The multinucleon transfer processes feeding the double charge exchange (DCE) channel are analyzed in the ${}^{40}\mathrm{Ca}({}^{14}\mathrm{C},$ ${}^{14}\mathrm{O}){}^{40}\mathrm{Ar} \text{and} {}^{40}\mathrm{Ca}({}^{18}\mathrm{O},{}^{18}\mathrm{Ne}){}^{40}\mathrm{Ar}$ reactions at 51 MeV and 270 MeV incident energies, respectively. Although one aims to theoretically isolate the meson-induced DCE, multinucleon transfer routes can be present in the measured cross sections. These two mechanisms cannot be isolated experimentally, as they add coherently in the DCE cross section, thus calling for accurate calculations to evaluate their individual contribution and indicate the appropriate conditions for meson exchange to dominate. Nowadays, interest in studying meson-induced DCE reactions has increased since their nuclear matrix element might be used as a surrogate to access those expected for a neutrinoless ββ decay rate. From the meson-induced DCE, indeed, it is possible to investigate the response of the second-order isovector components of the nucleon-nucleon interaction. On the other hand, multinucleon transfer reactions feeding DCE process, which is a mean field problem, open a great opportunity to explore the single- or two-particle nature of the wave functions of the states populated by the transferred particle(s) in the final partition. In this work, we present the cross section calculations for all the routes of multinucleon transfer in the ${}^{40}\mathrm{Ca}({}^{14}\mathrm{C},$ ${}^{14}\mathrm{O}){}^{40}\mathrm{Ar} \text{and} {}^{40}\mathrm{Ca}$(${}^{18}\mathrm{O},$ ${}^{18}\mathrm{Ne}){}^{40}\mathrm{Ar}$ reactions considering the coupled channel Born approximation. Large-scale shell model calculations are performed to derive the spectroscopic amplitudes for one- and two-particle valence.

Both hot QCD matter and extremely strong electromagnetic fields are generated in relativistic heavy-ion collisions. We employ the transport model and the equivalent photon approximation (EPA) to study charmonium hadroproduction and photoproduction in nucleus-nucleus collisions, respectively. In photoproduction, quasireal photons may interact with the whole nucleus or individual nucleons, which are called coherent and incoherent processes, respectively. The typical momentum of charmonium produced in the two processes is located in $p_T\lesssim 1/R_A$ and $p_T\lesssim 1/R_N$, where $R_A$ and $R_N$ are the radii of nucleus and the nucleon. Both kinds of photoproduction and also hadroproduction are considered to calculate charmonium production in different transverse momentum bins, rapidity bins, and collision centralities, incorporating modifications from hot QCD matter and initial cold nuclear matter effects. Our calculations explain experimental data on charmonium nuclear modification factors and the production cross section in ultraperipheral collisions. Charmonium nuclear modification is far above the unit at extremely low $p_T$ ($p_T<0.1\mathrm{GeV}/c$) in peripheral collisions with centrality 70–90%, attributed to coherent photoproduction.

The notion of charge balance function, originally designed to study the evolution of charge production in heavy-ion collisions, is extended to consider quark flavor balancing. This extension is considered based on simulations performed with the PYTHIA 8 event generator in the context of $\mathrm{pp}$ collisions at $\sqrt{s}=13.6, 7, \text{and} 2.76 \text{TeV}$ but can be trivially applied to any other scenario and implemented in measurements of correlated particle production in $\mathrm{pp}$, $\mathrm{pA}$, and $\mathrm{AA}$ collisions at colliders. Correlation of selected flavor balancing pairs is examined as a function of the produced charged particle multiplicity. One finds that the amplitude of the correlations increases monotonically with the number of balanced flavors and the actual flavor content of correlated particles.

The recently developed extended Skyrme effective interaction based on the so-called N3LO Skyrme pseudopotential is generalized to the general $\mathrm{N}n\mathrm{LO}$ case by incorporating the derivative terms up to $2n\mathrm{th}$ order into the central term of the pseudopotential. The corresponding expressions of Hamiltonian density and single-nucleon potential are derived within the Hartree-Fock approximation under general nonequilibrium conditions. The inclusion of the higher-order derivative terms provides additional higher-order momentum dependence for the single-nucleon potential, and in particular, we find that the N5LO single-nucleon potential with momentum-dependent terms up to $p^{10}$ can give a nice description for the empirical nucleon optical potential up to energy of $2\mathrm{GeV}$. At the same time, the density-dependent terms in the extended Skyrme effective interaction are extended correspondingly in the spirit of the Fermi momentum expansion, which allows highly flexible variation of density behavior for both the symmetric nuclear matter equation of state and the symmetry energy. Based on the Skyrme pseudopotential up to N3LO, N4LO, and N5LO, we construct a series of interactions with the nucleon optical potential having different high-momentum behaviors and with the symmetry potentials featuring different linear isospin-splitting coefficients for nucleon effective mass, by which we study the properties of nuclear matter and neutron stars. Furthermore, within the lattice Boltzmann-Uehling-Uhlenbeck transport model, some benchmark simulations with selected interactions are performed for the $\mathrm{Au}+\mathrm{Au}$ collisions at a beam energy of $1.23\mathrm{GeV}\mathrm{per}\mathrm{nucleon}$, and the predicted collective flows for protons are found to nicely agree with the data measured by HADES collaboration.

A good knowledge of nuclear fragmentation cross sections is important to interpret the fluxes of secondary cosmic rays from the Galaxy. Here we report new measurements of nuclear fragmentation with the NA61/SHINE experiment at the CERN SPS. The specific focus is on cross sections important for the production of boron in the Galaxy from the interactions of ${}^{12}\mathrm{C}$ nuclei with hydrogen in the interstellar medium, including the contribution from the decay of the short-lived ${}^{11}\mathrm{C}$ fragments. The data were taken with the secondary ${}^{12}\mathrm{C}$ beam at beam momentum of 13.5 $\text{GeV}/c\mathrm{per}$ nucleon and two fixed targets, polyethylene (${\mathrm{CH}}_2$) and graphite (C), from which we derive the cross sections of carbon on hydrogen. We present the measurement of the fragmentation cross sections of ${}^{11}\mathrm{C}, {}^{11}\mathrm{B}$, and ${}^{10}\mathrm{B}$ as well as the mass- and charge-changing cross sections.

The first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of ${}^{208}\mathrm{Pb}$ nuclei in the ALICE experiment at the Large Hadron Collider are presented. The EMD protons and neutrons emitted at very forward rapidities are detected by the proton and neutron zero degree calorimeters of the ALICE experiment. The emission cross sections of zero, one, two, and three protons accompanied by at least one neutron were measured in ultraperipheral ${}^{208}\mathrm{Pb}\text{−}{}^{208}\mathrm{Pb}$ collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=5.02\mathrm{TeV}$. The 0p and 3p cross sections are described by the RELDIS model within their measurement uncertainties, while the 1p and 2p cross sections are underestimated by the model by 17–25%. According to this model, these 0p, 1p, 2p, and 3p cross sections are associated, respectively, with the production of various isotopes of Pb, Tl, Hg, and Au in the EMD of ${}^{208}\mathrm{Pb}$. The cross sections of the emission of a single proton accompanied by the emission of one, two, or three neutrons in EMD were also measured. The data are significantly overestimated by the RELDIS model, which predicts that the (1p,1n), (1p,2n), and (1p,3n) cross sections are very similar to the cross sections for the production of the thallium isotopes ${}^{206,205,204}\mathrm{Tl}$.

We develop the quasiclassical (WKB) approximation of the synchrotron radiation by a fermion embedded into a uniformly rotating system in external magnetic field. We show that it gives an accurate approximation of the exact expression that we recently obtained at a tiny fraction of the numerical cost. Our results can be used to compute the electromagnetic radiation of the quark-gluon plasma produced in relativistic heavy-ion collisions.

Simultaneous, broadband, high-precision direct mass measurements of thermalized exotic nuclides are reported. The FRS Ion Catcher and, in particular, its high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) was used to measure neutron-rich nuclides in the element range from barium to europium, produced by the spontaneous fission of ${}^{252}\mathrm{Cf}$. Results include the measurement of 64 masses, including 13 masses with no previous direct determination; for four nuclides, a measurement with improved uncertainty is reported. Relative mass uncertainties below $1\times {10}^{-7}$ are routinely achieved. This work shows the first use of a multiple-reflection time-of-flight mass spectrometer to map a larger region of the nuclear chart covering 51 masses measured simultaneously in a single setting. The broadband capability is a design feature of the MR-TOF-MS of the FRS Ion Catcher which enables the large-scale mapping of the mass surface. The obtained data are compared to existing literature values and predictions of mass models and are used to study the shape-phase transition at $N$ = 90. A theoretical study, employing a Hartree-Fock-BCS approach with adjustable pairing strengths, is implemented to examine the evolution of the two-neutron separation energies along this region of the chart of nuclei.

We study the $N=20$ island of inversion region in the odd-$A$ Ne and Mg isotopes from the fundamental nuclear forces based on chiral two- and three-nucleon interactions. The state-of-the-art ab initio valence space in medium similarity renormalization method was used for this purpose. Our study focuses on the evolution of single-particle states and discusses their transition into the island of inversion through particle-hole excitations across the $N=20$ shell gap. The computed low-lying states and magnetic moments are in good agreement with the experimental data. We presented the rotational band structures, established via $E2$ transitions, in ${}^{31}\mathrm{Mg}$ and ${}^{33}\mathrm{Mg}$, which emerge from both normal and intruder configurations at low excitation energies. Our results suggest the presence of weak, moderate, and strongly prolate-deformed configurations at low energy in both isotopes. The present work offers valuable insights into the configurations and shapes of low-lying states in nuclei within the island of inversion, enhancing our understanding of the structures of exotic nuclei from first principles.

A systematic analysis of $E2$ matrix elements of ${}^{72}\mathrm{Ge}$, ${}^{76}\mathrm{Ge}$, ${}^{168}\mathrm{Er}$, ${}^{186}\mathrm{Os}$, ${}^{188}\mathrm{Os}$, ${}^{190}\mathrm{Os}$, ${}^{192}\mathrm{Os}$, and ${}^{194}\mathrm{Pt}$ nuclides is performed using the beyond mean-field approach of triaxial projected shell model (TPSM). For these nuclei, large sets of $E2$ matrix elements have been deduced from the multistep Coulomb excitation experiments, and it is shown that TPSM approach provides a reasonable description of the measured transitions. We have evaluated 1496 $E2$ matrix elements up to spin, $I=10$ for the eight nuclei studied, and tabulate them for future experimental and theoretical comparisons. Further, shape invariant analysis has been performed with the calculated $E2$ transitions using the Kumar-Cline sum rules. It is inferred from the analysis that the resulting shape, after configuration mixing of the quasiparticle states, transforms from $\gamma$-rigid to that of $\gamma$-soft for some nuclei, in conformity with the experimental data.

The mechanism of ${}^9\mathrm{Be}$ breakup and neutron stripping leading to the breakup of ${}^8\mathrm{Be}(\to \alpha +\alpha )$ was investigated in this study. Exclusive measurements of $\alpha \text{−}\alpha$ pair were performed over a wide angular range using a detector array consisting of double-sided silicon strip detectors for ${}^9\mathrm{Be}+{}^{124}\mathrm{Sn}$ system at two incident energies, $E_{\mathrm{lab}}=35.2$ and 29.1 MeV, around the Coulomb barrier. Correlations between measured relative energy and $Q$-value were utilized to identify various breakup and transfer processes. From the measured angular distribution, angle-integrated cross sections were obtained. Coupled-channels calculations were performed to estimate various breakup and transfer reactions, and the results were found to be in good agreement with the data.

This paper presents a phenomenological study on the angle between the standard and winner-take-all (WTA) jet axes $\left(\mathrm{\Delta }{R}_{\mathrm{axis}}^{\mathrm{WTA}\text{–}\mathrm{Std}}\right)$ in high-energy nuclear collisions. The $p+p$ baseline is provided by the Pythia8 event generator. The in-medium jet propagation is simulated by the linear Boltzmann transport (Lbt) model, which considers both the elastic and inelastic jet-medium interactions. Our theoretical results calculated by the Lbt model show that the $\mathrm{\Delta }{R}_{\mathrm{axis}}^{\mathrm{WTA}\text{–}\mathrm{Std}}$ distribution in $\mathrm{Pb}+\mathrm{Pb}$ at $\sqrt{s}=5.02\mathrm{TeV}$ is narrower than that in $p+p$, which agrees well with the recent ALICE measurements. The narrowing of $\mathrm{\Delta }{R}_{\mathrm{axis}}^{\mathrm{WTA}\text{–}\mathrm{Std}}$, which seems to violate the nature of intrajet broadening due to jet quenching, may be attributed to the influence of “selection bias.” However, the physical details still need to be fully understood. Utilizing a matching-jet method to track the jet evolution in the QGP to remove the selection bias in the Monte Carlo simulations, we observe that the $\mathrm{\Delta }{R}_{\mathrm{axis}}^{\mathrm{WTA}\text{–}\mathrm{Std}}$ distribution becomes broader due to the jet-medium interactions. At the same time, by rescaling the quark- and gluon-jet fractions in $\mathrm{Pb}+\mathrm{Pb}$ collisions to be the same as that in $p+p$, we find that the fraction change may not significantly influence the modification pattern of jet $\mathrm{\Delta }{R}_{\mathrm{axis}}^{\mathrm{WTA}\text{–}\mathrm{Std}}$. On the other hand, the selected jet sample in $\mathrm{A}+\mathrm{A}$ collisions has a significantly narrower initial $\mathrm{\Delta }{R}_{\mathrm{axis}}^{\mathrm{WTA}\text{–}\mathrm{Std}}$ distribution than the $p+p$ baseline, and such a biased comparison between $p+p$ and $\mathrm{A}+\mathrm{A}$ conceals the actual intrajet broadening effect in the experimental measurements. The investigations presented in this paper will deepen our understanding of the relationship between the actual intrajet modifications in the QGP and the experimental observations.

Excited states ranging from low to high spin in ${}^{135}\mathrm{Nd}$ have been investigated using the ${}^{100}\mathrm{Mo}({}^{40}\mathrm{Ar}$, $5n)$ heavy ion fusion evaporation reaction with the JUROGAM II $\gamma$-ray spectrometer. In the present work we report a new $17/2_3^{-}$ state and a new band composed of $E2$ transitions at high spin. The configuration assigned to the $17/2_3^{-}$ state is obtained by coupling one neutron in the $1/2^{+}\left[400\right]$ orbital to the $8^{-}$ isomer in ${}^{134}\mathrm{Nd}$ based on the $\nu 7/2^{+}\left[404\right]\otimes 9/2^{-}\left[514\right]$ configuration. The deduced ratio of reduced transition probabilities of 2.0(5) from the new $17/2_3^{-}$ state to the $13/2_2^{-}$ and $13/2_1^{-}$ states supports the tilted precession interpretation of the band built on the $13/2_2^{-}$ state, in which, instead of the rotation around the intermediate axis present in the yrast band, the rotation is around the long axis of the intrinsic reference frame. The configuration of the newly observed high-spin band is discussed in the framework of the cranked Nilsson-Strutinsky model. The calculated results provide evidence for large triaxiality of the discussed bands.

We study the evolution of total binding energy (TBE), mean field energy, and pairing energy of Pb, Hg, and Ar isotopes, as a function of the nuclear deformation. As for the nuclear model, we exploit a deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), and a deformed Skyrme Hartree-Fock plus BCS model. It is found that the dependence of pairing energy on the deformation is strongly correlated to that of the mean field energy, which is obtained by subtracting the pairing energy from the TBE; in other words, the energy minimum characterized by a large negative mean field energy has a smaller negative pairing energy or, equivalently, a smaller positive pairing gap, while a stronger pairing energy is found in the region away from the minimum of the total energy. Consequently, the two energies show an antisymmetric feature in their deformation dependence, although the energy scales are very different. Moreover, since the pairing energy has a negative sign with respect to to the pairing gap, the evolution of mean field energy follows closely that of the pairing gap. This implies that the pairing energy (or pairing gap) and the mean field energy “talk to each other” and work together along the potential energy curve to determine the energy minimum and/or the local minimum.

Jets clustered from heavy ion collision measurements combine a dense background of particles with those actually resulting from a hard partonic scattering. The background contribution to jet transverse momentum ($p_{\mathrm{T}}$) may be corrected by subtracting the collision average background; however, the background inhomogeneity limits the resolution of this correction. Many recent studies have embedded jets into heavy ion backgrounds and demonstrated a markedly improved background correction is achievable by using neural networks (NNs) trained with aspects of jet substructure which are used to map measured jet $p_{\mathrm{T}}$ to the embedded truth jet $p_{\mathrm{T}}$. However, jet quenching in heavy ion collisions modifies jet substructure and correspondingly biases the NNs' background corrections. This study investigates those biases by using simulations of jet quenching in central $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ with hydrodynamically modeled quark-gluon plasma (QGP) evolution. To demonstrate the magnitude of the effect of such biases in measurement, a leading jet nuclear modification factor ($R_{\mathrm{AA}}$) is calculated and reported using the NN background correction on jets quenched utilizing a brick of QGP.

The chemical freeze-out curve in heavy-ion collisions is investigated in the context of a quantum chromodynamics (QCD) critical point (CP) search at finite baryon densities. Taking the hadron resonance gas picture at face value, chemical freeze-out points at a given baryochemical potential provide a lower bound on the possible temperature of the QCD CP. We first verify that the freeze-out data in heavy-ion collisions are well described by a constant energy per particle curve, $E/N=\mathrm{const}$, under strangeness neutrality conditions (${\mu }_S\ne 0$, ${\mu }_Q\ne 0$). We then evaluate the hypothetical lower bound on the freeze-out curve based on this criterion in the absence of strangeness neutrality (${\mu }_S=0$, ${\mu }_Q=0$) and confront it with recent predictions on the CP location. We find that recent estimates based on Yang-Lee edge singularities from lattice QCD data on coarse lattices ($N_{\tau }=6$) place the CP significantly below the freeze-out curve, hinting at the importance of performing continuum extrapolation within this method. Predictions based on functional methods and holography place the CP slightly above the freeze-out curve, indicating that the QCD CP may be located very close to the chemical freeze-out in $A+A$ collisions at $\sqrt{s_{NN}}=3.5-6\mathrm{GeV}$.

With the use of martini, a model which considers evolving QCD jets against a fluid dynamical background, it is shown that the introduction of formation time to the parton shower after the initial hard scattering is essential for a simultaneous description of charged hadron and jet $R_{AA}$. This inclusion also improves jet shape ratios at small angle and jet fragmentation function ratios of leading charged hadrons. The martini framework is then aimed at a study of the leading-order, next-to-leading-order, and nonperturbative collision kernels. Sizable differences in the modification of jet substructure observables, i.e., jet shape and fragmentation functions, are observed. Such differences are caused by the difference in the radiation rates of relatively soft gluons that survive in the evolution in medium.

A search for short-lived isomers in ${}^{128}\mathrm{Xe}$ has been conducted using the generalized centroid difference method applied to $\gamma$-ray spectra measured with high-purity germanium detectors. A lifetime of 2.8 ($\pm 0.8\pm 0.5$) ns has been extracted for the $6^{-}$ state, and a shorter lifetime, of the order of one nanosecond, has been extracted for the $5^{-}$ state. This results emphasize the possibility to measure lifetimes of the order of a few nanoseconds using arrays of germanium detectors in fusion-evaporation reactions. The obtained results reveal an unexpected hindrance of the 271-keV, $6^{-}\to 5^{-}$ transition, which points to predominant $1/2^{+}\left[400\right]\otimes 9/2^{-}\left[514\right]$ and $3/2^{+}\left[402\right]\otimes 9/2^{-}\left[514\right]$ Nilsson configurations of the bands built on the $5^{-}$ and $6^{-}$ states, respectively. The obtained results are supported by projected shell-model calculations, which nicely reproduce the bands built on the $K^{\pi }=5^{-}$ and $K^{\pi }=6^{-}$ states, under the assumption of an attenuated monopole pairing strength.

Within the framework of the interacting boson model, we propose a novel algebraic scheme to describe spin-dependent structural evolutions in triaxial nuclei. Our analysis demonstrates that a triaxially to axially rotational shape phase transition can be induced by the high-order correction which is microscopically motivated by the pairing interaction on the $\gamma$-unstable rotation. This prescription is further applied to describe the structural evolutions along the yrast sequences of ${}^{132}\mathrm{Ba}$ and ${}^{130}\mathrm{Xe}$, providing an exemplary case for demonstrating a unified explanation of both low-energy collective structures and high-spin phenomena in O(6)-like nuclei.

Within a Bayesian statistical framework using a Gaussian process (GP) emulator for an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model simulator of heavy-ion reactions with momentum-independent Skyrme interactions, we infer from the proton directed and elliptical flow in mid-central $\mathrm{Au}+\mathrm{Au}$ reactions, measured at beam energies from 150 to 1200 MeV/nucleon by the FOPI Collaboration, the posterior probability distribution functions (PDFs) of the in-medium baryon-baryon scattering cross section (BBSCS) modification factor $X$ (with respect to their free-space values) and the stiffness parameter $K$ of dense nuclear matter. We find that the most probable value of $X$ evolves from around 0.7 to 1.0 as the beam energy $E_{\mathrm{beam}}/A$ increases. On the other hand, the posterior $\mathrm{PDF}\left(K\right)$ may have dual peaks having roughly the same height or extended shoulders at high $K$ values. More quantitatively, the posterior $\mathrm{PDF}\left(K\right)$ changes from having a major peak around 220 MeV, characterizing a soft EOS in the reaction at $E_{\mathrm{beam}}/A=150\mathrm{MeV}$, to one that peaks around 320 MeV, indicating a stiff EOS in the reactions at $E_{\mathrm{beam}}/A$ higher than about 600 MeV. The transition from soft to stiff happens in mid-central $\mathrm{Au}+\mathrm{Au}$ reactions at beam energies around 250 MeV/nucleon in which $K=220$ MeV and $K=320$ MeV are approximately equally probable. Altogether, the FOPI proton-flow excitation function data indicate a gradual hardening of hot and dense nuclear matter as its density and temperature increase in reactions with higher beam energies.