Excited states in the ${}^{66}\mathrm{Zn}$ nucleus were populated via a ${}^{56}\mathrm{Fe}({}^{12}\mathrm{C},2p\gamma$) fusion-evaporation reaction at a beam energy of $\approx 62$ MeV. The deexciting $\gamma$ rays were detected using the Indian National Gamma Array (INGA). The level scheme of the ${}^{66}\mathrm{Zn}$ nucleus has been updated by placing several new $\gamma$ rays as well as by assigning the spin and parity of various excited states from the present spectroscopic results. The microscopic structure of the observed states have been investigated in the light of large shell-model calculations. The shape of this nucleus in the low-spin regime has been studied under the framework of total Routhian surface (TRS) calculations. The lifetime of first $3^{-}$ state at 2826 keV is experimentally measured using the Doppler-shift attenuation method and the deduced $B\left(E1\right)$ value indicates the presence of octupole collectivity in this nucleus.

We present a formalism for the fermionic quasiparticle propagator in a superfluid fermionic system. Starting from a general many-body Hamiltonian confined by the two-body instantaneous interaction, the equation of motion for the fermionic propagator is obtained in the Dyson form. Before making any approximation, the interaction kernel is found to be decomposed into static and dynamical (time-dependent) contributions, where the latter translates to the energy-dependent and the former maps to the energy-independent terms in the energy domain. The three-fermion correlation function, being the heart of the dynamical part of the kernel, is factorized into the two-fermion and one-fermion ones. With the relaxed particle number constraint, the normal propagator is coupled to the anomalous one via both the static and dynamical kernels, which is formalized by introducing the generalized quasiparticle propagator of the Gor'kov type. The dynamical kernel in the factorized form is associated with the quasiparticle-vibration coupling (QVC), with the vibrations unifying both the normal and pairing phonons. The QVC vertices are related to the variations of the Hamiltonian of the Bogoliubov quasiparticles, which can be obtained by the finite amplitude method.

It is often computationally advantageous to model space as a discrete set of points forming a lattice grid. This technique is particularly useful for computationally difficult problems such as quantum many-body systems. For reasons of simplicity and familiarity, nearly all quantum many-body calculations have been performed on simple cubic lattices. Since the removal of lattice artifacts is often an important concern, it would be useful to perform calculations using more than one lattice geometry. In this paper we show how to perform quantum many-body calculations using auxiliary-field Monte Carlo simulations on a three-dimensional body-centered cubic (BCC) lattice. As a benchmark test we compute the ground state energy of 33 spin-up and 33 spin-down neutrons in the unitary limit, which is an idealized limit where the interaction range is zero and scattering length is infinite. As a fraction of the free Fermi gas energy $E_{\mathrm{FG}}$, we find that the ground state energy is $E_0/E_{\mathrm{FG}}=0.369\left(2\right),0.371\left(2\right),$ using two different definitions of the finite-system energy ratio. This is in excellent agreement with recent results obtained on a cubic lattice [He et al., Phys. Rev. A 101, 063615 (2020)]. We find that the computational effort and performance on a BCC lattice is approximately the same as that for a cubic lattice with the same number of lattice points. We discuss how the lattice simulations with different geometries can be used to constrain the size of lattice artifacts in simulations of continuum quantum many-body systems.

We study the nuclear isoscalar giant quadruple resonance (ISGQR) based on the Boltzmann-Uehling-Uhlenbeck (BUU) transport equation. The mean-field part of the BUU equation is described by the Skyrme nucleon-nucleon effective interaction, and its collision term, which embodies the two-particle–two-hole $(2\mathrm{p}-2\mathrm{h})$ correlation, is implemented through the stochastic approach. We find that the width of ISGQR for heavy nuclei is exhausted dominated by collisional damping, which is incorporated into the BUU equation through its collision term, and it can be well reproduced through employing a proper in-medium nucleon-nucleon cross section. Based on further Vlasov and BUU calculations with a number of representative Skyrme interactions, the isoscalar nucleon effective mass at saturation density is extracted, respectively, as $m_{s,0}^{*}/m=0.83\pm 0.04$ and $m_{s,0}^{*}/m=0.82\pm 0.03$ from the measured excitation energy $E_x$ of the ISGQR of ${}^{208}\mathrm{Pb}$. The small discrepancy between the two constraints indicates the negligible role of $2\mathrm{p}-2\mathrm{h}$ correlation in constraining $m_{s,0}^{*}$ with the ISGQR excitation energy.

To incorporate the effect of gluons on the evolution dynamics of the quark matter produced in relativistic heavy-ion collisions, we extend the three-flavor Nambu–Jona-Lasinio (NJL) transport model to include the contribution from the Polyakov loops. Imbedding the resulting pNJL partonic transport model in an extended multiphase transport (extended AMPT) model, we then study the elliptic flow splittings between particles and their antiparticles in relativistic heavy-ion collisions at beam energy scan energies. We find that a weak quark vector interaction in the partonic phase is able to describe the elliptic flow splitting between protons and antiprotons in heavy-ion collisions at $\sqrt{s_{NN}}=7.7$ to 39 GeV. Knowledge of the quark vector interaction is useful for understanding the equation of state of quark matter at large baryon chemical potentials and thus the location of the critical point in the QCD phase diagram.

$\alpha$-clustering structure is a significant topic in light nuclei. A Bayesian convolutional neural network (BCNN) is applied to classify initial nonclustered and clustered configurations, namely Woods-Saxon distribution and three-$\alpha$ triangular (four-$\alpha$ tetrahedral) structure for ${}^{12}\mathrm{C}$ $\left({}^{16}\mathrm{O}\right)$, from heavy-ion collision events generated within a multiphase transport (AMPT) model. Azimuthal angle and transverse momentum distributions of charged pions are taken as inputs to train the classifier. On a multiple-event basis, the overall classification accuracy can reach $95\%$ for ${}^{12}\mathrm{C}/{}^{16}\mathrm{O}+{}^{197}\mathrm{Au}$ events at $\sqrt{S_{NN}}=200\mathrm{GeV}$. With proper constructions of samples, the predicted deviations on mixed samples with different proportions of both configurations could be within $5\%$. In addition, setting a simple confidence threshold can further improve the predictions on the mixed dataset. Our results indicate promising and extensive possibilities of application of machine-learning-based techniques to real data and some other problems in physics of heavy-ion collisions.

We examine the spectrum of bremsstrahlung photons that results from the stopping of the initial net charge distributions in ultrarelativistic nucleus-nucleus collisions at the CERN Large Hadron Collier (LHC). This effect has escaped detection so far since it becomes sizable only at very low transverse momentum and at sufficiently forward rapidity. We argue that it may be within reach of the next-generation LHC heavy-ion detector ALICE-3 that is currently under study, and we comment on the physics motivation for measuring it.

Collisions of . light and heavy nuclei in relativistic heavy-ion collisions have been shown to be sensitive to nuclear structure. With a proposed ${}^{16}\mathrm{O}{}^{16}\mathrm{O}$ run at the CERN Large Hadron Collider (LHC) and at the BNL Relativistic Heavy Ion Collider (RHIC) we study the potential for finding $\alpha$ clustering in ${}^{16}\mathrm{O}$. Here we use the state-of-the-art iEBE-VISHNU package with ${}^{16}\mathrm{O}$ nucleonic configurations from ab initio nuclear lattice simulations. This setup was tuned using a Bayesian analysis on $p\mathrm{Pb}$ and PbPb systems. We find that the ${}^{16}\mathrm{O}{}^{16}\mathrm{O}$ system always begins far from equilibrium and that at LHC and RHIC it approaches the regime of hydrodynamic applicability only at very late times. Finally, by taking ratios of flow harmonics we are able to find measurable differences between $\alpha$-clustering, nucleonic, and subnucleonic degrees of freedom in the initial state.

The nature of the $1^{-}$ and $2^{-}$ excited states in ${}^{10}\mathrm{Be}$ is studied using the ${}^{11}\mathrm{Be}(p,d)$ transfer reaction in inverse kinematics at 10A MeV at TRIUMF ISAC-II, in particular to assess whether either of them can be considered as an excited halo state. The angular distributions for both states are extracted using deuteron-$\gamma$ coincidences and analyzed using a transfer model taking into account one-step and two-step processes. A good fit of the angular distributions is obtained considering only the one-step process, whereby an inner $p_{3/2}$ neutron of ${}^{11}\mathrm{Be}$ is removed, leaving the halo neutron intact. Higher-order processes however cannot be rejected. The small spectroscopic factors extracted suggest that the structure of both states is not uniquely halo-like, but rather display a more complex configuration mixing cluster and halo structures. Further insights are limited, as this experiment specifically probed the halo-like (but not cluster-like) ${}^{11}\mathrm{Be}(1/2^{+})\otimes {\left(\nu p_{3/2}\right)}^{-1}$ configuration in both states.

The measurements of neutron capture cross sections of neutron-rich nuclei are challenging but essential for understanding nucleosynthesis and stellar evolution processes in the explosive burning scenario. In the quest of $r$-process abundances, according to the neutrino-driven-wind model, light neutron-rich unstable nuclei may play a significant role as seed nuclei that influence the abundance pattern. Hence, experimental data for neutron capture cross sections of neutron-rich nuclei are needed. Coulomb dissociation of radioactive ion beams at intermediate energy is a powerful indirect method for inferring capture cross section. As a test case for validation of the indirect method, the neutron capture cross section ($n$, $\gamma$) for ${}^{14}\mathrm{C}$ was inferred from the Coulomb dissociation of ${}^{15}\mathrm{C}$ at intermediate energy ($600A$ MeV). A comparison between different theoretical approaches and experimental results for the reaction is discussed. We report for the first time experimental reaction cross sections of ${}^{28}\mathrm{Na}(n,\gamma ){}^{29}\mathrm{Na}$, ${}^{29}\mathrm{Na}(n,\gamma ){}^{30}\mathrm{Na}$, ${}^{32}\mathrm{Mg}(n,\gamma ){}^{33}\mathrm{Mg}$, and ${}^{34}\mathrm{Al}(n,\gamma ){}^{35}\mathrm{Al}$. The reaction cross sections were inferred indirectly through Coulomb dissociation of ${}^{29,30}\mathrm{Na}$, ${}^{33}\mathrm{Mg}$, and ${}^{35}\mathrm{Al}$ at incident projectile energies around 400–430 $A$ MeV using the FRS-LAND setup at GSI, Darmstadt. The neutron capture cross sections were obtained from the photoabsorption cross sections with the aid of the detailed balance theorem. The reaction rates for the neutron-rich Na, Mg, Al nuclei at typical $r$-process temperatures were obtained from the measured ($n,\gamma$) capture cross sections. The measured neutron capture reaction rates of the neutron-rich nuclei, ${}^{28}\mathrm{Na}$, ${}^{29}\mathrm{Na}$, and ${}^{34}\mathrm{Al}$ are significantly lower than those predicted by the Hauser-Feshbach decay model. A similar trend was observed earlier for ${}^{17}\mathrm{C}$ and ${}^{19}\mathrm{N}$ but in the case of ${}^{14}\mathrm{C}(n,\gamma ){}^{15}\mathrm{C}$ the trend is opposite. The situation is more complicated when the ground state has a multi-particle-hole configuration. For ${}^{32}\mathrm{Mg}$, the measured cross section is about $40\text{–}90\%$ higher than the Hauser-Feshbach prediction.

Background: The heaviest $T_z=0$ doubly-magic nucleus, ${}^{100}\mathrm{Sn}$, and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction. For instance, the structure of light-Sn nuclei has been shown to be affected by the delicate balance between nuclear-interaction components, such as pairing and quadrupole correlations. From Cd to Te, many common features and phenomena have been observed experimentally along the isotopic chains, leading to theoretical studies devoted to a more general and comprehensive study of the region. In this context, having only two proton holes in the $Z=50$ shell, the Cd isotopes are expected to present properties similar to those found in the Sn isotopic chain.

Purpose: The aim of this work was to measure lifetimes of excited states in neutron-deficient nuclei in the vicinity of ${}^{100}\mathrm{Sn}$.

Methods: The neutron-deficient nuclei in the $N\approx Z\approx 50$ region were populated using a multinucleon transfer reaction with a ${}^{106}\mathrm{Cd}$ beam and a ${}^{92}\mathrm{Mo}$ target. The beamlike products were identified by the VAMOS$++$ spectrometer, while the $\gamma$ rays were detected using the AGATA array. Lifetimes of excited states were determined using the recoil distance Doppler-shift method, employing the Cologne differential plunger.

Results: Lifetimes of low-lying states were measured in the even-mass ${}^{102–108}\mathrm{Cd}$ isotopes. In particular, multiple states with excitation energy up to $\approx 3$ MeV, belonging to various bands, were populated in ${}^{106}\mathrm{Cd}$ via inelastic scattering. The transition strengths corresponding to the measured lifetimes were compared with those resulting from state-of-the-art beyond-mean-field calculations using the symmetry-conserving configuration-mixing approach.

Conclusions: Despite the similarities in the electromagnetic properties of the low-lying states, there is a fundamental structural difference between the ground-state bands in the $Z=48$ and $Z=50$ isotopes. The comparison between experimental and theoretical results revealed a rotational character of the Cd nuclei, which have prolate-deformed ground states with ${\beta }_2\approx 0.2$. At this deformation $Z=48$ becomes a closed-shell configuration, which is favored with respect to the spherical one.

Electric quadrupole ($E2$) matrix elements provide a measure of nuclear deformation and related collective structure. Ground-state quadrupole moments in particular are known to high precision in many $p$-shell nuclei. While the experimental electric quadrupole moment only measures the proton distribution, both proton and neutron quadrupole moments are needed to probe proton-neutron asymmetry in the nuclear deformation. We seek insight into the relation between these moments through the ab initio no-core configuration interaction (NCCI), or no-core shell model (NCSM), approach. Converged ab initio calculations for quadrupole moments are particularly challenging due to sensitivity to long-range behavior of the wave functions. We therefore study more robustly converged ratios of quadrupole moments: across mirror nuclides, or of proton and neutron quadrupole moments within the same nuclide. In calculations for mirror pairs in the $p$ shell, we explore how well the predictions for mirror quadrupole moments agree with experiment and how well isospin (mirror) symmetry holds for quadrupole moments across a mirror pair. The comparison with experiment confirms the predictive power of the ab initio description, indicating that the predicted ratios are physically relevant for understanding proton-neutron structure as well.

We study the properties of the Cabibbo suppressed quasielastic production of $\mathrm{\Lambda }$ and $\mathrm{\Sigma }$ hyperons in antineutrino interactions with nuclei, including the effects of modified form factor axial mass, the second class current, and SU(3) flavor violations. The hyperon and nucleon are subjected to the nuclear potential and the outgoing hyperon can undergo final state interactions. The hyperon potential has a significant effect on their production through absorption. We predict a significant enhancement of $\mathrm{\Lambda }$ production compared with other hyperon production channels through $\mathrm{\Sigma }\to \mathrm{\Lambda }$ conversions. We produce predictions for several experiments by combining realistic neutrino energy distributions with suitable nuclear targets.

The $B(E2,2^{+}\to 0^{+})$ transition strengths of the $T=1$ isobaric triplet ${}^{70}\mathrm{Kr},$ ${}^{70}\mathrm{Br},$ ${}^{70}\mathrm{Se},$ recently measured at the RIKEN Radioactive Isotope Beam Factory (RIBF), are discussed in terms of state-of-the-art large scale shell model calculations using the JUN45 and $\mathrm{JUN}45+\mathrm{LNPS}$ plus Coulomb interactions. In this Letter we argue that, depending on the effective charges used, the calculations are either in line with the experimental data within statistical uncertainties, or the anomaly happens in ${}^{70}\mathrm{Br},$ rather than ${}^{70}\mathrm{Kr}$. In the latter case, we suggest that it can be due to the presence of a hitherto undetected $1^{+}$ $T=0$ state below the yrast $2^{+}$ $T=1$ state. Our results do not support a shape change of ${}^{70}\mathrm{Kr}$ with respect to the other members of the isobaric multiplet.

Calculations of inclusive $\alpha$ particle production are performed to interpret reaction experimental data induced by the two-neutron halo ${}^6\mathrm{He}$ and the isotopes ${}^{6,7}\mathrm{Li}$ on different target nuclei. We have implemented the zero-range post-form distorted-wave Born approximation (DWBA) to compute the elastic and nonelastic breakup cross sections. Integrated cross sections, angular distributions, and spectra are presented. Projectiles are approximated as two-body clusters, namely ${}^6\mathrm{He}$ as $\alpha +\text{dineutron}$ and ${}^6\mathrm{Li}$ (${}^7\mathrm{Li}$) are interpreted as $\alpha +\text{deuteron}$ (triton). The São Paulo optical potential is employed in the calculation of the distorted wave functions for the incident channels, while standard phenomenological interactions are taken for the fragment-target interactions. Calculations for ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ furnish a good description of the data, while the reaction involving ${}^6\mathrm{He}$ is found to be more complicated, where interpretation of the data must still be considered incomplete. The present analysis identifies an overall large contribution from inclusive breakup emission for all the cases studied.

Background: For its simplicity, the eikonal method is the tool of choice to analyze nuclear reactions at high energies ($E>100$ MeV/nucleon), including knockout reactions. However, so far, the effective interactions used in this method are assumed to be fully local.

Purpose: Given the recent studies on nonlocal optical potentials, in this work we assess whether nonlocality in the optical potentials is expected to impact reactions at high energies and then explore different avenues for extending the eikonal method to include nonlocal interactions.

Method: We compare angular distributions obtained for nonlocal interactions (using the exact R-matrix approach for elastic scattering and the adiabatic distorted wave approximation for transfer) with those obtained using their local-equivalent interactions.

Results: Our results show that transfer observables are significantly impacted by nonlocality in the high-energy regime. Because knockout reactions are dominated by stripping (transfer to inelastic channels), nonlocality is expected to have a large effect on knockout observables too. Three approaches are explored for extending the eikonal method to nonlocal interactions, including an iterative method and a perturbation theory.

Conclusions: None of the derived extensions of the eikonal model provide a good description of elastic scattering. This paper suggests that nonlocality removes the formal simplicity associated with the eikonal model.

We study the space-averaged electromagnetic (EM) fields weighted by the energy density in the central regions of heavy-ion collisions. These average quantities can serve as a barometer for the magnetic-field induced effects such as the magnetic effect, the chiral separation effect and the chiral magnetic wave. Comparing with the magnetic fields at the geometric center of the collision, the space-averaged fields weighted by the energy density are smaller in the early stage but damp slower in the later stage. The space average of squared fields as well as the EM anomaly $\mathbf{E}·\mathbf{B}$ weighted by the energy density are also calculated. We give parametrized analytical formulas for these average quantities as functions of time by fitting numerical results for collisions in the collision energy range $7.7–200$ GeV with different impact parameters.

The reduced transition probabilities $B(E2;0_{\text{g.s.}}^{+}\to 2_1^{+},2_2^{+})$ in ${}^{70}\mathrm{Zn}$ and the full $B(E2;0_{\text{g.s.}}^{+}\to 2^{+})$ strength up to ${\mathrm{S}}_n=7.79\mathrm{MeV}$ in ${}^{68}\mathrm{Ni}$ have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a ${}^{208}\mathrm{Pb}$ target. The $\gamma$ rays emitted in-flight were detected with an array of $46{\mathrm{BaF}}_2$ crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the $2^{+}$ states. The measured $B(E2;0_{\text{g.s.}}^{+}\to 2_1^{+})$ of 1432(124) $e^2{\mathrm{fm}}^4$ for ${}^{70}\mathrm{Zn}$ falls in the lower part of the published values which clustered either around 1600 or above $2000e^2{\mathrm{fm}}^4$, while the $B(E2;0_{\text{g.s.}}^{+}\to 2_2^{+})$ of 53(7) $e^2{\mathrm{fm}}^4$ agrees very well with the two published values. The relatively low $B(E2;0_{\text{g.s.}}^{+}\to 2_1^{+})$ of 301(38) $e^2{\mathrm{fm}}^4$ for ${}^{68}\mathrm{Ni}$ agrees with previous studies and confirms a local magicity at $Z=28$, $N=40$. Combining the results of the low-energy spectra of ${}^{68}\mathrm{Ni}$ and ${}^{70}\mathrm{Zn}$ and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate, and triaxial) are present. Finally, a summed $E2$ strength of only about $150e^2{\mathrm{fm}}^4$ has been found experimentally at high excitation energy, likely due to proton excitations across the $Z=28$ gap. The experimental distribution of this high-energy $E2$ excitation agrees with shell-model calculations, but its strength is about two times weaker.