The correlation between the mean transverse momentum of outgoing particles, $\langle p_t\rangle$, and the magnitude of anisotropic flow, $v_n$, has recently been measured in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN Large Hadron Collider, as a function of the collision centrality. We confirm the previous observation that event-by-event hydrodynamics predicts a correlation between $v_n$ and $\langle p_t\rangle$ that is similar to that measured in data. We show that the magnitude of this correlation can be directly predicted from the initial condition of the hydrodynamic calculation, for $n=2,3$, if one replaces $v_n$ by the corresponding initial-state anisotropy, ${\varepsilon }_n$, and $\langle p_t\rangle$ by the total energy per unit rapidity of the fluid at the beginning of the hydrodynamic expansion.

We propose the skewness of mean transverse momentum $\langle p_t\rangle$ fluctuations as a fine probe of hydrodynamic behavior in relativistic nuclear collisions. We describe how the skewness of the $\langle p_t\rangle$ distribution can be analyzed experimentally, and we use hydrodynamic simulations to predict its value. We predict, in particular, that $\langle p_t\rangle$ fluctuations have positive skew, which is significantly larger than if particles were emitted independently. We elucidate the origin of this result by deriving generic formulas relating the fluctuations of $\langle p_t\rangle$ to the fluctuations of the early-time thermodynamic quantities. We postulate that the large positive skewness of $\langle p_t\rangle$ fluctuations is a generic prediction of hydrodynamic models.

Background: The nucleosynthesis of heavy nuclei is affected by the reaction rates of radiative capture reactions. Many of the astrophysical relevant rates cannot be obtained from experiments but are obtained from theoretical models. The $\gamma$-decay widths that are derived from radiative strength functions are one of the key nuclear physics input parameters in those calculations. The explicit study of $\gamma$-ray strength functions has been thoroughly addressed in the last decade and various methods have been established to extract the dipole strength in atomic nuclei.

Purpose: The investigation of primary $\gamma$-ray transitions from the ${}^{93}\mathrm{Nb}(p,\gamma ){}^{94}\mathrm{Mo}$ reaction allows deducing the $\gamma$-ray strength function in ${}^{94}\mathrm{Mo}$. The results are compared to results obtained using other techniques and the impact of level densities, excitation mechanism, and excitation energy will be thoroughly investigated.

Method: The proton beam was delivered by the 10 MV FN-Tandem accelerator located at the Institute for Nuclear Physics at the University of Cologne, Germany. By means of in-beam $\gamma$-ray spectroscopy the intensity of primary $\gamma$ rays is determined. Additionally, the first generation $\gamma$-ray intensity is deduced from the secondary $\gamma$ rays using their branching and the coincidence detection efficiency. Absolute $\gamma$-ray strength function values as well as relative values using the ratio method will be extracted.

Results: Numerous states in ${}^{94}\mathrm{Mo}$ at excitation energies above 3 MeV have been identified for the first time and their decay behavior has been studied. We disentangled the effects of $M1$ and $E1$ radiation for the $\gamma$-ray emission channel in ${}^{94}\mathrm{Mo}$ and extracted strength function curves for both radiation types. Our results are in good agreement with experimental results using the Oslo method and photoinduced experiments as well as with recent theoretical quasiparticle random-phase approximation (QRPA) calculations. An enhancement of the $\gamma$-ray strength below the neutron separation energy was found that is most likely of $E1$ character. In addition, a significant increase of the dipole strength at low $\gamma$-ray energies was found which is most likely due to $M1$ strength.

Conclusion: Radiative proton capture reactions are a well-suited tool to study the $\gamma$-ray strength function in atomic nuclei. From the intensity of primary $\gamma$-ray transitions as well as from secondary $\gamma$-rays, information about the radiative dipole strength can be extracted. The $\gamma$-ray emission seems to be independent of the excitation energy in the studied mass and energy range. Detailed knowledge about the intrinsic properties of the nuclear states is very important and their uncertainties affect the uncertainty of the extracted $\gamma$-ray strength functions heavily.

We study the $a$, $b$, and $c$ coefficients of the isobaric-multiplet mass equation (IMME) using a macroscopic-microscopic approach developed by P. Möller and collaborators [At. Data Nucl. Data Tables 59, 185 (1995); At. Data Nucl. Data Tables 109-110, 1 (2016)]. We show that already the macroscopic part of the finite-range liquid-drop model (FRLDM) describes the general trend of the $a$ and $b$ coefficients relatively well, while the staggering behavior of $b$ coefficients for doublets and quartets can be understood in terms of the difference of average proton and neutron pairing energies. The sets of isobaric masses, predicted by the full macroscopic-microscopic approaches, are used to explore the general trends of IMME coefficients up to $A=100$. We conclude that while the agreement for $a$ coefficients is quite satisfactory, the full approaches have less sensitivity to predict the IMME $b$ and $c$ coefficients in detail. The best set of theoretical $b$ coefficients, as given by the modified macroscopic part of the FRLDM, is used to predict masses of proton-rich nuclei based on the known experimental masses of neutron-rich mirror partners, and subsequently to investigate their one- and two-proton separation energies in proton-rich nuclei up to the $A=100$ region. The estimated position of the proton drip line is in fair agreement with known experimental data. These masses are important for simulations of the astrophysical $rp$ process.

We introduce a two-particle, two-hole mixed configuration scheme to fit $E2$ strengths for the $0\leftrightarrow 2, 2\leftrightarrow 4$, and $4\leftrightarrow 6$ transitions in ${}^{194}\mathrm{Pt}$. The interaction includes two sets of pairing operators, {$S^{\pm }\left(t\right),S^0\left(t\right)$} $(t=s,d)$. Solutions within this framework are used to analyze energy spectra, $E2$ transitions, and band-mixing features of the model. The results confirm that mixing is small and similar for $J=2$, 4, and 6, with the calculated energies and transition matrix elements in excellent agreement with experimental data.

Within the framework of the dinuclear system model, the contributions of the constituent parts of the driving potentials in different orientation configurations in the ${}^{86}\mathrm{Kr}+{}^{166}\mathrm{Er}$ reaction are investigated. The Coulomb potential plays a predominant role in the change of driving potential among different configurations with mass number $A_1=52–200$. In the region of $A_1<52$ and $A_1>200$, the effects of the nuclear potential increased significantly. This work also studied the multinucleon transfer process of ${}^{204}\mathrm{Hg}+{}^{232}\mathrm{Th}$ in tip-to-tip and side-to-side configurations to produce unknown neutron-rich isotopes with $Z=62–75$. In the ${}^{204}\mathrm{Hg}+{}^{232}\mathrm{Th}$ reaction, the tip-to-tip configuration accounts for the main contribution to produce unknown neutron-rich isotopes with $Z=62–75$ because of the “inverse” quasifission process. The optimal incident energy is 678.1 MeV. Considering the experimental conditions provided by the experiments, there are 29 unknown isotopes whose production rate is greater than one count per day. Especially, the production rates per day of ${}^{179}\mathrm{Ho}, {}^{181,182}\mathrm{Er}, {}^{182,183,184}\mathrm{Tm}, {}^{186}\mathrm{Yb}, {}^{189}\mathrm{Lu}, {}^{191,192}\mathrm{Hf}$, and ${}^{195}\mathrm{Ta}$ are 21, 25, 13, 701, 1217, 29, 94, 29, 102, 29, and 20, respectively. The reaction of ${}^{204}\mathrm{Hg}+{}^{232}\mathrm{Th}$ at 678.1 MeV is a potential candidate to produce new neutron-rich nuclei with $Z=62–75$.

Background: The isoscalar $pn$ pair is expected to emerge in nuclei having the similar proton and neutron numbers but there is no clear experimental evidence for it.

Purpose: We aim to clarify the correspondence between the $pn$ pairing strength in many-body calculation and the triple differential cross section (TDX) of proton-induced deuteron knockout ($p,pd$) reaction on ${}^{16}\mathrm{O}$.

Methods: The radial wave function of the isoscalar $pn$ pair with respect to the center of ${}^{16}\mathrm{O}$ is calculated with the energy density functional (EDF) approach and is implemented in the distorted wave impulse approximation framework. The $pn$ pairing strength $V_0$ in the EDF calculation is varied and the corresponding change in the TDX is investigated.

Results: A clear $V_0$ dependence of the TDX is found for the ${}^{16}\mathrm{O}(p,pd){}^{14}\mathrm{N}(1_2^{+}$) at 101.3 MeV. The nuclear distortion is found to make the $V_0$ dependence stronger.

Conclusions: Because of the clear $V_0$-TDX correspondence, the ($p,pd$) reaction will be a promising probe for the isoscalar $pn$ pair in nuclei. For quantitative discussion, further modification of the description of the reaction process will be necessary.

The suppression of high-$p_{\perp }$ particles is one of the main signatures of parton energy loss during its passing through the quark-gluon plasma medium, and is reasonably reproduced by different theoretical models. However, a decisive test of the reliability of a certain energy-loss mechanism, apart from its path length, is its temperature dependence. Despite its importance and comprehensive dedicated studies, this issue is still awaiting more stringent constraints. To this end, we here propose a novel observable to extract the temperature-dependence exponent of a high-$p_{\perp }$ particle's energy loss, based on $R_{AA}$. More importantly, by combining analytical arguments, full-fledged numerical calculations, and comparison with experimental data, we argue that this observable is highly suited for testing the long-standing $\mathrm{\Delta }E/E\propto L^2{T}^3$ paradigm. The anticipated significant reduction of experimental errors will allow direct extraction of temperature dependence, by considering different centrality pairs in $A+A$ collisions (irrespective of the nucleus size) in the high-$p_{\perp }$ region. Overall, our results imply that this observable, which reflects the underlying energy-loss mechanism, is very important to distinguish between different theoretical models.

The triaxial nature of low-lying rotational bands of ${}^{166}\mathrm{Er}$ is presented from the viewpoint of the Bohr Hamiltonian and from that of many-fermion calculations by the Monte Carlo shell model and the constrained Hartree-Fock method with projections. A recently proposed novel picture of those bands suggests definite triaxial shapes of those bands, in contrast to the traditional view with the prolate ground-state band and the $\gamma$-vibrational excited band. Excitation level energies and $E2$ transitions can be described well by the Bohr Hamiltonian and by the many-fermion approaches, where rather rigid triaxiality plays vital roles, although certain fluctuations occur in shell-model wave functions. Based on the potential energy surfaces with the projections, we show how the triaxial rigidity appears and what the softness of the triaxiality implies. The excitation to the so-called double $\gamma$-phonon state is discussed briefly.

The initial energy density produced in heavy ion collisions can be estimated with the Bjorken energy density formula after choosing a proper formation time $\tau {}_{\mathrm{F}}$. However, the Bjorken formula breaks down at low energies because it neglects the finite nuclear thickness. Here we include both the finite time duration and finite longitudinal extension of the initial energy production. When $\tau {}_{\mathrm{F}}$ is not too much smaller than the crossing time of the two nuclei, our results are similar to those from a previous study that only considers the finite time duration. In particular, we find that at low energies the initial energy density has a much lower maximum value but evolves much longer than the Bjorken formula, while at large-enough $\tau {}_{\mathrm{F}}$ and/or high-enough energies our result approaches the Bjorken formula. We also find a qualitative difference in that our maximum energy density ${\epsilon }^{\max }$ at $\tau {}_{\mathrm{F}}=0$ is finite, while the Bjorken formula diverges as $1/\tau {}_{\mathrm{F}}$ and the previous result diverges as $ln(1/\tau {}_{\mathrm{F}})$ at low energies but as $1/\tau {}_{\mathrm{F}}$ at high energies. Furthermore, our solution of the energy density approximately satisfies a scaling relation. As a result, the $\tau {}_{\mathrm{F}}$ dependence of ${\epsilon }^{\max }$ determines the $A$ dependence, and the weaker $\tau {}_{\mathrm{F}}$ dependence of ${\epsilon }^{\max }$ in our results at low energies means a slower increase of ${\epsilon }^{\max }$ with $A$.

Mutual entrainment effects in hot neutron-proton superfluid mixtures are studied in the framework of the self-consistent nuclear energy-density functional theory. The local mass currents in homogeneous or inhomogeneous nuclear systems, which we derive from the time-dependent Hartree-Fock-Bogoliubov equations at finite temperatures, are shown to have the same formal expression as the ones we found earlier in the absence of pairing at zero temperature. Analytical expressions for the entrainment matrix are obtained for application to superfluid neutron-star cores. Results are compared to those obtained earlier using Landau's theory. Our formulas, valid for arbitrary temperatures and currents, are applicable to various types of functionals including the Brussels-Montreal series for which unified equations of state have been already calculated, thus, laying the ground for a fully consistent microscopic description of superfluid neutron stars.

Elliott's SU(3) model is at the basis of the shell-model description of rotational motion in atomic nuclei. We demonstrate that SU(3) symmetry can be realized in a truncated shell-model space if constructed in terms of a sufficient number of collective $S$, $D$, $G$,...pairs (i.e., with angular momentum zero, two, four,...) and if the structure of the pairs is optimally determined either by a conjugate-gradient minimization method or from a Hartree-Fock intrinsic state. We illustrate the procedure for six protons and six neutrons in the $pf$ ($sdg$) shell and exactly reproduce the level energies and electric quadrupole properties of the ground-state rotational band with $SDG$ ($SDGI$) pairs. The $SD$-pair approximation without significant renormalization, on the other hand, cannot describe the full SU(3) collectivity. A mapping from Elliott's fermionic SU(3) model to systems with $s$, $d$, $g$,... bosons provides insight into the existence of a decoupled collective subspace in terms of $S$, $D$, $G$,... pairs.

We present a comprehensive analysis of the deuteron charge and quadrupole form factors based on the latest two-nucleon potentials and charge-density operators derived in chiral effective field theory. The single- and two-nucleon contributions to the charge density are expressed in terms of the proton and neutron form factors, for which the most up to date empirical parametrizations are employed. By adjusting the fifth-order short-range terms in the two-nucleon charge-density operator to reproduce the world data on the momentum-transfer dependence of the deuteron charge and quadrupole form factors, we predict the values of the structure radius and the quadrupole moment of the deuteron: $r_{\mathrm{str}}=1.{9729}_{-0.0012}^{+0.0015}\mathrm{fm},Q_d=0.{2854}_{-0.0017}^{+0.0038}{\mathrm{fm}}^2.$ A comprehensive and systematic analysis of various sources of uncertainty in our predictions is performed. Following the strategy advocated in our recent publication [Filin, Baru, Epelbaum, Krebs, Möller, and Reinert, Phys. Rev. Lett. 124, 082501 (2020)], we employ the extracted structure radius together with the accurate atomic data for the deuteron-proton mean-square charge radii difference to update the determination of the neutron charge radius, for which we find $r_n^2=-0.{105}_{-0.006}^{+0.005}{\text{fm}}^2$. Given the observed rapid convergence of the deuteron form factors in the momentum-transfer range of $Q\simeq 1–2.5{\mathrm{fm}}^{-1}$, we argue that this intermediate energy domain is particularly sensitive to the details of the nucleon form factors and can be used to test different parametrizations.

We study the $\alpha$-decay energies ($Q_{\alpha }$) taken from the Atomic Mass Evaluation 2016 within the valence correlation scheme (VCS). A linear trajectory of $\alpha$-decay energies, derived from the VCS for nucleon separation energies, is put forward in terms of $\pm \alpha N_{\mathrm{p}}\mp \beta N_{\mathrm{n}}(N_{\mathrm{p}}$ and $N_{\mathrm{n}}$ are the valence proton and neutron numbers, respectively, counted as particles or holes from the nearest shell closure). It is applicable well to all available $\alpha$ emitters including even-even, odd-$A$, and odd-odd nuclei. This relationship can be understood via the Taylor expansion method based on the Bethe-Weizsäcker (BW) mass formula, leading to the recognition on the origin of the $\alpha$-decay energy to some extent as well. In fact, the present study can not only reconfirm the similar linear dependence of nucleon separation energies in the VCS, but also exhibit a regular pattern of $\alpha$-decay energy and provide a reasonable estimation on unknown $Q_{\alpha }$ values.

Background: About 50% of heavy elements are produced by the slow neutron capture process ($s$ process) in stars. The element gallium is mostly produced during the weak $s$ process in massive stars.

Purpose: Our activation at $k_{\mathrm{B}}T\approx 25$ keV is the first experiment in a series of activation and time-of-flight measurements on ${}^{69}\mathrm{Ga}$ and ${}^{71}\mathrm{Ga}$ relevant for astrophysics.

Methods: We activated ${}^{69}\mathrm{Ga}$ and ${}^{71}\mathrm{Ga}$ with a neutron distribution that corresponds to a quasistellar distribution with $k_{\mathrm{B}}T=25\mathrm{keV}$ at the Joint Research Centre (JRC), Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction ${}^7\mathrm{Li}(\mathrm{p},\mathrm{n})$. The produced activity was measured via the $\gamma$ emission by the decaying product nuclei by high-purity germanium detectors.

Results: We provide spectrum-averaged cross sections (SACS) and ratios of the cross sections ${\sigma }_{\text{Ga}}/{\sigma }_{\text{Au}}$ for the neutron spectrum of the activation. We obtain values of ${\sigma }_{69\mathrm{Ga},\mathrm{SACS}}=(186\pm 12)\mathrm{mb}$ and ${\sigma }_{71\mathrm{Ga},\mathrm{SACS}}=(112\pm 7)\mathrm{mb}$, and cross-section ratios of ${\sigma }_{\text{69Ga}}/{\sigma }_{\text{Au}}=0.29\pm 0.02$ and ${\sigma }_{\text{71Ga}}/{\sigma }_{\text{Au}}=0.17\pm 0.01$.

Conclusions: Our data disagree with the available evaluated data provided by KADoNiS v0.3, our cross-section ratio is about 20% higher for ${}^{69}\mathrm{Ga}$ and about 20% lower for ${}^{71}\mathrm{Ga}$.

We present new equations of state for applications in core-collapse supernova and neutron star merger simulations. We start by introducing an effective mass parametrization that is fit to recent microscopic calculations up to twice saturation density. This is important to capture the predicted thermal effects, which have been shown to determine the proto–neutron star contraction in supernova simulations. The parameter range of the energy-density functional underlying the equation of state is constrained by chiral effective field theory results at nuclear densities as well as by functional renormalization group computations at high densities based on QCD. We further implement observational constraints from measurements of heavy neutron stars, the gravitational wave signal of GW170817, and from the recent NICER results. Finally, we study the resulting allowed ranges for the equation of state and for properties of neutron stars, including the predicted ranges for the neutron star radius and maximum mass.

We apply a recently developed momentum-space semilocally regularized chiral potential to the ${}^2\mathrm{H}$ and ${}^3\mathrm{He}$ photodisintegration processes and to the (anti)neutrino induced deuteron breakup reactions. Specifically, the differential cross section, the photon analyzing power, and the final proton polarization have been calculated for deuteron photodisintegration at photon energies of 30 and 100 MeV. For ${}^3\mathrm{He}$ photodisintegration, predictions for the semi-inclusive and exclusive differential cross sections are presented for photon energies up to 120 MeV. The total cross section is calculated for (anti)neutrino disintegration of the deuteron for (anti)neutrino energies below 200 MeV. Predictions based on the Argonne V18 potential and on an older chiral force with regularization applied in coordinate space are used for comparison. Using the fifth-order chiral nucleon-nucleon potential supplemented with dominant contributions from the sixth order allows us to obtain converged predictions for observables in the investigated reactions. Our results based on the newest semilocal chiral potentials show even smaller cutoff dependence and a somewhat faster convergence for the considered electroweak observables than the previously reported ones with a coordinate-space regulator, which make them a promising tool to study electroweak processes.

The dipole strength of the nuclide ${}^{66}\mathrm{Zn}$ was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.5 and 13.4 MeV at the $\gamma \mathrm{ELBE}$ facility as well as using quasimonoenergetic and linearly polarized photon beams of 30 energies within the range of 4.3 to 9.9 MeV at the $\mathrm{HI}\gamma \mathrm{S}$ facility. A total of 128 $J=1$ states were identified, among them 9 with $1^{+}$ and 86 with $1^{-}$ assignments. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical $\gamma$-ray cascades. As a result, the photoabsorption cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model. The experimental $M1$ strengths from resolved $1^{+}$ states are compared with results of large-scale shell-model calculations.

The role of dense-matter properties in the tidal deformability of a cold nonaccreted neutron star is further investigated. Using the set of Brussels-Montreal unified equations of state, we have computed the gravitoelectric Love numbers $k_{\ell }$ and the gravitomagnetic Love numbers $j_{\ell }$ up to $\ell =5$. Their relative importance and their sensitivity to the symmetry energy and the neutron-matter stiffness are numerically assessed. Their impact on the phase of the gravitational-wave signal emitted by binary neutron star inspirals is also discussed.