Search

The matter radius of the doubly magic 56 Ni was extracted from a measurement of the differential cross section by employing, for the first time, elastic proton scattering in inverse kinematics with a radioactive beam at E kin = 390.2 MeV/nucleon circulating in a storage ring and passing an internal hydrogen gas-jet target with a revolution frequency of around 2 MHz. The novel experimental scheme is based on UHV-compatible Si detectors operated as active vacuum windows, which were implemented in the ESR storage ring at GSI. A matter radius < r m 2 > 1 / 2 = 3. 74 - 0.06 + 0.03 fm was extracted for the doubly-magic self-conjugate nucleus 56 Ni. [ABSTRACT FROM AUTHOR]

We investigate the contributions of various reaction channels to the interaction, reaction, charge-changing and neutron-changing cross sections. The goal is to investigate the relation between microscopic interactions and the symmetry energy component of the equation of state (EoS) of interest for the structure of neutron stars. We compare the neutron skins extracted from diverse experimental techniques with those obtained with Hartree–Fock–Bogoliubov calculations using 23 Skyrme and with eight density-dependent interactions used in the relativistic mean-field method. We show that no particular conclusion can be drawn on the best EoS in view of the wide range of uncertainty in the experimental data. We further investigate the prospects of using neutron-changing reactions to assess the isospin dependence of the neutron skin in neutron-rich nuclei. [ABSTRACT FROM AUTHOR]

PUMA, antiProton Unstable Matter Annihilation, is a nuclear-physics experiment at CERN aiming at probing the surface properties of stable and rare isotopes by use of low-energy antiprotons. Low-energy antiprotons offer a very unique sensitivity to the neutron and proton densities at the annihilation site, i.e. in the tail of the nuclear density. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: while not being a collider experiment, PUMA aims at transporting one billion antiprotons from ELENA, the Extra-Low-ENergy Antiproton ring, to ISOLDE, the rare-isotope beam facility of CERN. PUMA will enable the capture of low-energy antiprotons by short-lived nuclei and the measurement of the emitted radiations. In this way, PUMA will give access to the so-far largely unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei. The motivations, concept and current status of the PUMA experiment are presented. [ABSTRACT FROM AUTHOR]

Quasi-free scattering of electrons and protons has been extensively utilized in the past to study the single-particle structure of nuclei, clustering in light nuclei, and short-range correlated nucleon–nucleon pairs in nuclei. Recently, this approach has been applied in inverse kinematics using hydrogen targets. The characteristic features of this reaction and the experimental challenges and advantages of inverse-kinematics experiments are summarized. The applicability to radioactive beams opens a large research potential to study a variety of properties of neutron-to-proton asymmetric nuclei. Applications of quasi-free scattering in inverse kinematics and its potential are reviewed based on recent and ongoing research programs at different accelerator facilities worldwide. [ABSTRACT FROM AUTHOR]

The Reactions with Relativistic Radioactive Beams (R 3 B) collaboration of the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, has constructed an experimental setup to perform fundamental studies of nuclear matter, using as a probe reactions with exotic nuclei at relativistic energies. Among the various detection systems, one of the most recent upgrades consists of the installation of a large area, around 2 m 2 , multi-gap Resistive Plate Chamber (RPC). The chamber is equipped with twelve 0. 3 mm gaps and readout by 30 mm pitch strips, exhibiting a timing precision down to 50 ps and efficiencies above 98% for minimum ionizing particles in a previous characterization of the detector. The RPC was part of the setup of the FAIR Phase 0 experiment that focused on measuring for the first time, in spring 2022, nucleon–nucleon short-range correlations (SRC) inside an exotic nucleus (16C). The excellent timing precision of this detector will allow the measurement of the forward emitted proton momentum with a resolution of around 1%. In beam measurements show an RPC efficiency above 95% and a time precision better than 100 ps (including the contribution of a reference scintillator and the momentum spread of the particles) for forward emitted particles. [ABSTRACT FROM AUTHOR]

A new technique developed for measuring nuclear reactions at low momentum transfer with stored beams in inverse kinematics was successfully used to study isoscalar giant resonances. The experiment was carried out at the experimental heavy-ion storage ring (ESR) at the GSI facility using a stored 58 Ni beam at 100 MeV/u and an internal helium gas-jet target. In these measurements, inelastically scattered α -recoils at very forward center-of-mass angles ( θ cm ≤ 1.5 ° ) were detected with a dedicated setup, including ultra-high vacuum compatible detectors. Experimental results indicate a dominant contribution of the isoscalar giant monopole resonance at this very forward angular range. It was found that the monopole contribution exhausts 79 − 11 + 12 % of the energy-weighted sum rule (EWSR), which agrees with measurements performed in normal kinematics. This opens up the opportunity to investigate the giant resonances in a large domain of unstable and exotic nuclei in the near future. It is a fundamental milestone towards new nuclear reaction studies with stored ion beams. [ABSTRACT FROM AUTHOR]

We study the Coulomb excitation of pygmy dipole resonances (PDR) in heavy ion reactions at 100 MeV/nucleon and above. The reactions Ni 68 + Au 197 and Ni 68 + Pb 208 are taken as practical examples. Our goal is to address the question of the influence of giant resonances on the PDR as the dynamics of the collision evolves. We show that the coupling to the giant resonances affects considerably the excitation probabilities of the PDR, a result that indicates the need of an improved theoretical treatment of the reaction dynamics at these bombarding energies. [ABSTRACT FROM AUTHOR]

The coupling between bound quantum states and those in the continuum is of high theoretical interest. Experimental studies of bound drip-line nuclei provide ideal testing grounds for such investigations since they, due to the feeble binding energy of their valence particles, are easy to excite into the continuum. In this Letter, continuum states in the heaviest particle-stable Be isotope, 14Be, are studied by employing the method of inelastic proton scattering in inverse kinematics. New continuum states are found at excitation energies E* = 3.54(16) MeV and E* = 5.25(19) MeV. The structure of the earlier known 21+ state at 1.54(13) MeV was confirmed with a predominantly (0d5/2)² configuration while there is very clear evidence that the 22+ state has a predominant (1s1/2, 0d5/2) structure with a preferential three-body decay mechanism. The region at about 7 MeV excitation shows distinct features of sequential neutron decay via intermediate states in 13Be. This demonstrates that the increasing availability of energetic beams of exotic nuclei opens up new vistas for experiments leading towards a new understanding of the interplay between bound and continuum states. [ABSTRACT FROM AUTHOR]

We study (p,2p) and (p,pn) reactions at proton energies in the range of 100 MeV-1 GeV. Our purpose is to explore the most sensitive observables in unpolarized reactions with inverse kinematics involving radioactive nuclei. We formulate a model based on the eikonal theory to describe total cross sections and momentum distributions of the recoiled residual nucleus. The model is similar to the one adopted for knockout reactions with heavy ions. We show that momentum distributions are sensitive to the angular momentum of the ejected nucleón which can be used as an spectroscopic tool. The total cross sections are sensitive to the nucleón separation energies and to multiple scattering effects. Our calculations also indicate that a beam energy around 500 MeV/nucleon has a smaller dependence on the anisotropy of the nucleon-nucleon elastic scattering. [ABSTRACT FROM AUTHOR]

The article presents information on a new one-neutron knockout experiment from an isotope 14Be, identified as a two-neutron halo nucleus with a Borromean structure. It presents a review of the main data concerning 13Be and 14Be and describes an experiment followed by an outline of the analysis of the one-neutron knockout in a hydrogen target. An analysis of the new data is presented together with recent data from the natural sciences research institute RIKEN.

Abstract: The electric dipole response of atomic nuclei has attracted a lot of attention from experimentalists and theorists in the last decade. This review gives an overview about the present status of experimental approaches to study low-lying electric dipole strength (often denoted as Pygmy Dipole Resonance) in stable and radioactive atomic nuclei and discusses the implications of these findings. Data published until July 2012 have been taken into account. [Copyright &y& Elsevier]

Abstract: Resistive plate chamber (RPC) prototypes of 2m length were simulated and built. The experimental tests using a 31MeV electron beam, discussed in details, showed an efficiency higher than 90% and an excellent time resolution of around . Furthermore, comprehensive simulations were performed by Geant4 toolkit in order to study the possible use of these RPCs for fast neutron (200MeV–1GeV) detection and multi-neutron event identification. The validation of simulation parameters was carried out via a comparison to experimental data. A possible setup for invariant mass spectroscopy of multi-neutron emission is presented and the characteristics are discussed. The results show that the setup has a high detection efficiency. Its capability of determining the momentum of the outgoing neutrons and reconstructing the relative energy between the fragments from nuclear reactions is demonstrated for different scenarios. [Copyright &y& Elsevier]

Abstract: One-neutron knockout reactions from Borromean nuclei are analyzed using a profile function analysis technique. The profile function, which is derived as the square root of the variance of the measured fragment + neutron momenta as a function of their relative energy, is shown to be very sensitive to the angular momentum of the knocked out neutron. Three cases are studied here: 7He, where the profile function analysis shows a presence of component in the 8He ground-state wave-function, 10Li, where the presence of a 11(2)% d-wave contribution to the relative energy spectrum above 1.5 MeV is found and, finally, the presence of a major s contribution around 0.5 MeV relative energy in the 13Be case and that the observed decay to the 12Be state originates in a d state in 13Be. [Copyright &y& Elsevier]

Abstract: The NeuLAND detector at the R3B experiment at the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2–1.0GeV) with high time and spatial resolutions . This task can be performed either with a scintillator or based on the multigap resistive plate chamber (MRPC) technology. Here, prototyping and test for an MRPC-based solution are discussed. In order to reach 90% detection efficiency, the final detector must consist of 50 consecutive MRPC stacks. Each stack contains a 4mm thick anode made of iron converter material, with an additional 4mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPCs. As part of the ongoing development effort, a number of prototypes for this detector have been developed and built. They have been tested in experiments with a single-electron beam with picosecond resolution at the superconducting linac ELBE (Dresden, Germany). The results of the tests are presented here, and an outlook is given. [Copyright &y& Elsevier]

The neutron dripline has presently been reached only for the lightest nuclei up to the element oxygen. In this region of light neutron-rich nuclei, scattering experiments are feasible even for dripline nuclei by utilizing high-energy secondary beams produced by fragmentation. In the present article, reactions of high-energy radioactive beams will be exemplified using recent experimental results mainly derived from measurements of breakup reactions performed at the LAND and FRS facilities at GSI and at the S800 spectrometer at the NSCL. Nuclear and electromagnetically induced reactions allow probing different aspects of nuclear structure at the limits of stability related to the neutron-proton asymmetry and the weak binding close to the dripline. Properties of the valence-neutron wave functions are studied in the one-neutron knockout reaction, revealing the changes of shell structure when going from the beta-stability line to more asymmetric loosely bound neutron-rich systems. The vanishing of the N = 8 shell gap for neutron-rich systems like 11Li and 12Be, or the new closed N = 14, 16 shells for the oxygen isotopes are examples. The continuum of weakly bound nuclei and halo states can be studied by inelastic scattering. The dipole response, for instance, is found to change dramatically when going away from the valley of stability. A redistribution of the dipole strength towards lower excitation energies is observed for neutron-rich nuclei, which partly might be due to a new collective excitation mode related to the neutron-proton asymmetry. Halo nuclei, in particular, show strong dipole transitions to the continuum at the threshold, being directly related to the ground-state properties of the projectile. Finally, an outlook on future experimental prospects is given. [ABSTRACT FROM AUTHOR]

Nuclear knockout reactions at relativistic energies provide a sensitive tool to determine the ground state properties of nuclei close to the drip line. Studies with kinematically complete measurements reveal the initial correlations in the reacting systems and yield spectroscopic information on the continuum states populated in the decay channel. The coincident data of charged fragments and neutrons as well allows to unveil the possible influence of the reaction mechanism to the interpretation of the measurements. Two- and three-body correlations can be observed and allow to determine the internal momentum distributions of halo nuclei as well as the assignment of spins and parities to the populated states in the intermediate systems in the breakup process. [Copyright &y& Elsevier]

Coulomb breakup of unstable neutron-rich carbon isotopes 15,17C has been studied at energies around ∼500–600 MeV/nucleon. Non-resonant low-lying dipole strength is observed in these isotopes which can be explained by a direct breakup mechanism. In addition to the decay neutron from excited projectile, γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence, giving access to quantitative spectroscopic information. The spectroscopic factor deduced for a valence neutron occupying the s1/2 level in the 15C ground state is consistent with that obtained earlier from (d,p) transfer reactions. The analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in excited states. The predominant ground-state configuration of 17C is found to be 16C(2+)⊗νs,d. [Copyright &y& Elsevier]

Two 1− levels at 5.35(10) and 6.85(5) MeV were observed for the first time in 20O. The strong direct excitation and subsequent γ-ray decay of these states in virtual photon scattering at 100 MeV/nucleon, along with B(Eλ) predictions for 20O states in this energy region, established their dipole character. The extracted B(E1)↑ values of ≃0.062(16) e2 fm2 and ≃0.035(9) e2 fm2 for the 5.35 and 6.85 MeV states, respectively, are significantly larger than shell model calculations predict. Such large dipole strengths are not observed for low-lying 1− states in 18O, indicating a shift of dipole strength towards lower energies as one approaches the neutron drip-line. [Copyright &y& Elsevier]

Coulomb break up of the neutron-rich 15,17C and 17–22O isotopes has been studied experimentally using secondary beams at energies of 500–600 MeV/u. A comparison between differential cross sections, dσ/dE&ast;, with that obtained from a binary model shows that the main ground-state configuration of 15C is 14C(0+)⊗νS1/2 as expected. For 17C, our preliminary data analysis reveals that the predominant (∼64%) configuration of the ground state is 16C(2+)⊗νs,d. For 17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted sum rule strength depending on neutron number. The energy weighted E1 strength (integrated up to 15 MeV excitation energy) increases up to 20O then decreases for 21,22O. These data are compared to a shell model calculation. [Copyright &y& Elsevier]

The cerebellum's influence on voluntary movement is mediated, in large part, through the cerebello-thalamo-cortical (CTC) pathway. Of particular relevance here are those neurons in the cerebellar nuclei that project, via thalamus, to pyramidal tract neurons in primary motor cortex. Several lines of evidence implicate cerebello-thalamic (CT) synaptic plasticity as a neural substrate underlying movement adaptation in adult animals. CT synapses exhibit a number of structural characteristics suggestive of a capacity for both formation of new synapses, and alterations in efficacy of transmission across existing synapses. Long-term potentiation can be evoked across CT synapses in vitro by high frequency stimulation, albeit in young animals. Evidence regarding the contribution of CT synaptic plasticity to two different types of movement adaptation in adult animals is conflicting. Adaptation involving a strengthening and re-coordination of voluntary movement is associated with an increase in density of CT synaptic boutons and an increase in number of synaptic vesicles available for immediate neurotransmitter release within each bouton. On the other hand, adaptation involving associative conditioning of a reduced sensorimotor neural circuit is associated with plasticity at thalamo-cortical but not CT synapses. These conflicting findings may reflect differences in the extent of synaptic re-organization that occurs at thalamic versus cortical levels, differences in the neural circuitry mediating each behavior, and/or differences in the spatio-temporal convergence of activity in the thalamus during the adaptive processes. It is concluded that CT synaptic plasticity can underlie movement adaptation if the adaptation requires reorganization of the cerebellum's influence on cerebral cortex. [ABSTRACT FROM AUTHOR]

In this review article we discuss the present status of direct nuclear reactions and the nuclear structure aspects one can study with them. We discuss the spectroscopic information we can assess in experiments involving transfer reactions, heavy-ion-induced knockout reactions and quasifree scattering with (p , 2 p) , (p , p n) , and (e , e ′ p) reactions. In particular, we focus on the proton-to-neutron asymmetry of the quenching of the spectroscopic strength. [ABSTRACT FROM AUTHOR]

Reviews knowledge of multiphonon giant resonances in nuclei. Excitation mechanisms of multiphonon states; Description of applied techniques; Emphasis on electromagnetic excitations of double dipole resonances.

Abstract: In a recent paper by S.I. Sidorchuk et al., Phys. Rev. Lett. 108 (2012) 202502, angular correlations in the decay of 10He were interpreted as a coherent superposition of a , and states. It was concluded that it is the state that dominates in the energy region 4.5–6 MeV. It is here demonstrated here that the experimental data might be understood without assuming the presence of a low-lying state. [Copyright &y& Elsevier]

Coulomb breakup of neutron-rich Be, B, C, and O isotopes at relativistic energies (400-600 A MeV) was studied with kinematically complete measurements. The ground-state properties of these nuclei were deduced by comparing experimental data for Coulomb-dissociation cross-sections with direct-breakup model calculations. The dominant ground-state configurations of 15C, 11Be, 14B, and 23O were found to be 14C gs(0+) ⊗ νs,10Be gs(0+) ⊗ νs, 13B gs(3/2+) ⊗ νs,d, and 22O gs(0+) ⊗ νs, respectively, and 16C(2 +) ⊗ νs,d for 17C. The capture cross-section for 14C(n,γ) 15C relevant in astrophysical scenarios was measured indirectly through Coulomb dissociation. [ABSTRACT FROM AUTHOR]

An experimentally constrained equation of state of neutron-rich matter is fundamental for the physics of nuclei and the astrophysics of neutron stars, mergers, core-collapse supernova explosions, and the synthesis of heavy elements. To this end, we investigate the potential of constraining the density dependence of the symmetry energy close to saturation density through measurements of neutron-removal cross sections in high-energy nuclear collisions of 0.4 to 1GeV/nucleon. We show that the sensitivity of the total neutron-removal cross section is high enough so that the required accuracy can be reached experimentally with the recent developments of new detection techniques. We quantify two crucial points to minimize the model dependence of the approach and to reach the required accuracy: the contribution to the cross section from inelastic scattering has to be measured separately in order to allow a direct comparison of experimental cross sections to theoretical cross sections based on density functional theory and eikonal theory. The accuracy of the reaction model should be investigated and quantified by the energy and target dependence of various nucleon-removal cross sections. Our calculations explore the dependence of neutron-removal cross sections on the neutron skin of medium-heavy neutron-rich nuclei, and we demonstrate that the slope parameterLof the symmetry energy could be constrained down to ±10 MeV by such a measurement, with a 2% accuracy of the measured and calculated cross sections. [ABSTRACT FROM AUTHOR]

Nucleon knockout experiments using beryllium or carbon targets reveal a strong dependence of the quenching factors, i.e., the ratio ( R s ) of theoretical to the experimental spectroscopic factors ( C 2 S ), on the proton-neutron asymmetry in the nucleus under study. However, this dependence is greatly reduced when a hydrogen target is used. To understand this phenomenon, exclusive 1 H (17 Ne , 2 p 16 F) and inclusive 12 C (17 Ne , 2 p 16 F) X , 12 C (17 Ne , 16 F) X as well as 1 H (17 Ne , 16 F) X (X-denotes undetected reaction products) reactions with 16 F in the ground and excited states were analysed. The longitudinal momentum distribution of 16 F and the correlations between the detached protons were studied. In the case of the carbon target, there is a significant deviation from the predictions of the eikonal model. The eikonal approximation was used to extract spectroscopic factor values C 2 S . The experimental C 2 S value obtained with C target is markedly lower than that for H target. This is interpreted as rescattering due to simultaneous nucleon knockout from both reaction partners, 17 Ne and 12 C . [ABSTRACT FROM AUTHOR]

We present a theoretical study of the Maris polarization effect and its application in quasi-free reactions to assess information on the structure of exotic nuclei. In particular, we explore the dependence of the polarization effect on neutron excess and neutron-skin thickness. We discuss the uncertainties in the calculations of triple differential cross sections and of analyzing powers due the choices of various nucleon–nucleon interactions and optical potentials and the limitations of the method. Our study implies that polarization variables in (p, 2p) reactions in inverse kinematics can be an effective probe of single-particle structure of nuclei in radioactive-beam facilities. [ABSTRACT FROM AUTHOR]

A new technique to measure the lifetime τ of a neutron-radioactive nucleus that decays in-flight via neutron emission is presented and demonstrated utilizing MonteCarlo simulations. The method is based on the production of the neutron-unbound nucleus in a target, which at the same time slows down the produced nucleus and the residual nucleus after (multi-) neutron emission. The spectrum of the velocity difference of neutron(s) and the residual nucleus has a characteristic shape, that allows to extract the lifetime. If the decay happens outside the target there will be a peak in the spectrum, while events where the decay is in the target show a broad flat distribution due to the continuous slowing down of the residual nucleus. The method itself and the analysis procedure are discussed in detail for the specific candidate 26 O. A stack of targets with decreasing target thicknesses can expand the measurable lifetime range and improve the sensitivity by increasing the ratio between decays outside and inside the target. The simulations indicate a lower limit of measurable lifetime τ ∼ 0 . 2 ps for the given conditions. [ABSTRACT FROM AUTHOR]

The isospin characters of low-energy dipole excitations in neutron-rich unstable nucleus 20 O were investigated, for the first time in unstable nuclei. Two spectra obtained from a dominant isovector probe ( O 20 + Au ) and a dominant isoscalar probe ( O 20 + α ) were compared and analyzed by the distorted-wave Born approximation to extract independently the isovector and isoscalar dipole strengths. Two known 1 − states with large isovector dipole strengths at energies of 5.36(5) MeV ( 1 1 − ) and 6.84(7) MeV ( 1 2 − ) were also excited by the isoscalar probe. These two states were found to have different isoscalar dipole strengths, 2.70(32)% ( 1 1 − ) and 0.67(12)% ( 1 2 − ), respectively, in exhaustion of the isoscalar dipole-energy-weighted sum rule. The difference in isoscalar strength indicated that they have different underlying structures. [ABSTRACT FROM AUTHOR]

Abstract: Recent results from a first irradiation of multi-gap resistive plate chambers with fast neutrons are presented. The counters have been built at GSI and FZD. The experiment was performed at the “The Svedberg Laboratory” (TSL) in Uppsala, Sweden, utilizing a quasi-monoenergetic neutron beam with an energy E n =175MeV. For a 2×4 gap prototype operated at E=100kV/cm, an efficiency of (0.77 ±0.33)% was measured. [Copyright &y& Elsevier]

We present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R 3 B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision σ Δ E / Δ E of up to 1% and a time precision of up to 14 ps (sigma). Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible. [ABSTRACT FROM AUTHOR]

Experimental information on fragment emissions is important in understanding the dynamics of nuclear collisions and in the development of transport model simulating heavy-ion collisions. The composition of complex fragments emitted in the heavy-ion collisions can be explained by statistical models, which assume that thermal equilibrium is achieved at collision energies below 100 MeV/u. Our new experimental data together with theoretical analyses for light particles from Sn+Sn collisions at 270 MeV/u, suggest that the hypothesis of thermal equilibrium breaks down for particles emitted with high transfer momentum. To inspect the system's properties in such limit, the scaling features of the yield ratios of particles from two systems, a neutron-rich system of 132 Sn + 124 Sn and a nearly symmetric system of 108 Sn + 112 Sn , are examined in the framework of the statistical multifragmentation model and the antisymmetrized molecular dynamics model. The isoscaling from low energy particles agree with both models. However the observed breakdown of isoscaling for particles with high transverse momentum cannot be explained by the antisymmetrized molecular dynamics model. [ABSTRACT FROM AUTHOR]

The decay properties of the Pygmy Dipole Resonance (PDR) have been investigated in the semi-magic N = 82 nucleus 140 Ce using a novel combination of nuclear resonance fluorescence and γ – γ coincidence techniques. Branching ratios for transitions to low-lying excited states are determined in a direct and model-independent way both for individual excited states and for excitation energy intervals. Comparison of the experimental results to microscopic calculations in the quasi-particle phonon model exhibits an excellent agreement, supporting the observation that the Pygmy Dipole Resonance couples to the ground state as well as to low-lying excited states. A 10 % mixing of the PDR and the [ 2 1 + × PDR ] is extracted. [ABSTRACT FROM AUTHOR]

Properties of the nuclear equation of state (EoS) can be probed by measuring the dynamical properties of nucleus-nucleus collisions. In this study, we present the directed flow (v 1), elliptic flow (v 2) and stopping (VarXZ) measured in fixed target Sn + Sn collisions at ▪ with the S π RIT Time Projection Chamber. We perform Bayesian analyses in which EoS parameters are varied simultaneously within the Improved Quantum Molecular Dynamics-Skyrme (ImQMD-Sky) transport code to obtain a multivariate correlated constraint. The varied parameters include symmetry energy, S 0 , and slope of the symmetry energy, L , at saturation density, isoscalar effective mass, m s ⁎ / m N , isovector effective mass, m v ⁎ / m N and the in-medium cross-section enhancement factor η. We find that the flow and VarXZ observables are sensitive to the splitting of proton and neutron effective masses and the in-medium cross-section. Comparisons of ImQMD-Sky predictions to the S π RIT data suggest a narrow range of preferred values for m s ⁎ / m N , m v ⁎ / m N and η. [ABSTRACT FROM AUTHOR]

The CALIFA calorimeter is an advanced detector for gamma rays and light charged particles, accordingly optimized for the demanding requirements of the physics programme proposed for the R 3 B facility at FAIR. The multipurpose character of CALIFA is required to fulfil challenging demands in energy resolution (5–6% at 1 MeV for gamma rays) and efficiency. Charged particles, e.g. protons of energies up to 320 MeV in the Barrel section, should also be identified with an energy resolution better to 1%. CALIFA is divided into two well-separated sections: a “Forward EndCap” and a cylindrical “Barrel” covering an angular range from 43.2° to 140.3°. The Barrel section, based on long CsI(Tl) pyramidal frustum crystals coupled to large area avalanche photodiodes (LAAPDs), attains the requested high efficiency for calorimetric purposes. The construction of the CALIFA Demonstrator, comprising 20% of the total detector, has already been initiated, and commissioning experiments are expected for 2014. The assessment of the capabilities and expected performance of the detector elements is a crucial step in their design, along with the prototypes evaluation. For this purpose, the Barrel geometry has been carefully implemented in the simulation package R3BRoot, including easily variable thicknesses of crystal wrapping and carbon fibre supports. A complete characterization of the calorimeter response (including efficiency, resolution, evaluation of energy and reconstruction losses) under different working conditions, with several physics cases selected to probe the detector performance over a wide range of applications, has been undertaken. Prototypes of different sections of the CALIFA Barrel have been modeled and their responses have been evaluated and compared with the experimental results. The present paper summarizes the outcome of the simulation campaign for the entire Barrel section and for the corresponding prototypes tested at different European installations. [ABSTRACT FROM AUTHOR]

The radionuclide 60Fe has been of great interest to the nuclear astrophysics community for over a decade. An initial discrepancy between the observed and modeled Galactic 60Fe/26Al ratio motivated numerous studies focused on the nucleosynthesis of these two isotopes, though the cross section of the primary astrophysical production reaction, 59Fe(n, γ)60Fe, has remained purely theoretical. The present work offers a first experimental constraint on the 59Fe(n, γ)60Fe cross section at astrophysical energies, obtained indirectly via Coulomb dissociation, and demonstrates that the theoretical reaction rates used in present stellar models are not highly erroneous. [ABSTRACT FROM AUTHOR]

Abstract: The existing Nuclear Resonance Fluorescence (NRF) setup at the facility at the Triangle Universities Nuclear Laboratory at Duke University has been extended in order to perform coincidence experiments. The new setup combines large volume detectors and high resolution HPGe detectors in a very close geometry to offer high efficiency, high energy resolution as well as high count rate capabilities at the same time. The combination of a highly efficient spectroscopy setup with the mono-energetic high-intensity photon beam of provides a worldwide unique experimental facility to investigate the pattern of dipole excitations in atomic nuclei. The performance of the new setup has been assessed by studying the nucleus 32S at 8.125MeV beam energy. The relative branching ratio from the 1+ level at 8125.4keV to the first excited 2+ state was determined to 15.7(3)%. [Copyright &y& Elsevier]

The tetraneutron has attracted the attention of nuclear physicists during the past decades, but there is still no unambiguous confirmation of its existence or non-existence. A new experiment based on 8 He(p, 2p) 7 H{t+ 4 n } reaction, with direct detection of the four neutrons, has been carried out at RIBF, which can hopefully help to draw a definite conclusion on the tetraneutron system. [ABSTRACT FROM AUTHOR]

Spin-1 states in 60Ni were excited with the (γ, γ') reaction, exploiting the High Intensity γ-ray Source at Triangle University Nuclear Laboratory. This facility is capable of providing fully linearly polarized, quasimonochromatic, Compton-backscattered photons in the entrance channel of the reaction. The depopulation of low-lying levels in an energy region far below the incident quasimonochromatic photons allows us to obtain average branching ratios of the excited spin-1 states. Levels within the energy region associated with the PDR showed regular behavior and ≈75% of their decays are direct ground-state decays. The levels in the energy region above the PDR exhibit a statistical decay behavior to a large number of low-lying excited states and have only ≈50-60% branches to the ground state. Within the framework of the quasiparticle phonon model this feature can be explained with the number of quasiparticles contributing to the wave functions of the excited spin-1 states. Quasimonochromatic photon beams provide a new method to test the microscopic nature of 1- levels. [ABSTRACT FROM AUTHOR]

Abstract: The very exotic nuclear resonance systems, 10He and 13Li, are produced in proton-knockout reactions from relativistic beams of 11Li and 14Be. The experimentally determined energy and angular correlations between their decay products, and , are analyzed using an expansion of decay amplitudes in a restricted set of hyperspherical harmonics. By considering only a small number of terms it is possible to extract the expansion coefficients directly from the experimental three-body correlations. This provides a model-independent way of getting information about the decay process, on the structure of the decaying nucleus and on the quantum characteristics of the binary subsystems. The results show that the relative-energy spectrum can be interpreted as consisting of two resonances, an ground state and an excited state. The relative-energy spectrum is interpreted as an ground state overlapping with excited states having a structure similar to the state in 10He but spread over several states due to the coupling to the core. The 13Li data also give evidence for a contribution of a configuration where the two neutrons occupy the d-shell. [ABSTRACT FROM AUTHOR]

Abstract: The unbound nuclei 9He and 10He have been produced in proton-knockout reactions from a 280 MeV/u 11Li beam impinging on a liquid hydrogen target at the ALADIN-LAND setup at GSI. Information on their nuclear structure has been obtained from the relative-energy spectra, and , employing reaction models incorporating the structure of 11Li. The relative-energy spectrum is dominated by a strong peak-like structure at low energy, which may be interpreted within the effective-range approximation as the result of an s-wave interaction with a neutron scattering length of . This spectrum also shows evidence for resonance states at and at 2.4 MeV above the threshold. It is argued that the s-state might not be the 9He ground state. For , the analysis of the relative-energy spectrum gives two alternative possibilities for an interpretation: either a narrow resonance at () superimposed on a correlated background, or two overlapping resonances, a ground state at 1.54(11) MeV () together with an excited state at 3.99(26) MeV (). The two possible interpretations are discussed. [Copyright &y& Elsevier]

Abstract: The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+)+n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies. [Copyright &y& Elsevier]

Abstract: 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 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. [Copyright &y& Elsevier]

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 ΔA/A ≈ 1.5%, lighter isotopes with atomic numbers Z ≤ 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. [ABSTRACT FROM AUTHOR]