Background: Accurate knowledge of the ${}^{237}\mathrm{Np}(n,\gamma ){}^{238}\mathrm{Np}$ cross section at fast neutron energies is important for applied nuclear science. The presently available experimental data have large disagreements in the fast neutron region.

Purpose: Perform a model-independent measurement of the ${}^{237}\mathrm{Np}(n,\gamma ){}^{238}\mathrm{Np}$ integral cross section using a well characterized fast neutron source and compare the result with previous measurements and current nuclear data evaluations. Provide an integral measurement that can be used as a benchmark for current evaluations.

Methods: Multiple samples of ${}^{237}\mathrm{Np}$ were irradiated in the Godiva-IV critical assembly. Following the irradiation, the samples placed in a $\gamma$-ray counting setup and the $\gamma$ rays emitted from the decay of ${}^{238}\mathrm{Np}$ were measured over a time period of approximately 7 d. Multiple $\gamma$-ray decay branches of ${}^{238}\mathrm{Np}$ were observed.

Results: The observed activity of ${}^{238}\mathrm{Np}$ was used to calculate the amount of ${}^{238}\mathrm{Np}$ produced during the irradiation via the ${}^{237}\mathrm{Np}(n,\gamma ){}^{238}\mathrm{Np}$ reaction and an integral cross section of 342(11) $mb$ was measured for the Godiva-IV neutron spectrum. The ${}^{238}\mathrm{Np}$ half-life has been measured with a result of 50.31(5) h.

Conclusion: The ${}^{237}\mathrm{Np}(n,\gamma ){}^{238}\mathrm{Np}$ integral cross section measured in this work is in agreement with overlapping $1\sigma$ error bands to ENDF/B-VIII.0. However, the measured value is $3\sigma$ away from the calculated integral cross section using JENDL-5. This measurement offers a reliable benchmark for future ${}^{237}\mathrm{Np}(n,\gamma ){}^{238}\mathrm{Np}$ cross section evaluations.

Measurements of exclusive $J/\psi , \psi \left(2s\right)$, and electron-positron ($e^{+}{e}^{-}$) pair photoproduction in $\mathrm{Au}+\mathrm{Au}$ ultraperipheral collisions are reported by the STAR experiment at $\sqrt{s_{{}_{\mathrm{NN}}}}=200\mathrm{GeV}$. We report several first measurements at the BNL Relativistic Heavy Ion Collider, which are (i) $J/\psi$ photoproduction with large momentum transfer up to ${2.2(\mathrm{GeV}/c)}^2$, (ii) coherent $J/\psi$ photoproduction associated with neutron emissions from nuclear breakup, (iii) the rapidity dependence of incoherent $J/\psi$ photoproduction, (iv) the $\psi \left(2s\right)$ photoproduction cross section at midrapidity, and (v) $e^{+}{e}^{-}$ pair photoproduction up to high invariant mass of $6\mathrm{GeV}/c^2$. For measurement (ii), the coherent $J/\psi$ total cross section of $\gamma +\mathrm{Au}\to \mathrm{J}/\psi +\mathrm{Au}$ as a function of the center-of-mass energy $W_{\gamma N}$ has been obtained without photon energy ambiguities. The data are quantitatively compared with the Monte Carlo models STARlight, Sartre, BeAGLE, and theoretical calculations of gluon saturation with color glass condensate, nuclear shadowing with leading twist approximation, quantum electrodynamics, and the next-to-leading-order perturbative QCD. At the photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent $J/\psi$ cross sections of Au nuclei are found to be $71\%\pm 10\%$ and $36\%\pm 7\%$, respectively, of that of free protons. These data provide an important experimental constraint for nuclear parton distribution functions and a unique opportunity to advance the understanding of the nuclear modification effect at the top RHIC energy.

A global analysis of proton electric form factor experimental data from Rosenbluth separation and low squared four-momentum transfer experiments is discussed for the evaluation of the spatial moments of the proton charge density based on the recently published integral method [Hoballah et al., Phys. Lett. B 808, 135669 (2020)]. Specific attention is paid to the evaluation of the systematic errors of the method, particularly the sensitivity to the choice of the mathematical expression of the form factor fitting function. Within this comprehensive analysis of proton electric form factor data, the moments of the proton charge density are determined for integer order moments, particularly: $\langle r^2\rangle =0.6{94\left(09\right)}_{\mathrm{stat}}{\left(16\right)}_{\mathrm{sys}}{\mathrm{fm}}^2, \langle r^3\rangle =0.{870\left(46\right)}_{\mathrm{stat}}{\left(80\right)}_{\mathrm{sys}}{\mathrm{fm}}^3$, and $\langle r^4\rangle =1.{47\left(25\right)}_{\mathrm{stat}}{\left(45\right)}_{\mathrm{stat}}{\mathrm{fm}}^4$.

The nuclear isomeric state ${}^{229m}\mathrm{Th}$ with an exceptionally low excitation energy makes the ${}^{229}\mathrm{Th}$ isotope a crucial candidate for nuclear clocks and many other applications. Efficient and controllable production of ${}^{229m}\mathrm{Th}$ is essential and still remains a challenge. Here we report a novel approach for efficient production of ${}^{229m}\mathrm{Th}$ by the excitation of ${}^{229}\mathrm{Th}$ to the above-lying excited state at 29.19 keV energy via the process of nuclear excitation by electron capture (NEEC). We show theoretically that the production rate of ${}^{229m}\mathrm{Th}$ per nucleus with accessible conditions can be six orders of magnitude larger than the value experimentally demonstrated using 29-keV synchrotron radiation for this indirect excitation. With the efficient production of ${}^{229m}\mathrm{Th}$, our results identify scenarios, as well as the characteristic NEEC signature with which NEEC events could be unambiguously identified, for a clear experimental identification of the long-sought NEEC phenomenon.

The first high-resolution in-beam $\gamma$-ray spectroscopy is reported for the neutron-rich nucleus ${}^{41}\mathrm{Si}$, a tenant of the $N=28$ island of inversion. Excited states were populated in the direct one-proton removal reaction from ${}^{42}\mathrm{P}$ projectiles and $pn$ removal from ${}^{43}\mathrm{P}$. Seven $\gamma$-ray transitions were observed, only one of which had been reported previously in the literature. This makes ${}^{41}\mathrm{Si}$ the most neutron-rich odd-even $N=27$ isotone with high-resolution excited-state information. For the one-proton removal, the measured partial cross-section distribution to all observed bound final states is contrasted with results from direct one-proton removal calculations that combine eikonal reaction dynamics with SDPF-MU shell-model spectroscopic factors and assume various possible initial states for the poorly known ${}^{42}\mathrm{P}$ projectile. Rather distinct calculated cross-section distributions emerge that, in comparison to the new data, imply that the initial state in ${}^{42}\mathrm{P}$ is most likely $3^{-}$ or $2^{-}$ rather than $1^{-}$ or $0^{-}$, the predicted shell-model ground state of ${}^{42}\mathrm{P}$. It is further shown that the level scheme from the novel VS-IMSRG calculation closely agrees with the one of SDPF-MU, the most successful phenomenological shell-model effective interaction in describing the much discussed neighboring isotope ${}^{42}\mathrm{Si}$, perhaps cross-validating these complementary approaches on the quest to model rapid shell evolution away from the valley of $\beta$ stability.

The excited structure of the single-hole nucleus ${}^{131}\mathrm{Sn}$ populated by the ${\beta }^{-}$ decay of ${}^{131}\mathrm{In}$ was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited $\nu h_{11/2}$ neutron-hole state was confirmed via an independent mass spectroscopy experiment performed at the Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. The level scheme of ${}^{131}\mathrm{Sn}$ was notably expanded with the addition of 31 new $\gamma$-ray transitions and 22 new excited levels. The $\gamma$-emitting excited levels above the neutron separation energy in ${}^{131}\mathrm{Sn}$ were investigated, revealing a large number of states, which in some cases decay by transitions to other neutron-unbound states. Our analysis showed the dependence between the population of these states in ${}^{131}\mathrm{Sn}$ and the $\beta$-decaying ${}^{131}\mathrm{In}$ state feeding them. Profiting from the isomer selectivity, it was possible to estimate the direct $\beta$ feeding to the $3/2^{+}$ ground and $11/2^{-}$ isomeric states, disentangling the contributions from the three indium parent states. This made possible to resolve the discrepancies in $\log ft$ for first-forbidden transitions observed in previous studies, and to determine the $\beta$-delayed neutron decay probability $\left(P_n\right)$ values of each indium isomers independently. The first measurement of subnanosecond lifetimes in ${}^{131}\mathrm{Sn}$ was performed in this work. A short $T_{1/2}=18\left(4\right)\text{−}\mathrm{ps}$ value was measured for the $1/2^{+}$ neutron single-hole 332-keV state, which indicates an enhanced $l$-forbidden $M1$ behavior for the $\nu 3s_{1/2}^{-1}\to \nu 3d_{3/2}^{-1}$ transition. The measured half-lives of high-energy states populated in the $\beta$ decay of the $(21/2^{+})$ second isomeric state $\left({}^{131m2}\mathrm{In}\right)$ provided valuable information on transition rates, supporting the interpretation of these levels as core-excited states analogous to those observed in the doubly-magic ${}^{132}\mathrm{Sn}$.

The influence of finite temperatures and pairing correlations on the ground-state properties of multi-$\mathrm{\Lambda }$ Ca, Sn, and Pb hypernuclei is explored using the finite-temperature Hartree-Fock-Bogoliubov approach and contact pairing interaction. A critical temperature is predicted and is in agreement with the Bardeen-Cooper-Schrieffer relationship $k_B{T}_C^{\mathrm{\Lambda }}\approx 0.5{\mathrm{\Delta }}_{\mathrm{\Lambda }}^{T=0}$, beyond which pairing correlations drop to zero. Particle densities, $\mathrm{\Lambda }$ single-particle energies, and nuclear radii are weakly impacted by pairing as well as by finite temperatures. However, other nuclear properties which are more sensitive to pairing correlations, such as $\mathrm{\Lambda }$-pairing gaps, condensation energies, and abnormal densities are also more impacted by finite temperature, especially around the critical temperature. Furthermore, calculations show the occurrence of the pairing re-entrance effect in the ${}_{70\mathrm{\Lambda }}{}^{280}\mathrm{Pb}$ hyperon drip-line hypernucleus. Our study provides insight into the thermal evolution of $\mathrm{\Lambda }$ pairing, i.e., the emergence and vanishing of pairing correlations in multi-$\mathrm{\Lambda }$ hypernuclei as a function of temperature.

Within the Langevin framework, we investigate the dynamics of the fusion process for production of transfermium elements in reactions of ${}^{48}\mathrm{Ca}$, ${}^{50}\mathrm{Ti}$, ${}^{54}\mathrm{Cr}$, and ${}^{58}\mathrm{Fe}$ with ${}^{208}\mathrm{Pb}$. After the reacting nuclei have made contact, the early dynamical stage is dominated by the dissipation of the initial radial kinetic energy, while the subsequent shape evolution is diffusive. The probability for surmounting the inner barrier and forming a compound system is obtained by simulating the evolution as a Metropolis random walk in a five-dimensional potential-energy landscape. Good agreement with the available data is obtained, especially for the maximal formation probability.

The production of exotic hadron $\mathrm{X}\left(3872\right)$ in $pp$ collisions at $\sqrt{s}=2.76\mathrm{TeV}$ is investigated by the parton and hadron cascade model PACIAE in this work. In the simulation the final partonic state (quark matter, QM) and the final hadronic state (hadron matter, HM) are continuously processed and recorded. The $\mathrm{X}\left(3872\right)$ compact tetraquark state and loose molecular state are, respectively, coalesced and recombined in the QM and HM with the quantum statistical mechanics inspired dynamically constrained phase-space coalescence model. The formation time, velocity, and temperature of QM (tetraquark state) and HM (molecular state) are proposed as identifying criteria between the two states. Our results in transverse momentum spectrum and rapidity distribution, etc. show a significant discrepancy between the two states and confirm that they are also valuable criteria identifying the $\mathrm{X}\left(3872\right)$ compact tetraquark state or molecular state.

We compute the static density and spin structure factors in the long wavelength limit for pure neutron matter at subsaturation densities relevant to core-collapse supernovae within the Brueckner-Hartree-Fock (BHF) approach. The BHF results are reliable at high densities, extending beyond the validity of the virial expansion. Motivated by the similarities between the dilute neutron gas and a unitary gas, we propose a phenomenological approach to derive the static structures with finite momentum transfer as well as the dynamic ones with simple analytical expressions, based on the computed static structures in the long wavelength limit. We also compare the in-medium neutrino-neutron scattering cross sections using different structure factors. Our study emphasizes the importance of accurately computing the static structure factors theoretically and utilizing the full dynamic structure factors in core-collapse supernova simulations.

The near-symmetric complete fusion reaction ${}^{78}\mathrm{Kr}+{}^{107}\mathrm{Ag}\to {}^{185}\mathrm{Bi}^{*}$ was studied at the gas-filled recoil separator SHANS with an attempt to synthesize the extremely neutron-deficient proton-unbound ${}^{182,183}\mathrm{Bi}$ isotopes. No decay events which could be attributed to them were observed. The two- and three-particle evaporation residues ${}^{180,179}\mathrm{Hg}$ ($\alpha p, \alpha pn$) and ${}^{183,182}\mathrm{Pb}$ ($pn, p2n$) were identified. Their production cross sections have been measured at two bombarding energies. Based on the yields of ${}^{182,183}\mathrm{Pb}$ in the present work and the systematics of the ratios between the cross sections of $p(x-1)n$ and $xn$ evaporation channels for the most neutron-deficient odd-$Z$ nuclei above lead, the upper limits for the half-lives of ${}^{182,183}\mathrm{Bi}$ were estimated to be less than $0.3\mu \mathrm{s}$.

The root-mean-square proton and neutron radii for ${}^{7,9–12,14}\mathrm{Be}, {}^{10–15,17}\mathrm{B}, {}^{12–19}\mathrm{C}, {}^{14,15,17–22}\mathrm{N}, {}^{16,18–24}\mathrm{O}$, and ${}^{18–21,23–26}\mathrm{F}$ isotopes are deduced from a systematic analysis of experimental charge-changing and interaction cross sections in the framework of the Glauber model. The calculations involve descriptions of nuclei based on Slater determinants using harmonic-oscillator single-particle wave functions. The extracted proton and neutron radii have been examined in the light of some important features such as neutron skin thickness, halo-like structure, and subshell closure observed in exotic isotopes.

For the first time, half-lives and energy spectra of forbidden $\beta$ decays are calculated within the realistic shell model. Namely, we approach this issue starting from a realistic nucleon-nucleon potential and deriving effective Hamiltonians and decay operators. Our goal is to explore the sensitivity of the shape of calculated energy spectra to the renormalization of forbidden $\beta$-decay operators, an operation that allows to take into account those configurations that are not explicitly included in the chosen model space. The region that has been considered for this investigation are nuclei outside the ${}^{78}\mathrm{Ni}$ core, more precisely we have studied the second-forbidden $\beta$ decays of ${}^{94}\mathrm{Nb}$ and ${}^{99}\mathrm{Tc}$, and fourth-forbidden $\beta$ decays of ${}^{113}\mathrm{Cd}$ and ${}^{115}\mathrm{In}$, that are currently of a renewed experimental interest in terms of novel spectroscopic techniques. Our results evidence that the introduction of a renormalized $\beta$-decay operator leads to a marked improvement of the reproduction of experimental half-lives. As regards the spectra of both second-forbidden and fourth-forbidden decays, we have found that their calculated shapes are in good agreement with the observed ones, even if scarcely responsive to the renormalization of the decay operator. We carry out also a detailed inspection of the different components of the calculated spectra for a deeper insight about their role in reproducing the experimental shapes.

The nucleus in the center-of-mass frame is described by $3A\text{−}3$ independent coordinates, including three Euler angles and three variables $\rho ,\beta ,\text{and}\gamma$ to describe orientation, size, and shape of the nuclear inertia ellipsoid as well as $3A\text{−}9$ generalized Euler angles to describe internal motion of the nucleons. Based on the idea that the incompressible nucleus has constant density, we suggest a definition of the deformation parameter $\beta$. It allows us to derive the Hamiltonian, which describes large-amplitude collective motions. At $\beta \ll 1$ it reduces to a sum of the Bohr Hamiltonian and the Hamiltonian of monopole $\rho$ vibrations. As a result of straightforward calculations we obtain explicit expressions for all the inertial parameters as functions of the variables $\rho ,\beta ,\text{and}\gamma$.

Mass-energy distributions for fission fragments produced in the reactions ${}^{18}\mathrm{O} + {}^{205}\mathrm{Tl}, {}^{209}\mathrm{Bi}$ are studied around the Coulomb barrier energies populating ${}^{223}\mathrm{Ac}$ and ${}^{227}\mathrm{Pa}$ compound nuclei at excitation energies $E^{*}\approx 26–36$ MeV. The experimental results, showing small shoulders on either side, indicate the presence of asymmetric fission along with symmetric fission. We have estimated the contribution of asymmetric fission by fitting the experimental data with a Gaussian function composed of three components (one symmetric and two asymmetric). A small fraction of the asymmetric fission component is observed at all excitation energies. The experimental results are found to be in reasonable agreement with the GEF predictions. The asymmetric fission observed at high excitation energies can be explained by using multichance fission in the GEF calculations.