Determination of the proper power-counting scheme is an important issue for the systematic application of Chiral Effective Field Theory in nuclear physics. We analyze the cutoff dependence of three-nucleon observables (the neutron-deuteron scattering lengths and the triton binding energy) at the leading and next-to-leading orders of a power counting that ensures order-by-order renormalization in the two-nucleon system. Our results confirm that, as usually assumed in the literature, three-body forces are not needed for renormalization of the three-nucleon system up to next-to-leading order.

One promising candidate for the first detection of nuclear excitation in plasma is the 463-keV, 20.26-min-lifetime isomeric state in ${}^{84}\mathrm{Rb}$, which can be excited via a 3.5-keV transition to a higher lying state. According to our preliminary calculations, under specific plasma conditions, nuclear excitation by electron transition (NEET) may be its strongest excitation process. Evaluating a reliable NEET rate requires, in particular, a thorough examination of all atomic transitions contributing to the rate under plasma conditions. We report the results of a detailed evaluation of the NEET rate based on multiconfiguration Dirac Fock (MCDF) atomic calculations, in a rubidium plasma at local thermodynamic equilibrium with a temperature of 400 eV and a density of ${10}^{-2}\mathrm{g}/{\mathrm{cm}}^3$ and based on a more precise energy measurement of the nuclear transition involved in the excitation.

Low-lying electric-dipole ($E1$) strength of a neutron-rich nucleus contains information on neutron-skin thickness, deformation, and shell evolution. We discuss the possibility of making use of total reaction cross sections on ${}^{40}\mathrm{Ca}, {}^{120}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ targets to probe the $E1$ strength of neutron-rich Ca, Ni, and Sn isotopes. They exhibit large enhancement of the $E1$ strength at neutron number $N>28$, 50, and 82, respectively, due to a change of the single-particle orbits near the Fermi surface participating in the transitions. The density distributions and the electric-multipole strength functions of those isotopes are calculated by the Hartree-Fock+BCS and the canonical-basis-time-dependent-Hartree-Fock-Bogoliubov methods, respectively, using three kinds of Skyrme-type effective interaction. The nuclear and Coulomb breakup processes are respectively described with the Glauber model and the equivalent photon method in which the effect of finite-charge distribution is taken into account. The three Skyrme interactions give different results for the total reaction cross sections because of different Coulomb breakup contributions. The contribution of the low-lying $E1$ strength is amplified when the low-incident energy is chosen. With an appropriate choice of the incident energy and target nucleus, the total reaction cross section can be complementary to the Coulomb excitation for analyzing the low-lying $E1$ strength of unstable nuclei.

We have studied the $\gamma p\to p{\pi }^0\eta$ reaction paying attention to the two main mechanisms at low energies, the $\gamma p\to \mathrm{\Delta }\left(1700\right)\to \eta \mathrm{\Delta }\left(1232\right)$ and the $\gamma p\to \mathrm{\Delta }\left(1700\right)\to \pi N\left(1535\right)$. Both are driven by the photoexcitation of the $\mathrm{\Delta }\left(1700\right)$ and the second one involves a mechanism that leads to a triangle singularity. We are able to evaluate quantitatively the cross section for this process and show that it agrees with the experimental determination. Yet there are some differences with the standard partial wave analysis which does not include explicitly the triangle singularity. The exercise also shows the convenience of exploring possible triangle singularities in other reactions and how a standard partial wave analysis can be extended to accommodate them.

We analyze the quark-mass dependence of electromagnetic properties of two- and three-nucleon states. To that end, we apply the pionless effective field theory (EFT) to experimental data and numerical lattice calculations which simulate QCD at pion masses of 450 and 806 MeV. At the physical pion mass, we postdict the magnetic moment of helium-3, ${\mu }_{{}^3\mathrm{He}}=-2.13$ nNM (natural nuclear magneton), and the magnetic polarizability of deuterium, ${\beta }_{\text{D}}=7.{3310}^{-2} {\mathrm{fm}}^3$. Magnetic polarizabilities of helium-3, ${\beta }_{{}^3\mathrm{He}}=9.{710}^{-4} {\mathrm{fm}}^3$, and the triton, ${\beta }_{{}^3\mathrm{H}}=8.{210}^{-4} {\mathrm{fm}}^3$, are predictions. Postdictions of the effective theory for the magnetic moments are found consistent with QCD simulations at 806 MeV pion mass, while our EFT result ${\beta }_{\text{D}}=2.{9210}^{-2} {\mathrm{fm}}^3$ was not extracted from the lattice. The deuteron would thus be relatively pliable compared to a three-nucleon state for which we postdict ${\beta }_{{}^3\mathrm{H}}=3.{910}^{-5} {\mathrm{fm}}^3$. At $m_{\pi }=450\mathrm{MeV}$, the magnetic moment of the triton is predicted, ${\mu }_{{}^3\mathrm{He}}=-2.15\left(5\right)$ nNM, based on a conjecture of its binding energy, $B_{{}^3\mathrm{H}}\cong 30$ MeV. For all three pion masses, we compare the point-charge radii of the two- and three-nucleon bound states. The sensitivity of the electromagnetic properties to the Coulomb interaction between protons is studied in anticipation of lattice calculations with dynamical QED.

The isospin mixing between projectile and target in central ${}^{96}\mathrm{Ru}\left({}^{96}\mathrm{Zr}\right)+{}^{96}\mathrm{Zr}\left({}^{96}\mathrm{Ru}\right)$ collisions at 50 to 400 MeV/nucleon is investigated within the isospin-dependent quantum molecular dynamics model in combination with the statistical decay code gemini. Four groups of parameters, which provide different density dependences of symmetry energy and effective $k$-mass splitting, are applied in the model. Calculations within the same effective $k$-mass splittings show that the isospin mixing is more likely to take place for soft symmetry energy than hard symmetry energy. Calculations within similar symmetry energies show that the isospin mixing is more likely to take place for $m_n^{*}<m_p^{*}$ than $m_n^{*}>m_p^{*}$. Significantly, the effects of effective $k$-mass splitting on the isospin mixing become stronger with increasing incident energies, while those of symmetry energy are similar at different incident energies.

Residual gold nuclei were produced via neutron transfer at multiple energies using a 130-MeV ${}^{13}\mathrm{C}$ beam incident on a stacked-foil target consisting of alternating layers of ${}^{197}\mathrm{Au}$ and ${}^{27}\mathrm{Al}$. Production cross sections, over an energy range of 56 to 129 MeV, for seven gold isotopes and two gold isomers were determined through activation analysis. By using the Wilczyński binary transfer model with a modified version of the recoil formula and a standard evaporation model, we were able to reproduce the isotopic production cross sections at high beam energy, with some disagreement at lower beam energies. This limiting angular momentum model does not predict the transfer of sufficient angular momentum to reproduce the observed isomeric populations.

Background: Experimental anisotropy in fission-fragment (FF) angular distribution in reactions involving weakly bound stable projectiles with actinide targets are enhanced compared to statistical saddle-point model (SSPM) predictions. Contributions from breakup- or transfer-induced fission to total fission are cited as possible reasons for such enhancement.

Purpose: To identify the breakup- or transfer-induced fission channels in ${}^6\mathrm{Li}$+${}^{232}\mathrm{Th}$ reaction and to investigate their effects on FF angular anisotropy.

Methods: The FF angular distributions have been measured exclusively at three beam energies (28, 32, and 36 MeV) around the Coulomb barrier in coincidence with projectile breakup fragments like $\alpha , d$, and $p$ using Si strip detectors. The angular anisotropy obtained for different exclusive breakup- or transfer-induced fission channels are compared with that for total fission. SSPM and pre-equilibrium fission models have been employed to obtain theoretical FF angular anisotropy.

Results: Angular anisotropy of the fission fragments produced by different transfer- or breakup-induced fission reactions have been obtained separately in the rest frame of respective recoiling nuclei. Some of these anisotropies were found to be stronger than those of the inclusive fission. Overall angular distributions of transfer or breakup fission, integrated over all possible recoil angles with weight factor proportional to differential cross section of the complementary breakup fragment emitted in coincidence in all possible directions, were obtained. It was observed that the overall FF angular anisotropy for each of these fission channels is less than or equal to the anisotropy of total fission at all the measured energies. Assuming isotropic out-of-plane correlations between the fission fragments and light-charged particles, the overall breakup- or transfer-induced fission fragment angular distributions do not explain the observed enhancement in FF anisotropy of total fission. Pre-equilibrium fission model provides a reasonable explanation of the enhanced experimental anisotropy of total fission.

Conclusions: Angular anisotropies for different breakup or transfer fission channels involving emission of $\alpha , d$, and $p$ in the reaction plane have been measured for the ${}^6\mathrm{Li}+{}^{232}\mathrm{Th}$ reaction. The overall FF angular anisotropies of breakup- or transfer-induced fissions do not explain the enhanced anisotropy of total fission at near-barrier energies. A measurement of out-of-plane correlation is necessary to confirm the above observation and obtain a complete picture on the effect of transfer or breakup on total fission.

The decay properties of the short-lived isotope ${}^{220}\mathrm{Pa}$ were re-investigated via the reaction ${}^{40}\mathrm{Ar}+{}^{187}\mathrm{Re}$ at the gas-filled recoil separator Spectrometer for Heavy Atoms and Nuclear Structure. The digital pulse processing technique was applied to resolve the evaporation residues–$\alpha$ ($\mathrm{ER}-\alpha$) pileup signals in the decay of ${}^{220}\mathrm{Pa}$. The $\alpha$-decay chain of ${}^{220}\mathrm{Pa}$ leading to the well-known ${}^{216}\mathrm{Ac}$ isotope was established for the first time. The $\alpha$ energy and half-life were measured to be $E_{\alpha }=9.520\left(16\right)\mathrm{MeV}$ and $T_{1/2}=0.90\left(13\right)\mu \mathrm{s}$, respectively. The spin parity of the ground state of ${}^{220}\mathrm{Pa}$ was assigned to be $1^{-}$, based on the reduced $\alpha$-decay width.

We report for the first time the $\beta$-decay scheme of ${}^{140}\mathrm{Te}$ ($Z=52$) to ${}^{140}\mathrm{I}$ ($Z=53$), with a specific focus on the Gamow-Teller strength along $N=87$ isotones. These results were obtained in an experiment performed at the Radioactive Ion Beam Factory (RIBF), RIKEN, where the parent nuclide, ${}^{140}\mathrm{Te}$, was produced through the in-flight fission of a ${}^{238}\mathrm{U}$ beam at 345 MeV per nucleon impinging on a ${}^9\mathrm{Be}$ target. Based on data from the high-efficiency $\gamma$-ray spectrometer, EUROBALL-RIKEN Cluster Array (EURICA), we constructed a decay scheme of ${}^{140}\mathrm{I}$. The half-life of ${}^{140}\mathrm{Te}$ has been determined to be 350(5) ms. A level at 926 keV has been assigned as a ($1^{+}$) state based on the $logft$ value of 4.89(6). This ($1^{+}$) state, commonly observed in odd-odd nuclei, can be interpreted in terms of the $\pi h_{11/2}\nu h_{9/2}$ configuration formed by the Gamow-Teller transition between a neutron in the $h_{9/2}$ orbital and a proton in the $h_{11/2}$ orbital. We observe a sharp contrast to this type of $\beta$-decay branching to the lower-lying $1^{+}$ states between ${}^{140}\mathrm{I}$ and ${}^{136}\mathrm{I}$, where we see a large reduction as the number of neutrons increases. This is in contrast to the prediction by large-scale shell model calculations. To investigate this type of the suppression, results of the Nilsson model calculations will be discussed. Along the isotones with $N=87$, we discuss a characteristic feature of the Gamow-Teller distributions at $1^{+}$ states with respect to the isospin difference.

The results of a neutron inelastic scattering experiment performed at the Geel Electron Linear Accelerator pulsed white neutron source of the European Commission Joint Research Centre are reported. The neutrons with energies up to 18 MeV interacted with a ${}^{\mathrm{nat}}\mathrm{Ti}$ sample and the $\gamma$ rays resulting from inelastic scattering reactions on the stable isotopes were detected using the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. We were able to measure the $\gamma$-production cross sections for 21 transitions in the five stable Ti isotopes. From these, the level cross sections and the total inelastic cross sections were determined. Our experimental results are compared with theoretical calculations performed using the talys 1.8 code, evaluated nuclear data libraries, and also with previously reported results.

Two-particle correlations in $p\mathrm{Pb}$ collisions at a nucleon-nucleon center-of-mass energy of $5.02\text{TeV}$ are studied as a function of the pseudorapidity separation ($\mathrm{\Delta }\eta$) of the particle pair at small relative azimuthal angle ($\left|\mathrm{\Delta }\varphi \right|<\pi /3$). The correlations are decomposed into a jet component that dominates the short-range correlations ($\left|\mathrm{\Delta }\eta \right|<1$), and a component that persists at large $\mathrm{\Delta }\eta$ and may originate from collective behavior of the produced system. The events are classified in terms of the multiplicity of the produced particles. Finite azimuthal anisotropies are observed in high-multiplicity events. The second and third Fourier components of the particle-pair azimuthal correlations, $V_2$ and $V_3$, are extracted after subtraction of the jet component. The single-particle anisotropy parameters $v_2$ and $v_3$ are normalized by their laboratory frame midrapidity value and are studied as a function of ${\eta }_{\text{c.m.}}$. The normalized $v_2$ distribution is found to be asymmetric about ${\eta }_{\text{c.m.}}=0$, with smaller values observed at forward pseudorapidity, corresponding to the direction of the proton beam, while no significant pseudorapidity dependence is observed for the normalized $v_3$ distribution within the statistical uncertainties.

Short-lived radionuclides (SLRs) with half-lives less than 100 Myr are known to have existed around the time of the formation of the solar system around 4.5 billion years ago. Understanding the production sources for SLRs is important for improving our understanding of processes taking place just after solar system formation as well as their timescales. Early solar system models rely heavily on calculations from nuclear theory due to a lack of experimental data for the nuclear reactions taking place. In 2013, Bowers et al. measured ${}^{36}\mathrm{Cl}$ production cross sections via the ${}^{33}\mathrm{S}$($\alpha ,p$) reaction and reported cross sections that were systematically higher than predicted by Hauser-Feshbach codes. Soon after, a paper by Peter Mohr highlighted the challenges the new data would pose to current nuclear theory if verified. The ${}^{33}\mathrm{S}(\alpha ,p){}^{36}\mathrm{Cl}$ reaction was re-measured at five energies between 0.78 MeV/nucleon and 1.52 MeV/nucleon, in the same range as measured by Bowers et al., and found systematically lower cross sections than originally reported, with the new results in good agreement with the Hauser-Feshbach code talys. Loss of Cl carrier in chemical extraction and errors in determination of reaction energy ranges are both possible explanations for artificially inflated cross sections measured in the previous work.

The “island of inversion” at $N\approx 20$ for the neon, sodium, and magnesium isotopes has long been an area of interest both experimentally and theoretically due to the subtle competition between 0p-0h and $n\mathrm{p}-n\mathrm{h}$ configurations leading to deformed shapes. However, the presence of rotational band structures, which are fingerprints of deformed shapes, have only recently been observed in this region. In this work, we report on a measurement of the low-lying level structure of ${}^{33}\mathrm{Mg}$ populated by a two-stage projectile fragmentation reaction and studied with the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA). The experimental level energies, ground-state magnetic moment, intrinsic quadrupole moment, and $\gamma$-ray intensities show good agreement with the strong-coupling limit of a rotational model.

The repulsive short-distance core is one of the main paradigms of nuclear physics which even seems confirmed by QCD lattice calculations. On the other hand nuclear potentials at short distances are motivated by high energy behavior where inelasticities play an important role. We analyze $\mathit{NN}$ interactions up to 3 GeV in terms of simple coarse grained complex and energy dependent interactions. We discuss two possible and conflicting scenarios which share the common feature of a vanishing wave function at the core location in the particular case of $S$ waves. We find that the optical potential with a repulsive core exhibits a strong energy dependence whereas the optical potential with the structural core is characterized by a rather adiabatic energy dependence which allows one to treat inelasticity perturbatively. We discuss the possible implications for nuclear structure calculations of both alternatives.

Background: The nuclear structure of the cluster bands in ${}^{20}\mathrm{Ne}$ presents a challenge for many theoretical approaches. It is especially difficult to explain the broad $0^{+}$ and $2^{+}$ states, both at around 9 MeV excitation energy. More reliable experimental data for these levels is important for proper quantitative assessment and development of theoretical methods.

Purpose: To obtain new data on the ${}^{20}\mathrm{Ne}$ $\alpha$-cluster structure.

Method: The thick target inverse kinematics (TTIK) technique was used to study ${}^{16}\mathrm{O}+\alpha$ resonance elastic scattering and the data were analyzed using an R-matrix approach. The ${}^{20}\mathrm{Ne}$ spectrum and the cluster and nucleon spectroscopic factors were calculated using the cluster-nucleon configuration interaction model (CNCIM).

Results: We determined the parameters of the broad resonances in ${}^{20}\mathrm{Ne}$: $0^{+}$ level at $8.77\pm 0.150$ MeV with a width of ${750}_{-220}^{+500}$ keV; $2^{+}$ level at $8.75\pm 0.100$ MeV with the width of $695\pm 120$ keV; the width of 9.48 MeV level of $65\pm 20$ keV; and we showed that the 9.19 MeV, $2^{+}$ level (if it exists) should have a width of $\le 10$ keV. A detailed comparison of the theoretical CNCIM predictions with the experimental data on cluster states was made.

Conclusions: Our experimental results obtained by the TTIK method generally confirm the adopted data on $\alpha$-cluster levels in ${}^{20}\mathrm{Ne}$. The CNCIM gives a good description of the ${}^{20}\mathrm{Ne}$ positive-parity states up to an excitation energy of $\sim 7$ MeV, predicting reasonably well the excitation energy of the states and their cluster and single-particle properties. At higher excitations, a qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.