The study of the ${}^{17}\mathrm{O}(n,\alpha ){}^{14}\mathrm{C}$ reaction has been performed by means of the Trojan horse method (THM) applied to the quasifree ${}^2\mathrm{H}\left({}^{17}\mathrm{O},\alpha {}^{14}\mathrm{C}\right){}^1\mathrm{H}$ reaction induced at a beam energy of 43.5 MeV. The THM allowed us to study the 8121-keV ${}^{18}\mathrm{O}^{*}$ resonant level, for which the previous THM investigation pointed out the ability of the method to overcome the centrifugal barrier suppression effects in the entrance channel. Here, in view of the developments of the method for resonant reactions, the detailed analysis of the performed experiment will be discussed, focusing on the extraction of the 8121-keV resonance strength for which no information is present in scientific literature. Moreover, the experimental results clearly show the excitation of the subthreshold level centered at $-6$ keV in the center-of-mass system, which is fundamental to determine the ${}^{17}\mathrm{O}(n,\alpha ){}^{14}\mathrm{C}$ reaction rate of astrophysical interest. Finally, a new recommended reaction rate is presented for future astrophysical application.

We present the first application of the newly developed extended Kuo-Krenciglowa (EKK) theory of the effective nucleon-nucleon interaction to shell-model studies of exotic nuclei, including those where conventional approaches with fitted interactions encounter difficulties. This EKK theory enables us to derive an interaction that is suitable for several major shells $(sd+pf$ in this work). By using such an effective interaction obtained from the Entem-Machleidt QCD-based $\chi {\mathrm{N}}^3\mathrm{LO}$ interaction and the Fujita-Miyazawa three-body force, the energies, $E2$ properties, and spectroscopic factors of low-lying states of neutron-rich Ne, Mg, and Si isotopes are nicely described, as the first shell-model description of the “island of inversion” without fit of the interaction. The long-standing question as to how particle-hole excitations occur across the $sd\text{−}pf$ magic gap is clarified with distinct differences from the conventional approaches. The shell evolution is shown to appear similarly to earlier studies.

The recent measurements of high energy photodisintegration of a ${}^3\mathrm{He}$ nucleus to a $pd$ pair at ${90}^{\circ }$ center of mass demonstrated an energy scaling consistent with the quark counting rule with an unprecedentedly large exponent of $s^{-17}$. To understand the underlying mechanism of this process, we extended the theoretical formalism of the hard rescattering mechanism (HRM) to calculate the $\gamma {}^3\mathrm{He}\to pd$ reaction. In HRM the incoming high energy photon strikes a quark from one of the nucleons in the target which subsequently undergoes hard rescattering with the quarks from the other nucleons, generating a hard two-body system in the final state of the reaction. Within the HRM we derived the parameter-free expression for the differential cross section of the reaction, which is expressed through the ${}^3\mathrm{He}\to pd$ transition spectral function, the cross section of hard $pd\to pd$ scattering, and the effective charge of the quarks being interchanged during the hard rescattering process. The numerical estimates of all these factors resulted in the magnitude of the cross section, which is surprisingly in good agreement with the data.

The neutron-induced reaction cross sections of ${}^{242m}\mathrm{Am}$ were measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. A new neutron-capture cross section was determined, and the absolute scale was set according to a concurrent measurement of the well-known ${}^{242m}\mathrm{Am}(n,f)$ cross section. The ($n,\gamma$) cross section was measured from thermal energy to an incident energy of 1 eV at which point the data quality was limited by the reaction yield in the laboratory. Our new ${}^{242m}\mathrm{Am}$ fission cross section was normalized to ENDF/B-VII.1 to set the absolute scale, and it agreed well with the ($n,f$) cross section reported by Browne et al. (1984) from thermal energy to 1 keV. The average absolute capture-to-fission ratio was determined from thermal energy to $E_n=0.1$ eV, and it was found to be 26(4)$\%$ as opposed to the ratio of $19\%$ from the ENDF/B-VII.1 evaluation.

By using halo effective field theory (EFT), an expansion in $R_{\text{core}}/R_{\text{halo}}$, where $R_{\text{core}}$ is the radius of the core and $R_{\text{halo}}$ the radius of the halo nucleus, the charge and neutron form factors of the two-neutron halo nuclei ${}^{11}\mathrm{Li}, {}^{14}\mathrm{Be}$, and ${}^{22}\mathrm{C}$ are calculated to next-to-leading order (NLO) by treating them as an effective three-body system. From the form factors, the point-charge and point-matter radii, inter-neutron distances, and neutron opening angles are extracted. Agreement is found with existing experimental extractions. Results are given for the point-charge and point-matter radii for arbitrary neutron core scattering effective range ${\rho }_{cn}$, which can be used for predictions once ${\rho }_{cn}$ is measured. Estimates for ${\rho }_{cn}$ are also used to make NLO predictions. Finally, the point-charge radii of this work are compared with other halo-EFT predictions, and setting the core mass equal to the neutron mass the point-charge radius is found to agree with an analytical prediction in the unitary limit.

Background: Aspects of the nuclear structure of light $\alpha$-conjugate nuclei have long been associated with nuclear clustering based on $\alpha$ particles and heavier $\alpha$-conjugate systems such as ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$. Such structures are associated with strong deformation corresponding to superdeformed or even hyperdeformed bands. Superdeformed bands have been identified in ${}^{40}\mathrm{Ca}$ and neighboring nuclei and find good description within shell model, mean-field, and $\alpha$-cluster models. The utility of the $\alpha$-cluster description may be probed further by extending such studies to more challenging cases comprising lighter $\alpha$-conjugate nuclei such as ${}^{24}\mathrm{Mg}, {}^{28}\mathrm{Si}$, and ${}^{32}\mathrm{S}$.

Purpose: The purpose of this study is to look for the number and energy of isoscalar $0^{+}$ states in ${}^{28}\mathrm{Si}$. These states are the potential bandheads for superdeformed bands in ${}^{28}\mathrm{Si}$ corresponding to the exotic structures of ${}^{28}\mathrm{Si}$. Of particular interest is locating the $0^{+}$ bandhead of the previously identified superdeformed band in ${}^{28}\mathrm{Si}$.

Methods: $\alpha$-particle inelastic scattering from a ${}^{\mathrm{nat}}\mathrm{Si}$ target at very forward angles including $0^{\circ }$ has been performed at the iThemba Laboratory for Accelerator-Based Sciences in South Africa. Scattered particles corresponding to the excitation energy region of 6 to 14 MeV were momentum-analysed in the K600 magnetic spectrometer and detected at the focal plane using two multiwire drift chambers and two plastic scintillators.

Results: Several $0^{+}$ states have been identified above 9 MeV in ${}^{28}\mathrm{Si}$. A newly identified 9.71 MeV $0^{+}$ state is a strong candidate for the bandhead of the previously discussed superdeformed band. The multichannel dynamical symmetry of the semimicroscopic algebraic model predicts the spectrum of the excited $0^{+}$ states. The theoretical prediction is in good agreement with the experimental finding, supporting the assignment of the 9.71-MeV state as the bandhead of a superdeformed band.

Conclusion: Excited isoscalar $0^{+}$ states in ${}^{28}\mathrm{Si}$ have been identified. The number of states observed in the present experiment shows good agreement with the prediction of the multichannel dynamical symmetry.

The half-life of the $15/2_1^{+}$ state of the 3-valence-proton nucleus ${}^{135}\mathrm{I}$ has been measured to be 1.74(8) ns using the EXILL-FATIMA mixed array of Ge and ${\mathrm{LaBr}}_3$ detectors. The nuclei were produced following the cold neutron-induced fission of a ${}^{235}\mathrm{U}$ target at the PF1B beam line of the Institut Laue-Langevin. The extracted $B(E2;15/2^{+}\to 11/2^{+})$ value enabled a test of seniority relations for the first time between $E2$ transition rates. Large-scale shell-model calculations were performed for ${}^{134}\mathrm{Te}$ and ${}^{135}\mathrm{I}$, and reinterpreted in a single-orbit approach. The results show that the two-body component of the $E2$ operator can be large whereas energy shifts due to the three-body component of the effective interaction are small.

A cluster-transfer experiment ${}^9\mathrm{Be}({}^9\mathrm{Be},{}^{14}\mathrm{C}^{*}\to \alpha +{}^{10}\mathrm{Be}){}^4\mathrm{He}$ was carried out using an incident beam energy of 45 MeV. This reaction channel has a large $Q$ value that favors populating the high-lying states in ${}^{14}\mathrm{C}$ and separating various reaction channels. A number of resonant states are reconstructed from the forward-emitting ${}^{10}\mathrm{Be}+\alpha$ fragments with respect to three sets of well-discriminated final states in ${}^{10}\mathrm{Be}$, most of which agree with the previous observations. A state at 22.5(1) MeV in ${}^{14}\mathrm{C}$ is found to decay predominantly into the states around 6 MeV in ${}^{10}\mathrm{Be}$ daughter nucleus, in line with the unique property of the predicted band head of the $\sigma$-bond linear-chain molecular states. A new state at 23.5(1) MeV is identified which decays strongly into the first excited state of ${}^{10}\mathrm{Be}$.

We develop a method to construct a microscopic optical potential from chiral interactions for nucleon-nucleus scattering. The optical potential is constructed by combining the Green's function approach with the coupled-cluster method. To deal with the poles of the Green's function along the real energy axis we employ a Berggren basis in the complex energy plane combined with the Lanczos method. Using this approach, we perform a proof-of-principle calculation of the optical potential for the elastic neutron scattering on ${}^{16}\mathrm{O}$. For the computation of the ground state of ${}^{16}\mathrm{O}$, we use the coupled-cluster method in the singles-and-doubles approximation, while for the $A\pm 1$ nuclei we use particle-attached/removed equation-of-motion method truncated at two-particle–one-hole and one-particle–two-hole excitations, respectively. We verify the convergence of the optical potential and scattering phase shifts with respect to the model-space size and the number of discretized complex continuum states. We also investigate the absorptive component of the optical potential (which reflects the opening of inelastic channels) by computing its imaginary volume integral and find an almost negligible absorptive component at low energies. To shed light on this result, we computed excited states of ${}^{16}\mathrm{O}$ using the equation-of-motion coupled-cluster method with singles-and-doubles excitations and we found no low-lying excited states below 10 MeV. Furthermore, most excited states have a dominant two-particle–two-hole component, making higher-order particle-hole excitations necessary to achieve a precise description of these core-excited states. We conclude that the reduced absorption at low energies can be attributed to the lack of correlations coming from the low-order cluster truncation in the employed coupled-cluster method.

The high-spin structures and isomers of the $N=81$ isotones ${}^{135}\mathrm{Xe}$ and ${}^{137}\mathrm{Ba}$ are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ and (ii) ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii) in the ${}^{136}\mathrm{Xe}+{}^{198}\mathrm{Pt}$ MNT reaction employing the $\gamma$-ray array GAMMASPHERE in combination with the gas-detector array CHICO, and (iv) via a ${}^{11}\mathrm{B}+{}^{130}\mathrm{Te}$ fusion-evaporation reaction with the HORUS $\gamma$-ray array at the University of Cologne. The high-spin level schemesof ${}^{135}\mathrm{Xe}$ and ${}^{137}\mathrm{Ba}$ are considerably extended to higher energies. The 2058-keV $(19/2^{-})$ state in ${}^{135}\mathrm{Xe}$ is identified as an isomer, closing a gap in the systematics along the $N=81$ isotones. Its half-life is measured to be 9.0(9) ns, corresponding to a reduced transition probability of $B(E2,19/2^{-}\to 15/2^{-})=0.52\left(6\right)$ W.u. The experimentally deduced reduced transition probabilities of the isomeric states are compared to shell-model predictions. Latest shell-model calculations reproduce the experimental findings generally well and provide guidance to the interpretation of the new levels.

Bandhead energies of all the physically admissible low-lying two-quasiparticle configuration states in the doubly-odd heavy actinide ${}_{101}{}^{254}\mathrm{Md}_{153}$ are evaluated using the well-tested two-quasiparticle rotor model with explicit inclusion of the residual proton-neutron interaction. A critical examination of these results, aimed at characterization of the long-lived ($t_{1/2}=10$ min and 28 min; $\%\varepsilon \le 100$) isomer pair, conclusively rules out a high-spin ($J\ge 5$) assignment for either of the isomers. Our analysis leads to $J^{\pi }K=1^{-}0\{p:1/2^{-}\left[521\right]\otimes n:1/2^{+})\left[620\right]\}$ and $3^{-}3\{p:7/2^{-}\left[514\right]\otimes n:1/2^{+}\left[620\right]\}$ assignments, respectively, to these isomers and designates the 10-min isomer as its ground state. Our study reveals a “landmark” position for ${}^{254}\mathrm{Md}$ in the decay path of super heavy elements. The as-yet unobserved electron capture decay branches from each of the two ${}^{254}\mathrm{Md}$ isomers to ${}^{254}\mathrm{Fm}$ levels are specified.

The temperature dependence of the symmetry energy for isotopic chains of even-even Ni, Sn, and Pb nuclei is investigated in the framework of the local density approximation (LDA). The Skyrme energy density functional with two Skyrme-class effective interactions, SkM* and SLy4, is used in the calculations. The temperature-dependent proton and neutron densities are calculated through the hfbtho code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. In addition, two other density distributions of ${}^{208}\mathrm{Pb}$, namely the Fermi-type density determined within the extended Thomas-Fermi (TF) method and symmetrized-Fermi local density obtained within the rigorous density functional approach, are used. The kinetic energy densities are calculated either by the hfbtho code or, for a comparison, by the extended TF method up to second order in temperature (with $T^2$ term). Alternative ways to calculate the symmetry energy coefficient within the LDA are proposed. The results for the thermal evolution of the symmetry energy coefficient in the interval $T=0–4$ MeV show that its values decrease with temperature. The temperature dependence of the neutron and proton root-mean-square radii and corresponding neutron skin thickness is also investigated, showing that the effect of temperature leads mainly to a substantial increase of the neutron radii and skins, especially in the more neutron-rich nuclei, a feature that may have consequences on astrophysical processes and neutron stars.

The absolute neutron-induced fission cross section of ${}^{242}\mathrm{Pu}$ was measured at five energies between 1 and 2.5 MeV at the low-scatter neutron measurement facility of the National Physical Laboratory, UK. The measurements are part of an effort to reduce uncertainties of nuclear data related to fast spectrum reactors. The neutron-induced fission results are in good agreement with the Evaluated Nuclear Data File/B-VII.1 but disagree with several recent measurements near the resonance-like structure around 1.1 MeV. Within the same experimental campaign, the spontaneous fission half-life of ${}^{242}\mathrm{Pu}$ was measured and it is in good agreement with previous results.

Comparative assessment of the total breakup proton-emission cross sections measured for 56 MeV deuteron interaction with target nuclei from ${}^{12}\mathrm{C}$ to ${}^{209}\mathrm{Bi}$, with an empirical parametrization and recently calculated microscopic neutron-removal cross sections was done at the same time with similar data measured at 15, 25.5, 70, and 80 MeV. Comparable mass dependencies of the elastic-breakup (EB) cross sections provided by the empirical parametrization and the microscopic results have been also found at the deuteron energy of 56 MeV, while the assessment of absolute-values variance up to a factor of two was not possible because of the lack of EB measurements at energies higher than 25.5 MeV. While the similarities represent an additional validation of the microscopic calculations, the cross-section difference should be considered within the objectives of further measurements.

Measurements of fission product yields play an important role for the understanding of fundamental aspects of the fission process. Recently, neutron-induced fission product-yield data of ${}^{239}\mathrm{Pu}$ at energies below 4 MeV revealed an unexpected energy dependence of certain fission fragments. In order to investigate whether this observation is prerogative to neutron-induced fission, a program has been initiated to measure fission product yields in photoinduced fission. Here we report on the first ever photofission product yield measurement with monoenergetic photons produced by Compton back-scattering of FEL photons. The experiment was performed at the High-Intensity Gamma-ray Source at Triangle Universities Nuclear Laboratory on ${}^{239}\mathrm{Pu}$ at $E_{\gamma }=11$ MeV. In this exploratory study the yield of eight fission products ranging from ${}^{91}\mathrm{Sr}$ to ${}^{143}\mathrm{Ce}$ has been obtained.

The EXO-200 Collaboration is searching for neutrinoless double $\beta$ decay using a liquid xenon (LXe) time projection chamber. This measurement relies on modeling the transport of charge deposits produced by interactions in the LXe to allow discrimination between signal and background events. Here we present measurements of the transverse diffusion constant and drift velocity of electrons at drift fields between 20 V/cm and 615 V/cm using EXO-200 data. At the operating field of 380 V/cm EXO-200 measures a drift velocity of $1.{705}_{-0.010}^{+0.014}\mathrm{mm}/\mu \mathrm{s}$ and a transverse diffusion coefficient of $55\pm 4{\mathrm{cm}}^2$/s.

Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For ${}^{124}\mathrm{Xe}$ this process has not yet been observed and its detection would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the $K$ shell of ${}^{124}\mathrm{Xe}$ using 7636 $\mathrm{kg}\mathrm{d}$ of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90% credibility limit on the half-life $T_{1/2}>6.5\times {10}^{20}$ yr. We have also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and found a sensitivity of $T_{1/2}>6.1\times {10}^{22}$ yr after an exposure of 2 $\mathrm{t}\mathrm{yr}$.

Quark-gluon plasma produced at the early stage of ultrarelativistic heavy-ion collisions is unstable, if weakly coupled, due to the anisotropy of its momentum distribution. Chromomagnetic fields are spontaneously generated and can reach magnitudes much exceeding typical values of the fields in equilibrated plasma. We consider a high-energy test parton traversing an unstable plasma that is populated with strong fields. We study the momentum broadening parameter $\widehat{q}$ which determines the radiative energy loss of the test parton. We develop a formalism which gives $\widehat{q}$ as the solution of an initial value problem, and we focus on extremely oblate plasmas which are physically relevant for relativistic heavy-ion collisions. The parameter $\widehat{q}$ is found to be strongly dependent on time. For short times it is of the order of the equilibrium value, but at later times $\widehat{q}$ grows exponentially due to the interaction of the test parton with unstable modes and becomes much bigger than the value in equilibrium. The momentum broadening is also strongly directionally dependent and is largest when the test parton velocity is transverse to the beam axis. Consequences of our findings for the phenomenology of jet quenching in relativistic heavy-ion collisions are briefly discussed.

In this work, the two-photon-exchange (TPE) effects in the unpolarized $\mu p$ scattering are discussed within the hadronic model where the intermediate states $N,\mathrm{\Delta }$, and $\sigma$ are considered. The contribution from the $N$ intermediate is close to the results given by Tomalak and Vanderhaeghen [Phys. Rev. D 90, 013006 (2014)] at small $Q$, and there is a sizable difference when $Q>0.25\mathrm{GeV}$ (where $Q^2$ is the four-momentum transfer). The contributions from the $\mathrm{\Delta }$ and the $\sigma$ intermediate states are much smaller than that from the $N$ intermediate at small $Q$. In the kinematic region with $k_i\subseteq [0.01,0.3]$ GeV and $Q\le 0.4\mathrm{GeV}$ (where $k_i$ is the three-momentum of initial muon in the laboratory frame), a naive expression for the TPE contributions is given, which can be used directly for other analysis.