We measured the ${}^8\mathrm{Li}(p,p){}^8\mathrm{Li}$, ${}^8\mathrm{Li}(p,d){}^7\mathrm{Li}$, and ${}^8\mathrm{Li}(p,\alpha ){}^5\mathrm{He}$ reactions at low energies using the thick target inverse kinematics method, with a polyethylene ${\left[{\mathrm{CH}}_2\right]}_n$ target and a radioactive ${}^8\mathrm{Li}$ beam available at the Radioactive Ion Beams in Brazil facility of São Paulo. By measuring simultaneously several reaction channels $(p,p)$, $(p,d)$, and $(p,\alpha )$, the still uncertain high-lying resonances of ${}^9\mathrm{Be}$, close to the proton threshold, can be studied and their parameters, such as energy, width, and spin parity can be more reliably determined. The experimental excitation functions of the reactions ${}^8\mathrm{Li}(p,p){}^8\mathrm{Li}$, ${}^8\mathrm{Li}(p,d){}^7\mathrm{Li}$, and ${}^8\mathrm{Li}(p,\alpha ){}^5\mathrm{He}$ were analyzed using the $R$-matrix theory, which allows us to infer the properties of the resonances. Multichannel $R$-matrix analysis provides evidence for a significant clustering in the $(p,d)$ channel. The experimental data and the multichannel $R$-matrix analysis will be presented.

In relativistic heavy-ion collisions, the production of heavy quarks at large transverse momenta is strongly suppressed compared to proton-proton collisions. In addition, an unexpectedly large azimuthal anisotropy was observed for the emission of charmed hadrons in noncentral collisions. Both observations pose challenges to the theoretical understanding of the coupling between heavy quarks and the quark-gluon plasma produced in these collisions. Transport models for the evolution of heavy quarks in a QCD medium offer the opportunity to study these effects; two of the most successful approaches are based on the linearized Boltzmann transport equation and the Langevin equation. In this work, we develop a hybrid transport model that combines the strengths of both of these approaches: Heavy quarks scatter with medium partons using matrix-elements calculated in perturbative QCD, while between these discrete hard scatterings they evolve using a Langevin equation with empirical transport coefficients to capture the nonperturbative soft part of the interaction. With the hybrid transport model coupled to a state-of-the-art event-by-event bulk evolution model based on 2+1D relativistic viscous fluid dynamics, we study the azimuthal anisotropy and nuclear modification factor of heavy quarks in Pb+Pb collisions at $\sqrt{s}=5.02$ TeV. The parameters related to heavy-flavor transport are calibrated using a Bayesian analysis comparing them to available $D$-meson and $B$-meson data at the Large Hadron Collider. Using the calibrated model, we study the implications on heavy-flavor transport properties and predict observables.

The data on hadron transverse momentum spectra in different centrality classes of p + Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV have been analyzed to extract the freeze-out hypersurface within a simultaneous chemical and kinetic freeze-out scenario. The freeze-out hypersurface has been extracted for three freeze-out schemes that differ in the way strangeness is treated: (i) unified freeze-out for all hadrons at complete thermal equilibrium (1FO), (ii) unified freeze-out for all hadrons with an additional parameter ${\gamma }_S$ which accounts for possible out-of-equilibrium production of strangeness ($1\mathrm{FO}+{\gamma }_S$), and (iii) separate freeze-out for hadrons with and without strangeness content (2FO). Unlike in heavy-ion collisions where 2FO performs best in describing the mean hadron yields as well as the transverse momentum spectra, with p + Pb we find that $1\mathrm{FO}+{\gamma }_S$ with one fewer parameter than 2FO performs better. This confirms expectations based on previous analysis of system size dependence in the freeze-out scheme with mean hadron yields: while heavy-ion collisions that are dominated by constituent interactions prefer 2FO, smaller collision systems like proton + nucleus and proton + proton collisions with lesser constituent interaction prefer a unified freeze-out scheme with varying degrees of strangeness equilibration.

The double Gamow-Teller strength distributions in even-$A$ calcium isotopes were calculated using the nuclear shell model by applying the single Gamow-Teller operator two times sequentially on the ground state of the parent nucleus. The number of intermediate states actually contributing to the results was determined. The sum rules for the double Gamow-Teller operator in the full calculation were approximately fulfilled. In the case that the symmetry is restored approximately by introducing degeneracies of the $f$ levels, and the $p$ levels in the $fp$-model space, the agreement with the sum rules was very close.

Algebraic collective model (ACM) calculations for the even-even selenium isotopes ${}^{86,88}\mathrm{Se}$ have been performed to describe collective properties of these two transitional nuclei with only two and four valence neutrons, respectively. From the perspective of the ACM the nuclei turn out to be only weakly deformed, described by a very $\gamma$-soft potential. This is confirmed by Skyrme and Gogny energy density functional calculations. Additionally, the fully microscopic symmetry conserving configuration mixing method with the Gogny interaction has been applied to the study of these isotopes. The results show the transitional character of ${}^{86}\mathrm{Se}$ and the relevant role of the triaxial degree of freedom in the structure of these nuclei.

Background: Elastic scattering is a very important process to understand nuclear interactions in finite nuclei. Despite decades of efforts, the goal of reaching a coherent description of this physical process in terms of microscopic forces is still far from being completed.

Purpose: In previous papers we derived a nonrelativistic theoretical optical potential from nucleon-nucleon chiral potentials at fourth (${\mathrm{N}}^3\mathrm{LO}$) and fifth order (${\mathrm{N}}^4\mathrm{LO}$). We checked convergence patterns and established theoretical error bands. With this work we study the performances of our optical potential in comparison with those of a successful nonrelativistic phenomenological optical potential in the description of elastic proton scattering data on several isotopic chains at energies around and above 200 MeV.

Methods: We use the same framework and the same approximations as adopted in our previous papers, where the nonrelativistic optical potential is derived at the first-order term within the spectator expansion of the multiple scattering theory and adopting the impulse approximation and the optimum factorization approximation.

Results: The cross sections and analyzing powers for elastic proton scattering off calcium, nickel, tin, and lead isotopes are presented for several incident proton energies, exploring the range $156\le E\le 333$ MeV, where experimental data are available. In addition, we provide theoretical predictions for ${}^{56}\mathrm{Ni}$ at 400 MeV, which is of interest for the future experiments at EXL.

Conclusions: Our results indicate that microscopic optical potentials derived from nucleon-nucleon chiral potentials at ${\mathrm{N}}^4\mathrm{LO}$ can provide reliable predictions for the cross section and the analyzing power both of stable and exotic nuclei, even at energies where the reliability of the chiral expansion starts to be questionable.

We calculate the intraband electromagnetic transitions in the framework of a collective Hamiltonian for chiral and wobbling modes. By going beyond the mean-field approximation on the orientations of the rotational axis, the collective Hamiltonian provides descriptions of both the yrast band and collective excitation bands. For a system with one $h_{11/2}$ proton particle and one $h_{11/2}$ neutron hole coupled to a triaxial rotor ($\gamma =-{30}^{\circ }$), the intraband electromagnetic transitions given by the one-dimensional and two-dimensional collective Hamiltonian are compared with results obtained by using the tilted axis cranking approach and the particle rotor model. Compared with the tilted axis cranking approach, the electromagnetic transitions given by the collective Hamiltonian agree better with the transitions obtained by using the particle rotor model because quantum fluctuations are considered.

A simple two-state mixing model has been applied to members of the two lowest $0^{+}$ rotational bands in ${}^{106,108}\mathrm{Pd}$. Unique solutions are found for the $0^{+}$ and $2^{+}$ mixing in both cases, and for the E2 matrix elements connecting the basis states. The lower basis-state band is found to be somewhat more collective than the second one. Results indicate that ${}^{108}\mathrm{Pd}$ is slightly more collective than ${}^{106}\mathrm{Pd}$. In ${}^{106}\mathrm{Pd}$, The $2^{+}$ wave functions from the fit are used to compute matrix elements for 4 ↔ 2 transitions, one of which is unknown.

We examine the effects of the isovector-vector coupling and hypercharge-vector coupling in quark matter on hadron-quark coexistence in neutron-star matter. The relativistic mean field theory with the TM1 parameter set and an extended TM1 parameter set are used to describe hadronic matter, and the Nambu-Jona-Lasinio model with scalar, isoscalar-vector, isovector-vector, and hypercharge-vector couplings is used to describe deconfined quark matter. The hadron-quark phase transition is constructed via the Gibbs conditions for phase equilibrium. The isovector-vector and hypercharge-vector couplings in quark matter enhance the symmetry energy and hypercharge symmetry energy in neutron-star matter, while their effects are found to be suppressed at high densities by the strange quarks. As a result, the hadron-quark mixed phase shrinks with only isovector-vector coupling and moves to higher density with isovector-vector and hypercharge-vector couplings. The maximum mass of neutron star increases slightly with isovector-vector and hypercharge-vector couplings.

This paper reports the results of the first measurements of the differential cross section of the ${}^{80}\mathrm{Se}(\gamma ,n){}^{79}\mathrm{Se}$ reaction with a linearly polarized gamma-ray ($\gamma$-ray) beam. The cross section was measured at three incident $\gamma$-ray beam energies: 15.6, 15.8, and 16.0 MeV, with a beam energy spread of 3.0% full width at half-maximum (FWHM). The differential cross section for the excitation spectrum in ${}^{79}\mathrm{Se}$ was measured at two scattering angles in the plane of the beam polarization: $\theta ={90}^{\circ }$ and ${135}^{\circ }$, and at one angle in the plane perpendicular to the plane of polarization: $\theta ={90}^{\circ }$. The total photoneutron cross sections determined from these data are between 0.8 and 1.3 standard deviations smaller than previously published results. The excitation spectra measured in this work were fit with a Hauser-Feshbach model. Better fits to the data were obtained with a constant-temperature formulation of the nuclear level density (NLD) than with a Fermi-gas NLD model. The parameters for the constant-temperature NLD model obtained in this work are consistent with those obtained for medium-mass nuclei in previous studies.

The charge-independence breaking of the nuclear interaction is analyzed by means of energy differences among analog states in $T=1$ isobaric multiplets. Data on triplet energy differences in the $sd, pf$, and $pfg$ shells, i.e., $18\le A\le 66$, are reproduced with very good accuracy by large-scale shell-model calculations taking into account, aside from the Coulomb interaction, a single isotensor schematic interaction of monopole-pairing type. It is shown that the effect on the triplet energy differences of this isospin-breaking interaction is of the same magnitude as the Coulomb one. Moreover, its strength is the same for every single-particle orbital of the considered model space.

The $2\alpha +t$ cluster structure in ${}^{11}\mathrm{B}$ is investigated by the microscopic generator coordinate method with the Brink cluster wave functions. With a proper choice of the parameters of the effective interaction, the calculated energy spectrum shows reasonable agreement with the observed low-lying spectra of both parities. On the basis of the calculated radii, and monopole and $B\left(E2\right)$ transition strengths, several developed cluster states of ${}^{11}\mathrm{B}$ are suggested. For the negative-parity states, in addition to the well-known $3/2_3^{-}$ cluster state, the $1/2_2^{-}$ and $5/2_3^{-}$ states are also proposed as the well-developed cluster states. For the positive-parity states, it is found that many states around the $2\alpha +t$ threshold show the feature of developed clusters. In particular, the $1/2_2^{+}$ state is found to have a linear-chain-like structure, which is consistent with the previous antisymmetrized molecular dynamics calculation, but contradicts the orthogonality condition model calculation. It is also found that many of these positive-parity cluster candidates have non-negligible isoscalar dipole transition strengths, which require experimental confirmation.

Fluctuations of the baryon number in relativistic heavy-ion collisions are a promising observable to explore the structure of the QCD phase diagram. The cumulant ratios in heavy-ion collisions at intermediate energies ($\sqrt{s_{\mathit{NN}}}<5$ GeV) have not been studied to date. We investigate the effects of mean-field potential and clustering on the cumulant ratios of baryon and proton number distributions in Au+Au collisions at beam energy of 1.23 GeV/nucleon as measured by the HADES Collaboration at GSI. Ultrarelativistic quantum molecular dynamics (UrQMD) and the JAM model are used to calculate the cumulants with different mean-field potentials. It is found that the cumulant ratios are strongly time dependent. At the early stage, the effects of the potentials on the fluctuations of the particle multiplicity in momentum space are relatively weak. The mean fields enhance the fluctuations during the expansion stage, especially for small rapidity acceptance windows. The enhancement of cumulant ratios for free protons is strongly suppressed as compared to that for all baryons. The mean-field potentials and the clustering play an important role for the measured cumulant ratios at intermediate energy.

We present an approach to derive effective shell-model interactions from microscopic nuclear forces. The similarity transformed coupled-cluster Hamiltonian decouples the single-reference state of a closed-shell nucleus and provides us with a core for the shell model. We use a second similarity transformation to decouple a shell-model space from the excluded space. We show that the three-body terms induced by both similarity transformations are crucial for an accurate computation of ground and excited states. As a proof of principle we use a nucleon-nucleon interaction from chiral effective field theory, employ a ${}^4\mathrm{He}$ core, and compute low-lying states of ${}^{6–8}\mathrm{He}$ and ${}^{6–8}\mathrm{Li}$ in $p$-shell model spaces. Our results agree with benchmarks from full configuration interaction.

Neutron-activated sources of ${}^{103}\mathrm{Ru}$ and ${}^{103}\mathrm{Pd}$ both share the isomeric first-excited state in ${}^{103}\mathrm{Rh}$ as a daughter product. From independent measurements of both decays, we have measured the $K$ shell and total internal-conversion coefficients, ${\alpha }_K$ and ${\alpha }_T$, for the 39.8-keV $E3$ transition, which de-excites that state in ${}^{103}\mathrm{Rh}$, to be 141.1(23) and 1428(13), respectively. When compared with Dirac-Fock calculations, our new results disagree with the version of the theory that ignores the $K$-shell atomic vacancy, which is consistent with our conclusion drawn from a series of measurements on high multipolarity transitions in nuclei with higher $Z$. Calculations that include the atomic vacancy indicate that the transition actually has a small $M4$ component with mixing ratio $\delta =0.023$(5).

We investigate the nonlocal structure of optical model potentials for nucleon-nucleus scattering based on microscopic approaches. To this purpose, in medium folding optical potentials are calculated in momentum space and their corresponding coordinate-space counterpart are examined, paying special attention to their nonlocal shape. The nucleon-nucleon effective interaction consists of the actual full off-shell $g$ matrix in Brueckner-Hartree-Fock approximation. The nonlocality of effective interactions is preserved throughout all stages in the calculation. Argonne $v_{18}$ bare potential and chiral next-to-next-to-next-to-leading order bare interaction are used as starting point. The study is focused on proton elastic scattering off ${}^{40}\mathrm{Ca}$ at beam energies between 30 and 800 MeV. We find that the gradual suppression of high-momentum contributions of the optical potential results in quite different-looking coordinate-space counterparts. Despite this nonuniqueness in their nonlocal structure, the implied scattering observables remain unchanged for momentum cutoff above a critical one, which depends on incident energy of the projectile. We find that coordinate-space potentials with momentum cutoffs at the critical value yield the least structured nonlocal behavior. Implications of these findings are discussed.

The Pauli rearrangement potential given by the second-order diagram is evaluated for a nucleon optical model potential (OMP) with $G$ matrices of the nucleon-nucleon interaction in chiral effective field theory. The results obtained in nuclear matter are applied for ${}^{40}\mathrm{Ca}$ in a local-density approximation. The repulsive effect is of the order of 5–10 MeV at the normal density. The density dependence indicates that the real part of the microscopic OMP becomes shallower in a central region, but is barely affected in a surface area. This improves the overall resemblance of the microscopic OMP to the empirical one.

Based on an extended Skyrme interaction that includes the terms in relative momenta up to sixth order, corresponding to the so-called Skyrme pseudopotential up to next-to-next-to-next-to leading order (N3LO), we derive the expressions of Hamiltonian density and single-nucleon potential under general nonequilibrium conditions which can be applied in transport model simulations of heavy-ion collisions induced by neutron-rich nuclei. While the conventional Skyrme interactions, which include the terms in relative momenta up to second order, predict an incorrect behavior as a function of energy for nucleon optical potential in nuclear matter, the present extended N3LO Skyrme interaction can give a nice description for the empirical nucleon optical potential. We also construct three interaction sets with different high-density behaviors of the symmetry energy by fitting both the empirical nucleon optical potential up to energy of 1 GeV and the empirical properties of isospin asymmetric nuclear matter. These extended N3LO Skyrme interactions will be useful in transport model simulations of heavy-ion collisions induced by neutron-rich nuclei at intermediate and high energies, and they can also be useful in nuclear structure studies within the mean-field model.

Photoneutron cross sections were measured for ${}^{58}\mathrm{Ni},{}^{60}\mathrm{Ni},{}^{61}\mathrm{Ni}$, and ${}^{64}\mathrm{Ni}$ at energies between the one-neutron and two-neutron thresholds using quasimonochromatic $\gamma$-ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. These photoneutron data are used to extract the $\gamma$-ray strength function above the neutron threshold, complementing the information obtained by the Oslo method below the threshold. We discuss radiative neutron-capture cross sections and the Maxwellian-averaged cross sections for Ni isotopes including ${}^{63}\mathrm{Ni}$, a branching point nucleus along the weak $s$-process path. The cross sections are calculated with the experimentally constrained $\gamma$-ray strength functions from the Hartree-Fock-Bogolyubov plus quasiparticle–random-phase approximation based on the Gogny D1M interaction for both $E1$ and $M1$ components and supplemented with the $M1$ upbend.