Background: A bound state of the $\mathrm{\Lambda }nn$ system has been reported, but at least three theoretical papers question the existence of such a bound state.

Purpose: We address the alternative question of whether there might exist a resonance in the $\mathrm{\Lambda }nn$ system, using a rank-one separable potential formulation of the Hamiltonian.

Methods: We examine the eigenvalues of the kernel of the Faddeev equation in the complex energy plane using contour rotation to allow us to analytically continue the kernel onto the second energy sheet. The model $\mathrm{\Lambda }n$ interaction is fitted to the $\mathrm{\Lambda }p$ scattering length and effective range.

Results: We follow the largest eigenvalue as the $\mathrm{\Lambda }n$ potentials are scaled and the $\mathrm{\Lambda }nn$ continuum is turned first into a resonance, and then into a bound state of the system.

Conclusions: Because a change in the strength of the $\mathrm{\Lambda }n$ potential of as little as 5% will produce a $\mathrm{\Lambda }nn$ resonance, we infer that an experiment of the ${}^3\text{H}(\text{e},{\text{e}}^{\prime }{\text{K}}^{+}){}_{\mathrm{\Lambda }}{}^3\text{n}$ type at JLAB could be used to constrain the properties of the $\mathrm{\Lambda }n$ interaction.

Nuclear excitation by electron transition (NEET) is predicted to be the dominant excitation process of the first ${}^{201}\text{Hg}$ isomeric state in a laser heated plasma. This process may occur when the energy difference between a nuclear transition and an atomic transition is close to zero, provided the quantum selection rules are fulfilled. At local thermodynamic equilibrium, an average atom model may be used, in a first approach, to evaluate the NEET rate in plasma. The statistical nature of the electronic transition spectrum is then described by the means of a Gaussian distribution around the average atom configuration. However, using a continuous function to describe the electronic spectrum is questionable in the framework of a resonant process, such as NEET. In order to get an idea of when it can be relied upon to predict a NEET rate in plasma, we present in this paper a NEET rate calculation using a model derived from detailed configuration accounting. This calculation allows us to define a confidence interval of the NEET rate around its average atom mean value, which is the first step to design a future experiment.

Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus and the daughter products.

Purpose: We explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide ${}^{240}\text{Pu}$ as an example.

Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate nonadiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data.

Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behavior. Those beginning just beyond the barrier explore large-amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation.

Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

The experimental data from quasi-elastic electron scattering from ${}^{12}\mathrm{C}$ are reanalyzed in terms of a new scaling variable suggested by the interacting relativistic Fermi gas with scalar and vector interactions, which is known to generate a relativistic effective mass for the interacting nucleons. By choosing a mean value of this relativistic effective mass $m_N^{*}=0.8m_N$, we observe that most of the data fall inside a region around the inverse parabola-shaped universal scaling function of the relativistic Fermi gas. This suggests a method to select the subset of data that highlight the quasi-elastic region, about two thirds of the total 2500 data. Regardless of the momentum and energy transfer, this method automatically excludes the data that are not dominated by the quasi-elastic process. The resulting band of data reflects deviations from perfect universality and can be used to characterize experimentally the quasi-elastic peak, despite the manifest scaling violation. Moreover, we show that the spread of the data around the scaling function can be interpreted as genuine fluctuations of the effective mass $M^{*}\equiv m_N^{*}/m_N\sim 0.8\pm 0.1$. Applying the same procedure we transport the scaling quasi-elastic band into a theoretical prediction band for the neutrino-scattering cross section that is compatible with the recent measurements and slightly more accurate.

Background: To access selected excited states of nuclei, within the framework of nuclear density functional theory, the quasiparticle random phase approximation (QRPA) is commonly used.

Purpose: We present a computationally efficient, fully self-consistent framework to compute the QRPA transition strength function of an arbitrary multipole operator in axially deformed superfluid nuclei.

Methods: The method is based on the finite amplitude method (FAM) QRPA, allowing fast iterative solution of QRPA equations. A numerical implementation of the FAM-QRPA solver module has been carried out for deformed nuclei.

Results: The practical feasibility of the deformed FAM module has been demonstrated. In particular, we calculate the quadrupole and octupole strengths in a heavy deformed nucleus ${}^{240}\mathrm{Pu}$, without any truncations in the quasiparticle space. To demonstrate the capability to calculate individual QRPA modes, we also compute low-lying negative-parity collective states in ${}^{154}\mathrm{Sm}$.

Conclusions: The new FAM implementation enables calculations of the QRPA strength function throughout the nuclear landscape. This will facilitate global surveys of multipole modes and $\beta$ decays and will open new avenues for constraining the nuclear energy density functional.

We present an efficient implementation of the Density Matrix Renormalization Group (DMRG) algorithm that includes an optimal ordering of the proton and neutron orbitals and an efficient expansion of the active space utilizing various concepts of quantum information theory. We first show how this new DMRG methodology could solve a previous 400 keV discrepancy in the ground state energy of ${}^{56}\mathrm{Ni}$. We then report the first DMRG results in the $pf+g9/2$ shell model space for the ground $0^{+}$ and first $2^{+}$ states of ${}^{64}\mathrm{Ge}$ which are benchmarked with reference data obtained from a Monte Carlo shell model. The corresponding correlation structure among the proton and neutron orbitals is determined in terms of two-orbital mutual information. Based on such correlation graphs we propose several further algorithmic improvement possibilities that can be utilized in a new generation of tensor network based algorithms.

We study relativistic mean-field (RMF) models including nucleons interacting with scalar, vector, and isovector mean fields and mean-field self- and cross-interaction terms. Usually, in such models the magnitude of the scalar field increases monotonically with the nucleon density, and the nucleon effective mass decreases. We demonstrate that the latter quantity stops decreasing and the equation of state stiffens, provided the mean-field self-interaction potential rises sharply in a narrow vicinity of the values of mean fields corresponding to nucleon densities $n\gtrsim n_{*}>n_0$, where $n_0$ is the nuclear saturation density. As a result the limiting neutron star mass increases. This procedure offers a simple way to stiffen the equation of state at densities above $n_{*}$ without altering it at densities $n\lesssim n_0$. The developed scheme allows a neutron star application of the RMF models, which are well fitted to finite nuclei but do not fulfill the experimental constraint on the limiting neutron star mass. The exemplary application of the method to the well-known FSUGold model allows us to increase the limiting neutron star mass from $1.72M_{\odot }$ to $M\ge 2.01M_{\odot }$.

The spectroscopy of ${}^{73}\text{Ge}$ has been investigated via the ${}^{70}\text{Zn}({}^7\text{Li},3np){}^{73}\text{Ge}$ fusion-evaporation reaction. A previously known band built on the $\nu \left(f_{5/2}\right)$ orbital is extended up to higher-spin states and a new rotational band built on the $\nu \left(g_{9/2}\right)$ orbital is established. The observed band crossing and shape evolution induced by the alignment in ${}^{73}\text{Ge}$ are studied in comparison with the similar structures in the neighboring $N=41$ isotones and the cranked Woods–Saxon–Strutinsky calculations by means of total-Routhian-surface (TRS) methods. The inversion of the order of the $g_{9/2}$ neutron and the $g_{9/2}$ proton crossing frequency observed in the negative-parity $\nu \left(f_{5/2}\right)$ bands between ${}^{73}\text{Ge}$ and ${}^{75}\text{Se}$, ${}^{77}\text{Kr}$ can be ascribed to their different triaxial deformations. At higher spins, both the $\nu \left(f_{5/2}\right)$ and $\nu \left(g_{9/2}\right)$ bands in ${}^{73}\text{Ge}$ undergo a shape evolution with sizable alignments occurring. The characters of large signature splitting in $\nu \left(g_{9/2}\right)$ band of ${}^{73}\text{Ge}$ are discussed.

We study the problem of an impurity in fully polarized (spin-up) low-density neutron matter with the help of an accurate quantum Monte Carlo method in conjunction with a realistic nucleon-nucleon interaction derived from chiral effective field theory at next-to-next-to leading order. Our calculations show that the behavior of the proton spin-down impurity is very similar to that of a polaron in a fully polarized unitary Fermi gas. We show that our results can be used to put tight constraints on the time-odd parts of the Skyrme energy density functional, independent of the time-even parts, in the density regime relevant to neutron-rich nuclei and compact astrophysical objects such as neutron stars and supernovae.

The spallation neutron source at the Los Alamos Neutron Science Center Weapons Neutron Research facility was used to populate excited states in ${}^{186}\mathrm{Re}$ via $(n,2n\gamma )$ reactions on an enriched ${}^{187}\mathrm{Re}$ target. Gamma rays were detected with the GErmanium Array for Neutron Induced Excitations spectrometer, a Compton-suppressed array of 18 HPGe detectors. Incident neutron energies were determined by the time-of-flight technique and used to obtain $\gamma$-ray excitation functions for the purpose of identifying $\gamma$ rays by reaction channel. Analysis of the singles $\gamma$-ray spectrum gated on the neutron energy range $10\le E_n\le 25\mathrm{MeV}$ resulted in five transitions and one level added to the ${}^{186}\mathrm{Re}$ level scheme. The additions include the placement of three $\gamma$ rays at 266.7, 381.2, and 647.7 keV which have been identified as feeding the $2.0\times {10}^5\mathrm{yr}$, $J^{\pi }=\left(8^{+}\right)$ isomer and yield an improved value of $148.2\left(5\right)\mathrm{keV}$ for the isomer energy. These transitions may have astrophysical implications related to the use of the Re-Os cosmochronometer.

We employ a relativistic mean field model with NL3 parametrization to investigate the ground state properties of the superheavy nucleus, $Z=124$. The nuclei selected (from among complete isotopic series) for detailed investigation show that the nucleon density at the center is very low and therefore, these nuclei can be treated as semi-bubble nuclei. The considerable shell gap appears at neutron numbers $N=172$, 184, and 198 showing the magicity corresponding to these numbers. The results are compared with the macro-microscopic finite range droplet model wherever possible.

In a coalescence plus independent fragmentation approach we calculate the $p_T$ spectra of the main hadrons: $\pi ,K,p,\overline{p},\mathrm{\Lambda },\varphi$ in a wide range of transverse momentum from low $p_T$ up to about 10 GeV. The approach in its main features was developed several years ago at Relativistic Heavy Ion Collider (RHIC) energy. Augmenting the model with the inclusion of some more main resonance decays, we show that the approach correctly predicts the evolution of the $p_T$ spectra from RHIC to LHC (Large Hadron Collider) energy and in particular the baryon-to-meson ratios $p/\pi ,\overline{p}/\pi ,\mathrm{\Lambda }/K$ that reach a value of the order of unit at $p_T\sim 3\mathrm{GeV}$. This is achieved without any change of the coalescence parameters. The more recent availability of experimental data up to $p_T\sim 10\mathrm{GeV}$ for $\mathrm{\Lambda }$ spectrum as well as for $p/\pi$ and $\mathrm{\Lambda }/K$ shows some lack of yield in a limited $p_T$ range around 6 GeV. This indicates that the baryons $p_T$ spectra from Albino-Kniehl-Kramer fragmentation functions are too flat at $p_T\lesssim 8\mathrm{GeV}$. We also show that in a coalescence plus fragmentation approach one predicts a nearly $p_T$ independent $p/\varphi$ ratio up to $p_T\sim 4\mathrm{GeV}$ followed by a significant decrease at higher $p_T$. Such a behavior is driven by a similar radial flow effect at $p_T<2\mathrm{GeV}$ and the dominance of fragmentation for $\varphi$ at larger $p_T$.

The effect of the mesons $f_0\left(975\right)$ and $\varphi \left(1020\right)$ on the surface gravitational redshift of the neutron star PSR J0348+0432 is examined in the framework of the relativistic mean field theory by choosing the suitable hyperon coupling constants. We find that compared with that without considering the mesons $f_0\left(975\right)$ and $\varphi \left(1020\right)$, the value range of the radius $R$ of the neutron star PSR J0348+0432 would be changed from a narrow range 12.964 km $\sim 12.364$ km to a wider range 12.941 km $\sim 11.907$ km corresponding to the observation mass $M=1.97M_{\odot }\sim 2.05M_{\odot }$. We also find that the value range of the surface gravitational redshift $z$ of the neutron star PSR J0348+0432 changes from 0.3469 $\sim 0.3997$ to 0.3480 $\sim 0.4263$ corresponding to the observation mass $M=1.97M_{\odot }\sim 2.05M_{\odot }$ with the mesons $f_0\left(975\right)$ and $\varphi \left(1020\right)$ being considered. This means that the radius $R$ and the surface gravitational redshift $z$ both will be constrained in a wider scope with the mesons $f_0\left(975\right)$ and $\varphi \left(1020\right)$ being considered. We also can see that the difference of the radius and the surface gravitational redshift is not so large whether the mesons $f_0\left(975\right)$ and $\varphi \left(1020\right)$ are considered or not. This indicates that the mesons $f_0\left(975\right)$ and $\varphi \left(1020\right)$ do not play a major role in the massive neutron star PSR J0348+0432.

Background: Complete fusion between two massive nuclei after capture inside the potential barrier is inhibited by competing fission-like processes. The target-projectile composite system may reseparate after capture without proceeding towards formation of the compound nucleus (CN), which is equilibrated in all degrees of freedom. The nature of these non-CN fission (NCNF) processes and factors that affect them are not completely known yet.

Purpose: The nuclear mass regions from where NCNF processes begin to manifest themselves are not clearly demarcated. This work aims to study the onset of NCNF, if any, in the mass region $\sim 200$.

Methods: Fission fragment (FF) mass and angular distribution (MAD) and pre-scission and post-scission neutron multiplicities were measured for the reaction ${}^{19}\text{F}+{}^{184}\text{W}$ at a laboratory energy $\left(E_{\mathrm{lab}}\right)$ range of 84–125 MeV. The measurements were carried out using two multiwire proportional counters (MWPC) to detect the FFs in coincidence and four neutron detectors to measure neutron time of flight (TOF). Statistical model (SM) calculation was performed.

Results: No significant mass-angle correlation was observed in the MAD plots. Extracted mass ratio distributions were single-peaked and of Gaussian shape. Measured pre-scission neutron multiplicity values indicated dissipative nature of CN decay for this reaction.

Conclusions: No clear signatures of NCNF were observed in the studied reaction, indicating that the target-projectile composite system predominantly proceeds towards formation of the CN after capture.

We compare the quantum mechanical procedures to estimate the total $\alpha$-decay width from deformed nuclei in the laboratory and intrinsic systems of coordinates. Our analysis shows that the total half-life estimated in the intrinsic frame by neglecting the rotational motion of the core (adiabatic approach) is one order of magnitude smaller at ${\beta }_2=0.3$ than the corresponding value in the spherical case. A similar calculation in the laboratory system of coordinates by considering the core motion (giving the correct theoretical estimate) predicts a reduction by only a factor of 2. The widely used “angular WKB” (Wentzel-Kramers-Brillouin) semiclassical procedure provides decay widths which are comparable to the adiabatic approach. We propose a new and very simple semiclassical “angular momentum WKB” procedure to evaluate the decay width in deformed nuclei. It provides decay widths very close to the ones obtained by the exact laboratory coupling channels procedure.

Background: Nuclear fusion has been shown to be a useful probe to study the different nuclear shapes. However, the possibility of testing octupole deformation of a nucleus with this tool has not been fully explored yet. The presence of a static octupole deformation in nuclei will enhance a possible permanent electric dipole moment, leading to a possible demonstration of parity violation.

Purpose: To check whether static octupole deformation and octupole vibration in fusion give different results so that both situations could be experimentally disentangled.

Method: Fusion cross sections are computed in the coupled-channel formalism making use of the ingoing-wave boundary conditions (IWBC) for the systems ${}^{16}\mathrm{O}+{}^{144}\mathrm{Ba}$ and ${}^{16}\mathrm{O}+{}^{224}\mathrm{Ra}$.

Results: Barrier distributions of the two considered schemes show slightly different patterns. In the case of ${}^{144}\mathrm{Ba}$, the difference between them is negligible. For the ${}^{224}\mathrm{Ra}$ case, perceptible differences are found in correspondence with its larger octupole deformation. However, the possibility of disentangling both schemes is not guaranteed and it will depend on the available experimental accuracy and the strength of the octupole deformation.

Conclusions: The measurement of barrier distributions could be a complementary probe to support the presence of octupole deformation.

We have analyzed the fusion dynamics of ${}_{20}{}^{40}\mathrm{Ca}+{}_{28}{}^{58,64}\mathrm{Ni}$ reactions by using the energy dependent Woods-Saxon potential (EDWSP) model and coupled channel model and subsequently the decay patterns of ${}_{48}{}^{98,104}\mathrm{Cd}^{*}$ nuclei are governed via the dynamical cluster-decay model (DCM). The influence of intrinsic degrees of freedom of colliding pairs, such as low lying surface vibrations and neutron transfer channels, are entertained within the context of coupled channel calculations. Interestingly, the energy dependence in the Woods-Saxon potential induces barrier modification effects (barrier height, barrier position, barrier curvature) in a somewhat similar way as that for coupled channel approach, hence adequately explains the observed fusion dynamics of ${}_{20}{}^{40}\mathrm{Ca}+{}_{28}{}^{58,64}\mathrm{Ni}$ reactions. In addition, the decay analysis of compound nuclei formed in the fusion of ${}_{20}{}^{40}\mathrm{Ca}+{}_{28}{}^{58,64}\mathrm{Ni}$ reactions is investigated by using DCM. The calculations are done for quadrupole $\left({\beta }_2\right)$ deformed fragments having optimum orientations for hot configurations. The experimental data for evaporation residues lying within the wide range of center of mass energy $\left(E_{\mathrm{c}.\mathrm{m}.}\right)$ of $64–88$ MeV is nicely addressed using the collective clusterization approach of the DCM. The comparative analysis of decay profiles of ${}_{48}{}^{98,104}\mathrm{Cd}^{*}$ is worked out by introducing angular momentum and temperature effects in the fragmentation potential and preformation factor.

The van der Waals (VDW) equation of state predicts the existence of a first-order liquid-gas phase transition and contains a critical point. The VDW equation with Fermi statistics is applied to a description of the nuclear matter. The nucleon number fluctuations near the critical point of nuclear matter are studied. The scaled variance, skewness, and kurtosis diverge at the critical point. It is found that the crossover region of the phase diagram is characterized by the large values of the scaled variance, the almost zero skewness, and the significantly negative kurtosis. The rich structures of the skewness and kurtosis are observed in the phase diagram in the wide region around the critical point; namely, they both may attain large positive or negative values.

We have developed a relativistic kinetic transport approach that incorporates initial-state fluctuations allowing to study the buildup of elliptic flow $v_2$ and high-order harmonics $v_3$, $v_4$, and $v_5$ for a fluid at fixed $\eta /s\left(T\right)$. We study the effect of the $\eta /s$ ratio and its $T$ dependence on the buildup of the $v_n\left(p_T\right)$ for two different beam energies: RHIC for Au+Au at $\sqrt{s}=200\text{GeV}$ and LHC for $\text{Pb}+\text{Pb}$ at $\sqrt{s}=2.76\text{TeV}$. We find that for the two different beam energies considered the suppression of the $v_n\left(p_T\right)$ due to the viscosity of the medium have different contributions coming from the crossover or QGP phase. Our study reveals that only in ultracentral collisions $(0–0.2\%)$ the $v_n\left(p_T\right)$ have a stronger sensitivity to the $T$ dependence of $\eta /s$ in the QGP phase and this sensitivity increases with the order of the harmonic $n$. Moreover, the study of the correlations between the initial spatial anisotropies ${\epsilon }_n$ and the final flow coefficients $v_n$ shows that at LHC energies there is more correlation than at RHIC energies. The degree of correlation increases from peripheral to central collisions, but only in ultracentral collisions at LHC, we find that the linear correlation coefficient $C(n,n)\approx 1$ for $n=2,3,4$, and 5. This suggests that the final correlations in the $(v_n,v_m)$ space reflect the initial correlations in the $({\epsilon }_n,{\epsilon }_m)$ space.

Recent data from $p+p$ and $p+\mathrm{Pb}$ collisions at the Large Hadron Collider (LHC), and $d+\mathrm{Au}$ and ${}^3\mathrm{He}+\mathrm{Au}$ collisions at the Relativistic Heavy Ion Collider (RHIC) reveal patterns that—when observed in the collision of heavy nuclei—are commonly interpreted as indicators of a locally equilibrated system in collective motion. The comparison of these data sets, including the forthcoming results from $p+\mathrm{Au}$ and $p+\mathrm{Al}$ collisions at RHIC, will help to elucidate the geometric dependence of such patterns. It has recently been shown that a multiphase transport model (AMPT) can describe some of these features in LHC data with a parton-parton scattering cross section comparable to that required to describe $A+A$ data. In this paper, we extend these studies by incorporating a full wave-function description of the ${}^3\mathrm{He}$ nucleus to calculate elliptical and triangular anisotropy moments $v_2$ and $v_3$ for $p+\mathrm{Au}$, $d+\mathrm{Au}$, and ${}^3\mathrm{He}+\mathrm{Au}$ collisions at the RHIC top energy of 200 GeV. We find reasonable agreement with the measured $v_2$ in $d+\mathrm{Au}$ and ${}^3\mathrm{He}+\mathrm{Au}$ and $v_3$ in ${}^3\mathrm{He}+\mathrm{Au}$ for transverse momentum $\left(p_T\right)\lesssim 1\mathrm{GeV}/c$, but underestimate these measurements for higher values of $p_T$. We predict a pattern of coefficients $(v_2,v_3)$ for $p+\mathrm{Au}$, dominated by differences in the number of induced local hot spots (i.e., one, two, or three) arising from intrinsic geometry. Additionally, we examine how this substantial azimuthal anisotropy accrues during each individual evolutionary phase of the collision in the AMPT model. The possibility of a simultaneous description of RHIC- and LHC-energy data, the suite of different geometries, and high multiplicity $p+p$ data is an exciting possibility for understanding the underlying physics in these systems.