The island of inversion for neutron-rich nuclei in the vicinity of $N=20$ has become the testing ground par excellence for our understanding and modeling of shell evolution with isospin. In this context, the structure of the transitional nucleus ${}^{29}\mathrm{Mg}$ is critical. The first quantitative measurements of the single-particle structure of ${}^{29}\mathrm{Mg}$ are reported, using data from the $d({}^{28}\mathrm{Mg}, p \gamma ){}^{29}\mathrm{Mg}$ reaction. Two key states carrying significant $\ell =3$ ($f$-wave) strength were identified at $2.40\pm 0.10$ ($J^{\pi }=5/2^{-}$) and $4.28\pm 0.04$ MeV ($7/2^{-}$). New state-of-the-art shell-model calculations have been performed and the predictions are compared in detail with the experimental results. While the two lowest $7/2^{-}$ levels are well described, the sharing of single-particle strength disagrees with experiment for both the $3/2^{-}$ and $5/2^{-}$ levels and there appear to be general problems with configurations involving the $p_{3/2}$ neutron orbital and core-excited components. These conclusions are supported by an analysis of the neutron occupancies in the shell-model calculations.

Background: Further studies of high-precision measurements of $\alpha$-induced reaction data below the Coulomb barrier have still raised questions about the $\alpha$-particle optical model potential (OMP) within various mass ranges, i.e., for ${}^{64}\mathrm{Zn}, {}^{108}\mathrm{Cd}, {}^{113,115}\mathrm{In}, {}^{121,123}\mathrm{Sb}$, and ${}^{191,193}\mathrm{Ir}$ target nuclei.

Purpose: The accuracy as well as eventual uncertainties and/or systematic errors of using a previous optical potential are much better considered by analysis of such accurate data.

Method: Statistical model (SM) calculations of the $(\alpha ,x)$ reaction cross sections have been carried out using model parameters that were previously obtained by analyzing independent data, particularly $\gamma$-ray strength functions, and taking into account their uncertainties and questions of extrapolation for nuclei without similar data.

Results: Consistent description of the recent $\alpha$-induced reaction data is provided by the above-mentioned optical potential with no empirical rescaling factors of either its own parameters or the $\gamma$ and/or nucleon widths. Effects of still uncertain SM parameters on calculated $\alpha$-induced reaction cross sections and conclusions on the $\alpha$-OMP can be now discussed due to unprecedented precision of the new data.

Conclusions: The $\alpha$-particle optical potential has been confirmed at incident energies below the Coulomb barrier using statistical-model parameters validated through a former analysis of independent data.

We report the effect of including repulsive interactions on various thermodynamic observables calculated using an $S$-matrix based hadron resonance gas (HRG) model applied to already available corresponding results with only attractive interactions [A. Dash, S. Samanta, and B. Mohanty, Phys. Rev. C 97, 055208 (2018)]. The attractive part of the interaction is calculated by parametrizing the two-body phase shifts using the $K$-matrix formalism, while the repulsive part is included by fitting to the experimental phase shifts which carry the information about the nature of the interaction. We find that the bulk thermodynamic variables for a gas of hadrons, such as energy density, pressure, entropy density, speed of sound, and specific heat, are suppressed by the inclusion of repulsive interactions and are more pronounced for second- and higher-order correlations and fluctuations, particularly for the observables ${\chi }_Q^2, {\chi }_B^2-{\chi }_B^4$, and $C_{BS}$ in the present model. We find a good agreement between lattice QCD simulations and the present model for $C_{BS}$. We have also computed two leading-order Fourier coefficients of the imaginary part of the first-order baryonic susceptibility at imaginary baryon chemical potential within this model and compared them with the corresponding lattice results. Additionally, assuming that the value of interacting pressure versus temperature for a gas of hadrons calculated in the $S$-matrix formalism is the same as that from a van der Waals HRG (VDWHRG) model, we have quantified the attractive and repulsive interactions in our model in terms of attractive and repulsive parameters used in the VDWHRG model. The values of parameters thus obtained are $a=1.54\pm 0.064$ GeV ${\text{fm}}^3$ and $r=0.81\pm 0.014$ fm.

Background: The Nijmegen extended-soft-core (ESC) model ESC16, as well as its predecessors ESC04–ESC08, describe the nucleon-nucleon ($NN$), hyperon-nucleon ($YN$), and hyperon-hyperon/nucleon ($YY/\mathrm{\Xi }N$) interactions in a unified way using broken SU(3) symmetry. SU(3) symmetry serves to connect the $NN$ with the $YN$ and the $YY$ channels. In the spirit of the Yukawa approach to the nuclear force problem, the interactions are studied from the meson-exchange picture viewpoint, using generalized soft-core Yukawa functions. The meson exchanges are supplemented with diffractive contributions due to multiple-gluon exchanges. The extended-soft-core (ESC) meson-exchange interactions consist of local and nonlocal potentials due to (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial-vector mesons, (ii) diffractive exchanges, (iii) two-pseudoscalar exchange (PS-PS), and (iv) meson-pair exchange (MPE). The OBE and MPE vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the BBM vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE.

Purpose: The evolution of the ESC approach to the ESC16 model for the baryon-baryon (BB) interactions of the SU(3) flavor octet of baryons (N, $\mathrm{\Lambda }$, $\mathrm{\Sigma }$, and $\mathrm{\Xi }$) is described and presented. In this first of a series of papers, the $NN$ model and results are reported in detail.

Methods: Important nonstandard ingredients in the OBE sector in the ESC models are (i) the axial-vector meson potentials, and (ii) a zero in the scalar- and axial-vector meson form factors. Furthermore, the strange scalar $\kappa$ meson is treated within the scheme of the Gell-Mann-Okubo mass relations, and like the $\rho$ and $\epsilon$ treated as a broad meson. The multiple-gluon exchanges are elaborated further by adding contributions due to odd number of gluon exchanges. A novel contribution is the incorporation of structural effects due to the quark core of the baryons. In establishing the parameters of the model a simultaneous fit to $NN$ and $YN$ channels has been performed. The meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the $NN\oplus YN$ analysis as input. In ESC16 the couplings are kept completely SU(3) symmetric. About 25 physical coupling parameters and 8 cutoff and diffractive masses were searched.

Results: In the fit to $NN$ and $YN$ many parameters are essentially fixed by the $NN$ data. A few, but severely constrained parameters, e.g., $F/(F+D)$ ratios, are left for determination of the $YN$ interactions and the $YY$ experimental indications. The simultaneous fit of the ESC models to the $NN$- and $YN$-scattering data with a single set of parameters has achieved excellent results for the $NN$ and $YN$ data, and for the $YY$ data in accordance with the experimental indications for $\mathrm{\Lambda }\mathrm{\Lambda }$ and $\mathrm{\Xi }N$. In the case of ESC16, the version discussed here, the achievements are: (i) For the selected 4313 $pp$ and $np$ scattering data with energies $0\le T_{\text{lab}}\le 350\mathrm{MeV}$, the model reaches a fit having ${\chi }^2/N_{\text{data}}=1.10$. (ii) The deuteron binding energy and all the $NN$ scattering lengths are fitted very nicely. (iii) The $YN$ data are described very well with ${\chi }^2/N_{\text{data}}=1.04$, giving at the same time a description of the $\mathrm{\Xi }N$ cross sections in agreement with the experimental indications.

Conclusions: The ESC approach leads to an excellent description of the $NN$ and $YN$ data, and for the scarce $YY$ data. The added innovations as well as the treatment of mass broken SU(3) make it possible to keep the meson coupling parameters and the $F/(F+D)$ ratios of the model qualitatively in accordance with the predictions of the ${}^{3}P_0$-dominated quark-antiquark pair creation (QPC) model. The information about estimates of (i) the $\mathrm{\Lambda }$- and $\mathrm{\Sigma }$-nuclear well-depth, and (ii) the $\mathrm{\Lambda }\mathrm{\Lambda }$ hypernuclei played an important role in the form of using constraints. In particular, the experimental indications for the $\mathrm{\Lambda }\mathrm{\Lambda }$-attraction and the $\mathrm{\Sigma }$-nuclear well-depth were directive.

Lifetimes of the $T=1$ isobaric analog $I^{\pi }=2^{+}$ states in ${}^{50}\mathrm{Mn}$ and ${}^{50}\mathrm{Cr}$ were measured simultaneously by employing the recoil distance Doppler-shift (RDDS) technique. The states were populated in a fusion-evaporation reaction with a ${}^{12}\mathrm{C}$ beam on a ${}^{40}\mathrm{Ca}$ target. An analysis of the data and the calculations from the present work, together with the available $B(E2:2^{+}\to 0^{+})$ data of the isobaric analog states in ${}^{50}\mathrm{Fe}$ and ${}^{50}\mathrm{Cr}$, were used to study isospin symmetry in the three $A=50$ isobaric nuclei. Shell-model calculations reproduce the magnitudes as well as the increasing trend of the $B\left(E2\right)$ data with increasing $Z$. To draw a firm conclusion on the level of isospin mixing in the triplet, a new precision measurement of the $2^{+}\to 0^{+}$ transition rate in ${}^{50}\mathrm{Fe}$ will be required.

We propose a simplified procedure for experimental application of the efficiency correction on higher order cumulants in heavy-ion collisions. By using the track-by-track efficiency, we can eliminate possible bias arising from the average efficiencies calculated within the arbitrary binning of the phase space. Furthermore, the corrected particle spectrum is no longer necessary for the average efficiency estimation and the time cost for calculation of the bootstrap statistical error can be significantly reduced.

We present two-particle $p_t$ correlations as a function of event centrality for Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=7.7$, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV show a power-law dependence on the number of participant nucleons and agree with the results for Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ from ALICE. As the collision energy is lowered from $\sqrt{s_{\mathrm{NN}}}=200$ to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power-law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to $\sqrt{s_{\mathrm{NN}}}=200$ GeV in contrast to previous measurements that showed little dependence on the collision energy.

The half-lives of three $\beta$-decaying states of ${}_{49}{}^{131}\mathrm{In}_{82}$ have been measured with the GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility to be $T_{1/2}(1/2^{-})=328\left(15\right)\mathrm{ms}$, $T_{1/2}(9/2^{+})=265\left(8\right)\mathrm{ms}$, and $T_{1/2}(21/2^{+})=323\left(55\right)\mathrm{ms}$, respectively. The first observation of $\gamma$ rays following the $\beta n$ decay of ${}^{131}\mathrm{In}$ into ${}^{130}\mathrm{Sn}$ is reported. The $\beta$-delayed neutron emission probability is determined to be $P_{1n}=12\left(7\right)\%$ for the $21/2^{+}$ state and $2.3\left(3\right)\%$ from the combined $1/2^{-}$ and $9/2^{+}$ states of ${}_{49}{}^{131}\mathrm{In}_{82}$ observed in this experiment. A significant expansion of the decay scheme of ${}^{131}\mathrm{In}$, including 17 new excited states and 35 new $\gamma$-ray transitions in ${}_{50}{}^{131}\mathrm{Sn}_{81}$ is also reported. This leads to large changes in the deduced $\beta$-branching ratios to some of the low-lying states of ${}^{131}\mathrm{Sn}$ compared to previous work with implications for the strength of the first-forbidden $\beta$ transitions in the vicinity of doubly magic ${}_{50}{}^{132}\mathrm{Sn}_{82}$.

Background: In the framework of nuclear energy density functional (EDF) methods, many nuclear phenomena are related to the deformation of intrinsic states. Their accurate modeling relies on the correct description of the change of nuclear binding energy with deformation. The two most important contributions to the deformation energy have their origin in shell effects that are correlated to the spectrum of single-particle states, and the deformability of nuclear matter, that can be characterized by a model-dependent surface energy coefficient $a_{\text{surf}}$.

Purpose: With the goal of improving the global performance of nuclear EDFs through the fine-tuning of their deformation properties, the purpose of this study is threefold. First, to analyze the impact of systematic variations of $a_{\text{surf}}$ on properties of nuclei; second, to identify observables that can be safely used to narrow down the range of appropriate values of $a_{\text{surf}}$ to be targeted in future parameter fits; third, to analyze the interdependence of $a_{\text{surf}}$ with other properties of a nuclear EDF.

Methods: Results for a large variety of relevant observables of deformed nuclei obtained from self-consistent mean-field calculations with a set of purpose-built SLy5sX parametrizations of the Skyrme EDF are correlated with the value of $a_{\text{surf}}$.

Results: The performance of the SLy5sX parametrizations for characteristic energies of the fission barriers of ${}^{180}\mathrm{Hg}, {}^{226}\mathrm{Ra}$, and ${}^{240}\mathrm{Pu}$, excitation energies, electromagnetic moments and moments of inertia of superdeformed states in the $A\approx 190$ region, properties of shape coexisting states at normal deformation in the Pb, Kr, and Zr region, properties of octupole-deformed ${}^{144}\mathrm{Ba}$, even-even Th isotopes, and ${}^{110}\mathrm{Zr}$, separation energies along isotopic and isotonic chains are compared with available experimental data.

Conclusions: The three main conclusions are that there is an evident preference for a comparatively low value of $a_{\text{surf}}$, as expected from the performance of existing parametrizations; that the isospin dependence of the surface energy also needs further fine-tuning in order to describe trends across the chart of nuclei; and that a satisfying simultaneous description of fission barriers and superdeformed states requires a better description of the single-particle spectra.

The shape and normalization of the $\beta$-delayed $\alpha$ spectrum from ${}^{11}\mathrm{Be}$ was measured by implanting ${}^{11}\mathrm{Be}$ ions in a segmented Si detector. The spectrum is found to be dominated by a well-known transition to the $3/2^{+}$ state at $E_x=9.87\mathrm{MeV}$ in ${}^{11}\mathrm{B}$. A significant increase in the observed decay strength towards the higher end of the $Q_{\beta }$ window means, however, that the $9.87\mathrm{MeV}$ state cannot alone be responsible for the transition. Using the $R$-matrix framework we find that the inclusion of an extra $3/2^{+}$ state at $E_x=11.49\left(10\right)\mathrm{MeV}$ is required to obtain a satisfactory description of the spectrum. Both states show large widths towards $\alpha$ decay, exhausting significant fractions of the Wigner limit, a typical signature of $\alpha$ clusterization. The observed Gamow-Teller strength indicates large overlaps between the two states and the ground state of ${}^{11}\mathrm{Be}$.

The ${}^{35}\mathrm{Cl}(n,p)$ and ${}^{35}\mathrm{Cl}(n,\alpha )$ cross sections at incident neutron energies between 2.42 and 2.74 MeV were measured using the Berkeley High Flux Neutron Generator. The cross sections for ${}^{35}\mathrm{Cl}(n,p)$ were more than a factor of 3 to 5 less than all of the values in the neutron absorption data libraries, while the ${}^{35}\mathrm{Cl}(n,\alpha )$ cross sections are in reasonable agreement with the data libraries. The measured energy-differential cross section is consistent with a single resonance with a width of 293(46) keV. This result suggests that, despite the high incident neutron energy, any attempt to model $(n,x)$ cross sections in the vicinity of the $N=Z=20$ shell gap requires a resolved resonance approach rather than a Hauser-Feshbach approach.

Various decay possibilities of the ${}^{216}\mathrm{Th}^{*}$ nuclear system formed via interaction of a ${}^{32}\mathrm{S}$ projectile on a ${}^{184}\mathrm{W}$ target are investigated within the collective clusterization approach of the dynamical cluster-decay model (DCM). The study is carried out at center-of-mass energies spread across the Coulomb barrier ($118.8\le E_{\mathrm{c}.\mathrm{m}.}\le 195.9\mathrm{MeV}$) by including the quadrupole deformations (${\beta }_2$ static) and optimum orientations (${\theta }_i^{\mathrm{opt}.}$) of the decay fragments. According to experimental observation, the noncompound nucleus (nCN) component competes with the compound nucleus (CN) processes [evaporation residue (ER) and fusion-fission (ff)]. The anomalous behavior of calculated fission anisotropies ($A$) for the ${}^{216}\mathrm{Th}^{*}$ nucleus indicates the presence of nCN contributions, such as quasifission (QF) and fast fission (FF). With an aim to have comprehensive analysis of CN and nCN fission mechanisms (ff, QF, FF), the role of center-of-mass energy ($E_{\mathrm{c}.\mathrm{m}.}$) and angular momentum ($\ell$) is explored in terms of various observables of DCM such as fragmentation potential, preformation probability, scattering potential, and penetrability. The fragmentation potential of the ${}^{216}\mathrm{Th}^{*}$ nucleus shows asymmetric fission mass distribution, independent of $E_{\mathrm{c}.\mathrm{m}.}$ and $\ell$ values. The capture excitation functions ${\sigma }_{\text{Cap.}}$ are obtained by adding the DCM-calculated CN (${\sigma }_{\mathrm{CN}}={\sigma }_{\mathrm{ER}}+{\sigma }_{\mathrm{ff}}$) and nCN (${\sigma }_{\mathrm{nCN}}={\sigma }_{\mathrm{QF}}+{\sigma }_{\mathrm{FF}}$) contributions. The calculated cross sections find nice agreement with the experimental data, and the evaporation residue contribution is predicted to be negligibly small. The compound nucleus fusion/formation probability $P_{\mathrm{CN}}$ is estimated as a function of $E_{\mathrm{c}.\mathrm{m}.}$, which in turn suggests that the maximum contribution from the CN channel is $\approx 66\%$. Finally, the effect of ${\beta }_2$-dynamic deformations on the various decay mechanisms of the ${}^{216}\mathrm{Th}^{*}$ nucleus is explored at highest center-of-mass energy (195.9 MeV), where nCN processes start competing with the CN decay mechanism.

The $E_{\alpha }^{\text{lab}}=0.83$ MeV resonance in the ${}^{22}\mathrm{Ne}(\alpha ,\gamma ){}^{26}\mathrm{Mg}$ reaction strongly impacts the reaction rates in the stellar temperature region crucial for the astrophysical s process. We report on a new measurement of the energy and strength of this resonance using techniques different from previous investigations. We use a blister-resistant ${}^{22}\mathrm{Ne}$-implanted target and employ $\gamma \gamma$-coincidence detection techniques. We find values for the resonance energy and strength of $E_{\alpha }^{\text{lab}}=835.2\pm 3.0$ keV and $\omega \gamma =(4.6\pm 1.2)\times {10}^{-5}$ eV, respectively. Our mean values are higher compared to previous values, although the results overlap within uncertainties. The uncertainty in the resonance energy has been significantly reduced. The spin-parity assignment, based on the present and previous work, is $J^{\pi }=$ ($0^{+}$, $1^{-}$, $2^{+}$, $3^{-}$).

Background: The density-dependent symmetry energy coefficient plays a crucial role in understanding a variety of issues in nuclear physics as well as nuclear astrophysics. It is quite interesting and crucial to determine the symmetry energy coefficient and its related observables for neutron-rich thermally fissile nuclei at finite temperature.

Purpose: We evaluate the symmetry energy coefficient, neutron pressure, and symmetry energy curvature of a finite nucleus from the corresponding quantities of infinite nuclear matter. Moreover, we correlate an effective symmetry energy coefficient and its related observables with the neutron skin thickness of neutron-rich thermally fissile nuclei at a finite temperature.

Methods: The temperature-dependent relativistic mean field model (TRMF) is used to obtain the ground and excited state bulk properties of finite nuclei and the energy density, pressure, and the symmetry energy for infinite nuclear matter. The TRMF model with FSUGarnet, IOPB-I, and NL3 parameter sets is used for the present analysis. The effective nuclear matter properties are used to estimate the corresponding quantities of finite nuclei by using the local density approximation.

Results: Nuclear bulk properties such as binding energy, quadrupole deformation, root-mean-square charge radius of the nuclei, and the equation of state and symmetry energy for infinite symmetric nuclear matter are estimated within the TRMF model. The nuclear matter observables at the local density of the nuclei serve as an input to obtain the effective symmetry energy coefficient, neutron pressure, and the symmetry energy curvature of ${}^{234,236,250}\mathrm{U}$ and ${}^{240}\mathrm{Pu}$ nuclei. The influence of temperature and density on these properties for neutron-rich thermally fissile nuclei is observed. A correlation is established between the neutron skin thickness and the neutron pressure of the nuclei.

Conclusions: The studied properties of nuclei such as effective symmetry energy coefficient, neutron pressure and symmetry energy curvature can be used in the synthesis of neutron-rich thermally fissile nuclei. The method presented here (fully microscopic) can be used further to study the properties of exotic and superheavy nuclei from the corresponding quantities of nuclear matter and vice versa.

The equation of state and fluctuations of conserved charges in a strongly interacting medium under equilibrium conditions form the baseline upon which are built various possible scenarios in relativistic heavy-ion collision experiments. Many of these quantities have been obtained in the lattice QCD framework with reliable continuum extrapolations. Recently the Polyakov–Nambu–Jona-Lasinio model has been reparametrized to some extent to reproduce quantitatively the lattice QCD equation of state at vanishing chemical potentials. The agreement was precise except at low temperatures, possibly due to inadequate representation of the hadronic degrees of freedom in the model. This disagreement was also observed for some of the fluctuations and correlations considered. Here we address this issue by introducing the effects of hadrons through the hadron resonance gas model. The total thermodynamic potential is now a weighted sum of the thermodynamic potential of the Polyakov–Nambu–Jona-Lasinio model and that of the hadron resonance gas model. We find that the equation of state and the fluctuations and correlations obtained in this hybrid model agree satisfactorily with the lattice QCD data in the low temperature regime.

Single-particle energies of the ${\mathrm{\Lambda }}_c$ charmed baryon are obtained in several nuclei from the relevant self-energy constructed within the framework of a perturbative many-body approach. Results are presented for a charmed baryon-nucleon ($Y_{c}N$) potential based on a SU(4) extension of the meson-exchange hyperon-nucleon potential $\tilde{A}$ of the Jülich group. Three different models (A, B, and C) of this interaction, which differ only on the values of the couplings of the scalar $\sigma$ meson with the charmed baryons, are considered. Phase shifts, scattering lengths, and effective ranges are computed for the three models and compared with those predicted by the $Y_{c}N$ interaction derived by Haidenbauer and Krein [Eur. Phys. A 54, 199 (2018)] from the extrapolation to the physical pion mass of recent results of the HAL QCD Collaboration. Qualitative agreement is found for two of the models (B and C) considered. Our results for ${\mathrm{\Lambda }}_c$ nuclei are compatible with those obtained by other authors based on different models and methods. We find a small spin-orbit splitting of the $p$-, $d$-, and $f$-wave states as in the case of single $\mathrm{\Lambda }$ hypernuclei. The level spacing of ${\mathrm{\Lambda }}_c$ single-particle energies is found to be smaller than that of the corresponding one for hypernuclei. The role of the Coulomb potential and the effect of the coupling of the ${\mathrm{\Lambda }}_{c}N$ and ${\mathrm{\Sigma }}_{c}N$ channels on the single-particle properties of ${\mathrm{\Lambda }}_c$ nuclei are also analyzed. Our results show that, despite the Coulomb repulsion between the ${\mathrm{\Lambda }}_c$ and the protons, even the less attractive one of our $Y_{c}N$ models (model C) is able to bind the ${\mathrm{\Lambda }}_c$ in all the nuclei considered. The effect of the ${\mathrm{\Lambda }}_{c}N\text{−}{\mathrm{\Sigma }}_{c}N$ coupling is found to be almost negligible due to the large mass difference of the ${\mathrm{\Lambda }}_c$ and ${\mathrm{\Sigma }}_c$ baryons.

Background: The first direct detection of a binary neutron star merger by the LIGO Scientific Collaboration and the Virgo Collaboration (LIGO-Virgo) [Phys. Rev. Lett. 119, 161101 (2017)] has opened the brand new era of multimessenger astronomy. This historic detection has been instrumental in providing initial constraints on the tidal polarizability (or deformability) of neutron stars. In turn, the tidal polarizability—an observable highly sensitive to stellar compactness—has been used to impose limits on stellar radii and ultimately on the underlying equation of state (EOS).

Purpose: Besides its strong dependence on the stellar compactness, the tidal polarizability is also sensitive to the second tidal Love number $k_2$. It is the main purpose of this paper to perform a detailed study of $k_2$ which, for a given compactness parameter, encodes the entire sensitivity of the tidal polarizability to the underlying equation of state. In particular, we examine the important role that the crustal component of the EOS plays in the determination of $k_2$.

Methods: A set of realistic models of the equation of state that yield an accurate description of the properties of finite nuclei support neutron stars of two solar masses and provide a Lorentz covariant extrapolation to dense matter are used to solve both the Tolman-Oppenheimer-Volkoff and the differential equations for the induced quadrupole gravitational field from which $k_2$ is extracted.

Results: Given that the tidal polarizability scales as the fifth power of the compactness parameter, a universal relation exists among the tidal polarizability and the compactness parameter that is highly insensitive to the underlying equation of state. Thus, besides an extraction of the tidal polarizabilities, a measurement of the individual stellar masses is also required to impact the mass-radius relation. However, we observe a strong sensitivity of the second Love number to the underlying equation of state—particularly to the contribution from the inner crust.

Conclusions: Although by itself the tidal polarizability cannot contribute to the determination of the mass-radius relation, future detections of binary neutron star mergers by the LIGO-Virgo Collaborations during the third observing run and beyond are poised to provide significant constraints on both the tidal polarizabilities and the masses of the individual stars, and thus ultimately on the mass-radius relation. Yet, subleading corrections to the tidal polarizability are encoded in the second Love number $k_2$, which displays a large sensitivity to the entire—crust-plus-core—equation of state.

Fission fragment mass distribution has been measured for ${}^{28}\mathrm{Si}+{}^{197}\mathrm{Au}$ reaction at bombarding energies around the Coulomb barrier ($V_b=126.5\mathrm{MeV}$). The experimental variance of the mass distribution shows a sudden change from monotonic decrease to a saturation at energies close to the Coulomb barrier and again a decreasing trend at sub-barrier energies. The variance of the mass distribution was also obtained from dynamical and statistical model calculations for the fission of a fully equilibrated compound nucleus. Both of the theoretical calculations show a monotonic change of the mass variance around the Coulomb barrier. The anomalous dependence of fission fragment mass width at energies around the barrier may be due to the dominance of the quasifission process as compared to compound nuclear fission.