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10th Conference on Nuclear Physics in Astrophysics, NPA-X 2022, Geneva, Switzerland, 5 Sep 2022 - 9 Sep 2022; The European physical journal / Web of Conferences 279, 04003 (2023). doi:10.1051/epjconf/202327904003, Published by EDP Sciences, Les Ulis

Direct proton-knockout reactions of Sc-55 at similar to 220 MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of Ca-54 were investigated through -ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological intemucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the Sc- 55 ground state with states in Ca-54. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of Sc-55, valence proton removals populated predominantly the ground state of Ca-54. This counterintuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.

A first gamma-ray study of Cl-47, Cl-49 spectroscopy was performed at the Radioactive Isotope Beam Factory with 50 Ar projectiles at 217 MeV/nucleon, impinging on the liquid hydrogen target of the MINOS device. Prompt deexcitation gamma rays were measured with the NaI(T1) array DALI2(+). Through the one-proton knockout reaction Ar-50(p, 2p), a spin assignment could be determined for the low- lying states of Cl-49 from the momentum distribution obtained with the SAMURAI spectrometer. A spin-parity J(pi) = 3/2(+) is deduced for the ground state of Cl-49, similar to the recently studied N = 32 isotope K-51. The evolution of the energy difference E(1/2(1)(+)) - E (3/2(1)(+)) is compared to state-of-the-art theoretical predictions.

The low-lying level structure of V-63 was studied for the first time by the inelastic proton scattering and the proton knock-out reaction in inverse kinematics. The comparison of the newly observed gamma- ray transitions at 696(8) keV and 889(16) keV with our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja interaction established two excited states proposed to be the first 11/2(-) and 9/2(-) levels. The (p, p') excitation cross sections were analyzed by the coupled channel formalism assuming pure quadrupole as well as quadrupole+hexadecapole deformations. This resulted in large deformation parameters placing V-63 in the island of inversion located below Ni-68.

Low-lying excited states in the N = 32 isotope Ar-50 were investigated by in-beam gamma-ray spectroscopy following proton- and neutron-knockout, multinucleon removal, and proton inelastic scattering at the RIKEN Radioactive Isotope Beam Factory. The energies of the two previously reported transitions have been confirmed, and five additional states are presented for the first time, including a candidate for a 3(-) state. The level scheme built using gamma gamma coincidences was compared to shell-model calculations in the sd-pf model space and to ab initio predictions based on chiral two- and three-nucleon interactions. Theoretical proton- and neutron-knockout cross sections suggest that two of the new transitions correspond to 2(+) states, while the previously proposed 4(1)(+) state could also correspond to a 2(+) state.

Detailed spectroscopy of the neutron-unbound nucleus F28 has been performed for the first time following proton/neutron removal from Ne29/F29 beams at energies around 230 MeV/nucleon. The invariant- mass spectra were reconstructed for both the F(*)27+n and F(*)26+2n coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the F28 ground state, with Sn(F28)=-199(6) keV, while analysis of the 2n decay channel allowed a considerably improved Sn(F27)=1620(60) keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of F28. Importantly, in the case of the ground state, the reconstructed F27+n momentum distribution following neutron removal from F29 indicates that it arises mainly from the 1p3/2 neutron intruder configuration. This demonstrates that the island of inversion around N=20 includes F28, and most probably F29, and suggests that O28 is not doubly magic.

The FOPI Collaboration at the GSI SIS-18 synchrotron measured charged kaons from central and semicentral collisions of Ni+Ni at a beam energy of 1.91A GeV. We present the distribution of the K−/K+ ratio on the energy vs polar angle plane in the nucleon-nucleon center-of-mass frame, with and without subtraction of the contribution of ϕ(1020) meson decays to the K− yield. The acceptance of the current experiment is substantially wider compared to the previous measurement of the same colliding system. The ratio of K− to K+ energy spectra is expected to be sensitive to the in-medium modifications of basic kaon properties like mass. Recent results obtained by the HADES Collaboration at 1.23A and 1.76A GeV indicate that after inclusion of the ϕ meson decay contribution to the K− production no difference between the slopes of the K− and K+ energy spectra is observed within uncertainties. For our data a linear fit to this ratio obtained after subtraction of the ϕ meson contribution still shows a decrease with kinetic energy, although a constant value cannot be rejected. The contribution of Λ(1520)→pK− decays estimated from fitting the thermal model to the experimental yields appears to be another factor of moderate relevance.

We analyzed the ϕ meson production in central Ni + Ni collisions at a beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found a production probability per event of [8.6±1.6(stat) ±1.5(syst)]×10−4. This new data point allows us for the first time to inspect the centrality dependence of subthreshold ϕ meson production in heavy-ion collisions. The rise of ϕ meson multiplicity per event with mean number of participants can be parametrized by a power function with exponent α=1.8±0.6. The ratio of ϕ to K− production yields seems not to depend, within the experimental uncertainties, on the collision centrality, and the average of measured values was found to be 0.36±0.05.

ϕ and K− mesons from Ni+Ni collisions at the beam energy of 1.91A GeV have been measured by the FOPI spectrometer, with a trigger selecting central and semicentral events amounting to 52% of the total cross section. The phase-space distributions, and the total yield of K−, as well as the kinetic energy distribution and the total yield of ϕ mesons are presented. The ϕ/ K− ratio is found to be 0.44±0.07(stat)+0.16−0.10(syst), meaning that about 22% of K−mesons originate from the decays of ϕ mesons, occurring mostly in vacuum. The inverse slopes of direct kaons are up to about 15 MeV larger than the ones extracted within the one-source model, signaling that a considerable share of gap between the slopes of K+ and K −could be explained by the contribution of ϕ mesons to negative kaons.

Azimuthal emission patterns of K+/- mesons have been measured in Ni + Ni collisions with the FOPI spectrometer at a beam kinetic energy of 1.91 A GeV. The transverse momentum p(T) integrated directed and elliptic flow of K+ and K- mesons as well as the centrality dependence of p(T) - differential directed flow of K+ mesons are compared to the predictions of hadron string dynamics and isospin quantum molecular dynamics transport models. The data exhibits different propagation patterns of K+ and K- mesons in the compressed and heated nuclear medium and favor the existence of a kaon-nucleon in-medium potential, repulsive for K+ mesons and attractive for K- mesons.

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Pionic fusion reactions where two nuclei fuse into a new one by emitting a pion need a highly coherent mechanism and therefore give an insight into the collective motion of nucleons in nuclei. The reaction 4He(3He,π0)7Be has been studied experimentally at beam energies about 10 MeV above the coherent production threshold. The experiment was performed at KVI, Groningen using the AGOR accelerator facility. The created nuclei were detected in a phoswich detector array in the focal plane of the Big-Bite Spectrometer in coincidence with the photons from neutral pion decay which were detected in the Plastic Ball detector. The Plastic Ball contains 552 phoswich detectors covering polar laboratory angles 50◦

Pionic fusion reactions where two nuclei fuse into a new one by emitting a pion need a highly coherent mechanism and therefore give an insight into the collective motion of nucleons in nuclei. The reaction ^4He(^3He, π^0)^7Be has been studied experimentally at beam energies about 10 MeV above the coherent production threshold. The experiment was performed at KVI, Groningen using the AGOR accelerator facility. The created nuclei were detected in a phoswich detector array in the focal plane of the Big-Bite Spectrometer in coincidence with the photons from neutral pion decay which were detected in the Plastic Ball detector. The Plastic Ball contains 552 phoswich detectors covering polar laboratory angles 50^o

Reakcija pionske fuzije u kojoj se dvije jezgre fuzioniraju u novu emitirajući pritom pion, zahtijeva veoma koherentni mehanizam i stoga pruža uvid u kolektivno gibanje nukleona u jezgri. Reakcija 4He(3He, π0)7Be se eksperimentalno proučavala na energiji snopa od oko 10 MeV iznad praga stvaranja. Eksperiment je izveden na KVI-u, u Groningenu na akceleratoru AGOR. Stvorene jezgre su detektirane pomoću niza phoswich detektora [1] u fokalnoj ravnini Big-Bite spektrometra [2] u koincidenciji s fotonima nastalim u raspadu neutralnog piona koji su detektirani u Plastic Ball detektoru [3]. Plastic Ball sadrži 552 phoswich detektora koji pokrivaju laboratorijske polarne kuteve 50

A 2 pi hemispherical detector consisting of 64 CsI(Tl) scintillator modules covering the angular range of 80 degrees -160 degrees has been constructed. This detector is employed as the Inner Shell of the Plastic Ball detector and was used in two experimental programs concerning the study of pionic fusion in light-ion systems. The geometry and construction are presented. The improved response of the combined detectors for photons are discussed. An energy calibration method using high energy cosmic muons for the Inner Shell and the Plastic Ball has been developed and the calibration results are compared to the results of the same method in the Monte-Carlo simulation. The improved acceptance of the combined detectors for the pi(0) detection in the (6)Li((4)He, pi(0))(10)B* experiment are presented and discussed. (C) 2010 Elsevier B.V. All rights reserved.

A new measurement of subthreshold K*(892)(0) and K-0 production is presented. The experimental data complete the measurement of strange particles produced in Al + Al collisions at 1.9A GeV measured with the FOPI detector at SIS at GSI (Darmstadt). The K*(892)(0)/K-0 yield ratio is found to be 0.0315 +/- 0.006(stat.) +/- 0.012(syst.) and is in good agreement with the transport model prediction. These measurements provide information on the in-medium cross section of K+-pi(-) fusion, which is the dominant process in subthreshold K*(892)(0) production.

The K0 meson production by - mesons of 1.15 GeV/c momentum on C, Al, Cu, Sn, and Pb nuclear targets was measured with the FOPI spectrometer at the Schwer-Ionen-Synchrotron accelerator of GSI. Inclusive production cross sections and the momentum distributions of K0 mesons are compared to scaled elementary production cross sections and to predictions of theoretical models describing the in-medium production of kaons. The data represent a new reference for those models, which are widely used for interpretation of the strangeness production in heavy-ion collisions. The presented results demonstrate the sensitivity of the kaon production to the reaction amplitudes inside nuclei and point to the existence of a repulsive KN potential of 20± ; 5 MeV at normal nuclear matter density.

Few-nucleon systems can be used as fundamental laboratories for studying details of the nuclear force effects. We performed a series of deuteron-deuteron scattering experiments at intermediate energies. The experiments exploited BINA and BBS experimental setups and polarized deuteron beams with kinetic energies of 65 and 90 MeV/nucleon. These experiments aim to measure differential cross sections, vector and tensor analyzing powers of all available reaction channels in deuteron-deuteron scattering. With these data we will provide a systematic database, which will be used to test present theoretical approximations and upcoming ab-initio calculations in four-nucleon system.

Two pionic fusion experiments have been performed using the AGOR accelerator facility at KVI in order to study the role of pions in the nuclear interaction. Pionic fusion is a highly coherent process in which two nuclei fuse to a united nucleus and the available centre-of-mass energy is emitted in the pion channel. The reactions 4He(3He, 

In order to study the role of pions and clustering phenomena in nuclei, two experiments have been performed using the AGOR accelerator facility. In collisions of two nuclei a pion and a fused nucleus were produced. The examined reactions were He-4(He-3, pi(0))Be-7 and Li-6(He-4, pi(0)) B-10 at beam energies about 10 MeV above the coherent pion production threshold (256 MeV and 236.4 MeV, respectively). Since the available energy is well below the pion production threshold in an elementary nucleon-nucleon process, a highly coherent mechanism is needed. We identified the reaction by measuring the fused system in the magnetic spectrometer and the produced neutral pions in the Plastic Ball detection system with large acceptance. Our experimental setup provided the exclusive cross sections by identifying all products in overdetermined kinematics. Here we present the preliminary results of die ongoing analysis for the second reaction. About 700 events fulfilling the kinematical conditions for an outgoing B-10 and a pi(0) decaying with large opening angle have been selected. Angular distribution of neutral pions will be discussed.

Two experiments aiming to study pionic fusion of light nuclei were performed using the AGOR accelerator facility. In such reactions a pion and a fused nucleus are produced in a collision of two nuclei. The examined reactions are 4He(3He, pi0)7Be and 6Li(4He, pi0)10B at beam energies about 10 MeV above the coherent pion production threshold (261 MeV and 234 MeV). Since the energy is well below the pion production threshold in an elementary nucleon-nucleon process a highly coherent mechanisms is needed (1). Produced nuclei were detected and identified in a phoswich detector array in the focal plane of the BBS spectometer (2) and photons originating from pion decay in the Plastic Ball detector (3). The Plastic Ball contains 552 phoswich modules covering polar laboratory angles between 60 and 160 degrees in almost the full azimuthal range. It is equipped with an inner shell of 64 CsI crystals in order to improve photon conversion. The results of the ongoing analyses of the first reaction will be presented. Approximately 700 good events fulfilling the kinematical condition for an outgoing 7Be and a pi0 decaying with large opening angle have been selected. The angular distribution of neutral pions will be discussed. (1)T. Kajino. H. Toki and K. Kubo, Phys. rev. C35, 1370 (1987) (2) A.M. van der Berg, Nucl. Instr. and Meth. B99, 637 (1995) (3) A. Baden et al., Nucl. Instr. and Meth. 203, 189 (1982)

Results on K+ and K0 meson production in 96 44Ru + 96 44Ru and 96 40Zr + 96 40Zr collisions at a beam kinetic energy of 1.528A GeV, measured with the FOPI detector at GSI-Darmstadt, are investigated as a possible probe of isospin effects in high-density nuclear matter. The measured double ratio (K+/K0)Ru/(K+/K0)Zr is compared to the predictions of a thermal model and a relativistic mean field transport model using two different collision scenarios and under different assumptions on the stiffness of the symmetry energy.We find good agreement with the thermal model prediction and the assumption of a soft symmetry energy for infinite nuclear matter, while more realistic transport simulations of the collisions show a similar agreement with the data but also exhibit a reduced sensitivity to the symmetry term.

First measurement of subthreshold Sigma(1385) production is presented. Experimental data are presented for Al+Al reactions at 1.9A GeV measured with the FOPI detector at SIS/GSI. The Sigma(1385)/Lambda ratio is found to be in good agreement with the transport and statistical model predictions. The results allowfor a better understanding of subthreshold strangeness production and strangeness exchange reaction which is the dominant process for K− production below and close-to threshold.

A series of nucleon-nucleon bremsstrahlung (NN gamma) experiments at 190 MeV incident beam energy have been performed at KVI in order to gain more insight into the dynamics governing the bremsstrahlung reaction. After initial measurements wherein the bremsstrahlung process was studied far away from the elastic limit, a new study was used to probe the process nearer to the elastic limit by measuring at lower photon energies. Measured cross sections and analyzing powers are compared with the predictions of a microscopic model and those of two soft-photon models. The theoretical calculations overestimate the data by up to approximate to 30%, for some kinematics.

We report on the first analysis of directed and elliptic flow with the new method of Lee– Yang zeros. Experimental data are presented for Ru+Ru reactions at 1.69A GeV measured with the FOPI detector at SIS/GSI. The results obtained with several methods, based on the event-plane reconstruction, on Lee– Yang zeros, and on multiparticle cumulants (up to fifth order) applied for the first time at SIS energies, are compared. They show conclusive evidence that azimuthal correlations between nucleons and composite particles at this energy are largely dominated by anisotropic flow.

We present measurements of the excitation function of elliptic flow at midrapidity in Au + Au collisions at beam energies from 0.09 to 1.49 GeV per nucleon. For the integral flow, we discuss the interplay between collective expansion and spectator shadowing for three centrality classes. A complete excitation function of transverse momentum dependence of elliptic flow is presented for the first time in this energy range, revealing a rapid change with incident energy below , followed by an almost perfect scaling at the higher energies. The equation of state of compressed nuclear matter is addressed through comparisons to microscopic transport model calculations.

The bremsstrahlung measurements have as goal to probe nucleon-nucleon interaction in a kinematical region where the nucleons are off their mass shell. At the KVI, a high quality proton beam of 190 MeV is used with a liquid hydrogen target to investigate the bremsstrahlung process in proton-proton scattering.

The understanding of the strong force acting between nucleons is one of the most fundamental problems addressed by nuclear physics. The simplest reactions to study this frce with, besides elastic scattering, is proton-proton real and virtual bremsstrahlung. Since the mid 90s, a series of experiments were setup at KVI to study real and virtual proton-proton bremsstrahlung at 190 MeV in which the kinematics are chosen such that one goes as far away as possible from the elastic channel, thereby producing high energy photons.

Sve je veći broj slučajeva kada je u eksploataciji neki strojni dio ili alat uz trošenje, izložen i značajnom korozijskom djelovanju. Unatoč tome što je općepoznato da neki od navedenih slojeva, osim što su otporni na trošenje pokazuju i izvjesnu korozijsku postojanost, ne postoje konkretni podatci o njihovoj učinkovitosti prema koroziji.U eksperimentalnom dijelu rada provedeni su pokusi u cilju određivanja otpornosti na koroziju nekih tipičnih slojeva proizvedenih modificiranjem ili prevlačenjem. Pri tome su korištene gravimetrijske i elektrokemijske metode ispitivanja otpornosti na koroziju.

Detaljno poznavanje medjudjelovanja izmedju dva nukleona neophodno je za opisivanje mnogih pojava u hadronskoj fizici. Eksperimenti sa sudarima protona osobito su pogodni za dobivanje preciznih informacija o tom medjujelovanju. Elasticno raspršenje, u kojem se medjujelujuci protoni nalaze na ljusci mase, vrlo dobro opisuju postojeci modeli. Medjutim, ponasanje protona izvan masene ljuske, primjerice protona vezanih u jezgri, jos nije dovoljno poznato. Na energijama ispod praga produkcije piona, procesi koji omogućuju proučavanje protona izvan masene ljuske su realno i virtualno zakočno zračenje, te dvofotonska emisija. Kako su to procesi koji uključuju slabu elektromagnetsku interakciju, njihov je udarni presjek mnogo manji od dominantnog elastičnog udarnog presjeka.

A necessary ingredient for the understanding of atomic nuclei and nuclear matter is detailed and precise knowledge of the nucleon-nucleon interaction.

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The understanding of the strong force acting between nucleons is one of the most fundamental problems addressed by nuclear physics. One of the simplest reactions to study this force, besides elastic scattering, is proton-proton bremsstrahlung.

Many propoerties of the strong force can be exhaustively examined in proton-proton collision experiments.

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Gustoća stanja jezgre 102Rh izračunata je u okviru modela međudjelujućih bozona sa slomljenim parovima i uspoređena s Betheovom formulom, Gaussovom formulom i formulom konstantne temperature.

Nuclear Physics in Astrophysics IX (NPA-IX), 15-20 September 2019, Frankfurt, Germany, NPA-IX, Frankfurt, Germany, 15 Sep 2019 - 20 Sep 2019; Journal of physics / Conference series 1668, 012016 (2020). doi:10.1088/1742-6596/1668/1/012016, Published by IOP Publ., Bristol

Polazište ovog rada je eksperiment izveden na institutu RIKEN u Japanu u kojem je proučavana nuklearna jednadžba stanja u sudarima izotopa kositra. Energijske distribucije i njihovi omjeri za izospinske parove poput para proton-neutron primjeri su opservabla koje mogu pokazivati osjetljivost na energiju simetrije - najmanje poznat član u nuklearnoj jednadžbi stanja, a u ovakvim sudarima one se nastoje izmjeriti. Cilj rada bio je rekonstruirati ove opservable energije simetrije iz mjerenja neutronskog detektora NeuLAND i vidjeti može li se iz njih zaključiti nešto o parametru γ u potencijalnom članu energije simetrije. Napravljene su simulacije eksperimenta u softverskom okruženju R3BRoot pomoću simulacijskog paketa GEANT4 i pomoću njih je određena efikasnost detekcije protona i neutrona u ovisnosti o energiji što je omogućilo rekonstrukciju distribucija za sustave 132Sn + 124Sn te 124Sn + 112Sn. Distribucije su uspoređene s rezultatima UrQMD transportnog modela za dvije parametrizacije energije simetrije: γ = 0.5 i γ = 1.5. Konačno, raspravljena je mogućnost izbora jedne od njih kao preferirajuće parametrizacije energije simetrije. Starting point of this work is the experiment conducted at RIKEN institute in Japan the focus of the which was the study of nuclear equation of state in collisions of tin isotopes. Energy distributions of isospin pairs like proton-neutron pair and their ratio are examples of observables which can show sensitivity to the symmetry energy - the least known part of nuclear equation of state. Purpose of mentioned collisions is to measure them. Hence, the aim of this work was to reconstruct these observables from measurements made by neutron detector NeuLAND and from them possibly conclude something about the parameter γ in potential part of the symmetry energy. Simulations of the experiment were made using software framework R3BRoot with transport machine GEANT4. Using simulations, proton and neutron efficiencies depending on particle energy were calculated which enabled reconstruction of energy distributions for systems 132Sn + 124Sn and 124Sn + 112Sn. These distributions were compared to UrQMD model results for two parametrizations of symmetry energy, namely γ = 0.5 and γ = 1.5. Work finishes with the discussion weather preference could be given to any of the two as the possible parametrization of symmetry energy.