Background: The observation of neutrinoless double-$\beta$ transitions would indicate physics beyond the standard model as the lepton number conservation is violated. For a complete degeneracy in the energy of the initial and final states, the neutrinoless double-electron capture is resonantly enhanced. This shortens the half-life to similar orders of magnitude as the neutrinoless double-$\beta$ decay and expands the set of nuclei for the search of neutrinoless double-$\beta$ transitions as the observation of either process would be equally likely.

Purpose: To clearly identify transitions that are resonantly enhanced, among other parameters the total energy of the decay, $Q_{\varepsilon \varepsilon }$, needs to be measured very precisely. Of the 12 initially identified candidates, the last remaining decay without a precise $Q_{\varepsilon \varepsilon }$ was ${}^{190}\mathrm{Pt}\left(0\nu \varepsilon \varepsilon \right){}^{190}\mathrm{Os}$.

Method: The $Q_{\varepsilon \varepsilon }$ value was determined with the Penning trap mass spectrometer LEBIT by measuring the ratio of the cyclotron frequencies of ${}^{190}\mathrm{Pt}^{+}$ and ${}^{190}\mathrm{Os}^{+}$ in a 9.4-T superconducting magnet.

Result: The $Q_{\varepsilon \varepsilon }$ value was determined to be 1401.57(47) keV with an uncertainty reduction of an order of magnitude compared to its previously known value. The absolute value is shifted by 17.17(623) keV relative to the previously accepted one. Furthermore, the mass value of ${}^{190}\mathrm{Pt}$ was found to be shifted by more than three standard deviations. In addition we improved the mass values for ${}^{186,190}\mathrm{Os}$ and ${}^{194}\mathrm{Pt}$.

Conclusion: Transitions to the two nuclear excited states of ${}^{190}\mathrm{Os}$ with 1326.9(5) and 1387.00(2) keV energy were identified to be resonantly enhanced within a $1\sigma$ uncertainty. The significantly reduced uncertainty of $Q_{\varepsilon \varepsilon }$ confirmed the potential for a resonantly enhanced transition.

We calculate the thermal conductivity of electrons for the strongly correlated multicomponent ion plasma expected in the outer layers of a neutron star's crust, employing a Path Integral Monte Carlo (PIMC) approach. This allows us to isolate the low energy response of the ions and use it to calculate the electron scattering rate and the electron thermal conductivity. We find that the scattering rate is enhanced by a factor 2–4 compared to earlier calculations based on the simpler electron-impurity scattering formalism. This finding impacts the interpretation of thermal relaxation observed in transiently accreting neutron stars, and has implications for the composition and nuclear reactions in the crust that occur during accretion.

The relative $\gamma$-decay probability ratios of the neutron resonance states in ${}^{94}\mathrm{Zr}$ and ${}^{92}\mathrm{Zr}$ populated via two-neutron transfer reactions, ${}^{92}\mathrm{Zr}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{94}\mathrm{Zr}$ and ${}^{90}\mathrm{Zr}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{92}\mathrm{Zr}$, have been measured to test the validity of the surrogate ratio method (SRM) in determining the $(n, \gamma )$ reaction cross section. The cross sections of the ${}^{93}\mathrm{Zr}(n,\gamma ){}^{94}\mathrm{Zr}$ reaction are derived from the experimentally obtained ratios and the cross sections of the ${}^{91}\mathrm{Zr}(n,\gamma ){}^{92}\mathrm{Zr}$ reaction in the equivalent neutron energy range of $E_n=0\text{–}8\mathrm{MeV}$. The deduced cross sections of ${}^{93}\mathrm{Zr}(n,\gamma ){}^{94}\mathrm{Zr}$ reaction agree with the directly measured ones in the low-energy region, and with the evaluated ENDF/B-VII.1 data at higher energies of $E_n>3\mathrm{MeV}$. The agreement supports the concept of the SRM method to indirectly determine the $\left(n,\gamma \right)$ reaction cross sections.

Background: In the past year we have been exploring the effect of the explicit inclusion of nonlocality in $(d,p)$ reactions.

Purpose: The goal of this paper is to extend previous studies to $(d,n)$ reactions, which, although similar to $(d,p)$ reactions, have specific properties that merit inspection.

Method: We apply our methods (both the distorted-wave Born approximation and the adiabatic wave approximation) to $(d,n)$ reactions on ${}^{16}\mathrm{O},{}^{40}\mathrm{Ca},{}^{48}\mathrm{Ca},{}^{126}\mathrm{Sn},{}^{132}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ at 20 and 50 MeV.

Results: We look separately at the modifications introduced by nonlocality in the final bound and scattering states as well as the consequences reflected on the differential angular distributions. The cross sections obtained when using nonlocality explicitly are significantly different than those using the local approximation, just as in $(d,p)$ reactions. Due to the particular role of the Coulomb force in the bound state, often we found the effects of nonlocality to be larger in $(d,n)$ than in $(d,p)$ reactions.

Conclusions: Our results confirm the importance of including nonlocality explicitly in deuteron-induced reactions.

The astrophysical capture process $\alpha +d\to {}^6\mathrm{Li}$ is studied in a three-body model. The initial state is factorized into the deuteron bound state and the ($\alpha +d$)-scattering state. The final nucleus ${}^6\mathrm{Li}\left(1^{+}\right)$ is described as a three-body bound state $\alpha +n+p$ in the hyperspherical Lagrange-mesh method. The contribution of the $E1$-transition operator from the initial isosinglet states to the isotriplet components of the final state is estimated to be negligible. An estimation of the forbidden $E1$ transition to the isosinglet components of the final state is comparable with the corresponding results of the two-body model. However, the contribution of the $E2$-transition operator is found to be much smaller than the corresponding estimations of the two-body model. The three-body model perfectly matches the new experimental data of the LUNA Collaboration with the spectroscopic factor of 2.586 estimated from the bound-state wave functions of ${}^6\mathrm{Li}$ and a deuteron.

Proton capture cross sections in the energy range of astrophysical interest for mass region 40–54 have been calculated in the Hauser-Feshbach formalism with the reaction code talys1.6. The density-dependent M3Y effective nucleon-nucleon interaction folded with target radial matter densities from the relativistic mean field approach is used to obtain the semimicroscopic optical potential. A definite normalization of potential well depths has been used over the entire mass region. The $(p,\gamma )$ rates of some reactions, important in the astrophysical scenario, are calculated using the potential in the relevant mass region.

The $\alpha$ decay of ${}^{222}\mathrm{Th}$ populating the low-lying $J^{\pi }=3^{-}$ state, and also a proposed $1^{-}$ state, in ${}^{218}\mathrm{Ra}$ has been observed. The observations suggest an excitation energy of 853 keV for the $1^{-}$ state, which is 60 keV above the $3^{-}$ state. The hindrance factors of these $\alpha$ decays give a possible boundary to the region of ground-state octupole deformation in the light-actinide nuclei. The relative positions of the $J^{\pi }=1^{-}$ and $3^{-}$ states suggest they are produced by an octupole-vibrational mechanism, as opposed to $\alpha$ clustering or rotations of a reflection-asymmetric octupole-deformed shape.

The spin cutoff parameter determining the nuclear level density spin distribution $\rho \left(J\right)$ is defined through the spin projection as ${\langle J_z^2\rangle }^{1/2}$ or equivalently for spherical nuclei, ${\left(\frac{\langle J(J+1)\rangle }{3}\right)}^{1/2}$. It is needed to divide the total level density into levels as a function of $J$. To obtain the total level density at the neutron binding energy from the $s$-wave resonance count, the spin cutoff parameter is also needed. The spin cutoff parameter has been calculated as a function of excitation energy and mass with a super-conducting Hamiltonian. Calculations have been compared with two commonly used semiempirical formulas. A need for further measurements is also observed. Some complications for deformed nuclei are discussed. The quality of spin cut off parameter data derived from isomeric ratio measurement is examined.

The decimal logarithm of spontaneous fission half-life of the superheavy nucleus ${}^{286}\mathrm{Fl}$ experimentally determined is ${log}_{10}{T}_f^{exp}\left(s\right)=-0.632$. We present a method to calculate the half-life based on the cranking inertia and the deformation energy, functions of two independent surface coordinates, using the best asymmetric two center shell model. Spherical shapes are assumed. In the first stage we study the statics. At a given mass asymmetry up to about $\eta =0.5$ the potential barrier has a two hump shape, but for larger $\eta$ it has only one hump. The touching point deformation energy versus mass asymmetry shows the three minima, produced by shell effects, corresponding to three decay modes: spontaneous fission, cluster decay, and $\alpha$ decay. The least action trajectory is determined in the plane $(R,\eta )$, where $R$ is the separation distance of the fission fragments and $\eta$ is the mass asymmetry. We may find a sequence of several trajectories one of which gives the least action. The parametrization with two deformation coordinates $(R,\eta )$ and the radius of the light fragment, $R_2$, exponentially or linearly decreasing with $R$ is compared with the simpler one, in which $R_2=\mathrm{constant}$ and with a linearly decreasing or linearly increasing $R_2$. The latter is closer to the reality and reminds us about the $\alpha$ or cluster preformation at the nuclear surface.

Background: The high complexity of the deuteron-nucleus interaction from the deuteron weak binding energy of 2.224 MeV is also related to a variety of reactions induced by the deuteron-breakup (BU) nucleons. Thus, specific noncompound processes as BU and direct reactions (DR) make the deuteron-induced reactions so different from reactions with other incident particles. The scarce consideration of only pre-equilibrium emission (PE) and compound-nucleus (CN) mechanisms led to significant discrepancies with experimental results so that recommended reaction cross sections of high-priority elements as, e.g., Ni have mainly been obtained by fit of the data.

Purpose: The unitary and consistent BU and DR account in deuteron-induced reactions on natural nickel may take advantage of an extended database for this element, including new accurate measurements of particular reaction cross sections.

Method: The activation cross sections of ${}^{64,61,60}\mathrm{Cu}$, ${}^{65,57}\mathrm{Ni}$, and ${}^{55,56,57,58,58m,60}\mathrm{Co}$ nuclei for deuterons incident on natural Ni at energies up to 20 MeV, were measured by the stacked-foil technique and high-resolution gamma spectrometry using U-120M cyclotron of CANAM, NPI CAS. Then, within an extended analysis of deuteron interactions with Ni isotopes up to 60 MeV, all processes from elastic scattering until the evaporation from fully equilibrated compound system have been taken into account while an increased attention is paid especially to the BU and DR mechanisms.

Results: The deuteron activation cross-section analysis, completed by consideration of the PE and CN contributions corrected for decrease of the total-reaction cross section from the leakage of the initial deuteron flux towards BU and DR processes, is proved satisfactory for the first time to all available data.

Conclusions: The overall agreement of the measured data and model calculations validates the description of nuclear mechanisms taken into account for deuteron-induced reactions on Ni, particularly the BU and DR that should be considered explicitly.

We apply the low-energy theorems to analyze the recent lattice QCD results for the two-nucleon system at a pion mass of $M_{\pi }\simeq 450$ MeV obtained by the NPLQCD Collaboration. We find that the binding energies of the deuteron and dineutron are inconsistent with the low-energy behavior of the corresponding phase shifts within the quoted uncertainties and vice versa. Using the binding energies of the deuteron and dineutron as input, we employ the low-energy theorems to predict the phase shifts and extract the scattering length and the effective range in the ${}^{3}S_1$ and ${}^{1}S_0$ channels. Our results for these quantities are consistent with those obtained by the NPLQCD Collaboration from effective field theory analyses but are in conflict with their determination based on the effective-range approximation.

From previous data for the reaction ${}^{14}\mathrm{C}\left(t,p\right){}^{16}\mathrm{C}$, I have extracted a width of 32.6(5) keV for the strong state at $E_x=6.11\mathrm{MeV}$. Here, I examine its likely $J^{\pi }$ and configuration. The predicted width of its mirror in ${}^{16}\mathrm{Ne}$ is estimated to be about 260 keV.

We present a generator-coordinate calculation, based on a relativistic energy-density functional, of the low-lying spectra in the isotopes ${}^{150}\mathrm{Nd}$ and ${}^{150}\mathrm{Sm}$ and of the nuclear matrix element that governs the neutrinoless double-$\beta$ decay of the first isotope to the second. We carefully examine the impact of octupole correlations on both nuclear structure and the double-$\beta$ decay matrix element. Octupole correlations turn out to reduce quadrupole collectivity in both nuclei. Shape fluctuations, however, dilute the effects of octupole deformation on the double-$\beta$ decay matrix element, so that the overall octupole-induced quenching is only about $7\%$.

Using an isospin- and momentum-dependent transport model, we examine the effects of an electric field induced by a variable magnetic field on the ${\pi }^{-}/{\pi }^{+}$ ratio in central to peripheral heavy-ion collisions at beam energies of 400 and 1500 MeV/nucleon. It is shown that while the induced electric field does not affect the total multiplicities of both ${\pi }^{-}$ and ${\pi }^{+}$ mesons at both the lower beam energy of 400 MeV/nucleon and the higher beam energy of 1500 MeV/nucleon, it reduces (enhances) the emission of ${\pi }^{-}\left({\pi }^{+}\right)$ mesons in midrapidity, but enhances (reduces) the emission of ${\pi }^{-}\left({\pi }^{+}\right)$ mesons in forward and backward rapidities especially for the more peripheral collisions at the lower beam energy because of the rapidly transient variable magnetic field at more peripheral collisions and the longer reaction duration time at the lower beam energy. These findings indicate that the total ${\pi }^{-}/{\pi }^{+}$ ratio is still a precisely reliable probe of symmetry energy at both the lower and the higher beam energies, but one should consider the induced electric field when using the differential ${\pi }^{-}/{\pi }^{+}$ ratio to probe the symmetry energy especially for the lower beam energy and more peripheral collisions. Finally, the relative suppression factor based on the ratio of ${\pi }^{-}/{\pi }^{+}$ in different rapidities is proposed to be an effective probe of the induced electric field generated in heavy-ion collisions due to its maximizing effects of induced electric fields on the differential ${\pi }^{-}/{\pi }^{+}$ ratio but minimizing effects of some uncertainty factors in heavy-ion collisions.

We analyze charged-current electron-neutrino cross sections on carbon. We consider two different theoretical approaches, on one hand the continuum random phase approximation (CRPA) which allows a description of giant resonances and quasielastic excitations, on the other hand the RPA-based calculations which are able to describe multinucleon emission and coherent and incoherent pion production as well as quasielastic excitations. We compare the two approaches in the genuine quasielastic channel, and find a satisfactory agreement between them at large energies while at low energies the collective giant resonances show up only in the CRPA approach. We also compare electron-neutrino cross sections with the corresponding muon-neutrino ones in order to investigate the impact of the different charged-lepton masses. Finally, restricting to the RPA-based approach, we compare the sum of quasielastic, multinucleon emission, coherent, and incoherent one-pion production cross sections (folded with the electron-neutrino T2K flux) with the charged-current inclusive electron-neutrino differential cross sections on carbon measured by T2K. We find a good agreement with the data. The multinucleon component is needed in order to reproduce the T2K electron-neutrino inclusive cross sections.

The first measurement of $\gamma$ rays from the ${}^{114}\mathrm{Sn}\left(n,\gamma \right)$ reaction using cold neutrons, performed with an array of Ge detectors at the PF1B facility of the Institute Laue-Langevin in Grenoble, has provided the most accurate energy, $Q_{\beta }=173\left(12\right)$ eV, of ${\beta }^{-}$ decay of the ${}^{115}\mathrm{In}$ ground state to the first excited state in ${}^{115}\mathrm{Sn}$. This is the lowest of all such energies in the known nuclear landscape. The accuracy of the neutron binding energy of ${}^{115}\mathrm{Sn}$ and the mass of ${}^{114}\mathrm{Sn}$ have been improved.

The penetrating nature of electromagnetic signals makes them suitable probes to explore the properties of the strongly interacting medium created in relativistic nuclear collisions. We examine the effects of the initial conditions and shear relaxation time on the spectra and flow coefficients of electromagnetic probes, using an event-by-event 3+1-dimensional viscous hydrodynamic simulation (music).

By extending the dynamical coupled-channels analysis performed in our previous work [Phys. Rev. C 88, 035209 (2013)] to include the available data of photoproduction of $\pi$ mesons off neutrons, the transition amplitudes for the photoexcitation of the neutron-to-nucleon resonances, $\gamma n\to N^{*}$, at the resonance pole positions are determined. The combined fits to the data for both the proton- and neutron-target reactions also revise our results for the resonance pole positions and the $\gamma p\to N^{*}$ transition amplitudes. Our results allow an isospin decomposition of the $\gamma N\to N^{*}$ transition amplitudes for the isospin $I=\frac{1}{2}{N}^{*}$ resonances, which is necessary for testing hadron structure models and gives crucial inputs for constructing models of neutrino-induced reactions in the nucleon resonance region.