arXiv subjects

D. Bazin

Publications and source records attributed to D. Bazin.

At least 19 recordsLinked to original sources

arXiv2026

Spectroscopy of $^{11}$Be from the $^{10}$Be($d,p$) reaction measured in inverse kinematics by the AT-TPC in SOLARIS

The spectroscopy of $^{11}$Be is explored using the $^{10}$Be$(d,p)$$^{11}$Be transfer reaction performed in inverse kinematics at $9.6\,\MeV/u$ using the Active Target Time Projection Chamber (AT-TPC) inside the SOLARIS solenoid. This experiment is the first attempt at coupling the AT-TPC with SOLARIS to perform a high luminosity transfer reaction measurement without compromising excitation energy and scattering angle resolutions. The angular momentum transfer for states up to $3.40\,\MeV$ are determined from distorted-wave Born approximation analysis of the measured angular distributions, from which the corresponding spectroscopic factors are deduced. These factors are compared with those from various shell model interactions, and those for the $3.40\,\MeV$ state are consistent with a positive parity assignment. Recent \textit{ab initio} no-core configuration interaction (NCCI) calculations with various nucleon-nucleon interactions are presented for the low-lying positive parity states of $^{11}$Be. The excitation energies produced using the Daejeon16 interaction are in good agreement with those found from both this experiment and the literature, thus supporting a positive parity assignment. The $3.40\,\MeV$ state, if assigned a tentative $J^\pi=3/2^+$, would then correspond to the second excited state of the $K^P=1/2^+$ one-neutron halo ground state rotational band also predicted from such NCCI calculations.

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arXiv2025

Valence $1s-0d$ proton vacancy of the $^{32}$Si ground state

The $^{32}$Si($^3$He,$d$)$^{33}$P reaction was studied in inverse kinematics at 6.3~MeV/$u$. States in $^{33}$P corresponding to the proton $1s-0d$ single-particle orbitals were identified up to $\sim$4.5 MeV in excitation energy. The ($^{3}$He,$d$) spectroscopic factors were determined from Distorted Wave Born Approximation calculations. When combined with complementary neutron-adding data, the $1s-0d$ proton vacancies in the $^{32}$Si ground state were extracted. In conjunction with a re-analysis of data from previous single-particle measurements, the trends in proton and neutron vacancy were explored across the $^{28,30,32,34}$Si isotopes. Both proton and neutron vacancy data show gradual changes in their occupancies. The proton $1s_{1/2}$ orbitals in $^{32}$Si and $^{34}$Si are both consistent with being empty. The ground-state nucleon distributions are described by shell-model calculations constrained to the $1s-0d$ model space.

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arXiv2025

Extraction of neutron-capture cross sections on $^{92}$Zr using the charge-exchange Oslo method

The $^{93}$Nb($t$,$^{3}$He) reaction at 115 MeV/u was studied to demonstrate that nuclear level densities and $\gamma$-ray strength functions can be extracted from charge-exchange reactions at intermediate energies using the Oslo technique. The matrix of excitation energy in $^{93}$Zr, reconstructed from the ($t$,$^{3}$He) reaction, versus the energy of $\gamma$ rays emitted by the excited $^{93}$Zr nuclei, was obtained in an experiment with the S800 Spectrograph operated in coincidence with the GRETINA $\gamma$-ray detector. The extracted level density and $\gamma$-ray strength function obtained by applying the Oslo method to this matrix were used to estimate the $^{92}$Zr($n$,$\gamma$)$^{93}$Zr cross section by combining the new results with other experimental data and theoretical calculations for $E$1 and $M$1 strength functions at higher energies. Good agreement with direct measurements of the $^{92}$Zr($n$,$\gamma$)$^{93}$Zr cross section was found. The contribution from the upbend in the extracted $\gamma$-ray strength function was important to achieve the consistency as the neutron-capture cross section without this contribution is significantly below the direct measurements otherwise. Since charge-exchange reactions at intermediate energies have long been used for extracting Gamow-Teller strengths, the successful demonstration of the charge-exchange Oslo method enables experiments in which ($n$,$\gamma$) cross sections and Gamow-Teller strengths can be measured simultaneously, which is of benefit for astrophysical studies.

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arXiv2025

Quenching of single-particle strength inferred from nucleon-removal transfer reactions on $^{15}$C

The difference in the proton and neutron separation energies ($\Delta S$) of the weakly bound $^{15}$C ground state is -19.86 MeV, an extreme value. Data from intermediate-energy heavy-ion induced (HI-induced) knockout reactions on nuclei spanning $-20\lesssim\Delta S\lesssim+20$ MeV, suggest that the degree to which single-particle strength is quenched, $R\mathrm{_{s}}$, has a negative correlation with $\Delta S$, decreasing from unity around $-20$~MeV to around 0.2 at $+20$~MeV. For the $^{15}$C ground state ($R_s=0.96(4)$ in HI-induced knockout), contrasting results have recently been obtained via the neutron-adding transfer reaction, which reveal a value of $R_s=0.64(15)$, similar to the value observed at modest $\Delta S$ and more extreme values of $\Delta S$ with reaction probes other than HI knockout. In order to explore the any potential differences between $adding$ and $removing$ processes in transfer reactions at extreme $\Delta S$, single-neutron removal transfer reactions on $^{15}$C were performed at 7.1MeV/u in inverse kinematics. The removal of a valence neutron in 2$s_{1/2}$ orbit using both ($p$,$d$) and ($d$,$t$) reactions shows consistent quenching factors and agrees with those from the neutron-adding reaction. The present results, which can be compared with neutron knockout reaction, suggest that correlations, represented by the quenching factor, show limited dependence on neutron-proton asymmetry under the most extreme asymmetry conditions so far achieved in transfer reactions.

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arXiv2025

Extraction of the non-spin- and spin-transfer isovector responses via the $^{12}\mathrm{C}(^{10}\mathrm{Be},{}^{10}\mathrm{B}+\gamma)^{12}\mathrm{B}$ reaction

The isovector response in $^{12}$B was investigated via the $^{12}$C($^{10}\mathrm{Be}$,$^{10}\mathrm{B}$+$\gamma$)$^{12}$B$^\ast$ reaction at $100 A \, \mathrm{MeV}$. By utilizing the $\gamma$-decay properties of the 1.74 MeV $0^{+}$ and 0.718 MeV $1^{+}$ states in $^{10}\mathrm{B}$, the separate extraction of the non-spin-transfer ($\Delta S=0$) and spin-transfer ($\Delta S=1$) isovector responses up to an excitation energy of 50 MeV in $^{12}$B in a single measurement is demonstrated. The experimental setup employed the S800 spectrometer to detect and analyze the $^{10}\mathrm{B}$ ejectiles and the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) for obtaining the Doppler-reconstructed spectrum for $\gamma$-rays emitted in-flight by $^{10}\mathrm{B}$. A $^{12}$C foil was placed at the pivot point of the spectrograph. The $^{12}$B reaction product was not detected. Contributions from transitions associated with the transfer of different units of angular momentum in the non-spin- and spin-transfer responses were analyzed using a multipole decomposition analysis. The extracted non-spin-dipole ($\Delta S=0$, $\Delta L=1$) and spin-dipole ($\Delta S=1$, $\Delta L=1$) responses were found to be consistent with available data from other charge-exchange probes, validating the non-spin- and spin-transfer filters used. While statistical uncertainties and experimental resolutions were relatively large due to the modest intensity of the $^{10}\mathrm{Be}$ secondary beam, the results show that, with the much higher intensities that will be available at new rare-isotope beam facilities, the ($^{10}\mathrm{Be}$,$^{10}\mathrm{B}$+$\gamma$) reaction and its $\Delta T_{z}=-1$ partner, the ($^{10}$C,$^{10}\mathrm{B}$+$\gamma$) reaction, are powerful tools for elucidating the isovector non-spin- and spin-transfer responses in nuclei.

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arXiv2025

Object Detection with Deep Learning for Rare Event Search in the GADGET II TPC

In the pursuit of identifying rare two-particle events within the GADGET II Time Projection Chamber (TPC), this paper presents a comprehensive approach for leveraging Convolutional Neural Networks (CNNs) and various data processing methods. To address the inherent complexities of 3D TPC track reconstructions, the data is expressed in 2D projections and 1D quantities. This approach capitalizes on the diverse data modalities of the TPC, allowing for the efficient representation of the distinct features of the 3D events, with no loss in topology uniqueness. Additionally, it leverages the computational efficiency of 2D CNNs and benefits from the extensive availability of pre-trained models. Given the scarcity of real training data for the rare events of interest, simulated events are used to train the models to detect real events. To account for potential distribution shifts when predominantly depending on simulations, significant perturbations are embedded within the simulations. This produces a broad parameter space that works to account for potential physics parameter and detector response variations and uncertainties. These parameter-varied simulations are used to train sensitive 2D CNN object detectors. When combined with 1D histogram peak detection algorithms, this multi-modal detection framework is highly adept at identifying rare, two-particle events in data taken during experiment 21072 at the Facility for Rare Isotope Beams (FRIB), demonstrating a 100% recall for events of interest. We present the methods and outcomes of our investigation and discuss the potential future applications of these techniques.

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arXiv2025

Near-threshold dipole strength in {^{10}}Be with isoscalar character

Isoscalar dipole transitions are a distinctive fingerprint of cluster structures. A {1^-} resonance at 7.27(10) MeV, located just below the {\alpha}-emission threshold, has been observed in the deuteron inelastic scattering reactions off 10Be. The deformation lengths of the excited states in 10Be below 9 MeV have been inferred from the differential cross sections using coupled channel calculations. This observed {1^-} resonance has isoscalar characteristics and exhausts approximately 5{\%}-15{\%} of the isoscalar dipole energy-weighted sum rule, providing evidence for pronounced {\alpha} cluster structure in 10Be. The Gamow coupled channel approach supports this interpretation and suggests the near-threshold effect might be playing an important role in this excitation energy domain. The {\alpha}+{\alpha}+n+n four-body calculation reproduces the observed enhanced dipole strength, implying that the four-body cluster structure is essential to describe the {1^-} states in 10Be.

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arXiv2024

In-beam $\gamma$-ray spectroscopy towards the proton dripline: The curious case of $^{32}$Ar

High-resolution in-beam $\gamma$-ray spectroscopy was used to study excited states of the neutron-deficient nucleus $^{32}$Ar populated in fast-beam induced four- and six-nucleon removal reactions from $^{36,38}$Ca. One new $\gamma$-ray transition and indications for an additional two were found, allowing for a glimpse at the level scheme beyond the known $2^+_1$ state. The nature of the new $1900(4)$-keV transition is discussed in the context of the known energy spectrum of the mirror nucleus $^{32}$Si and shell-model calculations using the FSU and SDPF-M cross-shell effective interactions. Its resulting parent state at $3767(5)$ keV, more than $1.3$ MeV above the proton separation energy, is tentatively assigned to have mixed sd-shell and $2p$-$2h$ character. It might either be the mirror of the $J^{\pi}=2^+_2$ state of $^{32}$Si at $4230.8(8)$ keV, but with a decay branch favoring a transition to the $2^+_1$ over the ground state, or the mirror of the $4983.9(11)$-keV state with quantum numbers $0^+$. The resulting mirror-energy differences of $-473(5)$ and $-1218(5)$ keV are both sizable when compared to systematics; in the latter case it would, in fact, be among the largest reported to date in the entire nuclear chart or suggest the potential existence of an additional, hitherto unidentified, low-lying $0^+$ state of $^{32}$Si.

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arXiv2024

In-beam $\gamma$-ray spectroscopy of negative-parity states of $^{37}$K populated in dissipative reactions

In-beam $\gamma$-ray spectroscopy was used to study excited states of the neutron-deficient nucleus $^{37}$K populated in fast-beam inelastic-scattering and proton-removal reactions at high-momentum loss. New $\gamma$-ray transitions and $\gamma\gamma$ coincidence relationships were established using the $\gamma$-ray tracking array GRETINA. The extension of the level scheme up to the first $(13/2^-)$ state highlights the potential of this recently demonstrated population pathway for studies of isospin symmetry involving mirror-energy differences. The nature of the newly identified states is discussed in comparison to shell-model calculations with the FSU cross-shell effective interaction. The calculated occupation numbers of individual orbitals are shown to offer a consistent explanation of the measured mirror-energy differences between $^{37}$K and $^{37}$Ar.

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arXiv2024

Proton removal from $^{73,75}$Br to $^{72,74}$Se at intermediate energies

We report new experimental data for excited states of $^{72,74}$Se obtained from proton removal from $^{73,75}$Br secondary beams on a proton target. The experiments were performed with the Ursinus-NSCL Liquid Hydrogen Target and the combined GRETINA+S800 setup at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University. Within uncertainties, the inclusive cross sections for proton removal from $^{73,75}$Br on a proton target are identical suggesting that the same single-particle orbitals contribute to the proton-removal reaction. In addition, details of the partial cross section fragmentation are discussed. The data might suggest that $l = 1, 2, 3$, and 4 angular momentum transfers are important to understand the population of excited states of $^{72,74}$Se in proton removal. Available data for excited states of $^{74}$Ge populated through the $^{75}$As$(d,{}^{3}{\mathrm{He}}){}^{74}$Ge proton-removal reaction in normal kinematics suggest indeed that the $fp$ and $sd$ shell as well as the $1g_{9/2}$ orbital contribute. A comparison to data available for odd-$A$ nuclei supports that the bulk of the spectroscopic strengths could be found at lower energies in the even-even Se isotopes than in, for instance, the even-even Ge isotopes. In addition, the population of high-$J$ states seems to indicate that multi-step processes contribute to proton-removal reactions at intermediate energies in these collective nuclei.

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arXiv2024

Evolution of the nuclear spin-orbit splitting explored via the $^{32}$Si($d$,$p$)$^{33}$Si reaction using SOLARIS

The spin-orbit splitting between neutron 1$p$ orbitals at $^{33}$Si has been deduced using the single-neutron-adding ($d$,$p$) reaction in inverse kinematics with a beam of $^{32}$Si, a long-lived radioisotope. Reaction products were analyzed by the newly implemented SOLARIS spectrometer at the reaccelerated-beam facility at the National Superconducting Cyclotron Laboratory. The measurements show reasonable agreement with shell-model calculations that incorporate modern cross-shell interactions, but they contradict the prediction of proton density depletion based on relativistic mean-field theory. The evolution of the neutron 1$p$-shell orbitals is systematically studied using the present and existing data in the isotonic chains of $N=17$, 19, and 21. In each case, a smooth decrease in the separation of the $1p_{3/2}$-$1p_{1/2}$ orbitals is seen as the respective $p$-orbitals approach zero binding, suggesting that the finite nuclear potential strongly influences the evolution of nuclear structure in this region.

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arXiv2024

Abrasion-fission reactions at intermediate energies

The availability of high-intensity, heavy-ion beams coupled to sensitive, large solid-angleacceptance spectrometers has enabled a detailed examination of the fission fragments produced in induced-fission reactions. The abrasion-fission process involves the formation of projectile-like prefragments in violent nuclear collisions at relative energies in excess of 100 MeV/u. At intermediate energies below this threshold, experiments suggest a change in the prefragment kinematic qualities. Information regarding the influence of this transitional phase upon the evolution of nuclei approaching the point of scission is scarce. In this article, data are presented for over 200 nuclei from nickel to palladium produced in abrasion-fission reactions of a 80 MeV/u 238U beam. Cross sections were obtained following yield measurements performed for the principal charge states of the identified fission fragments and a detailed analysis of the ion transmission. A full kinematic analysis of the fission fragments has been performed using the LISE++ software package, where the trajectory of an ion passing through a spectrometer can be reconstructed based upon measurements at the focal plane. The results obtained at the S800 spectrograph are compared with predictions obtained with a three-fission progenitor (3EER) model. Systematic studies of fission-fragment properties continue to provide a valuable experimental benchmark for theoretical efforts directed toward describing this complex decay channel, that is important in the context of planning experiments to explore the neutron-rich region of the nuclear chart at rare-isotope beam facilities.

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arXiv2024

Probing proton cross-shell excitations through the two-neutron removal from 38Ca

Bound states of the neutron-deficient, near-dripline nucleus $^{36}$Ca were populated in two-neutron removal from the ground state of $^{38}$Ca, a direct reaction sensitive to the single-particle configurations and couplings of the removed neutrons in the projectile wave function. Final-state exclusive cross sections for the formation of $^{36}$Ca and the corresponding longitudinal momentum distributions, both determined through the combination of particle and $\gamma$-ray spectroscopy, are compared to predictions combining eikonal reaction theory and shell-model two-nucleon amplitudes from the USDB, USDC, and ZBM2 effective interactions. The final-state cross-section ratio $\sigma(2^+_1)/\sigma(0^+)$ shows particular sensitivity and is approximately reproduced only with the two-nucleon amplitudes from the ZBM2 effective interaction that includes proton cross-shell excitations into the $pf$ shell. Characterizing the proton $pf$-shell occupancy locally and schematically, an increase of the $sd$-$pf$ shell gap by $250$ keV yields an improved description of this cross-section ratio and simultaneously enables a reproduction of the $B(E2;0^+_1\to2^+_1)$ excitation strength of $^{36}$Ca. This highlights an important aspect if a new shell-model effective interaction for the region was to be developed on the quest to model the neutron-deficient Ca isotopes and surrounding nuclei whose structure is impacted by proton cross-shell excitations.

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arXiv2023

Time Projection Chamber for GADGET II

Background: The established GADGET detection system, designed for measuring weak, low-energy $\beta$-delayed proton decays, features a gaseous Proton Detector with MICROMEGAS readout for calorimetric particle detection, surrounded by a Segmented Germanium Array for high-resolution prompt $\gamma$-ray detection. Purpose: To upgrade GADGET's Proton Detector to operate as a compact Time Projection Chamber (TPC) for the detection, 3D imaging and identification of low-energy $\beta$-delayed single- and multi-particle emissions mainly of interest to astrophysical studies. Method: A new high granularity MM board with 1024 pads has been designed, fabricated, installed and tested. A high-density data acquisition system based on Generic Electronics for TPCs has been installed and optimized to record and process the gas avalanche signals collected on the readout pads. The TPC's performance has been tested using a $^{220}$Rn $\alpha$-particle source and cosmic-ray muons. In addition, decay events in the TPC have been simulated by adapting the ATTPCROOT data analysis framework. Further, a novel application of 2D convolutional neural networks for GADGET II event classification is introduced. Results: The GADGET II TPC is capable of detecting and identifying $\alpha$-particles, as well as measuring their track direction, range, and energy. It has also been demonstrated that the GADGET II TPC is capable of tracking cosmic-ray muons. In addition to being one of the first generation of micro pattern gaseous detectors to utilize a resistive anode applied to low-energy nuclear physics, the GADGET II TPC will also be the first TPC surrounded by a high-efficiency array of high-purity germanium $\gamma$-ray detectors. \textbf{Conclusions:} The TPC of GADGET II has been designed, fabricated, tested, and is ready for operation at the FRIB for radioactive beam-line experiments.

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arXiv2023

Hexadecapole strength in the rare isotopes $^{74,76}$Kr

In the Ge-Sr mass region, isotopes with neutron number $N \leq 40$ are known to feature rapid shape changes with both nucleon number and angular momentum. To gain new insights into their structure, inelastic proton scattering experiments in inverse kinematics were performed on the rare isotopes $^{74,76}$Kr. This work focuses on observables related to the $J^{\pi} = 4^+_1$ states of the Kr isotopes and, in particular, on the hexadecapole degree of freedom. By performing coupled-channels calculations, hexadecapole deformation parameters $\beta_4$ were determined for the $J^{\pi} = 4^+_1$ states of $^{74,76}$Kr from inelastic proton scattering cross sections. Two possible coupled-channels solutions were found. A comparison to predictions from nuclear energy density functional theory, employing both non-relativistic and relativistic functionals, clearly favors the large, positive $\beta_4$ solutions. These $\beta_4$ values are unambiguously linked to the well deformed prolate configuration. Given the $\beta_2 - \beta_4$ trend, established in this work, it appears that $\beta_4$ values could provide a sensitive measure of the nuclear shell structure.

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arXiv2022

Dissipative reactions with intermediate-energy beams -- a novel approach to populate complex-structure states in rare isotopes

A novel pathway for the formation of multi-particle-multi-hole (np-mh) excited states in rare isotopes is reported from highly energy- and momentum-dissipative inelastic-scattering events measured in reactions of an intermediate-energy beam of 38Ca on a Be target. The negative-parity,complex-structure final states in 38Ca were observed following the in-beam gamma-ray spectroscopy of events in the 9Be(38Ca,38Ca+gamma)X reaction in which the scattered projectile lost longitudinal momentum of order p = 700 MeV/c. The characteristics of the observed final states are discussed and found to be consistent with the formation of excited states involving the rearrangement of multiple nucleons in a single, highly-energetic projectile-target collision. Unlike the far-less dissipative, surface-grazing reactions usually exploited for the in-beam gamma-ray spectroscopy of rare isotopes, these more energetic collisions appear to offer a practical pathway to nuclear-structure studies of more complex multi-particle configurations in rare isotopes - final states conventionally thought to be out of reach with high-luminosity fast-beam-induced reactions.

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arXiv2022

Investigation of octupole collectivity near the $A =72$ shape-transitional point

Enhanced octupole collectivity is expected in the neutron-deficient Ge, Se and Kr isotopes with neutron number $N \approx 40$ and has indeed been observed for $^{70,72}$Ge. Shape coexistence and configuration mixing are, however, a notorious challenge for theoretical models trying to reliably predict octupole collectivity in this mass region, which is known to feature rapid shape changes with changing nucleon number and spin of the system. To further investigate the microscopic configurations causing the prolate-oblate-triaxial shape transition at $A \approx 72$ and their influence on octupole collectivity, the rare isotopes $^{72}$Se and $^{74,76}$Kr were studied via inelastic proton scattering in inverse kinematics. While significantly enhanced octupole strength of $\sim 32$ Weisskopf units (W.u.) was observed for $^{72}$Se, only strengths of $\sim 15$ W.u. were observed for $^{74,76}$Kr. In combination with existing data, the new data clearly question a simple origin of enhanced octupole strengths around $N = 40$. The present work establishes two regions of distinct octupole strengths with a sudden strength increase around the $A=72$ shape transitional point.

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arXiv2022

Probing the quadrupole transition strength of 15C via deuteron inelastic scattering

Deuteron elastic scattering from 15C and inelastic scattering reactions to the first excited state of 15C were studied using a radioactive beam of 15C in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length δd = 1.04(11) fm has been extracted from the differential cross sections of inelastic scattering to the first excited state. The ratio of neutron and proton matrix elements Mn/Mp = 3.6(4) has been determined from this quadrupole transition. Neutron effective charges and core-polarization parameters of 15C were determined and discussed. Results from ab-initio no-core configuration interaction calculations were also compared with the experimental observations. This result supports a moderate core decoupling effect of the valence neutron in 15C similarly to its isotone 17O, in line with the interpretation of other neutron-rich carbon isotopes.

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