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Öğe A comparative study of statistical models for nuclear equation of state of stellar matter(ELSEVIER, 2013) Buyukcizmeci, N.; Botvina, A. S.; Mishustin, I. N.; Ogul, R.; Hempel, M.; Schaffner-Bielich, J.; Thielemann, F. -K.We compare three different statistical models for the equation of state (EOS) of stellar matter at sub-nuclear 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. (c) 2013 Elsevier B.V. All rights reserved.Öğe Critical Temperature of Nuclear Matter and Fragment Distributions in MultifragmentatioNuclein of Finite Nuclei(American Physical Soc, 2002) Oğul, R.; Botvina, A. S.The fragment production in multifragmentation of finite nuclei is affected by the critical temperature of nuclear matter. We show that this temperature can be determined on the basis of the statistical multifragmentation model (SMM) by analyzing the evolution of fragment distributions with the excitation energy. This method can reveal a decrease of the critical temperature that, e.g., is expected for neutron-rich matter. The influence of isospin on fragment distributions is also discussed.Öğe Formation of hypernuclei in evaporation and fission processes(AMER PHYSICAL SOC, 2016) Botvina, A. S.; Buyukcizmeci, N.; Ergun, A.; Ogul, R.; Bleicher, M.; Pochodzalla, J.There are excellent opportunities to produce excited heavy hyperresidues in relativistic hadron and peripheral heavy-ion collisions. We investigate the disintegration of such residues into hypernuclei 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 hypermatter. 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 hyperfragments is emphasized. New and exotic isotopes obtained within these processes may provide a unique opportunity for investigating hyperon interaction in nuclear matter.Öğe Influence of angular momentum and Coulomb interaction of colliding nuclei on their multifragmentation(AMER PHYSICAL SOC, 2015) Ergun, A.; Imal, H.; Buyukcizmeci, N.; Ogul, R.; Botvina, A. S.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. 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 the 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 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.Öğe Influence of the hyper-terms in mass formulae on yield of hypernuclei in nuclear reactions(AMER INST PHYSICS, 2017) Buyukcizmeci, N.; Botvina, A. S.; Ogul, R.Nowadays, hypernuclear physics has attracted great interest in many fields of physics. One of the particular interest is the understanding of strange particles in baryonic matter, since many questions in heavy-ion physics, particle physics and astrophysics are related to the effect of strangeness in nuclear matter. The contribution of hyperons strongly influences the masses of neutron stars as well. In the past decade a considerable amount of spectroscopic information was accumulated experimentally on the Lambda hypernuclei. We compared different mass formulas for single and multiple Lambda hypernuclei.Öğe INVESTIGATING THE ISOTOPIC EFFECTS IN NUCLEAR FRAGMENTATION(POLISH ACAD SCIENCES INST PHYSICS, 2011) Buyukcizmeci, N.; Bulut, F.; Erdogan, M.; Imal, H.; Ogul, R.; Botvina, A. S.; Mishustin, I. N.Modifications for symmetry energy coefficients of nuclear matter at freeze-out density are investigated on the basis of the Statistical Multifragmentation Model (SMM). In order to compare our predictions with MSU experimental data we consider the fragmentation of the projectiles (124)Sn and (112)Sn which were also used for the MSU experiments, and of the projectiles (124)Sn La and (107)Sn used for the ALADIN experiments. Comparing our results with the experimental data, it is confirmed that a significant reduction of the symmetry term coefficient is found necessary to reproduce the mean < N >/Z values of light fragments.Öğe Isospin-dependent multifragmentation of relativistic projectiles(AMER PHYSICAL SOC, 2011) Ogul, R.; Botvina, A. S.; Atav, U.; Buyukcizmeci, N.; Mishustin, I. N.; Adrich, P.; Aumann, T.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 < N >/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.Öğe Isotopic Yields and Symmetry Energy in Nuclear Multifragmentation Reactions(Iop Publishing Ltd, 2012) Buyukcizmeci, N.; Imal, H.; Ogul, R.; Botvina, A. S.; Mishustin, I. N.Isotopic yields of light intermediate mass fragments (Z 8) were studied with data from the MSU experiments for central collisions of 124 Sn + 124 Sn and 112Sn+112Sn at E/A = 50 MeV. Within the statistical multifragmentation model, microcanonical Markov-chain calculations were performed with the aim to reproduce experimental elemental and isotopic distributions. The effects of varying liquid-drop parameters of hot fragments formed inside the freeze-out volume on charge and isotopic distributions are demonstrated. It is seen that the isotopic distributions of these fragments are very sensitive to the variation of the symmetry energy of fragments. Comparing our results with the experimental data, it is seen that a significant reduction of the symmetry term coefficient leads to better reproduction of the isotopic distributions. Comparison with other statistical calculations has been made. This is in agreement with previous conclusions obtained from the interpretation of both central and peripheral heavy ion collisions.Öğe Linear Energy Transfer In Water Phantom Within SHIELD-HIT Transport Code(AMER INST PHYSICS, 2017) Ergun, A.; Sobolevsky, N.; Botvina, A. S.; Buyukcizmeci, N.; Latysheva, L.; Ogul, R.The effect of irradiation in tissue is important in hadron therapy for the dose measurement and treatment planning. This biological effect is defined by an equivalent dose H which depends on the Linear Energy Transfer (LET). Usually, H can be expressed in terms of the absorbed dose D and the quality factor K of the radiation under consideration. In literature, various types of transport codes have been used for modeling and simulation of the interaction of the beams of protons and heavier ions with tissue-equivalent materials. In this presentation we used SHIELD-HIT code to simulate decomposition of the absorbed dose by LET in water for O-16 beams. A more detailed description of capabilities of the SHIELD-HIT code can be found in the literature.Öğe Mass distribution in the disintegration of heavy nuclei(SPRINGER, 2013) Eren, N.; Buyukcizmeci, N.; Ogul, R.; Botvina, A. S.The disintegration of heavy nuclei at various excitation energies has been investigated on the basis of statistical models. For the fission channels at low energies, we obtain approximate interpolating formulas for masses of fission fragments from the analysis of experimental data. In particular, they describe the transition from symmetric to asymmetric fission. The sequential evaporation from the excited compound nucleus and fission fragments is also taken into account. We show the evolution of mass distributions from low to high excitation energies, and demonstrate a transition to multifragmentation channels at high energies.Öğe Mechanisms for the production of hypernuclei beyond the neutron and proton drip lines(AMER PHYSICAL SOC, 2013) Buyukcizmeci, N.; Botvina, A. S.; Pochodzalla, J.; Bleicher, M.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.Öğe Modification of surface energy in nuclear multifragmentation(AMER PHYSICAL SOC, 2006) Botvina, A. S.; Buyukcizmeci, N.; Erdogan, M.; Lukasik, J.; Mishustin, I. N.; Ogul, R.; Trautmann, W.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.Öğe Production of ?-hypernuclei and evaluation of their binding energies via the double yield ratio(SPRINGER, 2019) Buyukcizmeci, N.; Botvina, A. S.; Ogul, R.; Ergun, A.; Bleicher, M.Relativistic collisions of ions, hadrons and leptons with nuclei can produce various hypernuclei by the capture of hyperons in nuclear residues. In many cases the disintegration of such hypernuclear systems can be described with statistical approaches suggesting that the fragment production is related to the binding energies of hypernuclei. We demonstrate how the hyperon binding energies can be effectively evaluated from the yields of different hyper-isotopes using the double ratio method. Its universality and the possibility to involve many different isotopes are the advantages of this method. The same procedure can also be applied for multi-strange nuclei, for which binding energies were very difficult to measure in previous hypernuclear experiments. Modifications caused by secondary de-excitation processes in hot hypernuclei are considered additionally.Öğe Production of neutron-rich exotic nuclei in projectile fragmentation at Fermi energies(SPRINGER SINGAPORE PTE LTD, 2017) Ogul, R.; Buyukcizmeci, N.; Ergun, A.; Botvina, A. S.Isotopic fragment yields of projectile fragmentation in peripheral collisions of Kr-86 on Sn-124,Sn-112 and the mean neutron-to-proton ratios of the fragments are calculated, theoretically, within the ensemble approach of statistical multifragmentation model. Obtained data are compared to the experimental cross-section measurements for the projectile-like fragmentation in the reaction of Kr-25 MeV/nucleon Kr-86+Sn-124,Sn-112 at Texas A&M University. We show the enhancement in the production of neutron rich isotopes close to the projectile as observed in the experiments. We also demonstrate the universality of the limitation of the excitation energy induced in the projectile residues.Öğe Role of bulk energy in nuclear multifragmentation(AMER PHYSICAL SOC, 2008) Buyukcizmeci, N.; Botvina, A. S.; Mishustin, I. N.; Ogul, R.Because of thermal expansion and residual interactions, hot nuclear fragments produced in multifragmentation reactions may have nucleon density lower than the equilibrium density of cold nuclei. In terms of a 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.Öğe Statistical production and binding energy of hypernuclei(AMER PHYSICAL SOC, 2018) Buyukcizmeci, N.; Botvina, A. S.; Ergun, A.; Ogul, R.; Bleicher, M.High-energy nuclear reactions enable us to produce a large variety of hypernuclei through the capture of hyperons by nuclear residues. We explore the statistical disintegration of such hypernuclear systems and the connection of fragment production to the binding energies of hyperons. It has been demonstrated that the hyperon binding energies can be effectively evaluated from the yields of different isotopes of hypernuclei by using the double ratio method. The advantages of this procedure are its universality and the possibility to involve many different isotopes. This method can also be applied for multistrange nuclei, for which binding energies were very difficult to measure in previous hypernuclear experiments. Corrections caused by secondary deexcitation processes are also discussed.Öğe Surface and symmetry energies in isoscaling for multifragmentation reactions(IOP PUBLISHING LTD, 2009) Ogul, R.; Atav, U.; Bulut, F.; Buyukcizmeci, N.; Erdogan, M.; Imal, H.; Botvina, A. S.The possibilities of modifications for symmetry and surface energy coefficients of nuclear matter at freeze-out density are investigated theoretically by means of isoscaling (isotopic scaling) on the basis of a statistical multifragmentation model. It is seen that while the isoscaling parameters as predicted by Markov chain calculations for the single sources (124)Sn and (112)Sn are very sensitive to the symmetry term, the surface energy variation slightly affects the isoscaling parameters in the multifragmentation region. The influence of these changes on the mean neutron to proton ratios of light fragments for 2 <= Z <= 10 is also shown. Comparing our results with MSU experimental data, it is confirmed that a significant reduction of the symmetry-term coefficient is found necessary to reproduce the isoscaling parameters of Z <= 8 fragments.Öğe Surface and Symmetry Energy Effects in Nuclear Multifragmentation(AMER INST PHYSICS, 2009) Ogul, R.; Atav, U.; Bianchin, S.; Botvina, A. S.; Buyukcizmeci, N.; de Napoli, M.; Le Fevre, A.It has been shown that the symmetry energy and the surface energy of hot fragments at the low-density freeze-out can be considerably modified. The influence of these changes on fragment yields and isotope distributions is discussed by analyzing recent ALADIN experimental data on spectator fragmentation at incident energy 600 A MeV.Öğe THE SYMMETRY ENERGY IN NUCLEAR REACTIONS(WORLD SCIENTIFIC PUBL CO PTE LTD, 2010) Trautmann, W.; Bianchin, S.; Botvina, A. S.; Le Fevre, A.; Leifels, Y.; Sfienti, C.; Buyukcizmeci, N.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 Sn-124 primary and Sn-107 and La-124 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 Au-197 + Au-197 nuclei at 400MeV/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.Öğe TABULATED EQUATION OF STATE FOR SUPERNOVA MATTER INCLUDING FULL NUCLEAR ENSEMBLE(IOP PUBLISHING LTD, 2014) Buyukcizmeci, N.; Botvina, A. S.; Mishustin, I. N.This is an introduction to the tabulated database 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 (0.2MeV < T < 25 MeV), and 28 values of electron-to-baryon ratio (0.02 < Y-e < 0.56). The properties of stellar matter in beta equilibrium are also considered. The main ingredients of the SMSM are briefly outlined, and the data structure and content of the tables are explained.
