arXiv subjects

N. Buyukcizmeci

Publications and source records attributed to N. Buyukcizmeci.

At least 19 recordsLinked to original sources

arXiv2024

Production of double strange hypernuclei and exotic nuclei in central Au+Au collisions at $\sqrt{s_{NN}}$=3 GeV

We extend the theoretical approach which includes the dynamical and statistical stages for the description of the nucleosynthesis in central collisions of relativistic ions. Previously, this approach was successfully applied to describe experimental data on both normal nuclei and single strange hypernuclei production in the GSI and RHIC-BES energy range. We predict the multiplicities of double strange hypernuclei up to $^4_{ΛΛ}$H and further intermediate mass nuclei up to $^8$Be for Au+Au central collisions at $\sqrt{s_{NN}}$=3 GeV, recently explored by the STAR experiments. These new nuclei can be identified by the measurement of the correlated particles coming after their decay. Such observations are a crucial test for the nucleosynthesis mechanism.

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arXiv2024

Nucleation of baryons in relativistic hadron-nucleus collisions

We suggest a new theoretical method to describe the baryon clusterization of nuclei in hadron-nucleus reactions. As an example we have explored the nuclei production in $π^-+C$ and $π^-+W$ collisions at p$_{lab}$=1.7 GeV by using the hybrid approach consisting of the Ultra Relativistic Quantum Dynamics Model (UrQMD) and the Statistical Multifragmentation Model (SMM). The UrQMD describes the production of new baryons, and the propagation toward the subnuclear densities with the fluctuations leading to the formation of excited baryonic clusters. The SMM describes the production of final nuclei and hypernuclei after interaction of baryons inside these clusters. We demonstrate the transverse momenta, rapidity, mass distributions and excitation energies of both primary clusters and final nuclei (including hypernuclei). The results of the UrQMD and UrQMD+SMM model calculations for different clusterization parameters are compared with the available HADES experimental data on baryon production, providing a very promising window for future research on nuclei and hypernuclei formation in these reactions.

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arXiv2023

Nucleosynthesis of light nuclei and hypernuclei in central Au+Au collisions at $\sqrt{s_{NN}}$=3 GeV

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.

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arXiv2023

Neutrons from projectile fragmentation at 600 MeV/nucleon

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.

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arXiv2023

Isospin compositions of correlated sources in the Fermi energy domain

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.

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arXiv2022

Evolution of the statistical disintegration of finite nuclei toward high energy

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.

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arXiv2020

Coupling dynamical and statistical mechanisms for baryonic cluster production in nucleus collisions of intermediate and high energies

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.

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arXiv2020

The percolation phase transition and statistical multifragmentation in finite systems

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.

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arXiv2020

On survey of nuclei and hypernuclei in multifragmentation

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.

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arXiv2017

Evaluation of the hyperon binding energy via statistical production of hypernuclei

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.

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arXiv2016

Formation of hypernuclei in evaporation and fission processes

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.

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arXiv2015

Decomposition of the absorbed dose by LET in tissue-equivalent materials within the SHIELD-HIT transport code

The SHIELD-HIT transport code, in several versions, has been used for modeling the interaction of therapeutic beams of light nuclei with tissue-equivalent materials for a long time. All versions of the code include useful option of decomposition of the absorbed dose by the linear energy transfer (LET), but this option has not been described and published so far. In this work the procedure of decomposition of the absorbed dose by LET is described and illustrated by using the decomposition of the Bragg curve in water phantom, irradiated by beams of protons, alpha particles, and of ions lithium, carbon and oxygen.

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arXiv2015

Theoretical study of projectile fragmentation in the reactions $^{112}$Sn + $^{112}$Sn and $^{124}$Sn + $^{124}$Sn at 1 GeV/nucleon

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.

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arXiv2014

Influence of angular momentum and Coulomb interaction of colliding nuclei on their multifragmentation

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.

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arXiv2014

Tabulated equation of state for supernova matter including full nuclear ensemble

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}<ρ/ρ_0<$0.32, $ρ_0$=0.15 fm$^{-3}$ is the normal nuclear matter density), 35 values of temperature ($0.2<T<25$ MeV) and 28 values of electron-to-baryon ratio ($0.02<Y_e<0.56$). The properties of stellar matter in $β$-equilibrium are also considered. The main ingredients of the SMSM are briefly outlined, and the data structure and content of the tables are explained.

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arXiv2013

Mechanisms for production of hypernuclei beyond the neutron and proton drip lines

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.

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arXiv2013

A comparative study of statistical models for nuclear equation of state of stellar matter

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.

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arXiv2011

Neutrons from multifragmentation reactions

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.

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