We present the first triaxial beyond-mean-field study of even-even super-heavy nuclei. Calculations for the even Flerovium isotopes towards the supposed $N=184$ neutron shell closure were performed using the effective finite-range density-dependent Gogny force. They include the restoration of the particle-number and angular-momentum symmetries and the mixing of different shapes using the generator coordinate method. The importance of the $\gamma$ degree of freedom is highlighted by comparing the triaxial to axial-symmetric calculations performed within the same framework. For the three even Fl isotopes between the prolate ${}^{288}\mathrm{Fl}$ and the oblate ${}^{296}\mathrm{Fl}$ triaxial ground-state shapes are predicted, whereas axial-symmetric calculations suggest a sharp prolate-oblate shape transition between ${}^{290}\mathrm{Fl}$ and ${}^{292}\mathrm{Fl}$. A novel type of shape coexistence, namely, that between two different triaxial shapes, is predicted to occur in ${}^{290}\mathrm{Fl}$. Finally, the existence of a neutron shell closure at $N=184$ is confirmed, while no evidence is found for $Z=114$ being a proton magic number.

Mass-separated ${{}^{187}\mathrm{Ta}}_{114}$ in a high-spin isomeric state has been produced for the first time by multinucleon transfer reactions, employing an argon gas-stopping cell and laser ionization. Internal $\gamma$ rays revealed a $T_{1/2}=7.3\pm 0.9\mathrm{s}$ isomer at $1778\pm 1\mathrm{keV}$, which decays through a rotational band with perturbations associated with the approach to a prolate-oblate shape transition. Model calculations show less influence from triaxiality compared to heavier elements in the same mass region. The isomer-decay reduced $E2$ hindrance factor $f_{\nu }=27\pm 1$ supports the interpretation that axial symmetry is approximately conserved.

We show that the correlation between the elliptic momentum anisotropy $v_2$ and the average transverse momentum $[p_T]$ at fixed multiplicity in small system nuclear collisions carries information on the origin of the observed momentum anisotropy. A calculation using a hybrid IP-Glasma+music+UrQMD model that includes contributions from final state response to the initial geometry as well as initial state momentum anisotropies of the color glass condensate predicts a characteristic sign change of the correlator $\widehat{\rho }(v_2^2,[p_T])$ as a function of charged particle multiplicity in $p+\text{Au}$ and $d+\text{Au}$ collisions at $\sqrt{s}=200\mathrm{GeV}$, and $p+\mathrm{Pb}$ collisions at $\sqrt{s}=5.02\mathrm{TeV}$. This sign change is absent in calculations without initial state momentum anisotropies. The model further predicts a qualitative difference between the centrality dependence of $\widehat{\rho }(v_2^2,[p_T])$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s}=200\mathrm{GeV}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s}=5.02\mathrm{TeV}$, with only the latter showing a sign change in peripheral events. Predictions for $\mathrm{O}+\mathrm{O}$ collisions at different collision energy show a similar behavior. Experimental observation of these distinct qualitative features of $\widehat{\rho }(v_2^2,[p_T])$ in small and large systems would constitute strong evidence for the presence and importance of initial state momentum anisotropies predicted by the color glass condensate effective theory.

$\beta$-delayed one-proton emissions of ${}^{22}\mathrm{Si}$, the lightest nucleus with an isospin projection ${\mathrm{T}}_z=-3$, are studied with a silicon array surrounded by high-purity germanium detectors. Properties of $\beta$-decay branches and the reduced transition probabilities for the transitions to the low-lying states of ${}^{22}\mathrm{Al}$ are determined. Compared to the mirror $\beta$ decay of ${}^{22}\mathrm{O}$, the largest value of mirror asymmetry in low-lying states by far, with $\delta =209(96)$, is found in the transition to the first $1^{+}$ excited state. Shell-model calculation with isospin-nonconserving forces, including the $T=1$, $J=2$, 3 interaction related to the $s_{1/2}$ orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the $s_{1/2}$ orbit, can reproduce the observed data well and consistently explain the observation that a large $\delta$ value occurs for the first but not for the second $1^{+}$ excited state of ${}^{22}\mathrm{Al}$. Our results, while supporting the proton-halo structure in ${}^{22}\mathrm{Al}$, might provide another means to identify halo nuclei.

We propose a new Monte Carlo method called the pinhole trace algorithm for ab initio calculations of the thermodynamics of nuclear systems. For typical simulations of interest, the computational speedup relative to conventional grand-canonical ensemble calculations can be as large as a factor of one thousand. Using a leading-order effective interaction that reproduces the properties of many atomic nuclei and neutron matter to a few percent accuracy, we determine the location of the critical point and the liquid-vapor coexistence line for symmetric nuclear matter with equal numbers of protons and neutrons. We also present the first ab initio study of the density and temperature dependence of nuclear clustering.

The $\beta$ decay of ${}^{208}\mathrm{Hg}$ into the one-proton hole, one neutron-particle ${{}_{81}{}^{208}\mathrm{Tl}}_{127}$ nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the $N>126$, $Z<82$ quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the $Q_{\beta }$ window, only three negative parity states are populated directly in the $\beta$ decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden $\beta$ decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neutron capture process. Furthermore, the observation of the parity changing $0^{+}\to 0^{-}\beta$ decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators.

We present the first ab initio calculations for open-shell nuclei past the tin isotopic line, focusing on Xe isotopes as well as doubly magic Sn isotopes. We show that, even for moderately hard interactions, it is possible to obtain meaningful predictions and that the ${\mathrm{NNLO}}_{\mathrm{sat}}$ chiral interaction predicts radii and charge density distributions close to the experiment. We then make a new prediction for ${}^{100}\mathrm{Sn}$. This paves the way for ab initio studies of exotic charge density distributions at the limit of the present ab initio mass domain, where experimental data is becoming available. The present study closes the gap between the largest isotopes reachable by ab initio methods and the smallest exotic nuclei accessible to electron scattering experiments.

The cascading 3.21 and 4.44 MeV electric quadrupole transitions have been observed from the Hoyle state at 7.65 MeV excitation energy in ${}^{12}\mathrm{C}$, excited by the ${}^{12}\mathrm{C}(p,p^{\prime })$ reaction at 10.7 MeV proton energy. From the proton-$\gamma \text{−}\gamma$ triple coincidence data, a value of ${\mathrm{\Gamma }}_{\mathrm{rad}}/\mathrm{\Gamma }=6.2(6)\times {10}^{-4}$ was obtained for the radiative branching ratio. Using our results, together with ${\mathrm{\Gamma }}_{\pi }^{E0}/\mathrm{\Gamma }$ from Eriksen et al. [Phys. Rev. C 102, 024320 (2020)] and the currently adopted ${\mathrm{\Gamma }}_{\pi }(E0)$ values, the radiative width of the Hoyle state is determined as ${\mathrm{\Gamma }}_{\mathrm{rad}}=5.1(6)\times {10}^{-3}\mathrm{eV}$. This value is about 34% higher than the currently adopted value and will impact models of stellar evolution and nucleosynthesis.

The ${}^{80}\mathrm{Ge}$ structure was investigated in a high-statistics $\beta$-decay experiment of ${}^{80}\mathrm{Ga}$ using the GRIFFIN spectrometer at TRIUMF-ISAC through $\gamma$, $\beta \text{−}e$, $e\text{−}\gamma$, and $\gamma \text{−}\gamma$ spectroscopy. No evidence was found for the recently reported $0_2^{+}$ 639-keV level suggested as evidence for low-energy shape coexistence in ${}^{80}\mathrm{Ge}$. Large-scale shell model calculations performed in ${}^{78,80,82}\mathrm{Ge}$ place the $0_2^{+}$ level in ${}^{80}\mathrm{Ge}$ at 2 MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in ${}^{80}\mathrm{Ge}$.

The neutron capture cross sections of several unstable nuclides acting as branching points in the $s$ process are crucial for stellar nucleosynthesis studies. The unstable ${}^{171}\mathrm{Tm}$ ($t_{1/2}=1.92\mathrm{yr}$) is part of the branching around mass $A\sim 170$ but its neutron capture cross section as a function of the neutron energy is not known to date. In this work, following the production for the first time of more than 5 mg of ${}^{171}\mathrm{Tm}$ at the high-flux reactor Institut Laue-Langevin in France, a sample was produced at the Paul Scherrer Institute in Switzerland. Two complementary experiments were carried out at the neutron time-of-flight facility ($n\text{\_}\text{TOF}$) at CERN in Switzerland and at the SARAF liquid lithium target facility at Soreq Nuclear Research Center in Israel by time of flight and activation, respectively. The result of the time-of-flight experiment consists of the first ever set of resonance parameters and the corresponding average resonance parameters, allowing us to make an estimation of the Maxwellian-averaged cross sections (MACS) by extrapolation. The activation measurement provides a direct and more precise measurement of the MACS at 30 keV: 384(40) mb, with which the estimation from the $n\text{\_}\text{TOF}$ data agree at the limit of 1 standard deviation. This value is 2.6 times lower than the JEFF-3.3 and ENDF/B-VIII evaluations, 25% lower than that of the Bao et al. compilation, and 1.6 times larger than the value recommended in the KADoNiS (v1) database, based on the only previous experiment. Our result affects the nucleosynthesis at the $A\sim 170$ branching, namely, the ${}^{171}\mathrm{Yb}$ abundance increases in the material lost by asymptotic giant branch stars, providing a better match to the available pre-solar SiC grain measurements compared to the calculations based on the current JEFF-3.3 model-based evaluation.

The electron-capture decay followed by a prompt fission process was searched for in the hitherto unknown most neutron-deficient Md isotope with mass number 244. Alpha decay with $\alpha$-particle energies of 8.73–8.86 MeV and with a half-life of ${0.30}_{-0.09}^{+0.19}\mathrm{s}$ was assigned to ${}^{244}\mathrm{Md}$. No fission event with a similar half-life potentially originating from spontaneous fissioning of the short-lived electron-capture decay daughter ${}^{244}\mathrm{Fm}$ was observed, which results in an upper limit of 0.14 for the electron-capture branching of ${}^{244}\mathrm{Md}$. Two groups of fission events with half-lives of ${0.9}_{-0.3}^{+0.6}\mathrm{ms}$ and $5_{-2}^{+3}\mathrm{ms}$ were observed. The ${0.9}_{-0.3}^{+0.6}\mathrm{ms}$ activity was assigned to originate from the decay of ${}^{245}\mathrm{Md}$. The origin of eight fission events resulting in a half-life of $5_{-2}^{+3}\mathrm{ms}$ could not be unambiguously identified within the present data while the possible explanation has to invoke previously unseen physics cases.

The recent RIKEN experiment on the quenched $g_A$ in the superallowed Gamow-Teller transition from ${}^{100}\mathrm{Sn}$ indicates the role of scale anomaly encoded in the anomalous dimension ${\beta }^{\prime }$ of the gluonic stress tensor Tr ${\mathrm{G}}_{\mu \nu }^2$. This observation provides support to the notion of hidden scale symmetry emerging by strong nuclear correlations with an infrared (IR) fixed point realized—in the chiral limit—in the Nambu-Goldstone mode. We suggest there is an analogy in the way scale symmetry manifests in a nuclear medium to the continuity from the unitarity limit at low density (in light nuclei) to the dilaton limit at high density (in compact stars). In between the limits, say, at normal nuclear matter density, the symmetry is not visible, hence hidden.

We study the equation of state of symmetric nuclear matter at zero temperature over a wide range of densities using two complementary theoretical approaches. At low densities, up to twice nuclear saturation density, we compute the energy per particle based on modern nucleon-nucleon and three-nucleon interactions derived within chiral effective field theory. For higher densities, we derive for the first time constraints in a Fierz-complete setting directly based on quantum chromodynamics using functional renormalization group techniques. We find remarkable consistency of the results obtained from both approaches as they come together in density and the natural emergence of a maximum in the speed of sound $c_S$ at supranuclear densities. The presence of this maximum appears tightly connected to the formation of a diquark gap. Notably, this maximum is observed to exceed the asymptotic value $c_S^2=1/3$ while its exact position in terms of the density cannot yet be determined conclusively.

We report the first observation of two wobbling bands in ${}^{183}\mathrm{Au}$, both of which were interpreted as the transverse wobbling (TW) band but with different behavior of their wobbling energies as a function of spin. It increases (decreases) with spin for the positive (negative) parity configuration. The crucial evidence for the wobbling nature of the bands, dominance of the $E2$ component in the $\mathrm{\Delta }I=1$ transitions between the partner bands, is provided by the simultaneous measurements of directional correlation from the oriented states ratio and the linear polarization of the $\gamma$ rays. Particle rotor model calculations with triaxial deformation reproduce the experimental data well. A value of spin, $I_m$, has been determined for the observed TW bands below which the wobbling energy increases and above which it decreases with spin. The nucleus ${}^{183}\mathrm{Au}$ is, so far, the only nucleus in which both the increasing and the decreasing parts are observed and thus gives the experimental evidence of the complete transverse wobbling phenomenon.

Hydrodynamic attractors have recently gained prominence in the context of early stages of ultrarelativistic heavy-ion collisions at the RHIC and LHC. We critically examine the existing ideas on this subject from a phase space point of view. In this picture the hydrodynamic attractor can be seen as a special case of the more general phenomenon of dynamical dimensionality reduction of phase space regions. We quantify this using principal component analysis. Furthermore, we adapt the well known slow-roll approximation to this setting. These techniques generalize easily to higher dimensional phase spaces, which we illustrate by a preliminary analysis of a dataset describing the evolution of a five-dimensional manifold of initial conditions immersed in a 16-dimensional representation of the phase space of the Boltzmann kinetic equation in the relaxation time approximation.

Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of ${}^{239}\mathrm{Pu}$ in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and $\gamma$-emission probabilities for the ${}^{240}\mathrm{Pu}({}^4\mathrm{He},{}^4{\mathrm{He}}^{\prime })$ surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected $\gamma$-ray transitions, we measure the $\gamma$-emission probability. This enlarges the applicability of the surrogate-reaction method.

We establish the existence of a far-from-equilibrium attractor in weakly coupled gauge theory undergoing one-dimensional Bjorken expansion. We demonstrate that the resulting far-from-equilibrium evolution is insensitive to certain features of the initial condition, including both the initial momentum-space anisotropy and initial occupancy. We find that this insensitivity extends beyond the energy-momentum tensor to the detailed form of the one-particle distribution function. Based on our results, we assess different procedures for reconstructing the full one-particle distribution function from the energy-momentum tensor along the attractor and discuss implications for the freeze-out procedure used in the phenomenological analysis of ultrarelativistic nuclear collisions.

Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient $\widehat{q}$ in a dense QCD medium. The spatial gradient of $\widehat{q}$ perpendicular to the propagation direction can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the transverse gradient and path length of a propagating parton as shown by numerical solutions of the Boltzmann transport in the simplified form of a drift-diffusion equation. In high-energy heavy-ion collisions, this asymmetry with respect to a plane defined by the beam and trigger particle (photon, hadron, or jet) with a given orientation relative to the event plane is shown to be closely related to the transverse position of the initial jet production in full event-by-event simulations within the linear Boltzmann transport model. Such a gradient tomography can be used to localize the initial jet production position for more detailed study of jet quenching and properties of the quark-gluon plasma along a given propagation path in heavy-ion collisions.

We performed the first direct mass measurements of neutron-rich scandium, titanium, and vanadium isotopes around the neutron number 40 at the RIKEN RI Beam Factory using the time-of-flight magnetic-rigidity technique. The atomic mass excesses of ${}^{58-60}\mathrm{Sc}$, ${}^{60-62}\mathrm{Ti}$, and ${}^{62-64}\mathrm{V}$ were measured for the first time. The experimental results show that the two-neutron separation energies in the vicinity of ${}^{62}\mathrm{Ti}$ increase compared to neighboring nuclei. This shows that the masses of Ti isotopes near $N=40$ are affected by the Jahn-Teller effect. Therefore, a development of Jahn-Teller stabilization appears below the Cr isotopes, and the systematics in Sc, Ti, and V isotopes suggest that ${}^{62}\mathrm{Ti}$ is located close to the peak of the Jahn-Teller effect.