The properties of nuclear matter under extreme conditions of high temperature, density, and isospin asymmetry have attracted wide attention in recent years. At present, heavy ion reactions in combination with corresponding model simulations are one of the most important ways to investigate this subject. It is known that a strong magnetic field can be created in heavy ion collisions. However, its effect on the motion of charged particles is usually neglected in previous transport model simulations. In this work, within the ultrarelativistic quantum molecular dynamics (UrQMD) model, the temporal evolution and spatial distribution of the internal magnetic field are calculated. The magnetic field strength is found to reach about $eB\approx 470{\mathrm{MeV}}^2$ ($B\approx 8\times {10}^{16}$ G) for Au $+$ Au collisions at $E_{\text{lab}}=1\mathrm{GeV}/\mathrm{nucleon}$ with impact parameter of 7 fm. The magnetic field in Cu $+$ Au collisions exhibits somewhat different spatial distribution from that in Au $+$ Au collisions. The magnetic field is found to affect the directed flow of pions at forward and backward rapidities to some extent, dependent of the impact parameter and beam energy while the effect on the elliptic flow is small. In addition, the effects of the magnetic field on the ${\pi }^{-}/{\pi }^{+}$ ratio over the whole rapidity range and the elliptic flow difference $v_2^n\text{−}{v}_2^p$ between neutrons and protons at forward and backward rapidities are on the same order as those from the nuclear symmetry energy. The $v_2^n\text{−}{v}_2^p$ difference in the midrapidity region is not strongly affected by the magnetic field, and the total ${\pi }^{-}/{\pi }^{+}$ yield ratio is immune to it. It is advisable to include the magnetic field effects in future studies using pion flow, pion yield ratio, and nucleon elliptic flow difference to probe the symmetry energy at super saturation densities.

The hyperfine coupling constants of neutron deficient ${}^{37}\mathrm{Ca}$ were deduced from the atomic hyperfine spectrum of the $4s{}^{2}S_{1/2}\leftrightarrow 4p{}^{2}P_{3/2}$ transition in Ca ii, measured using the collinear laser spectroscopy technique. The ground-state magnetic-dipole and spectroscopic electric-quadrupole moments were determined for the first time as $\mu =+0.7453\left(72\right){\mu }_N$ and $Q=-15\left(11\right)e^2{\mathrm{fm}}^2$, respectively. The experimental values agree well with nuclear shell-model calculations using the universal sd model-space Hamiltonians versions A and B (USDA/B) in the $sd$-model space with a 95% probability of the canonical nucleon configuration. It is shown that the magnetic moment of ${}^{39}\mathrm{Ca}$ requires a larger non-$sd$-shell component than that of ${}^{37}\mathrm{Ca}$ for good agreement with the shell-model calculation, indicating a more robust closed subshell structure of ${}^{36}\mathrm{Ca}$ at the neutron number $N=16$ than ${}^{40}\mathrm{Ca}$. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two- and three-nucleon interactions.

An experiment has been performed to study excited states in the neutron-deficient nucleus ${}^{175}\mathrm{Ir}$ via the use of the JUROGAM II high-purity germanium detector array and the RITU gas-filled separator at JYFL, Jyväskylä. By using isomer tagging, an isomeric state with a half-life of 6.58(15) $\mu \mathrm{s}$ has been observed in ${}^{175}\mathrm{Ir}$ for the first time. It has been established that the isomer decays via a 45.2 ($E1$)–26.1 ($M1$) keV cascade to new states below the previously reported ground state in ${}^{175}\mathrm{Ir}$ with $I^{\pi }=(5/2^{-})$. We now reassign this ($5/2^{-}$) state to the isomeric state discovered in this study.

We study the description of single-species and isovector pairing correlations in the framework of the projected-BCS (PBCS) and the quartet condensation model (QCM) from a particle-hole perspective, and we introduce the representation of the QCM quartet condensate state in terms of particle-hole excitations with respect to the Hartree-Fock state. We also present a new bosonic approximation for both PBCS and QCM. In each case, the starting point is the reformulation of the pair and quartet condensate states in terms of particle-hole excitations with respect to the Hartree-Fock state. The main simplification of our approach is the assumption that the pair operators corresponding to both particle and hole states obey bosonic commutation relations. This simplifies tremendously the computations and allows for an analytic derivation of the averaged Hamiltonian on the condensate state as a function of the mixing amplitudes. We study both the pure bosonic approach and the renormalized version and compare the particle-hole bosonic version to the naive prescription of applying the boson approximation directly to the original condensate state. We compare the fermionic and the renormalized particle-hole bosonic approaches in the case of a picket-fence model of doubly degenerate states and in a realistic shell-model space with an effective interaction for the $N=Z$ nuclei above ${}^{100}\mathrm{Sn}$.

The Majorana Demonstrator is searching for neutrinoless double-beta decay ($0\nu \beta \beta$) in ${}^{76}\mathrm{Ge}$ using arrays of point-contact germanium detectors operating at the Sanford Underground Research Facility. Background results in the $0\nu \beta \beta$ region of interest from data taken during construction, commissioning, and the start of full operations have been recently published. A pulse shape analysis cut applied to achieve this result, named $AvsE$, is described in this paper. This cut is developed to remove events whose waveforms are typical of multisite energy deposits while retaining $(90\pm 3.5)\%$ of single-site events. This pulse shape discrimination is based on the relationship between the maximum current and energy, and tuned using ${}^{228}\mathrm{Th}$ calibration source data. The efficiency uncertainty accounts for variation across detectors, energy, and time, as well as for the position distribution difference between calibration and $0\nu \beta \beta$ events, established using simulations.

The self-energy effect on the neutron-proton ($np$) pairing gap is investigated up to the third order within the framework of the extend Brueckner–Hartree–Fock (BHF) approach combined with the BCS theory. The self-energy up to the second-order contribution turns out to reduce strongly the effective energy gap, while the renormalization term enhances it significantly. In addition, the effect of the three-body force on the $np$ pairing gap is shown to be negligible. To connect the present results with the $np$ pairing in finite nuclei, an effective density-dependent zero-range pairing force is established with the parameters calibrated to the microscopically calculated energy gap.

Background: The coupling of clusters and deformed structures is important for the dynamics of a nuclear structure. Threshold energy is discussed to explain cluster structure coupling to deformed states but the relation between threshold energy and excitation energy involves open problems. Negative-parity superdeformed (SD) states were observed via a $\gamma$-spectroscopy experiment in ${}^{35}\mathrm{Cl}$. However, their detailed structure is unclear.

Purpose: An analysis of the coupling of cluster structures in deformed states and high-lying cluster states in ${}^{35}\mathrm{Cl}$ is used to investigate cluster structures coupling to deformed states and excitation energy of high-lying cluster states.

Method: Antisymmetrized molecular dynamics (AMD) and the generator coordinate method (GCM) are used. An AMD wave function corresponds to a Slater determinant of Gaussian wave packets. Energy variational calculations with constraints on deformation and clustering are used to obtain wave functions of deformed structures and $\alpha \text{−}{}^{31}\mathrm{P}$ and $t\text{−}{}^{32}\mathrm{S}$ cluster structures. The wave functions are adopted as the GCM basis, and wave functions of ground and excited states are calculated.

Results: Various deformed bands are obtained and predicted. A $K^{\pi }={\frac{1}{2}}^{-}$ deformed band (corresponding to the observed SD band) dominates the deformed structure and compact $\alpha \text{−}{}^{31}\mathrm{P}$ and $t\text{−}{}^{32}\mathrm{S}$ cluster structure components. Particle-hole configurations of dominant components with deformed and cluster structures are similar. In high-lying states, almost pure $\alpha \text{−}{}^{31}\mathrm{P}$ and $t\text{−}{}^{32}\mathrm{S}$ cluster states are obtained in negative-parity states, and excitation energies of the $t\text{−}{}^{32}\mathrm{S}$ cluster states exceed those of $\alpha \text{−}{}^{31}\mathrm{P}$ cluster states.

Conclusions: Particle-hole configurations of cluster structures with a small intercluster distance are important for coupling to low-energy deformed states. Threshold energies reflect excitation energies of almost pure high-lying cluster states.

Half-lives of clusters emitted from radioactive nuclei is determined using modified generalized liquid drop model (MGLDM), where a new preformation factor is added to the existing generalized liquid drop theoretical model with proximity 77 potential. Half-lives for radioactive nuclei whose mass numbers vary from 221 to 242, emitting C, O, F, Ne, Mg, and Si clusters, are calculated theoretically considering deformation and orientation effects and the values are in exact agreement with experimental data. Standard deviation of logarithm of half-lives using present model is found to be 0.755, which is a much better result in comparison with those of GLDM1 and GLDM2 of Bao et al. [J. Phys. G: Nucl. Part. Phys. 39, 095103 (2012)], which are 1.84 and 1.114, respectively. Also, half-lives of various radioactive nuclei whose mass numbers vary from 220 to 250 are predicted. We hope that our present study on cluster half-lives may be helpful for future works in this field.

Recent JLAB measurements of inclusive ($e,A$) cross sections as a function of outgoing lepton momentum may provide information on the nucleon spectral function in targets that will be relevant for the planned DUNE neutrino long-baseline experiment. They also provide an important testing ground for neutrino generators. We have therefore used the transport theoretical framework and code gibuu to calculate the cross sections for the targets C, Ar, and Ti. We compare the calculations with the experimental data. The overall agreement is good. Relatively small discrepancies appear mainly on the low-electron-energy side of the QE peak where QE and 2p2h excitation processes overlap.

We investigate the effects of a magnetic field on the thermodynamics of a neutron system at finite density and temperature. Our main motivation is to deepen the understanding of the physics of a class of neutron stars known as magnetars, which exhibit extremely strong magnetic fields. Taking into account two facts, (i) the existence of a pressure anisotropy in the presence of a magnetic field and (ii) that the quantum field theory contribution to the pressure is non-negligible, we show that the maximum value that the inner magnetic field of a star can reach while being in agreement with the magnetohydrostatic equilibrium between the gravitational and matter pressures becomes ${10}^{17}$ G, an order of magnitude smaller than the previous value obtained through the scalar virial theorem; that the magnetic field has a negligible effect on the neutron system's equation of state; that the system's magnetic susceptibility increases with the temperature; and that the specific heat $C_V$ does not significantly change with the magnetic field in the range of temperatures characteristic of protoneutron stars.

Nuclear $\beta$ decay is a key process to understand the origin of heavy elements in the universe, while the accuracy is far from satisfactory for the predictions of $\beta$-decay half-lives by nuclear models to date. In this work, we pave a novel way to accurately predict $\beta$-decay half-lives with the machine learning based on the Bayesian neural network, in which the known physics has been explicitly embedded, including the ones described by the Fermi theory of $\beta$ decay, and the dependence of half-lives on pairing correlations and decay energies. The other potential physics, which is not clear or even missing in nuclear models nowadays, will be learned by the Bayesian neural network. The results well reproduce the experimental data with a very high accuracy and further provide reasonable uncertainty evaluations in half-life predictions. These accurate predictions for half-lives with uncertainties are essential for the $r$-process simulations.

I develop a microscopic three-cluster model for exotic light nuclei. I use the hyperspherical formalism, associated with the generator coordinate method. This model is well adapted to halo nuclei, since the long-range part of the radial wave functions is accurately reproduced. The core wave functions are described in the shell model, including excited states. This technique provides large bases, expressed in terms of projected Slater determinants. Matrix elements involve seven-dimension integrals, and therefore require long calculation times. I apply the model to ${}^{11}\mathrm{Li}, {}^{14}\mathrm{Be}, {}^{15}\mathrm{B}$, and ${}^{17}\mathrm{N}$ described by two neutrons surrounding a ${}^9\mathrm{Li}, {}^{12}\mathrm{Be}, {}^{13}\mathrm{B}$, and ${}^{15}\mathrm{N}$ core, respectively. The ${}^{17}\mathrm{Ne}$ (as ${}^{15}\mathrm{O}+\mathrm{p}+\mathrm{p}$) and ${}^{15}\mathrm{Ne}$ (as ${}^{13}\mathrm{O}+\mathrm{p}+\mathrm{p}$) mirror nuclei are briefly discussed. I present the spectra and some spectroscopic properties, such as r.m.s. radii or $E2$ transition probabilities. I also analyze the importance of core excitations.

We investigate an idea of how to use analysis of bremsstrahlung photons to study the internal structure of a proton under nuclear reaction with a nucleus. A new model is constructed to describe bremsstrahlung emission of photons which accompanies the scattering of protons off nuclei. Our bremsstrahlung formalism uses a many-nucleon basis that allows us to analyze coherent and incoherent bremsstrahlung emissions. Because a scattered proton can be under the influence of strong forces and produces the largest bremsstrahlung contribution to the full spectrum, we focus on accurate determination of its quantum evolution in relation to the nucleus based on quantum mechanics. For this purpose, we generalize the Pauli equation with an interacting potential describing evolution of a fermion inside the strong field, including the electromagnetic form factors of nucleons based on deep inelastic scattering theory. Anomalous magnetic momenta of nucleons reinforce our motivation to develop such a formalism. The full bremsstrahlung spectrum in our model (after renormalization) is dependent on form factors of the scattered proton. In our calculations we choose the scattering of $p+{}^{197}\mathrm{Au}$ at a proton beam energy of 190 MeV, where experimental bremsstrahlung data were obtained with high accuracy. We show that the full bremsstrahlung spectrum is sensitive to the form factors of the scattered proton. In the limit without such form factors, we reconstruct our previous result (where form factors of the scattered proton were not studied).

We report the measurement of a neutron radiative cross section on a target with a high gamma activity, at the Los Alamos DANCE detector (Detector for Advanced Neutron Capture Experiments) for the first time. The $(n,\gamma )$ reaction properties of the unstable ${}^{173}\mathrm{Lu}$ isotope were studied. Two experimental campaigns were needed to determine the ${}^{173}\mathrm{Lu}(n,\gamma )$ cross section. They were performed at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source facility. To this end, two targets were produced from an Hf sample using successively proton irradiation and chemical separations. They were composed of ${}^{173}\mathrm{Lu},{}^{174}\mathrm{Lu}$, and ${}^{175}\mathrm{Lu}$ isotopes. The two measurements were conducted at two-year intervals, taking advantage of the difference of the isotopic decay lifetimes in order to identify resonances from the ${}^{173}\mathrm{Lu}(n,\gamma )$ and ${}^{174}\mathrm{Lu}(n,\gamma )$ reactions. Just over one hundred new resonances were observed, the majority of which come from the ${}^{173}\mathrm{Lu}(n,\gamma )$ reaction. Only a few of them were assigned to the ${}^{174}\mathrm{Lu}(n,\gamma )$ reaction. As regards the ${}^{173}\mathrm{Lu}(n,\gamma )$ reaction, the radiative neutron capture cross section was determined over the energy range from thermal neutron up to 200 eV. The parameters of resonances in the resolved resonance region were extracted with the sammy code while calculations with talys determined the capture cross section in the unresolved resonances region. At the keV region, we performed standard talys calculations as well as other microscopic investigations by substituting the standard talys photon strength function by another one from QRPA models.

In this paper, we investigate the Kibble-Zurek scaling of the $\sigma$ field and net-protons within the framework of Langevin dynamics of model A. After determining the characteristic scales ${\tau }_{\text{KZ}},l_{\text{KZ}}$, and ${\theta }_{\text{KZ}}$ and properly rescaling the traditional cumulants, we construct universal functions for the $\sigma$ field and approximate universal functions for net-protons in the critical regime, which are insensitive to the relaxation time and the chosen evolving trajectory. Besides, the oscillating behavior for the higher order cumulants of net-protons near the critical point is also drastically suppressed, which converge into approximate universal curves with these constructed Kibble-Zurek functions.

We study the hadron-quark mixed phase, which may occur in the interior of neutron stars. The relativistic mean-field model is employed to describe the hadronic phase, while the Nambu-Jona-Lasinio model is used for the quark phase. We examine the effects of nuclear symmetry energy in the hadronic phase and repulsive vector interaction in the quark phase. For the treatment of hadron-quark mixed phase, we describe and compare four methods: (1) energy minimization method, (2) coexisting phases method, (3) Gibbs construction, and (4) Maxwell construction. The finite-size effects like surface and Coulomb energies are taken into account in the energy minimization and coexisting phases methods, which play a key role in determining the pasta configuration during the hadron-quark phase transition. It is found that massive neutron stars may contain hadron-quark pasta phases, but pure quark matter is unlikely to occur in the interior of neutron stars.

For the isospin-mixed $1^{-}$ states in ${}^{10}\mathrm{B}$, widths for deuteron and α decays provide an independent estimate of the amount of isospin mixing, which is consistent with results from γ decays. Analysis provides two solutions for the proton spectroscopic factors of the pure $T=0$ and 1 states.

Two fits of the pairing residual interaction in the rare-earth region are independently performed. One is made on the odd-even staggering of masses by comparing measured and explicitly calculated three-point binding-energy differences centered on odd-even nuclei. Another deals with the moments of inertia of the first $2^{+}$ states of well-deformed even-even nuclei upon comparing experimental data with the results of Inglis-Belyaev moments (supplemented by a crude estimate of the so-called Thouless-Valatin corrections). The sample includes 24 even-even and 31 odd-mass nuclei selected according to two criteria: They should have good rotor properties and should not correspond to low pairing-correlation regimes in their ground states. Calculations are performed in the self-consistent Hartree-Fock plus BCS framework (implementing a self-consistent blocking in the case of odd-mass nuclei). The Skyrme SIII parametrization is used in the particle-hole channel and the fitted quantities are the strengths of $|T_z|=1$ proton and neutron seniority residual interactions. As a result, the two fits yield sets of strengths in excellent agreement: about 0.1% for the neutron parameters and 0.2% for protons. In contrast, when one performs such a fit on odd-even staggering from quantities deduced from BCS gaps or minimal quasiparticle energies in even-even nuclei, as is traditional, one obtains results significantly different from those obtained in the same nuclei by a fit of moments of inertia. As a conclusion, beyond providing a phenomenological tool for microscopic calculations in this region, we have illustrated the proposition performed in the seminal paper of Bohr et al. [Phys. Rev. 110, 936 (1958)] that moments of inertia and odd-even staggering in selected nuclei were excellent measuring sticks of nuclear pairing correlations. Furthermore, we have assessed the validity of our theoretical approach which includes simple yet apparently reasonable assumptions (seniority residual interaction, parametrization of its matrix elements as functions of the nucleon numbers, and global Thouless-Valatin renormalization of Inglis-Belyaev moments of inertia).

The production of the $\rho {\left(770\right)}^0$ meson has been measured at midrapidity $\left(\right|y|<0.5)$ in $pp$ and centrality differential Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV with the ALICE detector at the Large Hadron Collider. The particles have been reconstructed in the $\rho {\left(770\right)}^0\to {\pi }^{+}{\pi }^{-}$ decay channel in the transverse-momentum ($p_T$) range 0.5–11 $\mathrm{GeV}/c$. A centrality-dependent suppression of the ratio of the integrated yields $2\rho {\left(770\right)}^0/({\pi }^{+}+{\pi }^{-})$ is observed. The ratio decreases by $\sim 40\%$ from $pp$ to central Pb-Pb collisions. A study of the $p_T$-differential $2\rho {\left(770\right)}^0/({\pi }^{+}+{\pi }^{-})$ ratio reveals that the suppression occurs at low transverse momenta, $p_T<2 \mathrm{GeV}/c$. At higher momentum, particle ratios measured in heavy-ion and $pp$ collisions are consistent. The observed suppression is very similar to that previously measured for the $K^{*}{\left(892\right)}^0/K$ ratio and is consistent with EPOS3 predictions that may imply that rescattering in the hadronic phase is a dominant mechanism for the observed suppression.

Background: The ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ bottleneck reaction in Type I x-ray bursts is the most important thermonuclear reaction rate to constrain experimentally, to improve the accuracy of burst light-curve simulations. A proposed technique to determine the thermonuclear rate of this reaction employs the ${}^{20}\mathrm{Mg}\left(\beta p\alpha \right){}^{15}\mathrm{O}$ decay sequence. The key ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ resonance at an excitation of 4.03 MeV is now known to be fed in ${}^{20}\mathrm{Mg}\left(\beta p\gamma \right){}^{19}\mathrm{Ne}$; however, the energies of the protons feeding the 4.03 MeV state are unknown. Knowledge of the proton energies will facilitate future ${}^{20}\mathrm{Mg}\left(\beta p\alpha \right){}^{15}\mathrm{O}$ measurements.

Purpose: To determine the energy of the proton transition feeding the 4.03 MeV state in ${}^{19}\mathrm{Ne}$.

Method: A fast beam of ${}^{20}\mathrm{Mg}$ was implanted into a plastic scintillator, which was used to detect $\beta$ particles. 16 high purity germanium detectors were used to detect $\gamma$ rays emitted following $\beta p$ decay. A Monte Carlo method was used to simulate the Doppler broadening of ${}^{19}\mathrm{Ne}\gamma$-ray lines and compare to the experimental data.

Results: The center of mass energy between the proton and ${}^{19}\mathrm{Ne}$, feeding the 4.03 MeV state, is measured to be $1.21{}_{-0.22}^{+0.25}\mathrm{MeV}$, corresponding to a ${}^{20}\mathrm{Na}$ excitation energy of $7.44{}_{-0.22}^{+0.25}\mathrm{MeV}$. Absolute feeding intensities and $\gamma$-decay branching ratios of ${}^{19}\mathrm{Ne}$ states were determined including the 1615 keV state, which has not been observed before in this decay. A new $\gamma$ decay branch from the 1536 keV state in ${}^{19}\mathrm{Ne}$ to the ground state is reported. The lifetime of the 1507 keV state in ${}^{19}\mathrm{Ne}$ is measured to be $4.3{}_{-1.1}^{+1.3}$ ps resolving discrepancies in the literature. Conflicting ${}^{20}\mathrm{Mg}(\beta p$) decay schemes in published literature are clarified.

Conclusions: The utility of this Doppler broadening technique to provide information on $\beta$-delayed nucleon emission and excited-state lifetimes has been further demonstrated. In particular, knowledge of the proton energies feeding the 4.03 MeV ${}^{19}\mathrm{Ne}$ state in ${}^{20}\mathrm{Mg}\beta$ decay will facilitate future measurements of the $\alpha$-particle branching ratio.