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The neutron emission in projectile fragmentation at relativistic energies was studied with the Large-Area-Neutron-Detector LAND coupled to the ALADIN forward spectrometer at the GSI Schwerionen-Synchrotron (SIS). Stable 124Sn and radioactive 107Sn and 124La beams with an incident energy of 600 MeV/nucleon were used to explore the N/Z dependence of the identified neutron source. A cluster-recognition algorithm is applied for identifying individual particles within the hit distributions registered with LAND. The obtained momentum distributions are extrapolated over the full phase space occupied by the neutrons from the projectile-spectator source. The mean multiplicities of spectator neutrons reach values of up to about 11 and depend strongly on the isotopic composition of the projectile. An effective source temperature of T \approx 2-5 MeV, monotonically increasing with decreasing impact parameter, is deduced from the transverse momentum distributions. For the interpretation of the data, calculations with the statistical multifragmentation model were performed. The variety of excited projectile spectators assumed to decay statistically is represented by an ensemble of excited sources with parameters determined previously from the fragment production observed in the same experiments. The obtained agreement is very satisfactory for more peripheral collisions where, according to the model, neutrons are mainly emitted during the secondary decays of excited fragments. The neutron multiplicity in more central collisions is underestimated, indicating that other sources besides the modeled statistical breakup contribute to the observed neutron yield. The choice made for the symmetry-term coefficient of the liquid-drop description of produced fragments has a weak effect on the predicted neutron multiplicities., Comment: 22 pages, 24 figures, to appear in Physical Review C

Isotopic yield distributions of nuclei produced in peripheral collisions of $^{80}$Kr+$^{40,48}$Ca at 35 MeV/nucleon are studied. Experimental results obtained by the FAZIA Collaboration at the LNS facility in Catania are compared with calculations performed with the statistical multifragmentation model (SMM). The fragments with atomic number $Z=19-24$ observed at forward angles are successfully described with the ensemble method previously established for reactions at higher energy. Using the SMM results, the isotopic compositions of the projectile residues are reconstructed. The results indicate a significant isospin exchange between the projectile and target nuclei, not far from isospin equilibrium, during the initial phase of the reaction. The two groups of light fragments with $Z=1-4$, experimentally distinguished by their velocities relative to coincident heavy projectile fragments, are found to originate from different sources. The isotopic composition of the slower group is consistent with emission from a low-density neck, enriched in neutrons, and satisfactorily reproduced with SMM calculations for a corresponding neck source of small mass., Comment: 15 pages, 12 figures, 3 tables, accepted for publication in Physical Review C

Interpreting high-energy, astrophysical phenomena, such as supernova explosions or neutron-star collisions, requires a robust understanding of matter at supranuclear densities. However, our knowledge about dense matter explored in the cores of neutron stars remains limited. Fortunately, dense matter is not only probed in astrophysical observations, but also in terrestrial heavy-ion collision experiments. In this work, we use Bayesian inference to combine data from astrophysical multi-messenger observations of neutron stars and from heavy-ion collisions of gold nuclei at relativistic energies with microscopic nuclear theory calculations to improve our understanding of dense matter. We find that the inclusion of heavy-ion collision data indicates an increase in the pressure in dense matter relative to previous analyses, shifting neutron-star radii towards larger values, consistent with recent NICER observations. Our findings show that constraints from heavy-ion collision experiments show a remarkable consistency with multi-messenger observations and provide complementary information on nuclear matter at intermediate densities. This work combines nuclear theory, nuclear experiment, and astrophysical observations, and shows how joint analyses can shed light on the properties of neutron-rich supranuclear matter over the density range probed in neutron stars., Comment: 7 pages, 2 figures, Supplemental Material, minor changes

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

The cumulant ratios up to fourth order of the $Z$ distributions of the largest fragment in spectator fragmentation following $^{107,124}$Sn+Sn and $^{124}$La+Sn collisions at 600 MeV/nucleon have been investigated. They are found to exhibit the signatures of a second-order phase transition established with cubic bond percolation and previously observed in the ALADIN experimental data for fragmentation of $^{197}$Au projectiles at similar energies. The deduced pseudocritical points are found to be only weakly dependent on the $A/Z$ ratio of the fragmenting spectator source. The same holds for the corresponding chemical freeze-out temperatures of close to 6 MeV. The experimental cumulant distributions are quantitatively reproduced with the Statistical Multifragmentation Model and parameters used to describe the experimental fragment multiplicities, isotope distributions and their correlations with impact-parameter related observables in these reactions. The characteristic coincidence of the zero transition of the skewness with the minimum of the kurtosis excess appears to be a generic property of statistical models and is found to coincide with the maximum of the heat capacity in the canonical thermodynamic fragmentation model., Comment: 13 pages, 5 figures

The elliptic flow of emitted particles and fragments observed in heavy-ion reactions at high energy has become an important observable reflecting the pressure generated in the dense collision zone. More recently, the strength of the nuclear symmetry energy has been investigated by measuring the ratios or differences of the elliptic flows exhibited by neutrons and charged particles in 197Au+197Au collisions at 400 MeV/nucleon incident energy at the GSI laboratory. A moderately soft to linear dependence on density was deduced for a range of densities shown to reach beyond twice the saturation value in these experiments. The known sources of uncertainties and possible model dependencies were thoroughly studied with transport models of the UrQMD and Tuebingen QMD type. A new source of information on the nuclear equation of state at high density has opened up with the observation of the first LIGO and Virgo GW170817 gravitational wave signal from a neutron star merger. The quantitative comparison of terrestrial and celestial results on the basis of measured or inferred neutron star radii or core pressures, including those obtained from X-ray observations, reveals a rather satisfactory agreement. Depending on the precision that can be achieved with future measurements and observations, it will thus become possible to assess the validity of the applied models and methods. The perspectives for improved experiments at FAIR using the NeuLAND and KRAB detection systems are outlined., Comment: 15 pages, 10 figures, to appear in the AIP Conference Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy (January 3 - 7, 2019, Xiamen, China)

Distributions of the largest fragment charge are studied using the ALADIN data on fragmentation of $^{197}$Au projectiles at relativistic energies. The statistical measures skewness and kurtosis of higher-order fluctuations provide a robust indication of the transition point, linked to a phase transition in the thermodynamic limit. Extensive comparisons with predictions of a bond percolation model corroborate the high accuracy of this model in reproducing the distributions as well as the whole fragmentation pattern as represented by the measured charge correlations. In analogy to percolation, the pseudocritical and critical points are identified in the fragmentation data. Questions concerning the distinction between different models and between first- and second-order phase transitions are discussed., Comment: 29 pages, 13 figures, submitted to Phys. Rev. C

New constraints for the nuclear equation of state at suprasaturation densities have been obtained by measuring collective particle flows in heavy-ion reactions at relativistic energies. Ratios and differences of neutron and hydrogen flows in 197Au + 197Au collisions at 400 MeV/nucleon were used in studies of the asymmetric-matter equation of state. The comparison with predictions of transport models favors a moderately soft to linear density dependence, consistent with ab-initio nuclear matter theories. Model predictions suggest that comprehensive data sets collected at higher bombarding energies will provide information on the asymmetric-matter equation of state in the density range up to two or three times the saturation value., Comment: 20 pages, 9 figures, paper dedicated to the memory of Prof. Walter Greiner, to appear in Walter Greiner Memorial Volume (World Scientific). arXiv admin note: substantial text overlap with arXiv:1205.2585

Directed and elliptic flows of neutrons and light charged particles were measured for the reaction 197Au+197Au at 400 MeV/nucleon incident energy within the ASY-EOS experimental campaign at the GSI laboratory. The detection system consisted of the Large Area Neutron Detector LAND, combined with parts of the CHIMERA multidetector, of the ALADIN Time-of-flight Wall, and of the Washington-University Microball detector. The latter three arrays were used for the event characterization and reaction-plane reconstruction. In addition, an array of triple telescopes, KRATTA, was used for complementary measurements of the isotopic composition and flows of light charged particles. From the comparison of the elliptic flow ratio of neutrons with respect to charged particles with UrQMD predictions, a value \gamma = 0.72 \pm 0.19 is obtained for the power-law coefficient describing the density dependence of the potential part in the parametrization of the symmetry energy. It represents a new and more stringent constraint for the regime of supra-saturation density and confirms, with a considerably smaller uncertainty, the moderately soft to linear density dependence deduced from the earlier FOPI-LAND data. The densities probed are shown to reach beyond twice saturation., Comment: 25 pages, 22 figures, accepted for publication in Physical Review C

Within the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, the transverse-velocity dependence of the elliptic flow of free nucleons from $^{197}$Au+$^{197}$Au collisions at the incident energy 400 MeV$/$nucleon is studied within different windows of the normalized c.m. rapidity $y_0$. It is found that the elliptic flow difference $v_{2}^{n}$-$v_{2}^{p}$ and ratio $v_{2}^{n}$/$v_{2}^{p}$ of neutrons versus protons are sensitive to the density dependence of the symmetry energy, especially the ratio $v_{2}^{n}$/$v_{2}^{p}$ at small transverse velocity in the intermediate rapidity intervals $0.4<|y_0|<0.6$. By comparing either transverse-momentum dependent or integrated FOPI/LAND elliptic flow data of nucleons and hydrogen isotopes with calculations using various Skyrme interactions, all exhibiting similar values of isoscalar incompressibility but very different density dependences of the symmetry energy, a moderately soft to linear symmetry energy is extracted, in good agreement with previous UrQMD or T\"{u}bingen QMD model calculations but contrasting results obtained with $\pi^-/\pi^+$ yield ratios available in the literature., Comment: 20 pages, 6 figures, accepted by Phys. Rev. C

We analyze the production cross sections and isotopic distributions of projectile-like residues in the reactions $^{112}$Sn + $^{112}$Sn and $^{124}$Sn + $^{124}$Sn at an incident beam energy of 1 GeV/nucleon measured with the FRS fragment separator at the GSI laboratory. Calculations within the statistical multifragmentation model (SMM) for an ensemble of excited sources were performed with ensemble parameters determined previously for similar reactions at 600 MeV/nucleon. The obtained good agreement with the experiment establishes the universal properties of the excited spectator systems produced during the dynamical stage of the reaction. It is furthermore confirmed that a significant reduction of the symmetry-energy term at the freeze-out stage of reduced density and high temperature is necessary to reproduce the experimental isotope distributions. A trend of decreasing symmetry energy for large neutron-rich fragments of low excitation energy is interpreted as a nuclear-structure effect., Comment: Accepted for publicatiion in Phys.Rev.C (8 pages, 6 figures)

Flow observables in heavy-ion reactions at incident energies up to about 1 GeV per nucleon have been shown to be very useful for investigating the reaction dynamics and for determining the parameters of reaction models based on transport theory. In particular, the elliptic flow in collisions of neutron-rich heavy-ion systems emerges as an observable sensitive to the strength of the symmetry energy at supra-saturation densities. The comparison of ratios or differences of neutron and proton flows or neutron and hydrogen flows with predictions of transport models favors an approximately linear density dependence, consistent with ab-initio nuclear-matter theories. Extensive parameter searches have shown that the model dependence is comparable to the uncertainties of existing experimental data. Comprehensive new flow data of high accuracy, partly also through providing stronger constraints on model parameters, can thus be expected to improve our knowledge of the equation of state of asymmetric nuclear matter., Comment: 20 pages, 24 figures, review to appear in EPJA special volume on nuclear symmetry energy

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes., Comment: Invited Talk given at the Conference Nuclear Physice in Astrophysics VI (NPA6), Lisbon, Portugal, May 19-24 2013. To appear in the NPA6 Proceedings in Journal of Physics: Conference Series (JPCS)

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

A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy-ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear products of 6Li projectiles on a carbon target at 2 AGeV was performed. Signals of the \Lambda-hyperon and 3\Lambda H and 4\Lambda H hypernuclei were observed for final states of p+\pi^-, 3He+\pi^- and 4He+\pi^-, respectively, with significance values of 6.7, 4.7 and 4.9\sigma. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be $262 ^{+56}_{-43} \pm 45$ ps for \Lambda, $183 ^{+42}_{-32} \pm 37$ ps for 3\Lambda H, and $140 ^{+48}_{-33}\pm 35 $ ps for 4\Lambda H., Comment: 13 pages, 10 figures, accepted for publication in Nuclear Physics A, v2 : revised few references

The Skyrme potential energy density functional is introduced into the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model and the updated version is applied to studying the directed and elliptic flows of light particles (protons, neutrons, deuterons, tritons, $^3$He and $^4$He) in $^{197}$Au+$^{197}$Au collisions at beam energies 150, 250 and 400 MeV/nucleon. The results are compared with the recent FOPI experimental data. It is found that the yields and collective flows of light particles can be described quite well. The influence of the equation of state (EoS), medium-modified nucleon-nucleon elastic cross sections (NNECS) and cluster recognition criteria on the directed and elliptic flows is studied in detail. It is found that the flows of light particles are sensitive to the medium-modified NNECS, but not sensitive to the isospin dependent cluster recognition criteria. It seems difficult, however, even with the new data and calculations, to obtain a more accurate constraint on the nuclear incompressibility $K_0$ than the interval 200-260 MeV., Comment: 23 pages, 8 figures,revised version accepted for publication in Phys. Rev. C

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

The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich heavy-ions systems at intermediate energies has been proposed as an observable sensitive to the strength of the symmetry term in the nuclear Equation Of State (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011., Comment: Talk given by P. Russotto at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS)

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 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., Comment: 16 pages, 8 figures

The neutron emission in the fragmentation of stable and radioactive Sn and La projectiles of 600 MeV per nucleon has been studied with the Large Neutron Detector LAND coupled to the ALADIN forward spectrometer at SIS. A cluster-recognition algorithm is used to identify individual particles within the hit distributions registered with LAND. The obtained momentum distributions are extrapolated over the full phase space occupied by the neutrons from the projectile-spectator source. The mean multiplicities of spectator neutrons reach values of up to 12 and depend strongly on the isotopic composition of the projectile. An effective source temperature of T approx. 3 - 4 MeV is deduced from the transverse momentum distributions. For the interpretation of the data, calculations with the Statistical Multifragmentation Model for a properly chosen ensemble of excited sources were performed. The possible modification of the liquid-drop parameters of the fragment description in the hot environment is studied, and a significant reduction of the symmetry-term coefficient is found necessary to simultaneously reproduce the neutron multiplicities and the mean neutron-to-proton ratios /Z of Z <= 10 fragments. Because of the similarity of the freeze-out conditions with those encountered in supernova scenarios, this is of astrophysical interest., Comment: 9 pages, 6 figures, XLIX International Winter Meeting on Nuclear Physics, Bormio 2011, contribution to the proceedings, to be published in Proceedings of Science

The 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 iso-scalar and iso-vector 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 be sensitive to the collectivity of heavy-ion collisions. At INDRA energies ($\le 150$~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 mid-rapidity fairly well., Comment: 28 pages,8 figures, 3 tables

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 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<=10 fragments. The calculations are, furthermore, used to address open questions regarding the modification of the surface-term coefficient at freeze-out, the N/Z dependence of the nuclear caloric curve, and the isotopic evolution of the spectator system between its formation during the initial cascade stage of the reaction and its subsequent breakup., Comment: 23 pages, 29 figures, published in Physical Review C

ALADIN multifragmentation data show features characteristic of a critical behavior, which are very well reproduced by a bond percolation model. This suggests, in the context of the lattice gas model, that fragments are formed at nearly normal nuclear densities and temperatures corresponding to the Kertesz line. Calculations performed with a lattice gas model have shown that similarly good reproduction of the data can also be achieved at lower densities, particularly in the liquid-gas coexistence region., Comment: 7 pages, 4 figures, Proceedings of the International Workshop on Multifragmentation and Related Topics (IWM2009), Catania, Italy, November 2009.

A phase transition signature associated with cumulants of the largest fragment size distribution has been identified in statistical multifragmentation models and examined in analysis of the ALADIN S254 data on fragmentation of neutron-poor and neutron-rich projectiles. Characteristics of the transition point indicated by this signature are weakly dependent on the A/Z ratio of the fragmenting spectator source. In particular, chemical freeze-out temperatures are estimated within the range 5.9 to 6.5 MeV. The experimental results are well reproduced by the SMM model., Comment: 7 pages, 3 figures, Proceedings of the International Workshop on Multifragmentation and Related Topics (IWM2009), Catania, Italy, November 2009.

Aladin data on fragmentation of 197Au projectiles are remarkably well reproduced by a bond percolation model. A critical behavior is identified on the basis of fluctuations of the largest fragment size., Comment: 4 pages, 2 figures, Proceedings of International Workshop on Multifragmentation and Related Topics (IWM2009), Catania, Italy, 4 Nov - 7 Nov 2009.

New results for the strength of the symmetry energy are presented which illustrate the complementary aspects encountered in reactions probing nuclear densities below and above saturation. A systematic study of isotopic effects in spectator fragmentation was performed at the ALADIN spectrometer with 124Sn primary and 107Sn and 124La secondary beams of 600 MeV/nucleon incident energy. The analysis within the Statistical Fragmentation Model shows that the symmetry-term coefficient entering the liquid-drop description of the emerging fragments decreases significantly as the multiplicity of fragments and light particles from the disintegration of the produced spectator systems increases. Higher densities were probed in the FOPI/LAND study of nucleon and light-particle flows in central and mid-peripheral collisions of 197Au+197Au nuclei at 400 MeV/nucleon incident energy. From the comparison of the measured neutron and hydrogen squeeze-out ratios with predictions of the UrQMD model a moderately soft symmetry term with a density dependence of the potential term proportional to (rho/rho_0)^{gamma} with gamma = 0.9 +- 0.3 is favored., Comment: 11 pages, 7 figures, Proceedings of IWND09, August 22 - 25, 2009, Shanghai (China)

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

The elliptic flow 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 = 0.9 +- 0.3., Comment: 4 pages, 2 figures, contribution to Proceedings of the XLVII International Winter Meeting on Nuclear Physics, Bormio (Italy), Jan. 26-30, 2009

Isotopic effects in projectile fragmentation at relativistic energies have been studied with the ALADIN forward spectrometer at 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. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z ratio of the produced spectator sources, consistent with predictions for expanded systems. Consequences for the proposed interpretation of chemical breakup temperatures as representing the limiting temperatures predicted by microscopic models are discussed., Comment: 7 pages, 4 figures, 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

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., Comment: 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

The A/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of 124Sn and radioactive beams of 124La and 107Sn at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects (\Delta T \approx 0.6 MeV) appear for residue production near the onset of multifragmentation., Comment: 11 pages, 3 figures, accepted for publ. in Phys. Rev. Lett

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 systematic data set on isotopic effects in spectator fragmentation collected recently at the GSI laboratory permits the investigation of the N/Z dependence of the nuclear caloric curve which is of interest in several respects. In particular, new light is shed on the proposed interpretation of chemical breakup temperatures as a manifestation of the limiting temperatures predicted by the Hartree-Fock model. The obtained results are discussed within the general context of temperature measurements in multifragmentation reactions., Comment: 9 pages, 6 figures, contribution to XLVI International Winter Meeting on Nuclear Physics, January 20-26 2008, Bormio, Italy

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

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 INDRA at GSI, a prolate shape aligned along the beam direction with an axis ratio of 1:0.7 is deduced. The sensitivity of the method is discussed in comparison with conventional fragment-fragment velocity correlations., Comment: 12 pages, 5 figures, subm. to Phys. Lett. B

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, fragment size and fluctuation observables. A Fisher scaling is observed for all the data. The pseudo-critical energies extracted from the Fisher scaling are consistent between Xe+Sn central collisions and Au quasi-projectiles. In the latter case it also corresponds to the energy region at which fluctuations are maximal. The critical energies deduced from the Zipf analysis are higher than those from the Fisher analysis., Comment: 30 pages, accepted for publication in Nuclear Physics A, references corrected

Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were determined for spectator fragmentation, following collisions of 197Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations., Comment: 14 pages, 10 figures, submitted to Phys. Rev. C, small changes as suggested by the editors and referees

We present results of a flow analysis for the set of reactions of 124,129Xe projectiles and 112,124Sn targets at incident energies 100 and 150 A MeV studied with the INDRA detector at GSI. The dependence on centrality and on p_t of the directed and elliptic flow are determined for isotopically selected reaction products with Z \le 3. The flow parameters v_1 and v_2, in general, follow expected trends but isotopic effects are small., Comment: 3 pages, 2 figures, contributed talk at INPC, Tokyo, June 3-8, 2007, to appear in the proceedings

The spallation of $^{56}$Fe in collisions with hydrogen at 1 A 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 de-excitation channels. Detailed information on the evolution of these de-excitation channels with excitation energy has also been obtained. The comparison of the data with predictions of several de-excitation models coupled to the INCL4 intra-nuclear 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., Comment: 4 pages, 5 figures, revised version accepted in Phys. Rev. Lett

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

The fluctuations of the largest fragment charge of a partition and of the charge asymmetries of the two or three largest fragments in spectator decays following 197Au + 197Au collisions at 1000 MeV per nucleon are investigated. The observed bimodal distributions at specific values of the sorting variable Z_bound exhibit features known from percolation theory where they appear as finite-size effects. The underlying configurational fluctuations seem generic for fragmentation processes in small systems., Comment: 10 pages, 7 figures, to appear in Proceedings of the XLVth International Winter Meeting on Nuclear Physics}, Bormio, Italy, January 2007 (one reference added after submission)

A systematic study of isotopic effects in the break-up of projectile spectators at relativistic energies has been performed at the GSI laboratory with the ALADiN spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn produced at the FRS fragment separator have been used in order to extend the range of isotopic compositions. The gross properties of projectile fragmentation are very similar for all the studied systems but specific isotopic effects have been observed in both neutron and charged particle production. The breakup temperatures obtained from the double ratios of isotopic yields have been extracted and compared with the limiting-temperature expectation., Comment: 10 pages, 5 figures, Proceeding of the XLV International Winter Meeting on Nuclear Physics, Bormio (Italy), 14-21 January 2007

During the collapse of massive stars, and the supernova type-II explosions, stellar matter reaches densities and temperatures which are similar to the ones obtained in intermediate-energy nucleus-nucleus collisions. The nuclear multifragmentation reactions can be used for determination of properties of nuclear matter at subnuclear densities, in the region of the nuclear liquid-gas phase transition. It is demonstrated that the modified properties of hot nuclei (in particular, their symmetry energy) extracted from the multifragmentation data can essentially influence nuclear composition of stellar matter. The effects on weak processes, and on the nucleosynthesis are also discussed., Comment: 6 pages, 4 figures, a talk at the International Conference on Nucleus-Nucleus Collisions, Rio de Janeiro, Brazil, 2006

Isotopic effects in spectator fragmentations following heavy-ion collisions at relativistic energies are investigated using data from recent exclusive experiments with SIS beams at GSI. Reactions of 12C on 112,124Sn at incident energies 300 and 600 MeV per nucleon were studied with the INDRA multidetector while the fragmentation of stable 124Sn and radioactive 107Sn and 124La projectiles was studied with the ALADIN spectrometer. The global characteristics of the reactions are very similar. This includes the rise and fall of fragment production and deduced observables as, e.g., the breakup temperature obtained from double ratios of isotope yields. The mass distributions depend strongly on the neutron-to-proton ratio of the decaying system, as expected for a simultaneous statistical breakup. The ratios of light-isotope yields from neutron-rich and neutron-poor systems follow the law of isoscaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. This is not compensated by an equivalent rise of the breakup temperatures which suggests a reduction of the symmetry term required in a liquid-drop description of the fragments at freeze-out., Comment: 10 pages, 5 figures, invited talk at IX International Conference on Nucleus Nucleus Collisions, Rio de Janeiro, Brazil August 28 - September 1, 2006

The results from ten statistical multifragmentation models have been compared with each other using selected experimental observables. Even though details in any single observable may differ, the general trends among models are similar. Thus these models and similar ones are very good in providing important physics insights especially for general properties of the primary fragments and the multifragmentation process. Mean values and ratios of observables are also less sensitive to individual differences in the models. In addition to multifragmentation models, we have compared results from five commonly used evaporation codes. The fluctuations in isotope yield ratios are found to be a good indicator to evaluate the sequential decay implementation in the code. The systems and the observables studied here can be used as benchmarks for the development of statistical multifragmentation models and evaporation codes., Comment: To appear on Euorpean Physics Journal A as part of the Topical Volume "Dynamics and Thermodynamics with Nuclear Degrees of Freedom

Excitation functions of flow and stopping observables for the Au+Au system at energies from 40 to 1500 MeV per nucleon are presented. The systematics were obtained by merging the results of the INDRA and FOPI experiments, both performed at the GSI facility. The connection to the nuclear equation of state is discussed., Comment: Contribution to the WCI book "Dynamics and Thermodynamics with Nucleonic Degrees of Freedom"

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 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 bi-modality, i.e. a sudden transition between different fragmentation pattern as a function of the 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 which is confirmed by FOPI experiments for the same system., Comment: published version

Within the statistical multifragmentation model we study modifications of the surface and symmetry energy of primary fragments in the freeze-out volume. The ALADIN experimental data on multifragmentation obtained in reactions induced by high-energy projectiles with different neutron richness are analyzed. We have extracted the isospin dependence of the surface energy coefficient at different degrees of fragmentation. We conclude that the surface energy of hot fragments produced in multifragmentation reactions differs from the values extracted for isolated nuclei at low excitation. At high fragment multiplicity, it becomes nearly independent of the neutron content of the fragments., Comment: 11 pages with 13 figures