The evolution of shapes and low-energy shape coexistence is analyzed in neutron-deficient Nd and Sm nuclei, using a five-dimensional quadrupole collective Hamiltonian (5DCH). Deformation energy surfaces, calculated with the relativistic energy density functional PC-PK1 and a separable finite-range pairing interaction, exhibit a transition from spherical shapes near $N=80$, to $\gamma$-soft shapes, and to prolate deformed minima in lighter isotopes. The corresponding 5DCH model calculation, based on the self-consistent mean-field potentials, reproduces the empirical isotopic trend of characteristic collective observables, and predicts significantly different deformations for the first two $0^{+}$ states in the $N=74$ isotones ${}^{134}\mathrm{Nd}$ and ${}^{136}\mathrm{Sm}$. In addition to bands based on the triaxial $\gamma$-soft ground state, in excellent agreement with data, the occurrence of a low-energy rotational band is predicted, built on the prolate deformed ($\beta \sim 0.4$) excited state $0_2^{+}$.

Background: While a large-scale shell model calculation (LSSM) is a powerful model to describe the nuclear spectroscopic information, it requires a huge amount of computational resources. As an efficient approximation framework to the LSSM, we have introduced the variational Monte Carlo (VMC) method [T. Mizusaki et al., Phys. Rev. C 85, 021301(R) (2012)]. However, this framework was applicable only to even-mass nuclei.

Purpose: We aim to extend the VMC method for better precision and to make it applicable to odd-mass nuclei.

Methods: We investigate two kinds of extensions for the VMC method with the Pfaffian in the nuclear shell-model calculations. One is the extension to odd-mass nuclei, for which we find a new Pfaffian expression of the VMC matrix elements. The other is the extension of the variation after angular-momentum projection.

Results: We successfully implement the full angular-momentum projected trial state into the VMC method, which can provide us with precise yrast energies. We also find a unique characteristic, namely that this angular-momentum projection in the VMC can be even “approximately” performed.

Conclusions: A unified VMC framework with the variation after projection is given both for even and odd-mass nuclei. The approximate angular-momentum projection is useful not only for efficient computation but also for precise estimation of the yrast energies through the energy-variance extrapolation.

We construct a multiplicity distribution characterized by large factorial cumulants (integrated correlation functions) from a simple combination of two ordinary multiplicity distributions characterized by small factorial cumulants. We find that such a model, which could be interpreted as representing two event classes, reproduces the preliminary data for the proton cumulants measured by the STAR collaboration at 7.7 GeV very well. This model then predicts very large values for the fifth and sixth order factorial cumulants, which can be tested in experiment.

We measured direct photons for $p_T<5\mathrm{GeV}/c$ in minimum bias and 0%–40% most-central events at midrapidity for $\mathrm{Cu}+\mathrm{Cu}$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$. The $e^{+}{e}^{-}$ contribution from quasireal direct virtual photons has been determined as an excess over the known hadronic contributions in the $e^{+}{e}^{-}$ mass distribution. A clear enhancement of photons over the binary scaled $p+p$ fit is observed for $p_T<4\mathrm{GeV}/c$ in $\mathrm{Cu}+\mathrm{Cu}$ data. The $p_T$ spectra are consistent with the $\mathrm{Au}+\mathrm{Au}$ data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the $p+p$ baseline are $285\pm 53\left(\mathrm{stat}\right)\pm 57\left(\mathrm{syst}\right)\mathrm{MeV}/c$ and $333\pm 72\left(\mathrm{stat}\right)\pm 45\left(\mathrm{syst}\right)\mathrm{MeV}/c$ for minimum bias and 0%–40% most-central events, respectively. The rapidity density, $dN/dy$, of photons demonstrates the same power law as a function of $d{N}_{\mathrm{ch}}/d\eta$ observed in $\mathrm{Au}+\mathrm{Au}$ at the same collision energy.

We investigate the charge-dependent flow induced by magnetic and electric fields in heavy-ion collisions. We simulate the evolution of the expanding cooling droplet of strongly coupled plasma hydrodynamically, using the iEBE-VISHNU framework, and add the magnetic and electric fields as well as the electric currents they generate in a perturbative fashion. We confirm the previously reported effect of the electromagnetically induced currents [Gursoy et al., Phys. Rev. C 89, 054905 (2014)], that is a charge-odd directed flow $\mathrm{\Delta }{v}_1$ that is odd in rapidity, noting that it is induced by magnetic fields (à la Faraday and Lorentz) and by electric fields (the Coulomb field from the charged spectators). In addition, we find a charge-odd $\mathrm{\Delta }{v}_3$ that is also odd in rapidity and that has a similar physical origin. We furthermore show that the electric field produced by the net charge density of the plasma drives rapidity-even charge-dependent contributions to the radial flow $\langle p_T\rangle$ and the elliptic flow $\mathrm{\Delta }{v}_2$. Although their magnitudes are comparable to the charge-odd $\mathrm{\Delta }{v}_1$ and $\mathrm{\Delta }{v}_3$, they have a different physical origin, namely the Coulomb forces within the plasma.

The γ-emission probability of the 66.73 keV line in the decay of ${}^{171}\mathrm{Tm}$ has been experimentally determined using γ spectrometry and inductively coupled mass spectrometry. Using a set of two reference sources, namely ${}^{60}\mathrm{Co}$ as primary standard and ${}^{44}\mathrm{Ti}/{}^{44}\mathrm{Sc}$ in secular equilibrium as secondary standard, we were able to deduce the detection efficiency at 66.73 keV of the used γ-spectrometry setup. The emission probability of the 66.73 keV γ transition in the decay of ${}^{171}\mathrm{Tm}$ has been determined afterwards with a set of three radioisotopically pure ${}^{171}\mathrm{Tm}$ samples to be 0.159(5)%.

A number of fission products possess isomeric states which have a nuclear spin significantly different from that of the ground state. The yield ratio of these states following fission is influenced by the angular momentum present in the fissioning system. The ${}^{134m,134}\mathrm{Sb}$ yield ratio had not been previously measured in the spontaneous fission of ${}^{252}\mathrm{Cf}$; however, it had previously been observed to favor the ($7^{-}$) isomer over the ($0^{-}$) ground state in ${}^{235}\mathrm{U}(n_{th},f$) and ${}^{232}\mathrm{Th}$(25 MeV $p,f$). Using a mass-separated beam of low-energy ${}^{134,134m}\mathrm{Sb}$ ions produced by ${}^{252}\mathrm{Cf}$ spontaneous fission at the CARIBU facility, $\beta$ particles and $\gamma$ rays were detected using the SATURN/X-Array decay station to determine the fission-yield ratio and $\beta$-decay half-lives. The ${}^{134m}\mathrm{Sb}$ to ${}^{134}\mathrm{Sb}$ fission yield was determined to be $2.03\pm 0.05$ and the half-lives of ${}^{134m}\mathrm{Sb}$ and ${}^{134}\mathrm{Sb}$ were found to be $9.87\pm 0.08$ s and $0.674\pm 0.004$ s, respectively. These results represent the first isomeric yield ratio measurement for this nucleus, and improved measurements of the ${}^{134}\mathrm{Sb}$ ground state and the ${}^{134m}\mathrm{Sb}$ isomer half-lives.

In this paper, we extend the framework of the improved version of a simplified method to take into account the tensor contribution $\left(i\mathrm{SMT}\right)$ and propose the AQCM-T, a tensor version of the antisymmetrized quasicluster model (AQCM). Although the AQCM-T is phenomenological, we can treat the ${}^3\mathrm{S}\text{−}{}^3\mathrm{D}$ coupling in the deuteronlike $T=0NN$ pair induced by the tensor interaction in a very simplified way, which allows us to proceed to heavier nuclei. Using the AQCM-T and the V2m interaction, where the triplet-even channel of the Volkov no. 2 interaction is weakened to 60% so as to reproduce the binding energy of ${}^4\mathrm{He}$ after including the tensor term of a realistic interaction, the significant tensor contribution in ${}^4\mathrm{He}$ is shown, which is almost comparable to the central interaction, where the $D$ state mixes by 8% to the major $S$ state. The AQCM-T with the new interaction is also applied to ${}^8\mathrm{Be}$. It is found that the tensor suppression gives a significant contribution to the short-range repulsion between two $\alpha$ clusters.

The knowledge of prompt fission $\gamma$-ray emission has been of major interest in reactor physics for a few years. Only few experimental spectra were published until now for fast-neutron-induced fission, and measurements would be also valuable in order to improve our understanding of the fission process. A simple experimental method was used to measure the first prompt fission $\gamma$-ray spectra up to 10 MeV. In this approach, the $\gamma$ rays are measured with a bismuth germanate (BGO) detector which offers two significant advantages with respect to other $\gamma$-ray detectors: a high peak-to-total ratio and a high efficiency. The prompt fission neutrons are rejected by the time-of-flight technique between the BGO detector and a fission trigger given by a fission chamber. Prompt fission $\gamma$-ray spectra were measured for 1.6 ± 0.1, 5.1 ± 0.2 and 15.0 ± 0.6 MeV neutron-induced fission on ${}^{238}\mathrm{U}$ at the CEA, DAM, DIF Van de Graaff accelerator; average multiplicity and mean photon energy per fission were deduced from the spectra.

Distributions of the largest fragment charge are studied using the ALADIN data on fragmentation of ${}^{197}\mathrm{Au}$ projectiles at relativistic energies. The statistical measures skewness and kurtosis of higher-order fluctuations provide a robust indication of the transition point, linked to a phase transition in the thermodynamic limit. Extensive comparisons with predictions of a bond percolation model corroborate the high accuracy of this model in reproducing the distributions as well as the whole fragmentation pattern as represented by the measured charge correlations. In analogy to percolation, the pseudocritical and critical points are identified in the fragmentation data. Questions concerning the distinction between different models and between first- and second-order phase transitions are discussed.

Background: The precompound emission process in light-ion fusion interactions has been a topic of considerable interest to nuclear physicists for many years. Although widespread theoretical and experimental efforts have been devoted to understand the reaction dynamics of precompound emission, no systematic study has been carried out to determine the driving input parameters in such reactions.

Purpose: The importance of this study has large impact on reaction dynamics. In order to get parameters describing the precompound emission, excitation functions have been measured by using an $\alpha$-particle beam on ${}^{141}\mathrm{Pr}$ target nuclei. Further, a sensitive analysis of excitation functions has been performed to investigate the systematics of the precompound process with mass number of target nuclei.

Method: The off-line $\gamma$-ray-spectrometry-based activation technique has been used for the measurement of the excitation functions. The presently measured excitation functions on the system $\alpha +{}^{141}\mathrm{Pr}$ (and those experimental values taken from literature on the $\alpha +{}^{51}\mathrm{V}, \alpha +{}^{55}\mathrm{Mn}, \alpha +{}^{93}\mathrm{Nb}, \alpha +{}^{121}\mathrm{Sb}$, and $\alpha +{}^{123}\mathrm{Sb}$ systems) have been analyzed within the framework of compound and precompound emissions by using model code alice.

Results: The analysis performed by using code alice with the same set of precompound parameters indicates that the experimentally measured excitation functions could be reproduced only when the precompound emission, simulated theoretically, has been taken into account. The influence of various important precompound parameters of the code alice with their physically accepted values for these systems has been judged and a systematics on precompound emission process is achieved with mass number of the target nuclei.

Conclusions: The developed systematics for $\alpha$-induced reactions on target nuclei ${}^{51}\mathrm{V}, {}^{55}\mathrm{Mn}, {}^{93}\mathrm{Nb}, {}^{121}\mathrm{Sb}, {}^{123}\mathrm{Sb}$, and ${}^{141}\mathrm{Pr}$ indicates that the precompound process is governed by the excitation energy available to the nucleons at the surface the composite systems. Furthermore, mass number of the target nuclei may also play an important role in precompound process at low projectile energies.

Background: Observation of lepton number violation via detection of neutrinoless double $\beta$ decay requires that the neutrino be a Majorana particle. If the neutrino is a Dirac particle, a potential lepton-number violating process is neutrinoless quadruple $\beta$ decay. Only a few nuclei can undergo neutrinoless quadruple $\beta$ decay; one of these nuclei is ${}^{150}\mathrm{Nd}$.

Purpose: This study yields the first half-life limit of the neutrinoless quadruple $\beta$ decay to the excited $0_1^{+}$ state of ${}^{150}\mathrm{Gd}$.

Methods: We searched for neutrinoless quadruple $\beta$ decay events to excited final states of ${}^{150}\mathrm{Gd}$ by detecting the deexcitation $\gamma$ rays of the daughter nucleus in coincidence. These $\gamma$ rays have energies of 569.031 and 638.050 keV, and are emitted in coincidence through a $0_1^{+}\to 2_1^{+}\to 0_{gs}^{+}$ transition.

Results: The enriched ${\mathrm{Nd}}_2{\mathrm{O}}_3$ sample consisted of $40.33\pm 0.02$ g ${}^{150}\mathrm{Nd}$ and was observed for 642.8 days at the Kimballton Underground Research Facility. A half-life limit for the decay to the $0_1^{+}$ state of ${}^{150}\mathrm{Gd}$ was found to be $T_{1/2}>1.76\times {10}^{20}$ years (90% CL).

Conclusions: We report the first search for this decay to excited final states. Though the predicted half-life of this decay is many orders of magnitudes larger, constraining this value experimentally is vital to check for potential enhancements to the decay rate.

In this paper, the in-medium $NN\to N\mathrm{\Delta }$ cross section is calculated in the framework of the one-boson exchange model by including the isovector mesons, i.e., $\delta$ and $\rho$ mesons. Due to the isospin exchange in the $NN\to N\mathrm{\Delta }$ process, the vector self-energies of the outgoing particles are modified relative to the incoming particles in isospin asymmetric nuclear matter, and it leads to the effective energies of the ingoing $NN$ pair being different from the outgoing $N\mathrm{\Delta }$ pair. This effect is investigated in the calculation of the in-medium $NN\to N\mathrm{\Delta }$ cross section. With the corrected energy conservation, the cross sections of the ${\mathrm{\Delta }}^{++}$ and ${\mathrm{\Delta }}^{+}$ channels are suppressed, and the cross sections of the ${\mathrm{\Delta }}^0$ and ${\mathrm{\Delta }}^{-}$ channels are enhanced relative to the results obtained without properly considering the potential-energy changes. Our results further confirm the dependence of medium correction factor $R={\sigma }_{NN\to N\mathrm{\Delta }}^{*}/{\sigma }_{NN\to N\mathrm{\Delta }}^{\mathrm{free}}$ on the charge state of $NN\to N\mathrm{\Delta }$ especially around the threshold energy, but the isospin splitting of medium correction factor $R$ becomes weak at high beam energies.

We explore giant resonance spectra and low-lying dipole strength in the Ni and Sn chains from proton-rich to very neutron-rich isotopes, relevant in astrophysical reaction chains. For the theoretical description we employ the random-phase approximation plus many-body effects through a phonon-coupling model with optimized selection of phonons. The nuclear force is based on the Skyrme-Hartree-Fock energy functional carried consistently through all steps of modeling. The main effect of phonon coupling is a broadening of the spectral distributions (collisional width). This broadening is particularly dramatic for low-lying dipole strength in very neutron-rich nuclei delivering there a qualitative change of the spectra.

Nuclear pasta topology is an essential ingredient to determine transport properties in the inner crust of neutron stars. We perform semiclassical molecular dynamics simulations of nuclear pasta for proton fractions $Y_p=0.30$ and $Y_p=0.40$ near one-third of nuclear saturation density, $n=0.05{\mathrm{fm}}^{-3}$, at a temperature $T=1.0\mathrm{MeV}$. Our simulations are, to our knowledge, the largest nuclear pasta simulations to date and contain up to $3276800$ nucleons in the $Y_p=0.30$ and $819200$ nucleons in the $Y_p=0.40$ case. An algorithm to determine which nucleons are part of a given sub-domain in the system is presented. By comparing runs of different sizes we study finite-size effects, equilibration time, the formation of multiple domains and defects in the pasta structures, as well as the structure factor dependence on simulation size. Although we find qualitative agreement between the topological structure and the structure factors of runs with 51 200 nucleons and those with $819200$ nucleons or more, we show that simulations with hundreds of thousands of nucleons may be necessary to accurately predict pasta transport properties.

Previously published particle-$\gamma$ coincidence data on the ${}^{64}\mathrm{Ni}(p,p^{\prime }\gamma ){}^{64}\mathrm{Ni}$ and ${}^{64}\mathrm{Ni}(d,p\gamma ){}^{65}\mathrm{Ni}$ reactions were further analyzed to study the statistical properties of $\gamma$ decay in ${}^{64,65}\mathrm{Ni}$. To do so, the $\gamma$ decay to the quasicontinuum region and discrete low-lying states was investigated at $\gamma$-ray energies of 2.0–9.6 and 1.6–6.1 MeV in ${}^{64}\mathrm{Ni}$ and ${}^{65}\mathrm{Ni}$, respectively. In particular, the dependence of the $\gamma$-strength function with initial and final excitation energy was studied to test the validity of the generalized Brink-Axel hypothesis. Finally, the role of fluctuations in transition strengths was estimated as a function of $\gamma$-ray and excitation energy. The $\gamma$-strength function is consistent with the hypothesis of the independence of initial excitation energy, in accordance with the generalized Brink-Axel hypothesis. The results show that the $\gamma$ decay to low-lying levels displays large fluctuations for low initial excitation energies.

The ${\pi }^{-}+{}^2\mathrm{H}\to \gamma +n+n$, ${\pi }^{-}+{}^3\mathrm{He}\to \gamma +{}^3\mathrm{H}$, ${\pi }^{-}+{}^3\mathrm{He}\to \gamma +n+d$, ${\pi }^{-}+{}^3\mathrm{He}\to \gamma +n+n+p$, and ${\pi }^{-}+{}^3\mathrm{H}\to \gamma +n+n+n$ capture reactions are studied with the AV18 two-nucleon potential and the Urbana IX three-nucleon potential. We provide for the first time realistic predictions for the differential and total capture rates for all these processes, treating consistently the initial and final nuclear states. Our results are based on the single-nucleon Kroll-Ruderman-type transition operator and concentrate on the full treatment of the nuclear final state interactions. They are compared with older theoretical predictions and experimental data.

Brueckner-Hartree-Fock theory allows one to derive the $G$ matrix as an effective interaction between nucleons in the nuclear medium. It depends on the center-of-mass momentum $\mathit{P}$ of the two particles and on the two relative momenta $\mathit{q}$ and ${\mathit{q}}^{\prime }$ before and after the scattering process. In the evaluation of the total energy per particle in nuclear matter, usually the angle-averaged center-of-mass momentum approximation has been used. We derive in detail the exact expressions of the angular integrations of the momentum $\mathit{P}$ within relativistic Brueckner-Hartree-Fock (RBHF) theory, especially for the case of asymmetric nuclear matter. In order to assess the reliability of the conventional average momentum approximation for the binding energy, the saturation properties of symmetric and asymmetric nuclear matter are systematically investigated based on the realistic Bonn nucleon-nucleon potential. It is found that the exact treatment of the center-of-mass momentum leads to non-negligible contributions to the higher order physical quantities. The correlations between the symmetry energy $E_{\mathrm{sym}}$, the slope parameter $L$, and the curvature $K_{\mathrm{sym}}$ of the symmetry energy are investigated. The results of our RBHF calculations for the bulk parameters characterizing the equation of state are compared with recent constraints extracted from giant monopole resonance and isospin diffusion experiments.

Background: The reconstruction of the neutrino energy is crucial in oscillation experiments that use interactions with nuclei to detect the neutrino. The common reconstruction procedure is based on the kinematics of the final-state lepton. The interpretation of the reconstructed energy in terms of the real neutrino energy must rely on a model for the neutrino-nucleus interaction. The relativistic Fermi gas (RFG) model is frequently used in these analyses.

Purpose: We examine the effects of nuclear structure and dynamics going beyond a Fermi gas model on the reconstruction procedure.

Method: In the Hartree-Fock (HF) model for a quasielastic nucleon knockout, the bound nucleon wave functions are obtained through a calculation using an effective nucleon-nucleon force. The final-state wave function is constructed from continuum states in the same potential which have the correct asymptotic behavior. The continuum random-phase approximation (CRPA) model extends the HF approach taking long-range correlations into account in a self-consistent way.

Results: Considering only single-nucleon processes, the distributions of (reconstructed) neutrino energies obtained within the HF-CRPA approach are compared with the results of the RFG, a relativistic plane-wave impulse approximation calculation, and the $\mathrm{RPA}+n\mathrm{p}-n\mathrm{h}$ model of Martini et al. [Phys. Rev. C 80, 065501 (2009)].

Conclusions: We find that the distributions of reconstructed energies for a fixed incoming energy in the HF-CRPA display additional strength in the lower reconstructed energy tails compared to models without elastic distortion of the outgoing nucleon and the mean-field description of the initial nucleon. This asymmetry redistributes strength from higher to lower values of the reconstructed energy. The mean-field description of the nuclear dynamics results in a reshaping of the reconstructed energy distribution that cannot be accounted for in a plane-wave impulse approximation model even by modifying ad hoc parameters, such as the binding energy. In particular, it is shown that in the RFG calculations there is no value of the binding energy which is able to reproduce the entire ${\nu }_{\mu }$ oscillated spectrum of the T2K experiment as calculated in HF-CRPA.

We reanalyze the experiment of Schmitt et al. on the ${}^{10}\mathrm{Be}(d,p){}^{11}\mathrm{Be}$ transfer reaction [Phys. Rev. Lett. 108, 192701 (2012)] by exploring the beam-energy and angular ranges at which the reaction is strictly peripheral. We consider the adiabatic distorted wave approximation (ADWA) to model the reaction and use a Halo-EFT description of ${}^{11}\mathrm{Be}$ to systematically explore the sensitivity of our calculations to the short-range physics of the ${}^{10}\mathrm{Be}-n$ wave function. We find that by selecting the data at low beam energy and forward scattering angle the calculated cross sections scale nearly perfectly with the asymptotic normalization coefficient (ANC) of the ${}^{11}\mathrm{Be}$ bound states. Following these results, a comparison of our calculations with the experimental data gives a value of $C_{1s1/2}=0.785\pm 0.03{\mathrm{fm}}^{-1/2}$ for the ${\frac{1}{2}}^{+}$ ground-state ANC and $C_{0p1/2}=0.135\pm 0.005{\mathrm{fm}}^{-1/2}$ for the ${\frac{1}{2}}^{-}$ excited state, which are in perfect agreement with the ab initio calculations of Calci et al., who obtain $C_{1/2^{+}}^{\mathit{ab}\mathit{initio}}=0.786{\mathrm{fm}}^{-1/2}$ and $C_{1/2^{-}}^{\mathit{ab}\mathit{initio}}=0.129{\mathrm{fm}}^{-1/2}$ [Phys. Rev. Lett. 117, 242501 (2016)].