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A very comprehensive review paper on total reaction cross section, by L. F. Canto, V. Guimaraes, J. Lubian and M.S. Hussein, was just submitted to EPJA. (see copy at arXiv)
1) Transfer reactions induced by 13C+9Be (Status: ongoing)
Spokesperson: Valdir Guimarães
Experiment in Tandar - Argentina (Performed June 2022)
The experiment was performed in Argentina. Several reaction channels were open and angular distribution for several transfer reactions will be obtained:
1) Neutron transfer reactions, 9Be(13C,14C)8Be and 9Be(13C,12C)10B. From DWBA spectroscopic factors and ANC for <14C|13C+n> and <13C|12C+n> will be obtained and will be used to infer about the neutron capture 13C(n,g)14C and , 12C(n,g)13C reactions.
Status: Data being analysed by Laura Maria Figueroa (master degree)
2) Elastic 9Be(13C,13C), Elastic transfer 9Be(13C,9Be)13C and transfer 9Be(13C,10Be)12C reactions. Spectroscopic factor for the <14C|9Be+a> at everal excitation energies will be obtained.
Status: data being analysed by Fernando Miletto (PhD student) and Marlete Assunção.
3) Transfer 9Be(13C,15N)7Li and 9Be(13C,7Li)15N reactions. Both 15N and 7Li were detected and the full angular distribution with the combination of both reactions will be obtained. The transfer mechanism will be discussed.
Status: data being analysed by Pierre Nistal (master degree) and Adriana Barioni
4) Deuteron Transfer 9Be(13C,11B)11B. Angular distributions for several 11B excited states will be obtained.
Status: data being analysed by Marlete Assunção
2) Spectroscopic investigation 12Be nucleus by 8He+4He resonant scattering using ACTAR. (Status: ongoing) - Experiment in GANIL - France (To be performed 01 April 2024)
Spokesperson of the experiment: François de Oliveira and Valdir Guimaraes - Data analysis: Juan Zamora
In the light nuclei both stable and instable, the clustering plays important role to define their configuration. for instance, as in the case in the famous Hoyle state. In terms of clustering, 12Be is very interesting nucleus, as well as the beryllium isotopes in general. However, description of light exotic nuclei such as 12Be is a challenge both for experiments and for theoretical calculations. Many excited states do not have a definite spin/parity assignment. In this project we are proposing to investigate the structure of 12Be with the resonant elastic scattering reaction 4He(8He,8He)4He and any possible decay in open channels [5He+7He, 4He+8He(g.s. or 2+1), 6He+8He(g.s. or 2+1), xBe+ xn]. The reaction will be measured using the ACTAR TPC detector filled with the He gas and CF4 as a quencher.
Status: Experiment scheduled to be performed in April 2024
3) Searching for resonances in 6Be (Status: ongoing)
Experiment in CRIB - RIKEN - Japan (Performed in 2007)
Spokesperson: Rubens Lichtenthaler and Valdir Guimaraes
The structure of nuclear system with mass A=6 is of particular interest in association with cluster and quasi-molecular nature of resonances in light nuclei. Many resonances not observed yet in A=6 nuclei are predicted by large scale shell model and three-body with hypersherical functions calculations. Several bound states and resonances were identified in 6Li, 6He but only a few states in the isobar 6Be. The possible existence of resonances near to this threshold (at about 11 MeV in the 6Be excitation energy) could have strong implications in the pp burning in stars since the 3He+3He capture is one the most important captures in the pp chain. Possible resonances in this capture reaction at low energies would have consequences in the 3He destruction and in the Solar neutrino problem. In this project we used the 3He(7Be,α)6Be transfer reaction to populate the 6Be. which favors the formation of an 3He-3He molecule state in the exit channel.
Status: Data analysis being finalized by Juan Alcantara Nunez
4) Searching for resonances in 6Be using AT-TPC and Helios (Status: ongoing)
Experiment in Argonne - USA - (To be performed November 2023)
Spokesperson: Juan Zamora and Valdir Guimarães - Data analysis: Juan Zamora
In this project we are proposing to investigate the resonances in the unbound 6Be nucleus using the 7Be(d,t)6Be neutron stripping reaction. The 7Be, produced by Atlas with 13 MeV/A will be impiged on the SOLARIS (combination of AT-TPC and Helios). The energy spectra and complete trajectory of the tritons will be determined. Another important motivation for a new measurement to investigate the structure of 6Be is to better understand the mechanism for the three-body decay, which can proceed via sequential or democratic decay. In particular, the angular and energy correlations between emitted nucleons are of great interest, as they provide invaluable information on the interplay between structure and reaction aspects of the nuclear open quantum systems. In addition, the simultaneous measurement of 3He and tritons will allow the investigation of analog states in 6Be and 6Li.
Status: Experiment scheduled to be performed in November 2023
5) Spectrocopy of the 23Mg nucleus by the 24Mg(3He,4He)23Mg reaction. (Status: ongoing)
Experiment in IPN-Orsay - France (Performed in 2015)
Spokesperson: Valdir Guimaraes
The investigation of the resonances in 23Mg above the proton threshold is important to understand the proton capture 22Na(p,g)23Mg and the abundance of 22Na in Nova explosion and AGB stars. We performed the experiment in Orsay using the 24Mg(3He,4He) reaction to populate the excited states in 23Mg. Resonances between 7.5 and 9.5 is going to be investigated. We used the splitpole spetrometer. Data is being analysed.
Status: Data being analyzed by Asellsandro Luis de Lara and Valdir Guimaraes
6) Elastic scattering and breakup measurements for the 12N+208Pb. (ongoing)
Experiment in Texas A&M - USA - (Performed in April 2022)
Spokesperson: Valdir Guimarães.
The main motivation of this proposal is to investigate the possible halo structure of the 12N projectile by measuring angular distribution for the elastic on 208Pb target at 75 MeV. We are also planning to detect the 11C fragments from the breakup of 12N on 208Pb to investigate the mechanism involved in the process. The energy at which we are planning to measure the angular distributions are a little above the Coulomb barrier, which is about VB=68 MeV for this system. The 12N proton rich nucleus has a low binding energy for the 12N-˃11C+p decay (Sp=0.601 MeV) and breakup might be an important channel in the interaction of this nucleus with 208Pb target. We are proposing to perform these measurements by using the 12N secondary beam produced by the recoil separator MARS of Texas A&M University (TAMU).
Status: Data analysis Roberto Linares and Pedro L. D. Magro - Writing the paper and dissertion.
7) Elastic scattering and breakup measurement by 8B, 11Be, 11C, 12N, 12B, 13O, 13B, 13C, 13N + 208Pb
Responsible for measurements: Yanyun Yang .
Experiment performed in RIBLL Lanzhou - China
Collaboration: Danyang Pang - Valdir Guimaraes - Antonio Moro.
This is a collaboration project with the group in Lanzhou (RIBLL) on elastic scattering and breakup measurement. The group of Lanzhou has performed elastic scattering and breakup experiments induced by radioactive nuclei such as 8B, 11Be, 11C and 12N on 208Pb target at energies three times the Coulomb barrier. A strong suppression of the Coulomb nuclear interference peak is observed in the measured quasielastic scattering angular distribution for 11Be while no supression is observed for 8B. The measured breakup angular distributions have been analized with the NEB (No elastic breakup) model.
Paper on 11Be + 208Pb Phys. Lett. B 811, 135942 (2020).
Paper on 8B + 208Pb Phys. Rev. C 103, 024606 (2020).
Paper on 13O, 13B + 208Pb Phys. Rev. C 105, 054616 (2022).
Paper on 12N and 12B + 208Pb elastic and breakup being prepared.
Paper on 13B, 13O, and 13N being prepared
Data analysis on 11C, 13C and 14C is being performed
8) Elastic scattering measurements for the 13C+208Pb. (Status: ongoing)
Experiment performed in Tandar - Argentina - (June 2022).
Spokesperson of the experiment: Valdir Guimarães - Data analysis: Pedro Domingues (Master degree student) and Marlete Assunção.
The manin motivation of this project is to investigate the role of transfer and inelastic scattering in the elastic scattering for this sytesm. The measurement have been performed in Tandar Laboratory at ELAB = 50, 55 and 60 MeV (energies close to the barrier). This measurement will be part of the elastic scattering investigation of A=13 projectiles.
9) Spectrocopy of the 23Mg nucleus by the 24Mg(3He,4He) reaction. (Status: ongoing)
Experiment performed in IPN-Orsay - France (2016) - Data analysis: Alessandro L. Lara (Master)
Spokesperson of the experiment: Valdir Guimaraes
The proton capture 22Na(p,g)23Mg reaction is the key reaction that influences the 22Na abundance in the novae ejecta. The rate for this reaction is dominated by narrow, isolated resonances in the region close to 9 MeV excitation energy in the compound nucleus 23Mg and some of them are still controversy or poorly known. This motivated the study of the spectroscopy of 23Mg in the astrophysical region of interest through 24Mg(3He,4He)23Mg neutron transfer reaction. The 22Ne(p,g)23Na capture reaction determines the abundance of 22Ne and 20Ne and plays an important role in the understanding of the so-called Ne-E Problem (E for extraordinary). The 22Ne/20Ne abundance ratio is a signature of the classical novae, and therefore, can be used to infer the nature of the underlying white dwarf and the novae type. The experiment was performed december 2016 at ALTO-Facility in Orsay using the Split-Pole spectrometer.
Spokesperson: Valdir Guimarães - Data analysis: Matheus Angelo Bonfim and Marlete Assunção.
Experiment in Tandar - Argentina: 10B+10B (2019) - 6Li+6Li (August 2022)
Collaborators: NEAN group, Andres Arazi and Tandar group, F. L. Canto.
The angular distribution of scattering of identical particles exhibits some oscillation called “Mott oscillations”, which is related to a general quantum effect of scattering of charged particles. These oscillations has been used to test models such as QCD and to discuss small deviations from the Coulomb force law owing to QED-related corrections such as vacuum polarization. These oscillations can also be used to investigate the presence of physical nuclear effects in the predominantly Coulomb interaction. F. Canto and Hussein found that, at a certain critical value of the Sommerfeld parameter, the Mott-oscillations are dumped and the angular distribution in the region of 60-120 degrees becomes quite flat. This phenomenon is called “Transverse Isotropy (TI)”. For the 10B+10B system we expect to have the influence of the nuclear potential in the disappearance of the Mott-oscillations. In this project we are proposing to measure and analyse the elastic scattering of 10B+10B and 6Li+6Li systems at energies near the Coulomb barrier to investigate the influence of the nuclear potential.
11) Spectrocopy of the 11B nucleus by the resonant scattering of 10Be+p. (Status: ongoing)
Experiment to be performed in University of Notre Dame - USA - (2023)
Spokesperson: Valdir Guimaraes - Data analysis: Laura Maria Figueroa (PhD ?)
The purpose of this project is to investigate the structure of 11B above the 10Be+p threshold by the resonant scattering 10Be(p,p)10Be and the 10Be(p,t)2a and 10Be(p,a)7Li reactions. Possible resonance at 200 keV above the 10Be+p threshold in 11B is associate to the strong beta decay of 11Be with possible relation with dark matter production. From the astrophysics point of view, the resonances in 11B is important in the transfer reactions induced by 10Be on protons. According to the sensitivity evaluation, preformed by A. Coc, the most important reactions in the primordial CNO cycle would be 10Be(a,n)13C, 8Li(t,n)10Be, 10Be(p,a)7Li and 10Be(p,t)2a. These reactions would be important also to define the abundance and evolution of population II stars.
12) Spectrocopy of the 12C nucleus by the resonant scattering of 11B+p. (Status: ongoing)
Experiment to be performed in Tandar Argentina (2022)
Spokesperson: Valdir Guimaraes - Data analysis: Laura Maria Figueroa (master)
This project consists in the spectroscopy investigation of the 12C nucleus at high excitation energies by the resonant scattering of 11B+p system. We are going to measure the excitation function for the resonant scattering 11B(p,p)11B, using the thick target method in inverse kinematic. With this method, we will be able to investigate resonances in the 12C compound nucleus above the 11B+p threshold (E*>16.0 MeV). The excitation functions for the 11B(p,p)11B reactions obtained both in direct kinematics (from the literature) and in inverse kinematics (to be measured) will be analyzed with the R-matrix formalism, which can provide the energy, width and spin information of the resonances.
13) Gas target implantation with IBAD technic (18O and 22Ne). (Status: ongoing)
Spokesperson: Valdir Guimaraes
In this project we are proposing to develop the use of the IBAD (ion beam assisted deposition) technique to make implanted 18O and 22Ne thin foils. These foil would used as targets nuclear physics in experiments with interest for astrophysics. This project will be developed in collaboration with the group of Prof. Jose Chubaci.
Analysis and projet to be performed by the a under grad student (scientific iniciation).
14) Spectrocopy of the 24Mg nucleus by the 24Mg(p,p') reactions. (Status: ongoing)
Experiment performed in IPN-Orsay - France (2015)
Spokesperson: Iulian Stefan - Data analysis: Valdir Guimaraes
The fusion reactions 12C(12C,α)20Ne and 12C(12C,p)23Na are referred to as carbon burning in stars, following the hydrogen and helium burning stages. These reactions represent key processes in nuclear astrophysics since they influence not only the nucleosynthesis of 20Ne and 23Na but also the subsequent evolution of a star. The cross section of the carbon fusion reactions in the astrophysical energy region is presumably dominated by resonances which are presently inaccessible in direct experiments. This proposal aims at carrying out spectroscopy of the corresponding levels in the 24Mg compound nucleus. The high excitation levels around 15.5 MeV in 24Mg, coresponding to 1.5 MeV Ecm for 12C+12C system, will be investigated by the inelastic scattering reaction 24Mg(p,p’)24Mg using the Splitpole spectrometer.
Spectrocopy of the 11C nucleus by the resonant scattering of 10B+p. (Status: Finished)
Experiment performed in São Paulo with RIBRAS
Spokesperson of the experiment: Valdir Guimarães - Data analys: Gurpreet Kaur
The purpose of this project is to investigate the structure of 11C above the 10B+p threshold by the resonant scattering 10B(p,p)10B, using the thick target method. The level structure of 11C above the proton threshold is investigated. There are discrepancies and uncertainties about the existence of resonances and lack of spin-parity assignment for resonances above the proton threshold. We measured the excitation function of the interaction of 10B beam on hydrogen (CH2 plastic) target in inverse kinematics with the thick target method at 0, 5, 10, 15, 20, 30 and 40. The 10B beam was scattering in the production target and refocused by the solenoid of the RIBRAS into the plastic target.
Paper published in Phys. Rev. C(2022)
Machine Learning in the investigation of nuclear reactions with Active Targets. (Status: finished)
Spokesperson: Juan Zamora
In this project we are proposing to implement Machine Learning tools to improve and speed analysis of experimental data of nuclear reactions using active targets. For this aim, we will analyze data obtained from an experiment carried out in October 2019 at the University of Notre Dame, USA. In this experiment, radioactive beams of 14O and 14C, produced and focused by the TWINSOL system, were impinged on an active target of the type pAT-TPC (Time Projection Chamber), filled with 4He gas. I
Analysis performed by the master degree Student Guilherme Ferrari Fortino.
Paper published in Nucl. Instr. and Methods A (2022)
Fusion of the 8B+40Ar system by using Active Target TexAct (Status: Finished)
Experiment performed in Texas A&M - USA (2018).
Spokesperson: Valdir Guimaraes and Grigory Rogachev - Data analysis: Juan Zamora
J. C. Zamora, S. Ahn, J. Lubian, E.N. Cardozo, E. Aboud, M. Assuncao, M. Barbui, J. Bishop, A. Bosh, J. Hooker, C. Hunt, H. Jayatissa, E. Koshchiy, S. Lukyanov, R O’Dwyer, Y. Penionzhkevich, B.T. Roeder, A. Saastamoinen, and S. Upadhyayula.
Direct measurements of the total fusion cross section for 8B+40Ar with the active target technique. The fusion excitation function was extracted at energies near the Coulomb barrier. The cross section is well described by a coupled reaction channels calculation. The data were compared with previous 8B fusion experiments on 28Si and 58Ni targets. No evidence of striking enhancement of the total fusion cross section at near the Coulomb barrier, that was previously reported for the 8B + 58Ni system, was observed in these direct measurements.
Paper published Physics Letters B (2021).