Search

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

We analyze the experimental data on nuclei and hypernuclei yields recently obtained by the STAR collaboration. The hybrid dynamical and statistical approaches which have been developed previously are able to describe the experimental data reasonably. We discuss the intriguing difference between the yields of normal nuclei and hypernuclei which may be related to the properties of hypermatter at subnuclear densities. Most importantly new (hyper-)nuclei could be detected via particle correlations, and such measurements are relevant to pin down the production mechanism., Comment: 8 pages, 6 figures

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

We develop a statistical approach for the description of complex nuclei formation from dynamically produced baryons in high energy heavy-ion reactions. We consider a finite highly-excited expanding nuclear system formed after central nucleus-nucleus collisions. This system is sub-divided into primary equilibrated nucleon clusters. The final nuclei are produced after the decay of these excited clusters. By the successful comparison with the FOPI experimental data we prove the possibility of such a local equilibrium in nuclear matter with the temperature corresponding to the phase coexistence region. The regularities obtained in this new nuclei production mechanism are shown., Comment: 13 pages, 12 figures, to be submitted to Phys. Rev. C 2022. arXiv admin note: text overlap with arXiv:2012.07679

There has been much work in recent years pertaining to viability studies for the intranuclear observation of neutron-antineutron transformations. These studies begin firstly with the design and implementation of an event generator for the simulation of this rare process, where one hopes to retain as much of the underlying nuclear physics as possible in the initial state, and then studying how these effects may perturb the final state observable particles for detector efficiency studies following simulated reconstruction. There have been several searches for intranuclear neutron-antineutron transformations, primarily utilizing the ${}^{16}_{8}$O nucleus, and completed within large underground water Cherenkov detectors such as Super-Kamiokande. The latest iteration of a generator is presented here for use in such an experiment. This generator includes several new features, including a new radial (position) annihilation probability distribution and related intranuclear suppression factor for ${}^{16}_{8}$O, as well as a highly general, modern nuclear multifragmentation model with photonic de-excitations. The latter of these may allow for improved identification of the signal using large underground detectors such as Super-Kamiokande and the future Hyper-Kamiokande, potentially increasing the overall signal efficiencies of these rare searches. However, it should be noted that certain fast photonic de-excitations may be washed out by $\pi^0$ decays to photons. These new features implemented in these $\bar{n}$\isotope[15][8]{O} simulations increase the overall physical realism of the model, and are easily portable to other future searches such as to extranuclear $\bar{n}{}^{12}_{6}$C for the ESS NNBAR experiment, as well as intranuclear $\bar{n}{}^{39}_{18}$Ar used in DUNE., Comment: 16 pages, 12 figures

Central nucleus-nucleus collisions produce many new baryons and the nuclear clusters can be formed from these species. The phenomenological coalescence models were sufficiently good for description of light nuclei yields in a very broad range of collision energies. We demonstrate that in reality the coalescence process can be considered as 1) the formation of primary diluted excited baryon clusters and 2) their following statistical decay leading to the final cold fragment production. We argue that the formation of such excited systems from the interacting baryons is a natural consequence of the nuclear interaction at subnuclear densities resulting in the nuclear liquid-gas type phase transition in finite systems. In this way one can provide a consistent interpretation of the experimental fragment yields (FOPI data) including the important collision energy dependence in relativistic ion reactions. We investigate the regularities of this new kind of fragment production, for example, their yield, isospin, and kinetic energy characteristics. A generalization of such a clusterization mechanism for hypernuclear matter is suggested. The isotope yields and particle correlations should be adequate for studying these phenomena., Comment: 18 pages, 23 figures, to be submitted to Phys. Rev. C 2020

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

Multifragmentation reactions are dominating processes for the decomposition of highly excited nuclei leading to the fragment production in heavy-ion collisions. At high energy reactions strange particles are abundantly produced. We present a novel development of the Statistical multifragmentation model (SMM) as its generalization for the hyper-matter which is formed after the hyperon capture. In this way, it is possible to describe its disintegration into normal and hyper-nuclei. Some properties of hyper-nuclei and their binding energies can be determined from the comparison of the isotope yields. The main focus of this method is to investigate strange and multi-strange hypernuclei since their properties are not easy to measure in traditional hyper-nuclei experiments., Comment: 13 pages, 7 figures, to be submitted Phys. Scr

Ion-ion collisions at relativistic energies have been shown recently to be a promising technique for the production of hypernuclei. In this article, we further investigate the production of light $\Lambda$ hypernuclei by use of a hybrid dynamical model, cascade-coalescence followed by Fermi breakup. The predictions are then compared with the available experimental data. The dependence of the production cross section upon the beam energy, beam mass number as well as different projectile-target combinations is investigated. In particular, we evaluate the yields and signal-over-background ratio in the invariant-mass spectrum for carbon projectiles impinging on hydrogen and carbon targets and various coincidence conditions in the experiment using the theoretical calculation as an input. It is found that comparing with carbon target, hydrogen target also leads to sizable hypernuclear yields, even for exotic species, and the hydrogen target could improve significantly signal-over-background ratio in some hypernuclear invariant mass studies.

In nuclear reactions of high energy one can simultaneously produce a lot of hypernuclei after the capture of hyperons by nuclear residues. We consider statistical disintegration of such hypernuclear systems and the connection of fragment production with the binding energies of hyperons. It is demonstrated that the hyperon binding energies can be effectively evaluated from the yields of different isotopes of hypernuclei. The double ratio method is suggested for this purpose. The advantage of this procedure is its universality and the possibility to involve many different isotopes. This method can also be applied for multi-strange nuclei, which binding energies were very difficult to measure in previous hypernuclear experiments., Comment: 10 pages, submitted to Jour. Phys. G:Nuclear and Particle Physics

Recent experiments at RHIC and LHC have demonstrated that there are excellent opportunities to produce light baryonic clusters of exotic matter (strange and anti-matter) in ultra-relativistic ion collisions. Within the hybrid-transport model UrQMD we show that the coalescence mechanism can naturally explain the production of these clusters in the ALICE experiment at LHC. As a consequence of this mechanism we predict the rapidity domains where the yields of such clusters are much larger than the observed one at midrapidity. This new phenomenon can lead to unique methods for producing exotic nuclei., Comment: 15 pages, 4 figures, to be published in Phys. Rev. C

There are excellent opportunities to produce excited heavy hyper residues in relativistic hadron and peripheral heavy-ion collisions. We investigate the disintegration of such residues into hyper nuclei via evaporation of baryons and light clusters and their fission. Previously these processes were well known for normal nuclei as the decay channels at low excitation energies. We have generalized these models for the case of hyper-matter. In this way we make extension of nuclear reaction studies at low temperature into the strange sector. We demonstrate how the new decay channels can be integrated in the whole disintegration process. Their importance for mass and isotope distributions of produced hyper-fragments is emphasized. New and exotic isotopes obtained within these processes may provide a unique opportunity for investigating hyperon interaction in nuclear matter., Comment: 32 pages, 13 figures, accepted to Phys. Rev. C

In relativistic ion collisions there are excellent opportunities to produce and investigate hyper-nuclei. We have systematically studied the formation of hypernuclear spectator residues in peripheral heavy-ion collisions with the transport DCM and UrQMD models. The hyperon capture was calculated within the potential and coalescence approaches. We demonstrate that even at the beam energies around and lower than the threshold for producing Lambda hyperons in binary nucleon-nucleon interactions a considerable amount of hypernuclei, including multi-strange ones, can be produced. This is important for preparation of new experiments on hypernuclei in the wide energy range. The uncertainties of the predictions are investigated within the models, and the comparison with the strangeness production measured in experiments is also performed., Comment: 24 pages, 11 figures. Submitted to Phys. Rev. C

Within a combined approach we investigate the main features of the production of hyper-fragments in relativistic heavy-ion collisions. The formation of hyperons is modelled within the UrQMD and HSD transport codes. To describe the hyperon capture by nucleons and nuclear residues a coalescence of baryons (CB) model was developed. We demonstrate that the origin of hypernuclei of various masses can be explained by typical baryon interactions, and that it is similar to processes leading to the production of conventional nuclei. At high beam energies we predict a saturation of the yields of all hyper-fragments, therefore, this kind of reactions can be studied with high yields even at the accelerators of moderate relativistic energies., Comment: 9 pages, 9 figures, submitted to Phys. Lett. B

Theoretical calculations are performed to investigate the angular momentum and Coulomb effects on fragmentation and multifragmentation in peripheral heavy-ion collisions at Fermi energies. Inhomogeneous distributions of hot fragments in the freeze-out volume are taken into account by microcanonical Markov chain calculations within the Statistical Multifragmentation Model (SMM). Including an angular momentum and a long-range Coulomb interaction between projectile and target residues leads to new features in the statistical fragmentation picture. In this case, one can obtain specific correlations of sizes of emitted fragments with their velocities and an emission in the reaction plane. In addition, one may see a significant influence of these effects on the isotope production both in the midrapidity and in the kinematic regions of the projectile/target. The relation of this approach to the simulations of such collisions with dynamical models is also discussed., Comment: 9 pages, 7 figures, submitted to Phys. Rev. C 2014

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)

We discuss several new developments in the field of strange and heavy flavor physics in high energy heavy ion collisions. As shown by many recent theoretical works, heavy flavored particles give us a unique opportunity to study the properties of systems created in these collisions. Two in particular important aspects, the production of (multi) strange hypernuclei and the properties of heavy flavor mesons, are at the core of several future facilities and will be discussed in detail., Comment: 6 pages 8 figures, Opening talk of the Strangeness in Quark Matter conference 2013

Within a dynamical and statistical approach we study the main regularities in production of hypernuclei coming from projectile and target residues in relativistic ion collisions. We demonstrate that yields of hypernuclei increase considerably above the energy threshold for Lambda hyperons, and there is a saturation for yields of single hypernuclei with increasing the beam energy up to few TeV. Production of specific hypernuclei depend very much on the isotopic composition of the projectile, and this gives a chance to obtain exotic hypernuclei that may be difficult to reach in traditional hypernuclear experiments. Possibilities for the detection of such hypernuclei with planned and available relativistic ion facilities are discussed., Comment: 20 pages with 8 figures, submitted to Phys. Rev. C

We analyze hypernuclei coming from fragmentation and multifragmentation of spectator residues obtained in relativistic ion collisions. These hypernuclei have a broad distribution in masses and isospin. They reach beyond the neutron and proton drip lines, and they are expected to be stable with respect to neutron and proton emission. This gives us the opportunity to investigate the properties of exotic hypernuclei, as well as the properties of normal nuclei beyond the drip lines, which can be produced after weak decay of such hypernuclei., Comment: 25 pages, 10 figures, accepted to Phys. Rev. C

Pioneering experiments on production of hypernuclei can be performed with nuclotron beams on fixed targets, and at the future NICA facility. The peripheral collisions of relativistic ions are very promising for searching mutli-strange and exotic hypernuclei which are not easy accessible with other experimental methods. In these experiments one can also get information on the Equation of State of hyper-matter around nuclear saturation density at low and moderate temperatures., Comment: Proposal of new experiments with the nuclotron beams at JINR (Dubna), submitted to the NICA White Book. 8 pages, 2 figures

This is an introduction to the tabulated data base of stellar matter properties calculated within the framework of the Statistical Model for Supernova Matter (SMSM). The tables present thermodynamical characteristics and nuclear abundances for 31 values of baryon density (10$^{-8}<\rho/\rho_0<$0.32, $\rho_0$=0.15 fm$^{-3}$ is the normal nuclear matter density), 35 values of temperature ($0.2

We compare three different statistical models for the equation of state (EOS) of stellar matter at subnuclear densities and temperatures (0.5-10 MeV) expected to occur during the collapse of massive stars and supernova explosions. The models introduce the distributions of various nuclear species in nuclear statistical equilibrium, but use somewhat different nuclear physics inputs. It is demonstrated that the basic thermodynamical quantities of stellar matter under these conditions are similar, except in the region of high densities and low temperatures. We demonstrate that mass and isotopic distributions have considerable differences related to the different assumptions of the models on properties of nuclei at these stellar conditions. Overall, the three models give similar trends, but the details reflect the uncertainties related to the modeling of medium effects, such as the temperature and density dependence of surface and bulk energies of heavy nuclei, and the nuclear shell structure effects. We discuss importance of new physics inputs for astrophysical calculations from experimental data obtained in intermediate energy heavy-ion collisions, in particular, the similarities of the conditions reached during supernova explosions and multifragmentation reactions., Comment: 52 pages including 24 figures, accepted to Nucl.Phys. A

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

We study the formation of large hyper-fragments in relativistic heavy-ion collisions within two transport models, DCM and UrQMD. Our goal is to explore a new mechanism for the formation of strange nuclear systems via capture of hyperons by relatively cold spectator matter produced in semi-peripheral collisions. We investigate basic characteristics of the produced hyper-spectators and evaluate the production probabilities of multi-strange systems. Advantages of the proposed mechanisms over an alternative coalescence mechanism are analysed. We also discuss how such systems can be detected taking into account the background of free hyperons. This investigation is important for the development of new experimental methods for producing hyper-nuclei in peripheral relativistic nucleus-nucleus collisions, which are now underway at GSI and are planned for the future FAIR and NICA facilities., Comment: 28 pages, including 10 figures. Submitted to Phys. Rev. C

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

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.

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d+Au collitions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multibody Coulomb trajectory calculations under the assumption of various decay timees of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emossion time is found to be less than 40 fm/c., Comment: Accepted for publication in Bulletin of the Russian Academy of Sciences. Physics

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)

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

Some characteristics of midvelocity emissions in semiperipheral heavy-ion collisions at Fermi energies are discussed in the framework of a multifragmenting scenario. We report on binary dissipative collisions of 93Nb + 93Nb at 38AMeV in which we measured an abundant emission of particles and fragments not originated from the usual evaporative decay of hot primary fragments. We checked the compatibility of these emissions with the multifragmentation of a source which forms in the overlap region. One can fairly well reproduce the data assuming a hot and dilute source, possibly more n-rich than the initial nuclei; the results appear to be insensitive to the source size., Comment: 6 pages, 2 figures

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

We formulate a statistical model for description of nuclear composition and equation of state of stellar matter at subnuclear densities and temperature up to 20 MeV, which are expected during the collapse and explosion of massive stars. The model includes nuclear, electromagnetic and weak interactions between all kinds of particles, under condition of statistical equilibrium. We emphasize importance of realistic description of the nuclear composition for understanding stellar dynamics and nucleosynthesis. It is demonstrated that the experience accumulated in studies of nuclear multifragmentation reactions can be used for better modelling properties of stellar medium., Comment: 35 pages including 23 figures, submitted to Nuclear Physics A

In nuclear reactions induced by hadrons and ions of high energies, nuclei can disintegrate into many fragments during a short time (~100 fm/c). This phenomenon known as nuclear multifragmentation was under intensive investigation last 20 years. It was established that multifragmentation is an universal process taking place in all reactions when the excitation energy transferred to nuclei is high enough, more than 3 MeV per nucleon, independently on the initial dynamical stage of the reactions. Very known compound nucleus decay processes (sequential evaporation and fission), which are usual for low energies, disappear and multifragmentation dominates at high excitation energy. For this reason, calculation of multifragmentation must be carried on in all cases when production of highly excited nuclei is expected, including spallation reactions. From the other hand, one can consider multifragmentation as manifestation of the liquid-gas phase transition in finite nuclei. This gives way for studying nuclear matter at subnuclear densities and for applications of properties of nuclear matter extracted from multifragmentation reactions in astrophysics. In this contribution, the Statistical Multifragmentation Model (SMM), which combines the compound nucleus processes at low energies and multifragmentation at high energies, is described. The most important ingredients of the model are discussed., Comment: 10 pages, Report to Joint ICTP-IAEA Advanced Workshop on Model Codes for spallation reactions, Trieste, Italy, 4-8th February 2008

Reactions of nuclear multifragmentation of excited finite nuclei can be interpreted as manifestation of the nuclear liquid-gas phase transition. During this process the matter at subnuclear density clusterizes into hot primary fragments, which are located in the vicinity of other nuclear species. In recent experiments there were found evidences that the symmetry and surface energies of primary fragments change considerably as compared to isolated cold or low-excited nuclei. The new modified properties of primary fragments should be taken into account during their secondary de-excitation., Comment: 7 pages (incl. 4 figures), in Proceedings IWM2007: Caen, France, 4-7th Nov 2007

Critical temperature Tc for the nuclear liquid-gas phase transition is stimated both from the multifragmentation and fission data. In the first case,the critical temperature is obtained by analysis of the IMF yields in p(8.1 GeV)+Au collisions within the statistical model of multifragmentation (SMM). In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with Tc as a free parameter. It is concluded for both cases that the critical temperature is higher than 16 MeV., Comment: 15 pages, 8 figures

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

Because of thermal expansion and residual interactions, hot nuclear fragments produced in multifragmentation reactions may have lower nucleon density than the equilibrium density of cold nuclei. In terms of liquid-drop model this effect can be taken into account by reducing the bulk energy of fragments. We study the influence of this change on fragment yields and isotope distributions within the framework of the statistical multifragmentation model. Similarities and differences with previously discussed modifications of symmetry and surface energies of nuclei are analyzed., Comment: 8 pages, 7 figures, to be published in Phys. Rev. C

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

In peripheral collisions of relativistic heavy ions highly excited spectators containing Lambda-hyperons can be produced. Such strange spectator matter may undergo a break-up into many fragments (multifragmentation) as it is well established for ordinary nuclear systems. We generalize the statistical multifragmentation model, previously successfully used for the description of experimental data, for the case of hypernuclear systems. We predict relative yields of hypernuclei and the main characteristics of such a break-up. We point at a connection of this phenomenon with a liquid-gas phase transition in hypermatter., Comment: 4 pages including 4 figures

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

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

Isoscaling and its relation to the symmetry energy in the fragmentation of excited residues produced at relativistic energies were studied in two experiments conducted at the GSI laboratory. The INDRA multidetector has been used to detect and identify light particles and fragments with Z <= 5 in collisions of 12C on 112,124Sn at incident energies of 300 and 600 MeV per nucleon. Isoscaling is observed, and the deduced parameters decrease with increasing centrality. Symmetry term coefficients, deduced within the statistical description of isotopic scaling, are near gamma = 25 MeV for peripheral and gamma < 15 MeV for central collisions. In a very recent experiment with the ALADIN spectrometer, the possibility of using secondary beams for reaction studies at relativistic energies has been explored. Beams of 107Sn, 124Sn, 124La, and 197Au were used to investigate the mass and isospin dependence of projectile fragmentation at 600 MeV per nucleon. The decrease of the isoscaling parameters is confirmed and extended over the full fragmentation regime covered in these reactions., Comment: Proceedings of the IWM2005, Catania, Italy, Nov 2005

We show that the large sequential decay corrections obtained by Ono {\it et al} [nucl-ex/0507018], is in contradiction with both the other dynamical and statistical model calculations carried out for the same systems and energy. On the other hand, the conclusion of Shetty {\it {et al.}} $[$Phys. Rev. C 70, 011601R (2004)$]$, that the experimental data favors Gogny$-$AS interaction (obtained assuming a significantly smaller sequential decay effects), is consistent with several other independent studies., Comment: 2 pages, 1 figure