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Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a $^{12}$Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the $^{12}$C(d,p) reaction to well-known states in $^{13}$C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for $^{13}$Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in $^{13}$C were extracted to better than 90 keV, paving a way for extracting information on $^{13}$Be., 8 pages, 6 figures

Two nucleon transfer reactions at low bombarding energies are an ideal tool to investigate nucleon-nucleon correlations. With heavy ions one has the possibility to transfer several nucleon pairs, involving both neutrons and protons at the same time. In this work we will study how pair correlations can be probed in heavy ion collisions , and how the strong Coulomb field influences the reaction dynamic.

8 pags., 9 figs., We measured absolute cross sections for neutron transfer channels populated in the Rb-94 + Pb-208 binary reaction. Cross sections have been extracted identifying directly the lead isotopes with the high efficiency MINIBALL gamma-ray array coupled to a particle detector combined with a radioactive Rb-94 beam delivered at E-lab = 6.2 MeV/nucleon by the HIE-ISOLDE facility. We observed sizable cross sections in the neutron-rich mass region, where the heavy partner acquires neutrons. A fair agreement between the measured cross sections with those from GRAZING calculations gives confidence in the cross-section predictions of more neutron-rich nuclei produced via a larger number of transferred nucleons., This work was partly supported by the HORIZON 2020 ENSAR2 Grant Agreement no. 654002, and Marie Skłodowska-Curie COFUND (EU-CERN) grant agreement no. 665779, and by STFC (U.K.). This work has been supported in part by the Croatian Science Foundation under Project no. 7194 and in part under Project no. IP-2018-01- 1257, and the German BMBF under contract 05P18PKCIA + Verbundprojekt 05P2018

International audience; Multinucleon transfer channels, populated in the inverse kinematic reaction ^197Au+^130Te at E_lab = 1.07 GeV, were studied by means of a high-resolution kinematic coincidence set-up composed of the large acceptance magnetic spectrometer PRISMA coupled to a new detection system acting as second arm. The comparison of the experimental mass-mass correlation matrix with Monte Carlo simulations allowed us to investigate the role of neutron evaporation in the population of neutron-rich heavy nuclei around A = 200.

The low energy excited $0_{2,3}^+$ states in $^{96}$Sr are amongst the most prominent examples of shape coexistence across the nuclear landscape. In this work, the neutron $[2s_{1/2}]^2$ content of the $0_{1,2,3}^+$ states in $^{96}$Sr was determined by means of the d($^{95}$Sr,p) transfer reaction at the TRIUMF-ISAC2 facility using the SHARC and TIGRESS arrays. Spectroscopic factors of 0.19(3) and 0.22(3) were extracted for the $^{96}$Sr ground and 1229~keV $0^+$ states, respectively, by fitting the experimental angular distributions to DWBA reaction model calculations. A detailed analysis of the $\gamma$-decay of the isomeric $0_3^+$ state was used to determine a spectroscopic factor of 0.33(13). The experimental results are compared to shell model calculations, which predict negligible spectroscopic strength for the excited $0^+$ states in $^{96}$Sr. The strengths of the excited $0_{2,3}^+$ states were also analyzed within a two-level mixing model and are consistent with a mixing strength of $a^2$=0.40(14) and a difference in intrinsic deformations of $|\Delta \beta|=0.31(3)$. These results suggest coexistence of three different configurations in $^{96}$Sr and strong shape mixing of the two excited $0^+$ states., Comment: Phys Lett B accepted

The measurements of cross sections for deuteron elastic scattering and (d,p) reaction on 124Sn nuclei have been performed with aim to study the features of sub-barrier deuteron interaction with heavy nuclei. Experimental data were obtained on the electrostatic Tandem accelerator EGP-10K of the Institute for Nuclear Research (Kyiv) at the deuteron beam energies Ed = 4.0; 5.0 and 5.5 MeV. Cross sections of deuteron elastic scattering were calculated in approach where the deuteron interaction potential with heavy nuclei at sub-barrier energies has been constructed in the framework of single folding model using the complex dynamic polarization potential. It is shown that the account of finite deuteron size leads to the increasing the nuclear potential in outer region of interaction and significantly improves the description of the experimental data. The calculations of elastic scattering cross sections were performed without any variations of the nuclear potential parameters. The analysis of measured integral cross sections of the 124Sn(d,p) reaction and calculated cross sections of deuteron breakup reaction 124Sn(d,p)n124Sn shows the dominant contribution of the neutron transfer reaction in the processes of the formation of protons and elastic scattering cross sections.

Recent advances in in-beam gamma-ray spectroscopy of actinide nuclei are based on highly efficient arrays of escape-suppressed spectrometers. The sensitivity of these detector arrays is greatly enhanced by the combination with powerful mass separators or particle detector systems. This technique is demonstrated by an experiment to investigate excited states in 234 U after the one-neutron-transfer reaction 235 U(d,t). In coincidence with the outgoing tritons, γ-rays were detected with the highly efficient MINIBALL spectrometer. In the near future an even enhanced sensitivity will be achieved by utilizing position sensitive HPGe detectors which will exploit the novel detection method of gamma-ray energy tracking in electrically segmented germanium detectors. An example for this novel approach is the investigation neutron-rich actinide Th and U nuclei after multi nucleon transfer reactions employing the AGATA demonstrator and PRISMA setup at LNL, Italy. A primary 136 Xe beam hitting a 238 U target was used to produce the nuclei of interest. Beam-like reaction products after neutron transfer were selected by the PRISMA spectrometer. Coincident γ-rays from excited states in beam and target like particles were measured with the position sensitive AGATA HPGe detectors. Improved Doppler correction and quality of the γ-spectra is based on the novel γ-ray tracking technique, which was successfully exploited in this region.

A systematic study of the change in proton single-particle occupancies in two neutrinoless double beta decay candidates, 130Te to 130Xe and 136Xe to 136Ba, has been performed.Final states in 129Sb, 129I, 135I and 135Cs have been populated using the (d,3He) single proton removal reaction. The deuterons were accelerated to 101 MeV using the coupled azimuthally varying field and Ring cyclotrons at the Research Center for Nuclear Physics, University of Osaka. The outgoing ejectiles were momentum analysed using the Grand Raiden magnetic spectrometer. Absolute cross sections were measured for states up to 7 MeV in excitation. Transferred angular momenta were identified through a comparison of angular distributions with those calculated using the distorted-wave Born approximation. Spectroscopic factors were extracted from the experimental cross sections. In addition to the 0v2B decay candidates the reaction was also performed on 128Te, 132Xe, 134Xe and 138Ba as a consistency check. The occupancies of the nuclei were determined from the spectroscopic factors, the reaction model was normalised using a common normalisation factor across all targets. The change in occupancies between the 0v2B decay candidates and their daughters were then determined. The change in occupancies were then compared with those calculated by interacting shell model, interacting boson model and quasiparticle random phase approximation. This comparison showed that whilst the three theories were qualitatively able to reproduce the change in occupancies, quantitatively there are significant discrepancies. These are the same models that are used to determine the nuclear matrix elements governing the rate of 0v2B decay.

Pairing across the particle emission threshold and the properties of corresponding quasiparticle strength functions are discussed in an extended mean-field approach. This particular type of dynamical correlations gives rise to a unique class of sharp low-lying resonances close to the particle emission threshold. Spectral functions for particle and hole states are discussed. They are explored theoretically by single-nucleon transfer reactions, populating the low energy continuum with respect to a core nucleus. The cross sections of the reaction d(9Li, 10Li)p at T lab = 2.36 A MeV , recently measured at REX-ISOLDE, are well reproduced by our calculations including a pairing resonance in the 3 / 2 − partial wave of purely coupled channels nature.

We developed a Monte-Carlo code for describing the reaction kinematics of the two-body direct processes employed of the EXOTIC beam-line of the Laboratori Nazionali di Legnaro (LNL) for the production of light weakly bound radioactive ion beams at energies of a few MeV/u. The program calculates the phase-space distribution of both primary and secondary beams at the target exit and uses these quantities to optimize the secondary beam selection with the EXOTIC spectrometer. The calculations have been performed and compared with the available experimental data for two reactions: (1)H(2)((17)O, (17)F)n and (3)He((6)Li, (8)B)n. (c) 2008 Elsevier B.V. All rights reserved.

International audience; We present the first missing mass spectrum of the unbound system 10He obtained from one nucleon transfer $^{11}$Li(d,$^{3}$He) reaction at 50 A MeV. We found rather large yields for the $^{6}$He + 4n decay channel especially for higher excitation energy, which suggest the importance of the $^{6}$He + 4n structure in $^{10}$He.

International audience; Neutron-rich chlorine isotopes were populated in the Ar-40 + Pb-208 multiple transfer reaction via the -1p channels in a fragment-gamma coincident measurement employing the Prisma-Clara setup. New gamma transitions have been identified and, together with already available data, level schemes have been revised and compared with the results of large-scale sd-pf shell-model calculations. The evolution of the energy splitting between the s(1/2) and d(3/2) orbitals and the increased mixing of different proton configurations in the populated Cl isotopic chain have been deduced by inspecting the shell-model wave functions.

International audience; Multinucleon transfer reactions between two heavy ions are an important tool for production and investigation of exotic neutron-rich nuclei, which are difficult to access by other methods. The 136Xe + 198Pt system is a candidate to efficiently produce neutron-rich nuclei around the neutron magic number N=126 for the KEK isotope separation project. In order to confirm this, measurements of the production cross sections with the large acceptance magnetic spectrometer VAMOS++ and de-excitation gamma rays from target-like fragments using the high efficiency germanium array EXOGAM at GANIL are reported. The measured isotopic distributions of the projectile-like fragments are compared with GRAZING calculations. The proton stripping channels show rough agreements between measurements and calculations. For the proton pick-up channels, the measured distributions are shifted toward the heavier masses and show enhanced cross sections in transfers of two or more protons.

International audience; The revival of transfer reaction studies benefited from the construction of the new generation large solid angle spectrometers, coupled to large gamma arrays. The recent results of gamma-particle coincident measurements in Ca-40+Zr-96 and Ar-40+Pb-208 reactions demonstrate a strong interplay between single-particle and collective degrees of freedom that is pertinent to the reaction dynamics. The development of collectivity has been followed in odd Ar isotopes populated in the Ar-40+Pb-208 reaction through the excitation of the 11/2(-) states, understood as the coupling of single particle degrees of freedom to nuclear vibration quanta. Pair transfer modes is another important degree of freedom which is presently being studied with Prisma in inverse kinematics at energies far below the Coulomb barrier. First results from the Zr-96+Ca-40 reaction elucidate the role played by nucleon-nucleon correlation.

Expérience GANIL/SPIRAL/MUST2/E525S; The low-lying spectroscopy of 6He was investigated via the 2-neutron transfer reaction p(8He, t) with the 8He beam delivered by the SPIRAL facility at 15.4 A MeV. The light charged particles produced by the direct reactions were measured using the MUST2 Si-strip telescope array. Above the known 2+ state, two new resonances were observed: at E∗ = 2.6±0.3 MeV (width Γ = 1.6±0.4 MeV) and at 5.3±0.3 MeV with Γ = 2 ± 1 MeV. Through the analysis of the angular distributions, they correspond to a 2+ state and to an L = 1 state, respectively. These new states, challenging the nuclear theories, could be used as benchmarks for checking the microscopic inputs of the newly improved structure models, and should trigger development of models including the treatments of both core excitation and continuum coupling effects.

We have measured the angular distributions of elastic scattering and 6,4He fragments produced in the collisions of an exotic beam of 8He on a 208Pb target at laboratory energies of 18 and 22 MeV, just around the Coulomb barrier (19 MeV). The measurements were performed at the SPIRAL/GANIL facility in Caen, France. In this paper, we present preliminary data on elastic cross sections and discuss the results using optical model and coupled reaction channel calculations. ispartof: ACTA PHYSICA POLONICA B vol:43 issue:2 pages:239-245 ispartof: location:Piaski, Poland status: published

Elastic, inelastic and one-nucleon transfer channels in the 48Ca+64Ni reaction have been mea- sured at ~ 6 MeV/A with the PRISMA-CLARA setup, at Legnaro National Laboratory, consisting in the coupling of a large solid angle magnetic spectrometer with a germanium array. By trajec- tory reconstruction the reaction products have been fully identi ed in mass, nuclear charge and kinetic energy, while coincident spectra of binary partners have been constructed after Doppler correction. Absolute di erential cross sections have been extracted for the inelastic excitation and one-nucleon transfer, also for speci c excited states. The data are in good agreement with semi-classical calculations and Distorted Wave Born approximation predictions. The work outlines an experimental method which can become valuable to extract structural information from heavy-ion reaction studies.

Multinucleon transfer reactions have been investigated in 40Ar+208Pb with the Prisma+Clara set-up. The experimental differential cross sections of different neutron transfer channels have been obtained at three different angular settings taking into account the transmission through the spectrometer. The experimental yields of the excited states have been determined via particle-γ coincidences. In odd Ar isotopes, we reported a signif cant population of 11/2− states, reached via neutron transfer. Their structure matches a stretched conf guration of the valence neutron coupled to vibration quanta.

6 pags.; 6 figs., Reactions of a 16.8 MeV 6He beam with a 9Be target have been investigated using highly segmented detector setup covering a large solid angle. Data on elastic and quasi-free scattering, as well as two-neutron transfer, are reported. The results for elastic scattering are fairly well reproduced by a CDCC calculation, in agreement with the interpretation of a breakup effect already observed for the scattering of 6He on other light targets. Exotic quasi-free scattering of 6He on α-cluster in 9Be is clearly observed. Inclusive and coincident events were used to extract information on the two-neutron transfer reaction 9Be(6He, α)11Be. Sequential decay of the 11Be state at the excitation energy Ex = 10.6 MeV through different channels is discussed. © 2010 SIF, Springer-Verlag Berlin Heidelberg., We would like to thank the technical staff at the RNB facility at the CRC-Louvain-la-Neuve for their valuable contributions to this work.

The yrast sequence of the neutron-rich dysprosium isotope 168Dy has been studied using multi-nucleon transfer reactions following collisions between a 460-MeV 82Se beam and a 170Er target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2+ and 4+ members of the previously measured ground state rotational band of 168Dy have been confirmed and the yrast band extended up to 10+. A tentative candidate for the 4+ to 2+ transition in 170Dy was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of Total Routhian Surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed., 15 pages, 7 figures, submitted to Phys. Rev. C

Multinucleon transfer cross sections in the system 40 Ca+ 96 Zr have been measured at bombarding energies ranging from the Coulomb barrier to ~ 25% below. Target-like (lighter) recoils in inverse kinematics have been completely identif ed in A,Z and Q-value with the large solid angle magnetic spectrometer PRISMA. The experimental slopes of the neutron transfer probabilities at large internuclear separation are consistent with the values derived from the binding energies. A phenomenological interpretation of the transfer probabilities indicates the presence of enhanced values for the even number of neutron transfers.

The 6 He+ 209 Bi reaction displays a remarkably large cross section for α -particle emission at energies near the Coulomb barrier. The possible reactions that may produce the observed α particles include two-neutron transfer, one-neutron transfer, and direct projectile breakup. Each of these mechanisms results in a distinctive angular correlation between the α particle and outgoing neutron(s). A neutron- α -particle coincidence experiment was performed to separate these different modes. The neutron data show significant angular correlations. Monte Carlo simulations of one-neutron transfer are compared with the experimental data. It is shown that approximately 20% of the observed α -particle yield is due to this process.

International audience; The structure of the unstable doubly magic nucleus $^{56}$Ni has been investigated by measuring one-and two-nucleon transfer reactions. The radioactive beam of $^{56}$Ni was produced at GANIL-Caen, France at 30 MeV/u by means of the LISE spectrometer. The experimental setup used consists of the TIARA-MUST2-EXOGAM combination which provides an almost 4$\pi$ coverage and the ability to perform particle-$\gamma$ coincidences. To probe the N=28 gap, we studied the spectroscopy of $^{55}$Ni through one-nucleon transfer reactions on $^{56}$Ni. The excitation energy spectrum is deduced by measuring the light ejec-tiles only, while particle-$\gamma$ coincidences are used to improve the resolution of the populated states and select the main ones. Comparison between the extracted angular distributions and DWBA calculations allows the extraction of the spectroscopic strength of the hole-and particle-states populated by these one neutron pickup reactions.