed at the end of the intranuclear cascade. Data taken at 1GeV per nucleon have been analysed. Preliminary results on coincidence observables are shown and compared to theoretical calculations. We emphasize on the identification of different types of multi-fragment final states which correspond to different decay channels and allow to probe different decay mechanisms.