Nowadays quantum-mechanical theory allows one to reliably calculate the processes of $2p$ radioactivity (true three-body decays) and the corresponding energy and angular correlations up to distances of the order of ${10}^3$ fm. However, the precision of modern experiments has now become sufficient to indicate some deficiency of the predicted theoretical distributions. In this paper we discuss extrapolation along the classical trajectories as a method to improve the convergence of the theoretical energy and angular correlations at very large distances (of the order of atomic distances), where only long-range Coulomb forces are still operating. The precision of this approach is demonstrated using the “exactly” solvable semianalytical models with simplified three-body Hamiltonians. It is also demonstrated that for heavy $2p$ emitters, the $2p$ decay momentum distributions can be sensitive to the effect of screening by atomic electrons. We compare theoretical results with available experimental data.

A simultaneous analysis of elastic scattering and fusion of the weakly bound projectile ${}^9\mathrm{Be}$ with the light deformed ${}^{27}\mathrm{Al}$ target,at energies close to the Coulomb barrier, is carried out by optical model calculations. The nuclear polarization potential $U$ is split into a volume part $U_F$, which accounts for fusion reactions and a surface part $U_{\mathrm{DR}}$, responsible for the direct reactions. The presence of the threshold anomaly in the elastic scattering is investigated. We also estimate the distance where breakup starts to occur. The present results are compared with those for the same projectile on the medium size and spherical ${}^{144}\mathrm{Sm}$ target, to investigate the effect of the Coulomb breakup and target deformation in the behavior of the elastic scattering.

Thermodynamics of the Polyakov-loop-extended two-flavor chiral quark-meson model (PQM) is explored. The analysis of the PQM model is based on the functional renormalization group method. An appropriate truncation of the effective action with quarks coupled to background gluonic fields is introduced. Within this scheme, we derive the renormalization group flow equation for the scale-dependent thermodynamic potential at finite temperature and density in the presence of a symmetry breaking external field. The influence of fluctuations and of the background gluon field on the properties of net-quark number density fluctuations and their higher moments is explored. We study the dependence of the kurtosis of quark-number fluctuations on the pion mass and show that, in the presence of a symmetry-breaking term, the fluctuations lead to a smoothing of observables near the crossover transition.

High-precision data for vector and tensor analyzing powers for the ${}^1\mathrm{H}$$(\mathrm{d⃗},\mathit{pp})n$ reaction at a 130-MeV deuteron beam energy have been measured over a large part of the phase space. Theoretical predictions based on various approaches to describe the three nucleon ($3N$) system reproduce very well the vector analyzing power data and no three-nucleon force effect is observed for these observables. Tensor analyzing powers are also very well reproduced by calculations in almost the whole studied region, but locally certain discrepancies are observed. For $A_{\mathit{xy}}$ such discrepancies usually appear, or are enhanced, when model $3N$ forces, TM99 or Urbana, are included. Problems of all theoretical approaches with describing $A_{\mathit{xx}}$ and $A_{\mathit{yy}}$ are limited to very small kinematical regions, usually characterized by the lowest energy of the relative motion of the two protons.

We calculate the properties of neutron matter and highlight the physics of chiral three-nucleon forces. For neutrons, only the long-range $2\pi$-exchange interactions of the leading chiral three-nucleon forces contribute, and we derive density-dependent two-body interactions by summing the third particle over occupied states in the Fermi sea. Our results for the energy suggest that neutron matter is perturbative at nuclear densities. We study in detail the theoretical uncertainties of the neutron matter energy, provide constraints for the symmetry energy and its density dependence, and explore the impact of chiral three-nucleon forces on the $S$-wave superfluid pairing gap.

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\gamma p\to \varphi p$, $\gamma d\to \varphi pn$, and $\gamma d\to \varphi d$ at forward production angles. A linearly polarized photon beam at $E_{\gamma }=1.6$–2.4 GeV was used for the production of $\varphi$ mesons. The natural-parity Pomeron exchange processes remain dominant near threshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from the nucleons but is greatly reduced in the coherent production from deuterons. There is no strong $E_{\gamma }$ dependence, but there is some dependence on momentum transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the $t$-channel is observed.

We have studied three-$\alpha$ states around ${}^{40}\mathrm{Ca}$ based on a microscopic $\alpha$-cluster model. Quite recently experimental evidence for such states has been obtained. This study was performed by introducing a Monte Carlo technique for the description of the Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function, which is called the “virtual THSR” wave function. The three-$\alpha$-cluster state around ${}^{40}\mathrm{Ca}$ has an energy below the Coulomb-barrier top energy with a spatial extension comparable to the second $0^{+}$ state of ${}^{12}\mathrm{C}$.

Nonempirical effective contact pairing forces to be used in self-consistent mean-field calculations are presented. These pairing forces, constructed so as to reproduce exactly any given microscopic pairing gaps in infinite homogeneous nuclear matter for any isospin asymmetry, are given in analytical form. As a by-product, this work provides an analytical solution of the BCS gap equations which could be applied to describe various many-body systems.

The isomeric and $\beta$-decay properties of neutron-rich ${}^{53-57}\mathrm{Sc}$ and ${}^{53,54}\mathrm{Ca}$ nuclei near neutron number $N=32$ are reported, and the low-energy level schemes of ${}^{53,54,56}\mathrm{Sc}$ and ${}^{53-57}\mathrm{Ti}$ are presented. The low-energy level structures of the ${}_{21}\mathrm{Sc}$ isotopes are discussed in terms of the coupling of the valence $1f_{7/2}$ proton to states in the corresponding ${}_{20}\mathrm{Ca}$ cores. Implications with respect to the robustness of the $N=32$ subshell closure are discussed, as well as the repercussions for a possible $N=34$ subshell closure.

It is crucially important to find an acceptance and late collision process independent observable in searching for the possible critical point predicted by QCD. By utilizing a multiphase transport (AMPT) model and ultrarelativistic quantum molecular dynamics (UrQMD) model, we study the centrality and evolution time dependence of higher moments of net baryon distribution in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=17.3$ GeV. The results suggest that kurtosis and skewness are less sensitive to the acceptance effect and late collision process. Thus, they should be good observables providing the information on the early stage of a heavy-ion collision. In addition, our study shows that the product of kurtosis times ${\sigma }^2$ of the net proton distribution is quite different from that of the net baryon distribution when the collision energy is lower than $\sqrt{s_{\mathit{NN}}}=20$ GeV, the Monte Carlo calculations on kurtosis$·{\sigma }^2$ have a deviation from the theoretical predictions.

In this paper, we investigate regular patterns of matrix elements of the nuclear shell model Hamiltonian $H$, by sorting the diagonal matrix elements from the smaller to the larger values. By using simple plots of nonzero matrix elements and lowest eigenvalues of artificially constructed submatrices $h$ of $H$, we propose a new and simple formula, which predicts the lowest eigenvalue with remarkable precision.

We present a calculation of spectroscopic factors within coupled-cluster theory. Our derivation of algebraic equations for the one-body overlap functions are based on coupled-cluster equation-of-motion solutions for the ground and excited states of the doubly magic nucleus with mass number $A$ and the odd-mass neighbor with mass $A-1$. As a proof-of-principle calculation, we consider ${}^{16}\mathrm{O}$ as well as the odd neighbors ${}^{15}\mathrm{O}$ and ${}^{15}\mathrm{N}$ and compute the spectroscopic factor for nucleon removal from ${}^{16}\mathrm{O}$. We employ a renormalized low-momentum interaction of the $V_{\text{low-}k}$ type derived from a chiral interaction at next-to-next-to-next-to-leading order. We study the sensitivity of our results by variation of the momentum cutoff and then discuss the treatment of the center of mass.

The cross sections for exclusive muon-pair production in nucleus-nucleus collisions are calculated and several differential distributions are shown. Realistic (Fourier transform of charge density) charge form factors of nuclei are used and the corresponding results are compared with the cross sections calculated with monopole form factor often used in the literature and discussed recently in the context of higher-order QED corrections. Absorption effects are discussed and quantified. The cross sections obtained with realistic form factors are significantly smaller than those obtained with the monopole form factor. The effect is bigger for large muon rapidities and/or large muon transverse momenta. The predictions for the STAR and PHENIX collaboration measurements at RHIC as well as the ALICE and CMS collaborations at LHC are presented.

This is the final installment of a series of work that we have done in the context of the meson cloud model that investigates $F_2$ and $g_1$ structure functions. In our previous work on $g_1$ structure function, we showed that having a spin-0 quark-diquark for the nucleon core along with both pseudoscalar and vector meson clouds was not sufficient to reproduce experimental observation(s) consistently. For the $F_2$ structure function, we found that both superposition of a spin-0 diquark and a spin-1 diquark in the nucleon core along with pseudoscalar and vector meson clouds are needed to reproduce the observed $F_2(x)$ and the Gottfried sum rule (GSR) violation. Therefore, in the present work, we consider the contribution of a spin-1 diquark in the nucleon core to the $g_1$ structure function. The calculation is performed in the light-cone frame. The dressed nucleon is assumed to be a superposition of the bare nucleon plus virtual light-cone Fock states of baryon-meson pairs. For the bare nucleon, we consider different quark-diquark configurations along with the possibility that there is no diquark inside the nucleon. The initial distributions are evolved. The final results are compared with experimental results and other theoretical predictions.

We calculate the Schiff moments of the nuclei ${}^{199}\mathrm{Hg}$ and ${}^{211}\mathrm{Rn}$ in completely self-consistent odd-nucleus mean-field theory by modifying the Hartree-Fock-Bogoliubov code hfodd. We allow for arbitrary shape deformation and include the effects of nucleon dipole moments alongside those of a pion-exchange nucleon-nucleon interaction that violates charge-parity (CP) symmetry. The results for ${}^{199}\mathrm{Hg}$ differ significantly from those of previous calculations when the CP-violating interaction is of isovector character.

We present the results of an ultracold neutron (UCN) production experiment in a pulsed-neutron beam line at the Los Alamos Neutron Scattering Center. The experimental apparatus allows for a comprehensive set of measurements of UCN production as a function of target temperature, incident neutron energy, target volume, and applied magnetic field. However, the low counting statistics of the UCN signal can be overwhelmed by the large background associated with the scattering of the primary cold-neutron flux that is required for UCN production. We have developed a background subtraction technique that takes advantage of the very different time-of-flight profiles between the UCN and the cold neutrons, in the pulsed beam. Using the unique timing structure, we can reliably extract the UCN signal. Solid ortho-${}^2\mathrm{H}$${}_2$ is used to calibrate UCN transmission through the apparatus, which is designed primarily for studies of UCN production in solid ${\mathrm{O}}_2$. In addition to setting the overall detection efficiency in the apparatus, UCN production data using solid ${}^2\mathrm{H}$${}_2$ suggest that the UCN upscattering cross section is smaller than previous estimates, indicating the deficiency of the incoherent approximation widely used to estimate inelastic cross sections in the thermal and cold regimes.

We study the linear response of the inner crust of neutron stars within the random phase approximation, employing a Skyrme-type interaction as effective interaction. We adopt the Wigner-Seitz approximation, and consider a single unit cell of the Coulomb lattice that constitutes the inner crust, with a nucleus at its center, surrounded by a sea of free neutrons. With the use of an appropriate operator, it is possible to analyze in detail the properties of the vibrations of the surface of the nucleus and their interaction with the modes of the sea of free neutrons, and to investigate the roles of shell effects and of resonant states.

Spectra of the ${}^9\mathrm{Be}$($e,e^{\prime }$) reaction have been measured at the Superconducting Darmstadt Electron Linear Accelerator at an electron energy of $E_0=73$ MeV and scattering angles of ${93}^{°}$ and ${141}^{°}$ with high-energy resolution up to excitation energies of $E_x=8$ MeV. The astrophysically relevant resonance parameters of the first excited $1/2^{+}$ state of ${}^9\mathrm{Be}$ have been extracted in a one-level approximation of $R$-matrix theory, resulting in resonance energy $E_R=1.748(6)$ MeV and width ${\Gamma }_R=274(8)$ keV, which are in good agreement with the latest ${}^9\mathrm{Be}$($\gamma ,n$) experiment but with considerably improved uncertainties. However, the reduced $B(E1)$ transition strength deduced from an extrapolation of the $(e,e^{\prime })$ data to the photon point is smaller by a factor of two. Implications of the new results for possible production of ${}^{12}\mathrm{C}$ in neutron-rich astrophysical scenarios are discussed.

High-spin states in ${}^{84}\mathrm{Rb}$ have been studied by using the ${}^{70}\mathrm{Zn}$(${}^{18}\mathrm{O},p3n)$${}^{84}\mathrm{Rb}$ reaction at beam energy of 75 MeV. The $\gamma$-$\gamma$ coincidence, excitation function, and ratios for directional correlation of oriented states were determined. A new level scheme was established in which the positive- and negative-parity bands have been extended up to ${17}^{+}$ and ${17}^{-}$ with an excitation energy of about 7 MeV. The signature splitting and signature inversion of the positive-parity yrast band were observed. To understand the microscopic origin of the signature inversion in the yrast positive-parity bands of doubly odd Rb nuclei, as an example, we performed calculations using the projected shell model to describe the energy spectra in ${}^{84}\mathrm{Rb}$. It can be seen that the main features are reproduced in the calculations. This analysis shows that the signature splitting, especially its inversion, can be reproduced by varying only the $\gamma$ deformation with increasing spin. To research the deformation of ${}^{84}\mathrm{Rb}$ carefully, we calculate the total Routhian surfaces of positive-parity yrast states by the cranking shell model formalism. In addition, the results of theoretical calculations about the negative-parity yrast band in ${}^{84}\mathrm{Rb}$ with configuration $\pi (p_{3/2},f_{5/2})\otimes \nu g_{9/2}$ are compared with experimental data, and a band diagram calculated for this band is also shown to extract physics from the numerical results.

We investigate the correlation between integrated proton-neutron interactions obtained by using the up-to-date experimental data of binding energies and the product $N_p{N}_n$ of valence proton number and valence neutron number with respect to the nearest doubly closed nucleus. We make corrections on a previously suggested formula for the integrated proton-neutron interaction. Our results demonstrate a nice, nearly linear, correlation between the integrated $p$-$n$ interaction and $N_p{N}_n$, which provides us with a firm foundation of the applicability of the $N_p{N}_n$ scheme to nuclei far from the stability line.