Lattice simulations are the only viable way to obtain ab initio quantum chromodynamics (QCD) predictions for low energy nuclear physics. These calculations are done, however, in a finite box and therefore extrapolation is needed to get the free space results. Here, we use nuclear effective field theory (EFT), designed to provide a low energy description of QCD using baryonic degrees of freedom, to extrapolate the lattice results from finite to infinite volumes. To this end, we fit the EFT to the results calculated with nonphysical high quark masses and solve it with the stochastic variational method in both finite and infinite volumes. Moreover, we perform similar EFT calculations of the physical point and predict the finite-volume effects to be found in future lattice QCD calculations for atomic nuclei with mass number $A\le 4$.

Background: Detailed information on the low-lying dipole response in atomic nuclei along isotonic or isotopic chains is well suited to systematically investigate the structure and evolution of the pygmy dipole resonance (PDR). Moreover, the dipole strength below and around the neutron separation energy $S_n$ has impact on statistical model calculations for nucleosynthesis processes.

Purpose: The photon strength function (PSF) of ${}^{87}\mathrm{Rb}$, which is directly connected to the photoabsorption cross section, is a crucial input for statistical model calculations constraining the Maxwellian-averaged cross section (MACS) of the neutron capture of the unstable $s$-process branching-point nucleus ${}^{86}\mathrm{Rb}$. Within this work, the photoabsorption cross section is investigated.

Methods: The photoabsorption cross section of the $N=50$ nucleus ${}^{87}\mathrm{Rb}$ was determined from photon-scattering experiments via the nuclear resonance fluorescence (NRF) technique. Bremsstrahlung beams at the $\gamma \mathrm{ELBE}$ facility in conjunction with monoenergetic photon beams at the $\mathrm{HI}\gamma \mathrm{S}$ facility were used to determine the integrated cross sections $I_s$ of isolated states as well as the averaged cross section as function of the excitation energy. Decays to the ground state were disentangled from decays to first low-lying excited states. Statistical and experimental approaches for the $\gamma$-decay properties at various excitation energies were applied. The linearly polarized photon beams at $\mathrm{HI}\gamma \mathrm{S}$ provide information on the ratio of electric and magnetic type of radiation.

Results: Within this work, more than 200 ground-state decays and associated levels in ${}^{87}\mathrm{Rb}$ were identified. Moreover, transitions below the sensitivity limit of the state-by-state analysis were taken into account via a statistical approach from the bremsstrahlung data as well as model-independently from the $\mathrm{HI}\gamma \mathrm{S}$ data. The photoabsorption cross sections at various excitation energies were determined. The dipole response between 6 and 10 MeV of ${}^{87}\mathrm{Rb}$ is in agreement with assuming contributions of electric multipolarity, only.

Conclusions: The photoabsorption cross section of ${}^{87}\mathrm{Rb}$ does not contradict with the trend of decreasing $E1$ strength with increasing proton number along the $N=50$ isotonic chain but might also be associated with a constant trend. The experimental $\gamma$ decay at various excitation energies of the $\mathrm{HI}\gamma \mathrm{S}$ data supports the statistical approach but does not provide a stringent proof due to the limited sensitivity in the decay channels. The additional $E1$ strength observed in the present experiments significantly enhances the MACSs compared only to recent microscopic $\mathrm{HFB}+\mathrm{QRPA}$ (Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation) calculations using the D1M interaction. Moreover, theoretical estimations provided by the KADoNiS project could be significantly improved.

Background: Recently, variational Hartree-Fock-Bogoliubov (HFB) mean-field equations were shown to possess a mathematically well-defined zero-pairing limit, independently of the closed- or open-shell character of the system under consideration. This limit is nontrivial for open-shell systems such that HFB theory does not reduce to the Hartree-Fock (HF) formalism in all cases.

Purpose: The present work extends this analysis to finite-temperature HFB (FTHFB) theory by investigating the behavior of this more general formalism in the combined zero-temperature and zero-pairing limits.

Methods: The zero-pairing and zero-temperature limits of the FTHFB statistical density operator constrained to carry an arbitrary (integer) number of particles A on average is worked out analytically and realized numerically using a two-nucleon interaction.

Results: While the FTHFB density operator reduces to the projector corresponding to a pure HF Slater determinant for closed-shell nuclei, the FTHFB formalism does not reduce to the HF theory in all cases in the zero-temperature and zero-pairing limits, i.e., for open-shell nuclei. However, the fact that a nucleus can be of open-shell character in these joint limits is necessarily the result of some symmetry restrictions. Whenever it is the case, the nontrivial description obtained for open-shell systems is shown to depend on the order with which both limits are taken, i.e., the two limits do not commute for these systems. When the zero-temperature limit is performed first, the FTHFB density operator is demoted to a projector corresponding to a pure state made out of a linear combination of a finite number of Slater determinants with different (even) numbers of particles. When the zero-pairing limit is performed first, the FTHFB density operator remains a statistical mixture of a finite number of Slater determinants with both even and odd particle numbers. While the entropy (pairing density) is zero in the first (second) case, it does not vanish in the second (first) case in spite of the temperature (pairing) tending towards zero. The difference between both limits can have striking consequences for the (thermal) expectation values of observables. For instance, the particle-number variance does not vanish in either case and has limiting values that differ by a factor of two in both cases.

Conclusions: While in the textbook situation associated with closed-shell nuclei Hartree-Fock-Bogoliubov (finite-temperature Hartree-Fock) theory reduces to Hartree-Fock theory in the zero-pairing (zero-temperature) limit, the present analysis demonstrates that a nontrivial and unexpected limit is obtained for this formalism in open-shell systems. This result sheds a new light on certain aspects of this otherwise very well-studied many-body formalism.

We measured the total capture cross section of the ${}^{16}\mathrm{O}(n,\gamma ){}^{17}\mathrm{O}$ reaction, as well as partial cross sections leading to the ground ($J^{\pi }=5/2^{+})$ and first-excited ($J^{\pi }=1/2^{+})$ states in ${}^{17}\mathrm{O}$. The measurement was carried out at average neutron energies of 157, 349, 398, 427, 468, 498, and 556 keV by using pulsed neutrons produced via the ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$ reaction and a $\gamma$-ray detection system based on an anti-Compton NaI(Tl) spectrometer. We observed the interference effect between the $3/2^{-}$ resonance state at 4554 keV of ${}^{17}\mathrm{O}$, corresponding to a neutron energy of 411 keV in the center-of-mass system, and a nonresonant contribution in the capture process. The measured partial cross sections are in good agreement with theoretical calculations obtained taking into account the interference between the $3/2^{-}$ resonance and a nonresonant $p$-wave direct radiative capture contribution. Using the present results, together with our previous measurement, we derived the Maxwellian-averaged capture cross sections (MACS) for thermal energies between $kT=5$ and 100 keV, key quantities for $s$ process nucleosynthesis studies in massive stars.

The in-medium mass and decay width of the $\varphi$ meson in hot asymmetric strange hadronic matter is calculated using an effective Lagrangian approach for the $\varphi K\overline{K}$ interaction. The in-medium contributions of the $K\overline{K}$ loop to the $\varphi$ meson self-energy are computed by the medium modified kaon and antikaon mass, which is evaluated using the chiral SU(3) model. To deal with the ultraviolet divergence, we regularize the loop integral of self-energy with a dipole form factor, and present the results for the range of cutoff mass ${\mathrm{\Lambda }}_c=$ 1–4 GeV. In chiral model calculations, for strange matter, we find that the mass of kaons and antikaons decreases with the increase in baryonic density, whereas the finite temperature causes an increase in the mass. We observed that the in-medium $\varphi$ meson mass decreases slowly with baryonic density whereas the decay width increases rapidly. The results in the present investigation support a result in the literature which indicates a small downward shift in mass and a large broadening in the decay width. In the asymmetric strange hadronic matter, the study of the $\varphi$ mesons can be relevant for compressed strange baryonic matter. The experimental observables such as dilepton spectra can perhaps be extracted from experiments in the future Facility for Antiproton and Ion Research (FAIR) facility at GSI.

Background: A puzzle has arisen recently caused by the apparent shift in maximum deformation from the expected ${}^{66}\mathrm{Dy}$ isotopic chain to the ${}_{60}\mathrm{Nd}$ isotopic chain in the $82<N<126$ and $50<Z<82$ midshell region.

Purpose: This work provides data for two specific nuclei with odd neutron numbers, ${}^{155}\mathrm{Nd}$ and ${}^{163}\mathrm{Gd}$, useful for constraining parameters in models that seek to answer the six proton shift in maximum deformation.

Method: Data from the spontaneous fission of ${}^{252}\mathrm{Cf}$ were taken by the Gammasphere detector array at Lawrence Berkeley National Laboratory to observe the excited states of ${}^{155}\mathrm{Nd}$ and ${}^{163}\mathrm{Gd}$.

Results: The structure of ${}^{163}\mathrm{Gd}$ has been expanded with the addition of two new levels and three new $\gamma$ rays, which are found to be consistent with previously published calculations and the structure of ${}^{165}\mathrm{Dy}$. In ${}^{155}\mathrm{Nd}$, nine new levels and 12 new $\gamma$ rays are observed. The spins and parities of the previously known levels in ${}^{155}\mathrm{Nd}$ have been reassigned from a $\nu 3/2^{-}\left[521\right]$ ground state configuration to a $\nu 5/2^{+}\left[642\right]$ isomeric configuration by comparison of these newly observed levels with levels in ${}^{153}\mathrm{Nd}$ and ${}^{155}\mathrm{Sm}$.

Conclusion: Further experimentation is required to determine the energy of the newly reassigned $\nu 5/2^{+}\left[642\right]$ level in ${}^{155}\mathrm{Nd}$ with respect to the suspected $\nu 3/2^{-}\left[521\right]$ ground state. Additionally, more experiments should be conducted to further determine the structure of neutron rich nuclei, rarely produced in the spontaneous fission of ${}^{252}\mathrm{Cf}$, such as ${}^{163}\mathrm{Gd}$.

Background: Time-dependent density-functional theory (TDDFT) continues to be useful in describing a multitude of low-energy static and dynamic properties. In particular, with recent advances of computing capabilities, large-scale TDDFT simulations are possible for fission dynamics as well as isovector dipole (IVD) resonances.

Purpose: Following a previous paper [Shi, Phys. Rev. C 98, 014329 (2018)], we first present a time-dependent extension of the density-functional theory to allow for dynamic calculations based on the obtained static Hartree-Fock + Bardeen-Cooper-Schrieffer (BCS) results. Second, we apply the TDDFT + BCS method to a systematic description of the IVD resonances in the Zr, Mo, and Ru isotopes.

Methods: To benchmark the TDDFT code, we compute the strengths of IVD resonances for light nuclei using two complementary methods: TDDFT and FAM-QRPA methods. For the TDDFT results, additional benchmark calculations have been performed using the well-tested code Sky3D. In these three calculations, the important ingredients which have major influence on the results, such as time-odd potentials, boundary conditions, smoothing procedures, spurious peaks, etc., have been carefully examined.

Results: The current TDDFT and the Sky3D codes yield almost identical response functions once both codes use the same time-odd mean fields and absorbing boundary conditions. The strengths of the IVD resonances calculated using the TDDFT and FAM-QRPA methods agree reasonably well with the same position of the giant dipole resonance. Upon seeing a reasonable accuracy offered by the implemented code, we perform systematic TDDFT + BCS calculations for spherical Zr and Mo isotopes near $N=50$, where experimental data exist. For neutron-rich Zr, Mo, and Ru isotopes where shape evolution exists we predict the photoabsorption cross sections based on oblate and triaxial minima.

Conclusions: The TDDFT + BCS code provides reasonable description for IVD resonances. Applying it to the spherical Zr and Mo nuclei, a reasonable agreement with experimental data has been achieved. For neutron-rich Zr isotopes, the photoabsorption cross section based on the two coexisting minima reflects the feature of the deformation of the minima. This suggests the possibility of obtaining additional information about the ground-state deformation by comparing the GDR data with the TDDFT + BCS results.

The lifetime of the $9^{-}$ state in the rotational band based on the 4.0 s, $K^{\pi }=8^{-}$, isomeric state (${}^{178}\mathrm{Hf}^{m_1}$) from the decay of the 31-yr isomer (${}^{178}\mathrm{Hf}^{m_2}$) was determined to be 99(2) ps by means of the fast-timing technique using two ${\mathrm{LaBr}}_3$(Ce) scintillators. The $\delta (E2/M1)$ mixing ratios of the $\mathrm{\Delta }I=1\gamma$ rays depopulating levels in this band were deduced from $\gamma \text{−}\gamma$ angular correlations by using a ${}^{178}\mathrm{Hf}^{m_2}$ radioactive source located at the center of the Gammasphere HPGe detector array. The new results, together with previous spectroscopic information, provide a different way to extract the intrinsic quadrupole moment of $Q_0=6.45\left(14\right)e\text{b}$ for the ${}^{178}\mathrm{Hf}^{m_1}$ band. A possible explanation for the reduction of the ${}^{178}\mathrm{Hf}^{m_1}$ nuclear charge radius is presented.

We study in the coalescence model the collision energy dependence of (anti-)deuteron and (anti-)triton production in the most central Au + Au collisions at $\sqrt{s_{\mathrm{NN}}}=7.7$, 11.5, 19.6, 27, 39, 62.4, and 200 GeV. The needed phase-space distribution of nucleons at the kinetic freeze-out is generated from a new three-dimensional hybrid dynamical model (iebe-music) by using a smooth crossover equation of state without a QCD critical point. Our model calculations predict that the coalescence parameters of (anti-)deuteron $[B_2\left(d\right)$ and $B_2\left(\overline{d}\right)]$ decrease monotonically as the collision energy increases, and the light nuclei yield ratio $N_t{N}_p/N_d^2$ remains approximately a constant with respect to the collision energy. These calculated observables fail to reproduce the nonmonotonic behavior of the corresponding data from the STAR Collaboration. Without including any effects of the critical point in our model, our results serve as the baseline predictions for the yields of light nuclei in the search for the possible QCD critical points from the experimental beam energy scan of heavy-ion collisions.

We use a recently developed dispersive approach to compute the two-photon exchange (TPE) correction to elastic electron-proton scattering, including contributions from hadronic $J^P=1/2^{\pm }$ and $3/2^{\pm }$ resonant intermediate states below 1.8 GeV. For the transition amplitudes from the proton ground state to the resonant excited states we employ new exclusive meson electroproduction data from CLAS at $Q^2\lesssim 5{\mathrm{GeV}}^2$, and we explore the effects of both fixed and dynamic widths for the resonances. Among the resonant states, the $N\left(1520\right)3/2^{-}$ becomes dominant for $Q^2\gtrsim 2{\mathrm{GeV}}^2$, with a sign opposite to the comparably sized $\mathrm{\Delta }\left(1232\right)3/2^{+}$ contribution, leading to an overall increase in the size of the TPE correction to the cross section relative to the nucleon only contribution at higher $Q^2$ values. The results are in good overall agreement with recent $e^{+}p$ to $e^{-}p$ cross-section ratio and polarization transfer measurements, and provide compelling evidence for a resolution of the electric to magnetic form factor ratio discrepancy.

Charge balance functions reflect the evolution of charged pair correlations throughout the stages of pair production, dynamical diffusion, and hadronization in heavy-ion collisions. Microscopic modeling of these correlations in the full collision volume shows that the balance functions are sensitive to the diffusivity of light quarks when studied as functions of relative azimuthal angle. By restricting our analysis to $K^{+}{K}^{-}$ and $p\overline{p}$ pairs, we find that the diffusivity of light quarks, a fundamental property not currently well understood, can be constrained by experimental measurement.

We study, at a qualitative level, production of jet pairs in ultrarelativistic nuclear collisions. We propose a new framework for combining $k_T$ factorization and a formalism for in-medium propagation of jet particles that takes into account stochastic transverse forces as well as medium-induced radiation. This approach allows to address dijet observables accounting for exact kinematics of the initial state. Using our framework, we provide a description of $R_{AA}$ data and study azimuthal decorrelations of the produced dijets. In particular, we find that the resulting dijet observables feature behavior deviating from that of jet pairs which undergo transverse-momentum broadening following the Gaussian distribution. We interpret this behavior as a consequence of dynamics encoded in the Blaizot–Dominguez–Mehtar-Tani–Iancu equation.

We investigate the temperature dependence of the shear viscosity to entropy density ratio $\eta /s$ using a piecewise linear parametrization. To determine the optimal values of the parameters and the associated uncertainties, we perform a global Bayesian model-to-data comparison on $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV and $\mathrm{Pb}+\mathrm{Pb}$ collisions at 2.76 TeV and 5.02 TeV, using a $2+1\mathrm{D}$ hydrodynamical model with the Eskola-Kajantie-Ruuskanen-Tuominen (EKRT) initial state. We provide three new parametrizations of the equation of state (EoS) based on contemporary lattice results and hadron resonance gas, and use them and the widely used $s95p$ parametrization to explore the uncertainty in the analysis due to the choice of the equation of state. We find that $\eta /s$ is most constrained in the temperature range $T\approx 150$–220 MeV, where, for all EoSs, $0.08<\eta /s<0.23$ when taking into account the 90% credible intervals. In this temperature range the EoS parametrization has only a small $\approx 10$% effect on the favored $\eta /s$ value, which is less than the $\approx 30$% uncertainty of the analysis using a single EoS parametrization. Our parametrization of $(\eta /s)\left(T\right)$ leads to a slightly larger minimum value of $\eta /s$ than the previously used parametrizations. When we constrain our parametrization to mimic the previously used parametrizations, our favored value is reduced, and the difference becomes statistically insignificant.

Background: Most of the heavier $p$ isotopes are believed to be produced in the $\gamma$ process whose reaction path crucially depends on the proton and $\alpha$-particle penetrability at sub-Coulomb energies. Both nuclei of the samarium $p$-process chronometer, ${}^{146}\mathrm{Sm}$ and ${}^{144}\mathrm{Sm}$, are produced in the $\gamma$ process, and their initial abundance ratio is very sensitive to the $(\gamma ,n)$ and $(\gamma ,\alpha )$ branching ratio on ${}^{148}\mathrm{Gd}$. The ${}^{148}\mathrm{Gd}(\gamma ,\alpha ){}^{144}\mathrm{Sm}$ reaction rate was measured roughly 20 years ago by means of the activation technique and its surprising results triggered adjustments to the global low-energy $\alpha +\text{nucleus}$ optical-model potentials (OMPs).

Purpose: We want to take advantage of modern $\alpha$-particle spectroscopy techniques in order to constrain the controversial previous results on the ${}^{148}\mathrm{Gd}(\gamma ,\alpha ){}^{144}\mathrm{Sm}$ reaction rate.

Method: The ${}^{148}\mathrm{Gd}(\gamma ,\alpha ){}^{144}\mathrm{Sm}$ reaction rate has been determined by measuring the cross section of the reverse reaction ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$, applying the activation technique to the $\alpha$ decay of ${}^{148}\mathrm{Gd}$. Targets have been irradiated at the cyclotron of the Physikalisch-Technische Bundesanstalt in Braunschweig, Germany. The $\alpha$-particle spectroscopy has been carried out with a state-of-the-art low-background ionization chamber of the Technische Universität Dresden, Germany.

Results: Cross sections for the ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$ reaction have been measured between 10.66 and 12.66 MeV with much higher precision than in the previous measurement. The results agree with earlier results within their uncertainties. The statistical-model analysis has been carried out using the talys code on the basis of the latest parametrizations of $\alpha$-OMPs. The best reproductions of the experimental results within the statistical model have been used to calculate the reaction rates.

Conclusion: The values presented here suggest a steeper increase in the astrophysical $S$ factor towards lower center-of-mass energies. Different parametrizations of the $\alpha$-OMP were able to describe the experimental values sufficiently. Further measurements at energies below 11.0 MeV are suggested.

The excitation function for the $pd\to dp{\pi }^0$ reaction has been measured by WASA-at-COSY experiment with the aim of searching for ${}^3\mathrm{He}\text{−}\eta$ mesic nuclei. The measurement in the vicinity of $\eta$ meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the $\eta$ mesic helium decays via the formation of an intermediate ${\text{N}}^{*}$(1535) resonance. No direct signal of the $\eta$ mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the $pd\to {\left({}^3\text{He-}\eta \right)}_{\mathrm{bound}}\to dp{\pi }^0$ process. It varies between 13 nb to 24 nb for the bound state with width in the range $\mathrm{\Gamma }\in (5,50)$ MeV.

Single-nucleon knockout cross sections from fast secondary beams of the proton-drip-line nuclei ${}^9\mathrm{C}$, ${}^{13}\mathrm{O}$, and ${}^{17}\mathrm{Ne}$ on a ${}^9\mathrm{Be}$ target have been studied with emphasis on the production of resonance states. These states were identified by their invariant mass, and resonances with two-, three-, and five-body exit channels were examined. The measured cross sections for these states were compared with eikonal-model predictions using shell-model or variational Monte Carlo spectroscopic factors. The experimental yields were found to be suppressed relative to the model predictions, especially when a well-bound neutron or proton is removed. This suppression exceeds that found systematically in measured inclusive cross sections to particle-bound final states. In neutron knockout from ${}^9\mathrm{C}$ and ${}^{13}\mathrm{O}$ projectiles, this suppression of the unbound ground-state residuals yield is a factor of two to three times larger than that found in the bound final-state studies. Modifications to the structure of these systems due to coupling of the shell-model configurations to the continuum is expected to contribute to this extra suppression, especially when the final state is a near-threshold resonance. However, other considerations including the role of nuclear dynamics may be required to explain all the observed trends.

We measured the neutron capture-to-fission cross-section ratio ($\alpha$ ratio) and the capture cross section of ${}^{235}\mathrm{U}$ between 0.2 and 200 eV at the n_TOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the n_TOF ${\mathrm{BaF}}_2$ Total Absorption Calorimeter (TAC), used for detection of $\gamma$ rays, in combination with a set of micromegas detectors used as fission tagging detectors. The energy dependence of the capture cross section was obtained with help of the ${}^6\mathrm{Li}(n,t)$ standard reaction determining the n_TOF neutron fluence; the well-known integral of the ${}^{235}\mathrm{U}(n,f)$ cross section between 7.8 and 11 eV was then used for its absolute normalization. The $\alpha$ ratio, obtained with slightly higher statistical fluctuations, was determined directly, without need for any reference cross section. To perform the analysis of this measurement we developed a new methodology to correct the experimentally observed effect that the probabilities of detecting a fission reaction in the TAC and the micromegas detectors are not independent. The results of this work have been used in a new evaluation of ${}^{235}\mathrm{U}$ performed within the scope of the Collaborative International Evaluated Library Organisation (CIELO) Project, and are consistent with the ENDF/B-VIII.0 and JEFF-3.3 capture cross sections below 4 eV and above 100 eV. However, the measured capture cross section is on average 10% larger between 4 and 100 eV.

We find that the proton separation energy, $S\left(p\right)$, of ${}^{73}\mathrm{Rb}$ is $-640\left(40\right)$ keV, deduced from the observation of $\beta$-delayed ground-state protons following the decay of ${}^{73}\mathrm{Sr}$. This lower-limit determination of the proton separation energy of ${}^{73}\mathrm{Rb}$ coupled with previous upper limits from nonobservation, provides a full constraint on the mass excess with $\mathrm{\Delta }M{(}^{73}\text{Rb})=-46.01\pm 0.04$ MeV. With this new mass excess and the excitation energy of the $J^{\pi }=5/2^{-}$ isobaric-analog state ($T=3/2$) in ${}^{73}\mathrm{Rb}$, an improved constraint can be put on the mass excess of ${}^{73}\mathrm{Sr}$ using the isobaric-multiplet mass equation (IMME), and we find $\mathrm{\Delta }M{(}^{73}\text{Sr})=-31.98\pm 0.37$ MeV. These new data were then used to study the composition of ashes on accreting neutron stars following Type I x-ray bursts. Counterintuitively, we find that there should be an enhanced fraction of $A>102$ nuclei with more negative proton separation energies at the ${}^{72}\mathrm{Kr}$ rp-process waiting point. Larger impurities of heavier nuclei in the ashes of accreting neutron stars will impact the cooling models for such astrophysical scenarios.

The saturation density of nuclear matter ${\rho }_0$ is a fundamental nuclear physics property that is difficult to predict from fundamental principles. The saturation density is closely related to the interior density of a heavy nucleus, such as ${}^{208}\mathrm{Pb}$. Parity-violating electron scattering can determine the average interior weak charge and baryon densities in ${}^{208}\mathrm{Pb}$. This requires not only measuring the weak radius $R_{\mathrm{wk}}$ but also determining the surface thickness of the weak charge density $a$. We use the PREX experimental result for the weak radius of Pb and assume a 10% theoretical uncertainty in the presently unmeasured surface thickness to obtain ${\rho }_0=0.150\pm 0.010{\mathrm{fm}}^{-3}$. Here the 7% error also has contributions from the extrapolation to infinite nuclear matter. These errors can be improved with the upcoming PREX II results and with a new parity-violating electron scattering experiment, at a somewhat higher momentum transfer, to determine $a$.