Exploiting the isobar model, kaon photo- and electroproduction on the proton in the resonance region comes under scrutiny. An upgrade of our previous model, comprising higher-spin nucleon and hyperon exchanges in the consistent formalism, was accomplished by implementing energy-dependent widths of nucleon resonances, which leads to a different choice of hadron form factor with much softer values of cutoff parameter for the resonant part. For a reliable description of electroproduction, the necessity of including longitudinal couplings of nucleon resonances to virtual photons was revealed. We present a new model whose free parameters were adjusted to photo- and electroproduction data and which provides a reliable overall description of experimental data in all kinematic regions. The majority of nucleon resonances chosen in this analysis coincide with those selected in our previous analysis and also in the Bayesian analysis with the Regge-plus-resonance model as the states contributing to this process with the highest probability.

We present a functional renormalization group (FRG) calculation of the equation of state (EoS) using our novel technique to treat fluctuations at finite chemical potential. The goal of this calculation was to provide a proof of concept for this technique as well as to estimate the size of the quantum effects in the equation of state and compact star parameters. We used the simplest nontrivial model where massless fermions are coupled to scalars through Yukawa coupling. We compared our results to the one-loop and the mean-field approximations of the same model and other high-density nuclear matter equations of state. We found a $10–20\%$ difference in the EoS between these approximations. We have also calculated the mass-radius relation for a compact star using the Tolmann-Oppenheimer-Volkov equation with this EoS and observed a $\sim 5\%$ effect due to quantum fluctuations.

Background: $\alpha +{}^{12}\mathrm{C}$ clustering in ${}^{16}\mathrm{O}$ has been of historical importance in nuclear clustering. In the last 15 years the $4\alpha$ condensate state has been proposed as a new-type cluster state.

Purpose: The aim is to reveal a dynamical process of the formation of different kinds of cluster states, in terms of a “container” aspect of clusters, in ${}^{16}\mathrm{O}$.

Method: The so-called THSR wave function for the $4\alpha$ clusters is extended to inclusion of two different “containers” occupied independently by the ${}^{12}\mathrm{C}\left(3\alpha \right)$ and $\alpha$ clusters.

Results: The five $J^{\pi }=0^{+}$ states with $4\alpha$ tetrahedral shape, $\alpha +{}^{12}\mathrm{C}$ cluster structures, and the $4\alpha$ condensate character, are found to be represented, to good approximation, by single configurations of the extended THSR wave function with “containers” of appropriate shape and size.

Conclusions: It is demonstrated in ${}^{16}\mathrm{O}$ that the dynamical evolution of cluster structures can be caused by size and shape evolution of a “container” occupied with clusters. The $\alpha$ condensate with gaslike $4\alpha$ configuration appears as a limit of the cluster formation.

A model-independent technique was used to determine the $\gamma$-ray strength function ($\gamma \mathrm{SF}$) of ${}^{56}\mathrm{Fe}$ down to $\gamma$-ray energies less than 1 MeV for the first time with GRETINA using the $(p,p^{\prime })$ reaction at 16 MeV. No difference was observed in the energy dependence of the $\gamma \mathrm{SF}$ built on $2^{+}$ and $4^{+}$ final states, supporting the Brink hypothesis. In addition, angular distribution and polarization measurements were performed. The angular distributions are consistent with dipole radiation. The polarization results show a small bias towards magnetic character in the region of the enhancement.

Using information from nearby nuclei and a simple model, I estimate that the lowest resonance in ${}^{16}\mathrm{B}$ should have $J^{\pi }=2^{-}$ and the structure ${}^{17}\mathrm{C}\left(1/2^{+}\right)\times {\left(p_{3/2}\right)}^{-1}$, and not $0^{-}$, as previously supposed. If the $2^{-}$ is not the ground state, it should be very close in energy.

Within the nuclear shell model, we investigate the correction ${\delta }_{RO}$ to the Fermi matrix element due to a mismatch between proton and neutron single-particle radial wave functions. Eight superallowed $0^{+}\to 0^{+}$ $\beta$ decays in the $sd$ shell, comprising ${}^{22}\mathrm{Mg}$, ${}^{26m}\mathrm{Al}$, ${}^{26}\mathrm{Si}$, ${}^{30}\mathrm{S}$, ${}^{34}\mathrm{Cl}$, ${}^{34}\mathrm{Ar}$, ${}^{38m}\mathrm{K}$, and ${}^{38}\mathrm{Ca}$, are reexamined. The radial wave functions are obtained from a spherical Woods-Saxon potential whose parametrizations are optimized in a consistent adjustment of the depth and the length parameters to relevant experimental observables, such as nucleon separation energies and charge radii, respectively. The chosen fit strategy eliminates the strong dependence of the radial mismatch correction to a specific parametrization, except for calculations with an additional surface-peaked term. As an improvement, our model proposes a new way to calculate the charge radii, based on a parentage expansion which accounts for correlations beyond the extreme independent-particle model. Apart from the calculations with a surface-peak term and the cases where we used a different model space, the new sets of ${\delta }_{RO}$ are in general agreement with the earlier result of Towner and Hardy [Phys. Rev. C 66, 035501 (2002)]. Small differences of the corrected average $\overline{\mathcal{F}t}$ value are observed.

Background: It is well known that effective nuclear interactions are in general nonlocal. Thus if nuclear densities obtained from ab initio no-core shell-model (NCSM) calculations are to be used in reaction calculations, translationally invariant nonlocal densities must be available.

Purpose: Though it is standard to extract translationally invariant one-body local densities from NCSM calculations to calculate local nuclear observables like radii and transition amplitudes, the corresponding nonlocal one-body densities have not been considered so far. A major reason for this is that the procedure for removing the center-of-mass component from NCSM wave functions up to now has only been developed for local densities.

Results: A formulation for removing center-of-mass contributions from nonlocal one-body densities obtained from NCSM and symmetry-adapted NCSM (SA-NCSM) calculations is derived, and applied to the ground state densities of ${}^4\mathrm{He}$, ${}^6\mathrm{Li}$, ${}^{12}\mathrm{C}$, and ${}^{16}\mathrm{O}$. The nonlocality is studied as a function of angular momentum components in momentum as well as coordinate space.

Conclusions: We find that the nonlocality for the ground state densities of the nuclei under consideration increases as a function of the angular momentum. The relative magnitude of those contributions decreases with increasing angular momentum. In general, the nonlocal structure of the one-body density matrices we studied is given by the shell structure of the nucleus, and cannot be described with simple functional forms.

A Coulomb-excitation experiment to study electromagnetic properties of ${}^{42}\mathrm{Ca}$ was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. $\gamma$ rays from excited states in ${}^{42}\mathrm{Ca}$ were measured with the AGATA spectrometer. The magnitudes and relative signs of ten $E2$ matrix elements coupling six low-lying states in ${}^{42}\mathrm{Ca}$, including the diagonal $E2$ matrix elements of $2_1^{+}$ and $2_2^{+}$ states, were determined using the least-squares code gosia. The obtained set of reduced $E2$ matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for $0_{1,2}^{+}$ and $2_{1,2}^{+}$ states, as well as triaxiality for $0_{1,2}^{+}$ states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in ${}^{42}\mathrm{Ca}$. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in ${}^{42}\mathrm{Ca}$.

Invariant differential yields of deuterons and antideuterons in $pp$ collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV and the yields of tritons, ${}^3\mathrm{He}$ nuclei, and their antinuclei at $\sqrt{s}$ = 7 TeV have been measured with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum ($p_{\text{T}}$) range in the rapidity interval $\left|y\right|<0.5$, extending both the energy and the $p_{\text{T}}$ reach of previous measurements up to 3 GeV/$c$ for $A=2$ and 6 GeV/$c$ for $A=3$. The coalescence parameters of (anti)deuterons and ${}^3\overline{\text{He}}$ nuclei exhibit an increasing trend with $p_{\text{T}}$ and are found to be compatible with measurements in $pA$ collisions at low $p_{\text{T}}$ and lower energies. The integrated yields decrease by a factor of about 1000 for each increase of the mass number with one (anti)nucleon. Furthermore, the deuteron-to-proton ratio is reported as a function of the average charged particle multiplicity at different center-of-mass energies.

We perform ab initio self-consistent Green's function calculations of the closed shell nuclei ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$, based on two-nucleon potentials derived from lattice QCD simulations, in the flavor SU(3) limit and at the pseudoscalar meson mass of 469 MeV/$c^2$. The nucleon-nucleon interaction is obtained using the hadrons-to-atomic-nuclei-from-lattice (HAL) QCD method, and its short-distance repulsion is treated by means of ladder resummations outside the model space. Our results show that this approach diagonalizes ultraviolet degrees of freedom correctly. Therefore, ground-state energies can be obtained from infrared extrapolations even for the relatively hard potentials of HAL QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total binding energies are sensibly improved by the full account of many-body correlations. The results suggest an interesting possible behavior in which nuclei are unbound at very large pion masses and islands of stability appear at first around the traditional doubly magic numbers when the pion mass is lowered toward its physical value. The calculated one-nucleon spectral distributions are qualitatively close to those of real nuclei even for the pseudoscalar meson mass considered here.

In this theoretical study, we establish a correlation between the neutron skin thickness and the nuclear symmetry energy for the even-even isotopes of Fe, Ni, Zn, Ge, Se, and Kr within the framework of the axially deformed self-consistent relativistic mean field for the nonlinear $\mathrm{NL}{3}^{*}$ and density-dependent DD-ME1 interactions. The coherent density functional method is used to formulate the symmetry energy, the neutron pressure, and the curvature of finite nuclei as a function of the nuclear radius. We have performed broad studies for the mass dependence on the symmetry energy in terms of the neutron-proton asymmetry for mass $70\le A\le 96$. From this analysis, we found a notable signature of a shell closure at $N=50$ in the isotopic chains of Fe, Ni, Zn, Ge, Se, and Kr nuclei. The present study reveals a interrelationship between the characteristics of infinite nuclear matter and the neutron skin thickness of finite nuclei.

High-spin states in ${}^{124}\mathrm{Cs}$ were populated in the ${}^{64}\mathrm{Ni}({}^{64}\mathrm{Ni},p3n)$ reaction and the Gammasphere detector array was used to measure $\gamma$-ray coincidences. Both positive- and negative-parity bands, including bands with chiral configurations, have been extended to higher spin, where a shape change has been observed. The configurations of the bands before and after the alignment are discussed within the framework of the cranked Nilsson-Strutinsky model. The calculations suggest that the nucleus undergoes a shape transition from triaxial to prolate around spin $I\simeq 22$ of the positive-parity states. The alignment gain of $8\hslash$, observed in the positive-parity bands, is due to partial alignment of several valence nucleons. This indicates the absence of band crossing due to paired nucleons in the bands.

Background: The isovector part of the nuclear equation of state remains partly unknown and is the subject of many studies. The degree of equilibration between the two main collision partners in heavy ion reactions may be used to study the equation of state since it is connected to isospin ($N/Z$) transport properties of nuclear matter.

Purpose: We aim to test chemical equilibrium attainment by measuring isotopic characteristics of emitted elements as a function of impact parameter.

Method: We study four ${}^{136,124}\mathrm{Xe}+{}^{124,112}\mathrm{Sn}$ reactions at 32 MeV/nucleon. The data were acquired with the INDRA detector at the GANIL (Caen, France) facility. Combined (projectile+target) systems are identical for two studied reactions, therefore it is possible to study the path towards chemical equilibrium from different neutron to proton ratio ($N/Z$) entrance channels. The study is limited to identified isotopes detected in the forward part of the center of mass in order to focus on the evolution of projectile-like fragment isotopic content and the benefit of excellent detection performances of the forward part of the apparatus.

Results: Light charged particle productions, multiplicities, and abundance ratios dependence against impact parameter are studied. It is measured to almost identical mean characteristics for the two ${}^{124}\mathrm{Xe}+{}^{124}\mathrm{Sn}$ and ${}^{136}\mathrm{Xe}+{}^{112}\mathrm{Sn}$ systems for central collisions. Comparing all four studied systems it is shown that mean values evolve from projectile $N/Z$ to projectile+target $N/Z$ dependence. Those identical mean characteristics concern all light charged particles except ${}^3\mathrm{He}$ whose mean behavior is strongly different.

Conclusions: Our inclusive analysis (no event selection) shows that $N/Z$ equilibration between the projectile-like and the target-like is realized to a high degree for central collisions. The light charged particle production mean value difference between ${}^{124}\mathrm{Xe}+{}^{124}\mathrm{Sn}$ and ${}^{136}\mathrm{Xe}+{}^{112}\mathrm{Sn}$ systems for central collisions is of the order of a few %. This slight difference could be explained by pre-equilibrium particle emission whose intensity may differ for the two reactions. This point is demonstrated using ${}^3\mathrm{He}$ mean characteristics whose production takes place before chemical equilibrium attainment. The realized $N/Z$ balance between projectile-like and target-like does not imply a pure two-body mechanism. Indeed a midrapidity production of light charged particle does exist and its $N/Z$ is different as compared to the projectile-like one: it is $n$ enriched. This point is touched using ${}^6\mathrm{He}$ midrapidity production which is favored by the drift phenomenon.

The ${}^{12}\mathrm{C}(n,2n){}^{11}\mathrm{C}$ cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the ${}^3\mathrm{H}\left(d,n\right){}^4\mathrm{He}$ reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the ${\beta }^{+}$ decay of ${}^{11}\mathrm{C}$. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via ${}^1\mathrm{H}\left(n,p\right)$ protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band.

The dynamics of fission of the excited compound nuclei ${}^{256}\mathrm{Fm}, {}^{215}\mathrm{Fr}, {}^{187}\mathrm{Ir}, {}^{172}\mathrm{Yb}, {}^{162}\mathrm{Yb}$, and ${}^{142}\mathrm{Ce}$ produced in fusion reactions with 158.8 MeV ${}^{18}\mathrm{O}$ has been studied by solving three- and four-dimensional Langevin equations with dissipation generated through the chaos weighted wall and window friction formula. The constant dissipation coefficients of $K, {\gamma }_K=0.077{\left(\mathrm{MeV}\mathrm{zs}\right)}^{-1/2}, {\gamma }_K=0.2{\left(\mathrm{MeV}\mathrm{zs}\right)}^{-1/2}$ and a nonconstant dissipation coefficient of $K$ have been used to reproduce the experimental data for both symmetric and asymmetric splitting of the fissioning systems. The average kinetic energies of fission fragments, the pre-scission neutron multiplicities, the fission time, and the variances of the mass and kinetic energy of fission fragments are calculated for the excited compound nuclei ${}^{256}\mathrm{Fm}, {}^{215}\mathrm{Fr}, {}^{187}\mathrm{Ir}, {}^{172}\mathrm{Yb}, {}^{162}\mathrm{Yb}, {}^{142}\mathrm{Ce}$, and results of the calculations are compared with each other and with the experimental data. Comparison of the theoretical results with the experimental data calculated by using different values of ${\gamma }_K$ shows that the difference is small between the results of calculations for symmetric and asymmetric simulations of the fission process of excited intermediate nuclei, whereas for heavy compound nuclei the difference is slightly high. In other words, the effect of the asymmetry parameter on the fission process of intermediate nuclei is smaller than the effect on heavy nuclei. Furthermore, we show that the pre-scission neutron multiplicity decreases rapidly with increasing fragment asymmetry.

Signatures of collective behavior have been measured in highly relativistic $p+p$ collisions, as well as in $p+\mathrm{A}, d+\mathrm{A}$, and ${}^3\mathrm{He}+\mathrm{A}$ collisions. Numerous particle correlation measurements in these systems have been successfully described by calculations based on viscous hydrodynamic and transport models. These observations raise the question of the minimum necessary conditions for a system to exhibit collectivity. Recently, numerous scientists have raised the question of whether the quarks and gluons generated in $e^{+}{e}^{-}$ collisions may satisfy these minimum conditions. In this paper we explore possible signatures of collectivity, or lack thereof, in $e^{+}{e}^{-}$ and $p+p$ collisions utilizing A Multi-Phase Transport (ampt) framework which comprises melted color strings, parton scattering, hadronization via coalescence, and hadron rescattering.

We calculate the electromagnetic fields generated in small systems by using a multiphase transport (AMPT) model. Compared to $A+A$ collisions, we find that the absolute electric and magnetic fields are not small in $p+\mathrm{Au}$ and $d+\mathrm{Au}$ collisions at energies available at the BNL Relativistic Heavy Ion Collider and in $p+\mathrm{Pb}$ collisions at energies available at the CERN Large Hadron Collider. We study the centrality dependencies and the spatial distributions of electromagnetic fields. We further investigate the azimuthal fluctuations of the magnetic field and its correlation with the fluctuating geometry using event-by-event simulations. We find that the azimuthal correlation $〈cos2({\mathrm{\Psi }}_{\mathrm{B}}-{\mathrm{\Psi }}_2)〉$ between the magnetic field direction and the second-harmonic participant plane is almost zero in small systems with high multiplicities, but not in those with low multiplicities. This indicates that the charge azimuthal correlation $〈cos({\varphi }_{\alpha }+{\varphi }_{\beta }-2{\mathrm{\Psi }}_{\mathrm{RP}})〉$ is not a valid probe to study the chiral magnetic effect (CME) in small systems with high multiplicities. However, we suggest searching for possible CME effects in small systems with low multiplicities.

Octupole deformation and the relevant spectroscopic properties of neutron-rich odd-mass barium isotopes are investigated in a theoretical framework based on nuclear density functional theory and the particle-core coupling scheme. The interacting-boson Hamiltonian that describes the octupole-deformed even-even core nucleus, as well as the single-particle energies and occupation probabilities of an unpaired nucleon, are completely determined by microscopic axially symmetric $({\beta }_2,{\beta }_3)$-deformation constrained self-consistent mean-field calculations for a specific choice of the energy density functional and pairing interaction. A boson-fermion interaction that involves both quadrupole and octupole degrees of freedom is introduced, and their strength parameters are determined to reproduce selected spectroscopic data for the odd-mass nuclei. The model reproduces recent experimental results for both even-even and odd-mass Ba isotopes. In particular, for ${}^{145,147}\mathrm{Ba}$ our results indicate, in agreement with recent data, that octupole deformation does not determine the structure of the lowest states in the vicinity of the ground state, and only becomes relevant at higher excitation energies.