In this study, $\alpha$ decay properties of yet unknown nuclei are investigated through the systematic behavior of the parameters of $\alpha$-nucleus double-folding (DF) potentials. To calculate DF potentials, the density distributions of the protons and neutrons are being employed by use of the self-consistent Hartree-Fock-Bogoliubov (HFB) calculations based on the SLy4 Skyrme interaction widely used for the $\alpha$-emitter systems and the superheavy region. In addition, a new set of effective Skyrme force parameters is presented so that more precise estimations, labeled OMGA, are optimized to describe the ground-state properties of superheavy nuclei with $82\le Z\le 120$. Consequently, a good mass fit and half-lives are thus obtained by the optimized Skyrme force with more consistency with experimental data.

New data for the ${}^{\text{nat}}\mathrm{V}(p,x)$ reactions have been measured in the range 26–70 MeV, with production of the nuclides ${}^{47}\mathrm{Sc}, {}^{43}\mathrm{Sc}, {}^{44m}\mathrm{Sc}, {}^{44g}\mathrm{Sc}, {}^{46}\mathrm{Sc}, {}^{48}\mathrm{Sc}, {}^{42}\mathrm{K}, {}^{43}\mathrm{K}, {}^{48}\mathrm{V}, {}^{48}\mathrm{Cr}, {}^{49}\mathrm{Cr}$, and ${}^{51}\mathrm{Cr}$. The focus is on the production of ${}^{47}\mathrm{Sc}$, a ${\beta }^{-}$ emitter suitable for innovative radiotheranostic applications in nuclear medicine. The measured cross sections for this radionuclide and its contaminants are compared with the theoretical excitation functions calculated with the talys code. In view of novel radiopharmaceutical applications, it is essential to accurately describe these cross sections for the evaluation of yields, purities, and dose releases. Hence, we optimize the level-density parameters of the microscopic models in the talys code to obtain the best possible descriptions of the new data. We consider different irradiation conditions to estimate the production yields from the cross sections determined in this paper.

Cross sections for the ${}^{35}\mathrm{Cl}(n,\alpha ){}^{32}\mathrm{P}$ reaction were systematically measured at incident neutron energies in the range of 3.3 to 5.3 MeV. The experiment was carried out on the Van de Graaff accelerator EG-5 at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Russia. Fast neutrons were produced in the reaction ${}^2\mathrm{H}(d,n){}^3\text{He}$. Alpha particles from the ($n,\alpha$) reactions were detected using a gridded ionization chamber (GIC) in which various ${}^{35}\mathrm{Cl}$ samples (NaCl and ${\text{BaCl}}_2$, on a tantalum backing) were placed back to back. The relative and absolute neutron fluxes were measured by two samples of ${}^{238}\mathrm{U}_3{}^{}\mathrm{O}_8$ ($99.999\%$) inside the GIC. Data obtained in this measurement were compared with other experimental data of the existing library and theoretical calculations by the talys code. Presented data for the ${}^{35}\mathrm{Cl}(n,\alpha ){}^{32}\mathrm{P}$ reaction should help to clarify discrepancies in the various published nuclear data.

The initial geometry effect on forward-backward multiplicity correlations $C(N_f,N_b)$ is studied in relativistic collisions between light nuclei by using a multiphase transport model. It is found that tetrahedron ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ gives a more uniform and symmetrical fireball which produces a more isotropic distribution of final particles after the expansion and evolution, and leads to a small $C(N_f,N_b)$. Forward-backward multiplicity correlation could be taken as a useful probe to distinguish the pattern of $\alpha$-clustered ${}^{16}\mathrm{O}$ in experiments by comparing the neighboring colliding nuclear systems like ${}^{14}\mathrm{N}+{}^{14}\mathrm{N}$ and ${}^{19}\mathrm{F}+{}^{19}\mathrm{F}$.

This paper combines the graph-theoretical ideas behind Moravcsik's theorem with a completely analytic derivation of discrete phase ambiguities, recently published by Nakayama. The result is a new graphical procedure for the derivation of certain types of complete sets of observables for an amplitude-extraction problem with $N$ helicity amplitudes. The procedure is applied to pseudoscalar meson photoproduction ($N=4$ amplitudes) and electroproduction ($N=6$ amplitudes), yielding complete sets with minimal length of $2N$ observables. For the case of electroproduction, this is the first time an extensive list of minimal complete sets is published. Furthermore, the generalization of the proposed procedure to processes with a larger number of amplitudes, i.e., $N>6$ amplitudes, is sketched. The generalized procedure is outlined for the next more complicated example of two-meson photoproduction ($N=8$ amplitudes).

We probe the outcomes of the baryon-quark phase transition in the hybrid neutron star (HNS) structure with the help of the Gibbs and Maxwell constructions, adopting a semiclassical mean-field (MF) model for the equation of state (EOS) of baryonic matter based on the Thomas-Fermi (TF) approximation and a nonlocal extension of the Nambu–Jona-Lasinio (NJL) model for the EOS of the deconfined quark phase. We find that the repulsive vector contribution of the nonlocal NJL (NNJL) EOS plays an inevitable role in modeling a stable $2M_{\odot }$ HNS. Our results exclude the emergence of the pure quark phase in the inner core of a stable HNS. Within the Gibbs construction, as the quark vector interaction becomes stronger, the contribution of the baryon-quark coexisting phase in the total HNS mass is reduced. On the other hand, a stable HNS is not predicted within the Maxwell construction because it does not include a pure quark core. A comparison is made to the corresponding results employing the local (standard) NJL (LNJL) model of quark matter. Fulfilling the observational constraints, our model indicates that a neutron star (NS) with canonical mass of around $1.4M_{\odot }$ is not massive enough to be described as an HNS.

The onset of octupole deformation and its impact on related spectroscopic properties is studied in even-even neutron-rich lanthanide isotopes Xe, Ba, Ce, and Nd with neutron number $86⩽N⩽94$. Microscopic input comes from the Hartree-Fock-Bogoliubov approximation with constrains on the axially symmetric quadrupole and octupole operators using the Gogny-D1M interaction. At the mean-field level, reflection asymmetric ground states are predicted for isotopes with neutron number around $N=88$. Spectroscopic properties are studied by diagonalizing the interacting boson model Hamiltonian, with the parameters obtained via the mapping of the mean-field potential energy surface onto the expectation value of the Hamiltonian in the $s, d$, and $f$ boson condensate state. The results obtained for low-energy positive- and negative-parity excitation spectra as well as the electric dipole, quadrupole, and octupole transition probabilities indicate the onset of pronounced octupolarity for $Z\approx 56$ and $N\approx 88$ nuclei.

One of the largest sets of collective excitations built on two-quasiparticle configurations in odd-odd nuclei of the proton-rich $A\approx 120$ mass region is reported in ${}^{118}\mathrm{Cs}$. Several new rotational bands and long-lived isomers have been identified. The $8^{+}$ bandhead of the $\pi h_{11/2}\otimes \nu h_{11/2}$ band is a short-lived isomer with a half-life in the nanosecond range, while the $7^{+}$ state below it is a long-lived isomer with a half-life of $T_{1/2}=0.55\left(6\right)\mu \mathrm{s}$. Two other long-lived isomers have been identified: a 66-keV transition detected at the MARA focal plane depopulates one of them, indicating a half-life in the microsecond range, while no depopulating transitions have been identified for the other, indicating a much longer half-life. Extensive particle number conserving cranked shell model calculations and alignment analysis have been employed to investigate the rich band structure of ${}^{118}\mathrm{Cs}$, which exhibits one of the most complete sets of two-quasiparticle configurations in nuclei close to the proton drip line.

Background: The shape of most nuclei is described by its quadrupole deformation (showing the deviation from spherical shape) and its triaxiality (showing the deviation from axial symmetry). Nuclei affected by triaxiality show additional collective rotational bands, called $\gamma$ bands, that appear at low excitation energy. The $\gamma$ bands can be caused by the precession of a nucleus with triaxial shape, but can also arise from small $\gamma$ vibrations around an axially symmetric shape.

Purpose: The aim of this work is to search for new collective excitations in ${}^{187}\mathrm{Os}$ in particular related with the $\gamma$ degree of freedom.

Methods: The rotational structures of ${}^{187}\mathrm{Os}$ were populated by the ${}^{186}\mathrm{W}({}^4\mathrm{He},3\mathrm{n}){}^{187}\mathrm{Os}$ reaction at a beam energy of 37 MeV. The measurements of $\gamma$ - $\gamma$ coincidences, angular distribution ratios and $\gamma$-ray intensities were performed using eleven Compton-suppressed Ge clover detectors.

Results: The previously known positive-parity band built on the $11/2^{+}$ isomer has been extended up and a new excited positive-parity band built above a $15/2^{+}$ state has been observed. The $11/2^{+}$ band was assigned a $\nu i_{13/2}$ configuration while the new $15/2^{+}$ band was associated with a coupling of the valence $i_{13/2}$ neutron with the $\gamma$ band of the even-even core. The quasiparticle-plus-triaxial-rotor model calculations provide a good agreement with the experimental data for both bands. They describe the $15/2^{+}$ band as a collective excitation with respect to the $11/2^{+}$ band that corresponds to a precession of the intermediate nuclear axis similarly to the precession of a rotating top.

Conclusions: As shown by the calculations, the new rotational band can be understood as resulting from the three-dimensional rotation of a triaxially-deformed nucleus. However, a description based on the vibrations of a $\gamma$-soft nuclear shape should also be investigated in order to firmly establish the nature of the excited positive-parity band. Further studies able to distinguish between these alternative descriptions will be beneficial.

We suggest the hybrid model for the description of the dipole spreading widths, in which the strength function is built on the one-phonon strength distribution folded with the energy-dependent Lorentzian. Its energy dependence is brought about by (i) the energy-dependent smearing parameter and (ii) the energy-dependent shift of the one-phonon states. These variables are estimated by means of the two-phonon density, provided by a modified Fermi gas model with uniformly spaced states, and with the aid of the weak constant interaction between the one-phonon states and the two-phonon states, considered as background states. Based on calculated one-phonon states, the model is analytically solvable. To explore the validity of the model we analyze the properties of the $1^{-}$ spectrum in ${}^{206}\mathrm{Hg}$, ${}^{206}\mathrm{Pb}$, and ${}^{210}\mathrm{Po}$ nuclei. Our results demonstrate that the description of the decay widths within the latter approach is in good agreement with that obtained in the quasiparticle random phase approximation, by means of the random distribution of the coupling between microscopic one-phonon states and two-phonon states, generated by the Gaussian orthogonal ensemble distribution.

The astrophysical ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ direct capture process is studied in the framework of a two-body single-channel model with potentials of the Gaussian form. A modified potential is constructed to reproduce the new experimental value of the $S$-wave-scattering length and the known astrophysical $S$ factor at the Gamow energy, extracted from the solar neutrino flux. The resulting potential is consistent with the theory developed by Baye [Phys. Rev. C 62, 065803 (2000)] according to which the $S$-wave scattering length and the astrophysical $S$ factor at zero energy divided by the square of the asymptotic normalization coefficient are related. The obtained results for the astrophysical $S$ factor at intermediate energies are in good agreement with the two data sets of Hammache et al. [Phys. Rev. Lett. 86, 3985 (2001); Phys. Rev. Lett.80, 928 (1998)]. Linear extrapolation to zero energy yields $S_{17}\left(0\right)\approx 20.{51}_{-1.85}^{+2.02}\mathrm{eV}\mathrm{b}$ consistent with the Solar Fusion II estimate. The calculated reaction rates are substantially lower than the results of the NACRE II Collaboration.

In the present work, the basis space in the triaxial projected shell-model approach is expanded to include three and five quasiparticle configurations for odd-proton systems. This extension allows us to investigate the high-spin band structures observed in odd-proton systems up to and including the second band-crossing region and, as a first major application of this development, the high-spin properties are investigated for odd-mass ${}^{125-137}\mathrm{Pr}$ and ${}^{127-139}\mathrm{Pm}$ isotopes. It is shown that band crossings in the studied isotopes have mixed structures with the first crossing dominated by one-proton coupled to two-neutron configuration for the lighter isotopes which then changes to three-proton configuration with increasing neutron number. Furthermore, $\gamma$ bands based on quasiparticle states are also delineated in the present work, and it is predicted that these band structures built on three-quasiparticle configurations become favored in energy for heavier systems in the high-spin region.

The energies and decay widths of the states of the exotic ${}^7\mathrm{He}$ nucleus are studied in an ab initio approach. The spectrum of these states is calculated using the no-core shell model (NCSM) and a corresponding extrapolation procedure. The Daejeon16 potential, well proved on a large amount of data, is used in the calculations. The previously developed NCSM-based approach, which includes a method for constructing the basis of functions of cluster channels and a procedure for matching the cluster form factors obtained within this method with the corresponding asymptotic wave functions, is applied to compute the decay widths of the levels. The possibilities of the approach are demonstrated for calculating the partial decay widths of nuclear states into various channels that strongly differ in type of fragmentation, spin, angular momentum of relative motion, and amplitude. The results obtained are compared with the results of other microscopic calculations.

The atomic masses of the isotopes ${}^{206,207}\mathrm{Ra}$ have been measured via decay-correlated mass spectroscopy using a multireflection time-of-flight mass spectrograph equipped with an $\alpha$-TOF detector. The Ra isotopes were produced as fusion-evaporation products in the ${}^{51}\mathrm{V}+{}^{159}\mathrm{Tb}$ reaction system and delivered by the gas-filled recoil ion separator GARIS-II at RIKEN. The $\alpha$-TOF detector provides for high-accuracy mass measurements by correlating time-of-flight signals with subsequent $\alpha$-decay events. The masses of ${}^{206}\mathrm{Ra}$ and ${}^{207g,m}\mathrm{Ra}$ were directly measured using a multireflection time-of-flight mass spectrograph equipped with an $\alpha$-TOF detector. The mass excesses of ${}^{206,207g}\mathrm{Ra}$ and the excitation energy of ${}^{207m}\mathrm{Ra}$ were determined to be $\text{ME}=3540\left(50\right)\mathrm{keV}/c^2, 3538\left(15\right)\mathrm{keV}/c^2$, and $E_{\mathrm{ex}}=552\left(42\right)$ keV, respectively. The $\alpha$-decay branching ratio of ${}^{207m}\mathrm{Ra}, b_{\alpha }=0.26\left(20\right)$, was directly determined from decay-correlated time-of-flight signals, and the reduced $\alpha$ width of ${}^{207m}\mathrm{Ra}$ was calculated to be ${\delta }^2={43}_{-34}^{+68}$ keV from the branching ratio. The spin-parity of ${}^{207m}\mathrm{Ra}$ was confirmed to be $J^{\pi }=13/2^{+}$ from decay correlated mass measurement results.

Nuclides sharing the same mass number (isobars) are observed ubiquitously along the stability line. While having nearly identical radii, stable isobars can differ in shape, and present different quadrupole deformations. We show that even small differences in these deformations can be probed by relativistic nuclear collisions experiments, where they manifest as deviations from unity in the ratios of elliptic flow coefficients taken between isobaric systems. Collider experiments with isobars represent, thus, a unique means to gain precise knowledge of the geometric shape of atomic nuclei.

Background: $\beta$-delayed neutron emission and fission are essential in $r$-process nucleosynthesis. Although the number of experimental studies covering $r$-process nuclei has recently increased, the uncertainties of $\beta$-delayed neutron emission and fission are still large for $r$-process simulations.

Purpose: Our aim is to introduce a theoretical framework for the description of $\beta$-delayed neutron-emission and fission rates based on relativistic nuclear energy density-functional and statistical models and investigate their properties throughout the nuclide map.

Methods: To obtain $\beta$ strength functions, the relativistic proton-neutron quasiparticle random-phase approximation is employed. Particle evaporations and fission from highly excited nuclear states are estimated by the Hauser-Feshbach statistical model. $\beta$-delayed neutron branching ratios $P_n$ are calculated and compared with experimental data, and the $\beta$-delayed fission branching ratio $P_f$ are also assessed by using different fission barrier data.

Results: Calculated $P_n$ are in a good agreement with the experimental data and the root mean square deviation is comparable to results of preceding works. It is found that energy withdrawal by $\beta$-delayed neutron-emission sensitivity varies $P_n$, especially for nuclei near the neutron drip line. $P_f$ depend sensitively on fission barrier data. It is found that not only the barrier height but also the number of barrier humps is important to evaluate $P_f$.

Conclusions: The framework introduced in this work provides an improved theoretical description of the $\beta$-delayed neutron emission and fission. Since $P_f$ as well as $P_n$ depend strongly on fission barrier information, four kinds of fission barrier data are used in this work to allow further sensitivity studies of the $r$-process nucleosynthesis on the nuclear fission. More studies on fission barrier are highly requested to assess the role of $\beta$-delayed fission in the $r$-process study. A complete set of calculated data for $\beta$-delayed neutron emission and fission are summarized as a table in supplemental material for its use in $r$-process studies as well as to complement a part of nuclear data in which no experimental data are available.

Recent data on the nuclear modification of $W$ and $Z$ boson production measured by the ATLAS collaboration in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ show an enhancement in peripheral collisions, seemingly contradicting predictions of the Glauber model. The data were previously explained by arguing that the nucleon-nucleon cross section may be shadowed in nucleus-nucleus collisions and hence suppressed compared with the proton-proton cross section at the same collision energy. This interpretation has quite significant consequences for the understanding of heavy-ion data, in particular in the context of the Glauber model. Instead, we provide an alternative explanation of the data by assuming that there is a mild bias present in the centrality determination of the measurement; on the size of the related systematic uncertainty. Using this assumption, we show that the data is in agreement with theoretical calculations using nuclear parton distribution functions. Finally, we speculate that the centrality dependence of the $W^{-}/W^{+}$ ratio may point to the relevance of a larger skin thickness of the Pb nucleus, which, if present, would result in a few percent larger PbPb cross section than currently accounted for in the Glauber model and may hence be the root of the centrality bias.

Angular correlation spectra of $e^{+}{e}^{-}$ pairs produced in the ${}^3\mathrm{H}(p,e^{+}{e}^{-}){}^4\mathrm{He}$ nuclear reaction have been studied at $E_p=510$, 610, and 900 keV proton energies. The main features of the spectra can be understood by taking into account the internal and external pair creations following the proton capture by ${}^3\mathrm{H}$. However, these processes cannot account for an observed peak around ${115}^{\circ }$ in the angular correlation spectra. This anomalous excess of $e^{+}{e}^{-}$ pairs can be described by the creation and subsequent decay of a light particle during the direct capture process. The derived mass of the particle is $m_{\mathrm{X}}{c}^2=16.94\pm 0.12\left(\mathrm{stat}\right)\pm 0.21\left(\mathrm{syst}\right)$ MeV. According to the mass this is likely the same X17 particle, which we recently suggested [Phys. Rev. Lett. 116, 042501 (2016)] for describing the anomaly observed in the decay of ${}^8\mathrm{Be}$.

Level density $\rho (E,A)$ is derived for a one-component nucleon system with a given energy $E$ and particle number $A$ within the mean-field semiclassical periodic-orbit theory beyond the saddle-point method of the Fermi gas model. We obtain $\rho \propto I_{\nu }\left(S\right)/S^{\nu }$, with $I_{\nu }\left(S\right)$ being the modified Bessel function of the entropy $S$. Within the micro-macro-canonical approximation (MMA), for a small thermal excitation energy $U$, with respect to rotational excitations $E_{\mathrm{rot}}$, one obtains $\nu =3/2$ for $\rho (E,A)$. In the case of excitation energy $U$ larger than $E_{\mathrm{rot}}$ but smaller than the neutron separation energy, one finds a larger value of $\nu =5/2$. A role of the fixed spin variables for rotating nuclei is discussed. The MMA level density $\rho$ reaches the well-known grand-canonical ensemble limit (Fermi gas asymptote) for large $S$ related to large excitation energies, and also reaches the finite micro-canonical limit for small combinatorial entropy $S$ at low excitation energies (the constant “temperature” model). Fitting the $\rho (E,A)$ of the MMA to the experimental data for low excitation energies, taking into account shell and, qualitatively, pairing effects, one obtains for the inverse level density parameter $K$ a value which differs essentially from that parameter derived from data on neutron resonances.

Background: Well-established coupled channel (CC) and coupled reaction channel (CRC) processes make contributions to elastic scattering that are absent from local density folding models.

Purpose: To establish and characterize the contribution to the proton optical model potential (OMP) made by the coupling to neutron pickup channels, in particular the proton OMP for 65 MeV protons on ${}^{48}\mathrm{Ca}$ and ${}^{40}\mathrm{Ca}$. Also to relate this contribution to results for ${}^{40}\mathrm{Ca}$ at lower energies; to investigate the dynamical nonlocality of this contribution; to characterize the effect on the OMP of breakup of the deuteron.

Methods: CRC calculations of neutron pickup and CC calculations of collective states, provide the elastic channel $S$ matrix $S_{lj}$. Inversion of $S_{lj}$ produces a local potential that yields, in a single channel calculation, the elastic scattering observables from the CC/CRC calculation. Subtracting the bare potential yields a local and $l$-independent representation of the dynamical polarization potential, DPP. From the DPPs due to a selection of channel couplings the influence of dynamically generated nonlocality can be identified. The effect of coupling to the deuteron breakup continuum is also identified.

Results: For ${}^{40}\mathrm{Ca}$, coupling to pickup channels has an effect on observables somewhat weaker than that at 30 MeV, and much less than for pickup coupling for ${}^{48}\mathrm{Ca}$. The DPPs have similar general properties in each case, but are much larger in magnitude for ${}^{48}\mathrm{Ca}$. Subsequent breakup of the deuteron makes a large contribution to the DPP, and hence to the OMP. The formal DPPs due to pickup coupling exhibit dynamical nonlocality.

Conclusions: The DPPs challenge local density folding models for elastic scattering. The breakup of the deuteron must henceforth be included in calculations of the DPP due to neutron pickup in proton scattering. Pickup coupling effects are still substantial at 65 MeV. No smoothly varying global OMP could fit proton elastic scattering from both ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$.