The Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium of the Ludwig-Maximilians-Universität München and the Technische Universität München (Garching, Germany), was used to study the ${}^{208}\mathrm{Pb}\left(\mathit{p},{\mathit{p}}^{\prime }\right)$, ${}^{206,207,208}\mathrm{Pb}\left(\mathit{d},\mathit{p}\right)$, and ${}^{208}\mathrm{Pb}\left(\mathit{d},{\mathit{d}}^{\prime }\right)$ reactions. One hundred fifty-one states at $E_x<6.20\mathrm{MeV}$ in ${}^{208}\mathrm{Pb}$ are identified and spin and parity assigned. Four states are newly identified and new spins and/or parities are assigned to 25 states. Tentative spin assignments are done to five states at $5.90<E_x<6.10\mathrm{MeV}$. Nearly 50 levels below $E_x=6.20\mathrm{MeV}$ listed by the Nuclear Data Sheets as of 2007 are recognized to be nonexistent or doubly placed. The schematic shell model describing one-particle–one-hole configurations without residual interaction is extended by including two-particle–two-hole configurations. The number of configurations thus predicted at $E_x<6.20\mathrm{MeV}$ nearly agrees with the number of states identified. Several states with dominant two-particle–two-hole configurations are identified. New isobaric analog resonances in ${}^{209}\mathrm{Bi}$ with two-particle–one-hole structure are discovered at $E^{\mathrm{res}}=17.6\mathrm{MeV}$. The excitation energies of 70 states with unnatural parity at $E_x<6.20\mathrm{MeV}$ are found to agree within about 200 keV with one-particle–one-hole configurations predicted by the extended schematic shell model. In contrast, the excitation energies of about 20 natural parity states are more than 0.5 MeV lower than predicted, demonstrating the residual interaction among the configurations to be much larger for natural parity than for unnatural parity.

Background: Multinucleon transfer (MNT) and quasifission (QF) processes are dominant processes in low-energy collisions of two heavy nuclei. They are expected to be useful to produce neutron-rich unstable nuclei. Nuclear dynamics leading to these processes depends sensitively on nuclear properties such as deformation and shell structure.

Purpose: We elucidate reaction mechanisms of MNT and QF processes involving heavy deformed nuclei, making detailed comparisons between microscopic time-dependent Hartree-Fock (TDHF) calculations and measurements for the ${}^{64}\text{Ni}+{}^{238}\text{U}$ reaction.

Methods: Three-dimensional Skyrme-TDHF calculations are performed. Particle-number projection method is used to evaluate MNT cross sections from the TDHF wave function after collision.

Results: Fragment masses, total kinetic energy (TKE), scattering angle, contact time, and MNT cross sections are investigated for the ${}^{64}\text{Ni}+{}^{238}\text{U}$ reaction. They show reasonable agreements with measurements. At small impact parameters, collision dynamics depends sensitively on the orientation of deformed ${}^{238}\text{U}$. In tip (side) collisions, we find a larger (smaller) TKE and a shorter (longer) contact time. In tip collisions, we find a strong influence of quantum shells around ${}^{208}\text{Pb}$.

Conclusions: It is confirmed that the TDHF calculations reasonably describe both MNT and QF processes in the ${}^{64}\text{Ni}+{}^{238}\text{U}$ reaction. Analyses of this system indicate the significance of the nuclear structure effects such as deformation and quantum shells in nuclear reaction dynamics at low energies.

The transition strengths of the first-excited $2^{+}$ states and deformation lengths of the nuclei ${}^{30}\mathrm{Ne}$ and ${}^{36}\mathrm{Mg}$ were determined via Coulomb- and nuclear-force-dominated inelastic scattering at intermediate energies. Beams of these exotic nuclei were produced at the RIKEN Radioactive Isotope Beam Factory and were incident on lead and carbon targets at energies above 200 MeV/$u$. Absolute excitation cross sections on the lead target yielded reduced transition probabilities of 0.0277(79) and 0.0528(121) $e^2{\mathrm{b}}^2$, while the measurements with the carbon target revealed nuclear deformation lengths of ${\delta }_N=1.98$(11) and 1.93(11) fm for ${}^{30}\mathrm{Ne}$ and ${}^{36}\mathrm{Mg}$, respectively. Corresponding quadrupole deformation parameters of ${\beta }_2\sim 0.5$ from the two probes were found comparable in magnitude, showing no indication for a reduction in deformation along isotopic and isotonic chains from ${}^{32}\mathrm{Mg}$ towards the neutron drip-line. Comparisons to shell-model calculations illustrate the importance of neutron excitations across the $N=20$ shell for ${}^{30}\mathrm{Ne}$ and suggest that shallow maximums of collectivity may occur around $N=22$ and 24 along the neon and magnesium isotopic chains, respectively.

The technique of accelerator mass spectrometry (AMS), offering a complementary tool for sensitive studies of key reactions in nuclear astrophysics, was applied for measurements of the ${}^{13}\mathrm{C}\left(n,\gamma \right){}^{14}\mathrm{C}$ and the ${}^{14}\mathrm{N}\left(n,p\right){}^{14}\mathrm{C}$ cross sections, which act as a neutron poison in $s$-process nucleosynthesis. Solid samples were irradiated at Karlsruhe Institute of Technology with neutrons closely resembling a Maxwell-Boltzmann distribution for $kT=25$ keV, and also at higher energies between $E_n=123$ and 182 keV. After neutron irradiation the produced amount of ${}^{14}\mathrm{C}$ in the samples was measured by AMS at the Vienna Environmental Research Accelerator (VERA) facility. For both reactions the present results provide important improvements compared to previous experimental data, which were strongly discordant in the astrophysically relevant energy range and missing for the comparably strong resonances above 100 keV. For ${}^{13}\mathrm{C}\left(n,\gamma \right)$ we find a four times smaller cross section around $kT=25$ keV than a previous measurement. For ${}^{14}\mathrm{N}\left(n,p\right)$, the present data suggest two times lower cross sections between 100 and 200 keV than had been obtained in previous experiments and data evaluations. The effect of the new stellar cross sections on the $s$ process in low-mass asymptotic giant branch stars was studied for stellar models of $2M_{\odot }$ initial mass, and solar and $1/{10}^{\mathrm{th}}$ solar metallicity.

Spectroscopy of a ${}_{\mathrm{\Lambda }}{}^{10}\mathrm{Be}$ hypernucleus was carried out at JLab Hall C using the $(e,e^{\prime }{K}^{+})$ reaction. A new magnetic spectrometer system (SPL+HES+HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of $\sim 0.78$ MeV (FWHM). The well-calibrated spectrometer system of the present experiment using $p(e,e^{\prime }{K}^{+})\mathrm{\Lambda },{\mathrm{\Sigma }}^0$ reactions allowed us to determine the energy levels; and the binding energy of the ground-state peak (mixture of $1^{-}$ and $2^{-}$ states) was found to be $B_{\mathrm{\Lambda }}=8.55\pm 0.07\left(\mathrm{stat}.\right)\pm 0.11\left(\mathrm{sys}.\right)$ MeV. The result indicates that the ground-state energy is shallower than that of an emulsion study by about 0.5 MeV which provides valuable experimental information on the charge symmetry breaking effect in the $\mathrm{\Lambda }N$ interaction.

We introduce an event-by-event perturbative-QCD + saturation + hydro (“EKRT”) framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading-order perturbative QCD using a saturation conjecture to control soft-particle production and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries against the LHC and RHIC measurements. We compare also the computed event-by-event probability distributions of relative fluctuations of elliptic flow and event-plane angle correlations with the experimental data from $\mathrm{Pb}+\mathrm{Pb}$ collisions at the LHC. We show how such a systematic multienergy and multiobservable analysis tests the initial-state calculation and the applicability region of hydrodynamics and, in particular, how it constrains the temperature dependence of the shear viscosity-to-entropy ratio of QCD matter in its different phases in a remarkably consistent manner.

Recent work has provided the means to rigorously determine properties of superhadronic matter from experimental data through the application of broad scale modeling of high-energy nuclear collisions within a Bayesian framework. These studies have provided unprecedented statistical inferences about the physics underlying nuclear collisions by virtue of simultaneously considering a wide range of model parameters and experimental observables. Notably, this approach has been used to constrain both the QCD equation of state and the shear viscosity above the quark-hadron transition. Although the inferences themselves have a clear meaning, the complex nature of the relationships between model parameters and observables has remained relatively obscure. We present here a novel extension of the standard Bayesian Markov-chain Monte Carlo approach that allows for the quantitative determination of how inferences of model parameters are driven by experimental measurements and their uncertainties. This technique is then applied in the context of heavy-ion collisions in order to explore previous results in greater depth. The resulting relationships are useful for identifying model weaknesses, prioritizing future experimental measurements, and, most importantly, developing an intuition for the roles that different observables play in constraining our understanding of the underlying physics.

We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at $\sqrt{s_{\mathit{NN}}}=2.76$ TeV as a function of collision centrality and the average transverse momentum of the pair $k_{\mathrm{T}}$. Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged one-dimensional radii are extracted. The radii decrease with $k_{\mathrm{T}}$, following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with ${\langle d{N}_{\mathrm{ch}}/d\eta \rangle }^{1/3}$. This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller $\sqrt{s_{\mathit{NN}}}$, a decrease in the ratio $R_{\mathrm{out}}/R_{\mathrm{side}}$ is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider.

${}^{82}\mathrm{Rb}$ is a positron-emitting isotope used in cardiac positron emission tomography (PET) imaging which has been reported to deliver a significantly lower effective radiation dose than analogous imaging isotopes like ${}^{201}\mathrm{Tl}$ and ${}^{99m}\mathrm{Tc}$ sestamibi. High-quality $\beta$-decay data are essential to accurately appraise the total dose received by the patients. A source of ${}^{82}\mathrm{Sr}$ was produced at the Brookhaven Linac Isotope Producer (BLIP), transported to Argonne National Laboratory, and studied with the Gammasphere facility. Significant revisions have been made to the level scheme of ${}^{82}\mathrm{Kr}$ including 12 new levels, 50 new $\gamma$-ray transitions, and the determination of many new spin assignments through angular correlations. These new high-quality data allow a precise reappraisal of the $\beta$-decay strength function and thus the consequent dose received by patients.

Background: Besides their intrinsic nuclear-structure value, nuclear mass models are essential for astrophysical applications, such as $r\text{-process}$ nucleosynthesis and neutron-star structure.

Purpose: To overcome the intrinsic limitations of existing “state-of-the-art” mass models through a refinement based on a Bayesian neural network (BNN) formalism.

Methods: A novel BNN approach is implemented with the goal of optimizing mass residuals between theory and experiment.

Results: A significant improvement (of about 40%) in the mass predictions of existing models is obtained after BNN refinement. Moreover, these improved results are now accompanied by proper statistical errors. Finally, by constructing a “world average” of these predictions, a mass model is obtained that is used to predict the composition of the outer crust of a neutron star.

Conclusions: The power of the Bayesian neural network method has been successfully demonstrated by a systematic improvement in the accuracy of the predictions of nuclear masses. Extension to other nuclear observables is a natural next step that is currently under investigation.

We use the finite-amplitude method for computing charge-changing Skyrme–quasiparticle random-phase approximation (QRPA) transition strengths in axially-deformed nuclei together with a modern Skyrme energy-density functional to fit several previously unconstrained parameters in the charge-changing time-odd part of the functional. With the modified functional we then calculate rates of ${\beta }^{-}$ decay for all medium-mass and heavy even-even nuclei between the valley of stability and the neutron drip line. We fit the Skyrme parameters to a limited set of $\beta$-decay rates, a set of Gamow-Teller resonance energies, and a set of spin-dipole resonance energies, in both spherical and deformed nuclei. Comparison to available experimental $\beta$-decay rates shows agreement at roughly the same level as in other global QRPA calculations. We estimate the uncertainty in our rates all the way to the neutron drip line through a construction that extrapolates the errors of known $\beta$-decay rates in nuclei with intermediate $Q$ values to less stable isotopes with higher $Q$ values.

We present a new measurement of the branching ratio for the decay of ${}^{14}\mathrm{O}$ to the ground state of ${}^{14}\mathrm{N}$. The experimental result, ${\lambda }_0/{\lambda }_{\mathrm{total}}=(4.934\pm 0.040(\mathrm{stat}.)\pm 0.061(\mathrm{syst}.))\times {10}^{-3}$, is significantly smaller than previous determinations of this quantity. The new measurement allows an improved determination of the partial half-life for the superallowed $0^{+}\to 0^{+}$ Fermi decay to the ${}^{14}\mathrm{N}$ first excited state, which impacts the determination of the $V_{ud}$ element of the CKM matrix. With the new measurement in place, the corrected ${}^{14}\mathrm{O}\mathcal{F}t$ value is in good agreement with the average $\mathcal{F}t$ for other superallowed $0^{+}\to 0^{+}$ Fermi decays.

We address the problem of the post-prior equivalence in inclusive breakup reactions induced by weakly bound nuclei. The problem is studied within the distorted-wave Born approximation (DWBA) model of Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)]. The post and prior formulas obtained in this model are briefly recalled and applied to several breakup reactions induced by deuterons and ${}^6\mathrm{Li}$ projectiles, to test their actual numerical equivalence. The different contributions of the prior-form formula are also discussed. A critical comparison with the prior-form DWBA model of Udagawa and Tamura [Phys. Rev. C 24, 1348 (1981)] is also provided.

We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients—quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level—are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for ${}^{62}\mathrm{Ni},{}^{98,100}\mathrm{Ru},{}^{106,108}\mathrm{Pd},{}^{110,112,114}\mathrm{Cd}$, and ${}^{118,120,122}\mathrm{Te}$ within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.

The information on the symmetry energy and its density dependence is deduced by comparing the available data on the electric dipole polarizability ${\alpha }_D$ of ${}^{68}\text{Ni}$, ${}^{120}\text{Sn}$, and ${}^{208}\text{Pb}$ with the predictions of the random-phase approximation, using a representative set of nuclear energy density functionals. The calculated values of ${\alpha }_D$ are used to validate different correlations involving ${\alpha }_D$, the symmetry energy at the saturation density $J$, the corresponding slope parameter $L$, and the neutron skin thickness $\mathrm{\Delta }{r}_{np}$, as suggested by the droplet model. A subset of models that reproduce simultaneously the measured polarizabilities in ${}^{68}\text{Ni}$, ${}^{120}\text{Sn}$, and ${}^{208}\text{Pb}$ are employed to predict the values of the symmetry energy parameters at saturation density and $\mathrm{\Delta }{r}_{np}$. The resulting intervals are $J=30–35$ MeV, $L=20–66$ MeV; and the values for $\mathrm{\Delta }{r}_{np}$ in ${}^{68}\text{Ni}$, ${}^{120}\text{Sn}$, and ${}^{208}\text{Pb}$ are in the ranges 0.15–0.19, 0.12–0.16, and 0.13–0.19 fm, respectively. The strong correlation between the electric dipole polarizabilities of two nuclei is instrumental to predict the values of electric dipole polarizabilities in other nuclei.

Levels in ${}^{17}\text{O}$ affect the astrophysical $s$ process in two opposite ways. The neutron production is enhanced by resonances in the ${}^{13}\text{C}(\alpha ,n){}^{16}\text{O}$ reaction at excitation energies around 7 MeV in ${}^{17}\text{O}$, and the number of available neutrons is reduced by low-lying resonances in the ${}^{16}\text{O}(n,\gamma ){}^{17}\text{O}$ reaction corresponding to levels in ${}^{17}\text{O}$ with excitation energies of $4–5\text{MeV}$. The present work uses the ${}^{19}\text{F}(d,\alpha ){}^{17}\text{O}$ reaction to determine absolute widths of the relevant levels in ${}^{17}\text{O}$. The results improve the uncertainties of the previously adopted values and resolve a discrepancy between recent studies for the $1/2^{+}$ level close to the threshold of the ${}^{13}\text{C}(\alpha ,n){}^{16}\text{O}$ reaction. In addition, improved excitation energies and widths are provided for several states in ${}^{17}\text{O}$ up to excitation energies close to 8 MeV.

Background: Nuclear pasta phases, present in the inner crust of neutron stars, are associated with nucleonic matter at subsaturation densities arranged in regular shapes. Those complex phases, residing in a layer which is approximately 100-m thick, impact many features of neutron stars. Theoretical quantum-mechanical simulations of nuclear pasta are usually carried out in finite three-dimensional boxes assuming periodic boundary conditions. The resulting solutions are affected by spurious finite-size effects.

Purpose: To remove spurious finite-size effects, it is convenient to employ twist-averaged boundary conditions (TABC) used in condensed matter, nuclear matter, and lattice quantum chromodynamics applications. In this work, we study the effectiveness of TABC in the context of pasta phase simulations within nuclear density functional theory.

Methods: We perform Skyrme-Hartree-Fock calculations in three dimensions by implementing Bloch boundary conditions. The TABC averages are obtained by means of Gauss-Legendre integration over twist angles.

Results: We benchmark the TABC for a free nucleonic gas and apply it to simple cases such as the rod and slab phases, as well as to more elaborate P-surface and gyroidal phases.

Conclusions: We demonstrate that by applying TABC reliable results can be obtained from calculations performed in relatively small volumes. By studying various contributions to the total energy, we gain insights into pasta phases in mid-density range.

A quantum reaction approach to low-energy collisions of weakly bound few-body nuclei, based on the time-dependent wave-packet method, is presented in detail. In contrast to existing models that use this perspective, the approach separates the complete and incomplete fusion from the total fusion. Calculations performed within a one-dimensional model with two degrees of freedom for ${}^6\text{Li}+{}^{209}\text{Bi}$ at energies around the Coulomb barrier demonstrate that converged reliable excitation functions for total, incomplete, and complete fusion can be obtained with this type of approach.

A novel theory of radiative electron capture in second forbidden non-unique transition is applied to reanalyze experimental data obtained previously for the decay of ${}^{59}\mathrm{Ni}$. The measured $\gamma$ spectrum is shown to be distorted at the high-energy end, presenting the first direct evidence for the virtual $\beta \text{−}\gamma$ transition through the excited state in ${}^{59}\mathrm{Co}$. The complete theoretical predictions, including both the direct and the virtual decay channels, as well as the interference between them, reproduce very well the experimental spectrum. The virtual nuclear component amounts to about 4% of the total $\gamma$ intensity.

This work presents a direct measurement of the ${}^{96}\mathrm{Ru}(p,\gamma ){}^{97}\mathrm{Rh}$ cross section via a novel technique using a storage ring, which opens opportunities for reaction measurements on unstable nuclei. A proof-of-principle experiment was performed at the storage ring ESR at GSI in Darmstadt, where circulating ${}^{96}\mathrm{Ru}$ ions interacted repeatedly with a hydrogen target. The ${}^{96}\mathrm{Ru}(p,\gamma ){}^{97}\mathrm{Rh}$ cross section between 9 and 11 MeV has been determined using two independent normalization methods. As key ingredients in Hauser-Feshbach calculations, the $\gamma$-ray strength function as well as the level density model can be pinned down with the measured ($p,\gamma$) cross section. Furthermore, the proton optical potential can be optimized after the uncertainties from the $\gamma$-ray strength function and the level density have been removed. As a result, a constrained ${}^{96}\mathrm{Ru}(p,\gamma ){}^{97}\mathrm{Rh}$ reaction rate over a wide temperature range is recommended for $p$-process network calculations.