We present the first measurements of identified hadron production, azimuthal anisotropy, and pion interferometry from $\mathrm{Au}+\mathrm{Au}$ collisions below the nominal injection energy at the BNL Relativistic Heavy-Ion Collider (RHIC) facility. The data were collected using the large acceptance solenoidal tracker at RHIC (STAR) detector at $\sqrt{s_{\mathit{NN}}}=9.2$ GeV from a test run of the collider in the year 2008. Midrapidity results on multiplicity density $\mathit{dN}/\mathit{dy}$ in rapidity $y$, average transverse momentum $\langle p_T\rangle$, particle ratios, elliptic flow, and Hanbury-Brown–Twiss (HBT) radii are consistent with the corresponding results at similar $\sqrt{s_{\mathit{NN}}}$ from fixed-target experiments. Directed flow measurements are presented for both midrapidity and forward-rapidity regions. Furthermore the collision centrality dependence of identified particle $\mathit{dN}/\mathit{dy}$, $\langle p_T\rangle$, and particle ratios are discussed. These results also demonstrate that the capabilities of the STAR detector, although optimized for $\sqrt{s_{\mathit{NN}}}=200$ GeV, are suitable for the proposed QCD critical-point search and exploration of the QCD phase diagram at RHIC.

The nuclei ${}^{163,164}\mathrm{Dy}$ have been investigated using the Oslo method on data from the pickup reaction ${}^{164}\mathrm{Dy}$(${}^3\mathrm{He}$,$\alpha \gamma$)${}^{163}\mathrm{Dy}$ and the inelastic scattering ${}^{164}\mathrm{Dy}$(${}^3\mathrm{He}$,${}^3\mathrm{He}$${}^{\prime }\gamma$)${}^{164}\mathrm{Dy}$, respectively. The radiative strength functions for both nuclei have been extracted, and a small resonance centered around $E_{\gamma }\approx 3$ MeV is observed in both cases. The parameters of this so-called pygmy $M1$ resonance (the scissors mode) are compared with previous results on ${}^{160,161,162}\mathrm{Dy}$ using the Oslo method, and with data on ${}^{163}\mathrm{Dy}$ measured by the Prague group using the two-step cascade method. In particular, the integrated reduced transition probability $B(M1\uparrow )$ of the pygmy resonance is compared with neighboring dysprosium isotopes. We also observe an enhanced strength in the region above $E_{\gamma }\approx 5$ MeV in ${}^{164}\mathrm{Dy}$. Possible origins of this feature are discussed.

Angular distributions for the elastic scattering of the weakly bound ${}^{6,7}\mathrm{Li}+{}^{144}\mathrm{Sm}$ systems were measured with high accuracy at bombarding energies from $85\%$ up to $170\%$ of the Coulomb barrier. An optical model analysis was performed, and the relevant parameters of the real and imaginary parts of the optical potential were extracted. The results are compared with those previously published for the tightly bound ${}^{12}\mathrm{C}+{}^{144}\mathrm{Sm}$ and ${}^{16}\mathrm{O}+{}^{144}\mathrm{Sm}$ systems. The usual threshold anomaly observed in the behavior of the potential of tightly bound systems was not observed for either weakly bound system. This absence is attributed to the repulsion due to breakup coupling which cancels the attraction arising from couplings with bound channels.

A neutron multiplication coefficient, $k_{\mathrm{eff}}$, has been estimated for spallation neutron flux using the data of spectrum average cross sections of all absorption, fission, and nonelastic reaction channels of ${}^{232}\mathrm{Th}$, ${}^{238}\mathrm{U}$, ${}^{235}\mathrm{U}$, and ${}^{233}\mathrm{U}$ fuel elements. It has been revealed that in spallation neutron flux (i) nonfission, nonabsorption reactions play an important role in the calculation of $k_{\mathrm{eff}}$, (ii) one can obtain a high value of $k_{\mathrm{eff}}$ even for fertile ${}^{232}\mathrm{Th}$ fuel, which is hardly possible in a conventional fast reactor, and (iii) spectrum average absorption cross sections of neutron poisons of a conventional reactor are relatively very small.

A joint analysis of the elastic-scattering angular distributions and fusion cross sections together with the $S$ factor for the ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ system near and below the Coulomb barrier is reported. To describe these observables within the framework of the optical model, a comparative study of microscopic $\alpha$-$\alpha$ double-folding clusters and phenomenological shallow potentials with surface-transparent imaginary parts is performed. Although the phenomenological Woods-Saxon type of shallow real potentials is unable to provide a consistent explanation of these data, the $\alpha$-$\alpha$ double-folding cluster potential obtained by considering the $\alpha$-cluster structure of ${}^{16}\mathrm{O}$ provides a considerable improvement. The $\alpha$-$\alpha$ double-folding cluster potential also reproduces the normalized resonant energy states of ${}^{32}\mathrm{S}$ for the $N=24$ cluster band.

A set of new global phenomenological optical model potential parameters for the actinide region with incident nucleon energies from 1 keV up to 300 MeV is obtained. They are based on a smooth, unique functional form for the energy dependence of the potential depths and on physically constrained geometry parameters. The available experimental data including the neutron total cross sections, nonelastic cross sections, elastic scattering cross sections, elastic scattering angular distributions, and proton reaction cross sections and elastic scattering angular distributions of ${}^{232}\mathrm{Th}$ and ${}^{238}\mathrm{U}$ are used. The new nucleon global optical model potential parameters obtained are analyzed and used to analyze the experimental data of nucleon-actinide reactions. It is found that the present form of the global optical model potential could reproduce both the neutron and the proton experimental data.

Using results from the chiral perturbation theory for the $s$-wave interaction and the $\Delta$-resonance model for the $p$-wave interaction of pions with nucleons, we evaluated the spectral functions of pions in asymmetric nuclear matter with unequal proton and neutron densities. We find that in hot dense neutron-rich matter the strength of the spectral function of positively charged pions at low energies is somewhat larger than that of negatively charged pions. In a thermal model, this isospin-dependent effect slightly reduces the ratio of negatively charged to positively charged pions that are produced in heavy ion collisions induced by radioactive beams. The relevance of our results to the determination of the nuclear symmetry energy from the measured ratio of negatively to positively charged pions produced in heavy ion collisions is discussed.

The cross sections for a variety of diffractive processes in proton-nucleus scattering, associated with large gaps in rapidity, are calculated within an improved Glauber-Gribov theory, where the inelastic shadowing corrections are summed to all orders by employing the dipole representation. The effects of nucleon correlations, leading to a modification of the nuclear thickness function, are also taken into account. Numerical calculations are performed for the energies of the Hadron-Electron Ring Accelerator-B experiment, the Relativistic Heavy Ion Collider and Large Hadron Collider, and for several nuclei. It is found that whereas the Gribov corrections generally make nuclear matter more transparent, nucleon correlations act in the opposite direction and have important effects in various diffractive processes.

Liquid xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of weakly interacting massive particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (${\mathcal{L}}_{\mathrm{eff}}$) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this article, we present new measurements that extend the energy down to 4 keV, finding that ${\mathcal{L}}_{\mathrm{eff}}$ decreases with decreasing energy. We also measure the quenching of scintillation efficiency caused by the electric field in LXe, finding no significant field dependence.

Several low-lying excited states in ${}_{86}^{205}{\mathrm{Rn}}_{119}$ and ${}_{84}^{201}{\mathrm{Po}}_{117}$ were identified for the first time following EC/${\beta }^{+}$ decay of ${}^{205}\mathrm{Fr}$ and ${}^{201}\mathrm{At}$, respectively, using $\gamma$-ray and conversion electron spectroscopy at the CERN isotope separator on-line (ISOLDE) facility. The EC/${\beta }^{+}$ branch from ${}^{205}\mathrm{Fr}$ was measured to be $1.5(2)\%$. The excited states of the daughter nuclei are understood in terms of the odd nucleon coupling to the neighboring even-even core. The neutron single-particle energies of the $p_{3/2}$ orbital relative to the $f_{5/2}$ ground state in ${}^{205}\mathrm{Rn}$, and the $f_{5/2}$ orbital relative to the $p_{3/2}$ ground state in ${}^{201}\mathrm{Po}$, were determined to be 31.4(2) and 5.7(3) keV, respectively. We tentatively identify a ${\frac{13}{2}}^{+}$ isomeric level at 657.1(5) keV in ${}^{205}\mathrm{Rn}$. The systematic behavior of the ${\frac{13}{2}}^{+}$ and ${\frac{3}{2}}^{-}$ levels is also discussed.

The $g$ factors of the ${12}^{+}$, ${11}^{-}$, and $8^{-}$ isomeric states in ${}^{188}\mathrm{Pb}$ were measured using the time-differential perturbed angular distribution method as $g({12}^{+})=-0.179(6)$, $g({11}^{-})=+1.03(3)$, and $g(8^{-})=-0.037(7)$. The $g$ factor of the ${12}^{+}$ state follows the observed slight down-sloping evolution of the $g$ factors of the $i_{13/2}^2$ neutron spherical states with decreasing $N$. The $g$ factors of the ${11}^{-}$ and $8^{-}$ isomers proposed as oblate and prolate deformed states, respectively, were interpreted within the rotational model, using calculated and empirical $g$ factor values for the involved single-particle orbitals.

We suggest the procedure of direct derivation of the symmetry energy from the shift of neutron-proton chemical potentials $\Delta \lambda ={\lambda }_n-{\lambda }_p$ for nuclei beyond the $\beta$-stability line. We observe the presence of anomalous strong (about $15\%$) shell oscillations at the symmetry energy coefficient $b_{\mathrm{sym}}$. Our results do not confirm the existence of exceptionally large values of the symmetry energy coefficient at mass number $A\approx 100$ that was reported in Ref. [2]. Using the fitting procedure, we evaluate the volume $b_{\mathrm{sym},\mathrm{vol}}$ and surface $b_{\mathrm{sym},\mathrm{surf}}$ contributions to the symmetry energy. We estimate the experimental value of surface-to-volume ratio as $r_{\mathrm{S}}/\mathrm{V}=\left|b_{\mathrm{sym},\mathrm{surf}}\right|/b_{\mathrm{sym},\mathrm{vol}}\approx 1.7$ for the fitting interval $A⩾50$.

We study the $(K^{-},p)$ reaction on nuclei with a 1 GeV/$c$ momentum kaon beam, paying special attention to the region of emitted protons having kinetic energy above 600 MeV, which was used to claim a deeply attractive kaon nucleus optical potential. Our model describes the nuclear reaction in the framework of a local density approach and the calculations are performed following two different procedures: one is based on a many-body method using the Lindhard function and the other is based on a Monte Carlo simulation. The simulation method offers flexibility to account for processes other than kaon quasielastic scattering, such as $K^{-}$ absorption by one and two nucleons, producing hyperons, and allows consideration of final-state interactions of the $K^{-}$, the $p$, and all other primary and secondary particles on their way out of the nucleus, as well as the weak decay of the produced hyperons into $\pi N$. We find a limited sensitivity of the cross section to the strength of the kaon optical potential. We also show a serious drawback in the experimental setup—the requirement for having, together with the energetic proton, at least one charged particle detected in the decay counter surrounding the target—as we find that the shape of the original cross section is appreciably distorted, to the point of invalidating the claims made in the experimental paper on the strength of the kaon nucleus optical.

We offer a new theoretical interpretation for the effect of enhanced electron density at the ${}^7\mathrm{Be}$ nucleus encapsulated in fullerene ${\mathrm{C}}_{60}$. Our ab initio Hartree-Fock calculations show that the electron density at the ${}^7\mathrm{Be}$ nucleus in ${}^7\mathrm{Be}$$@{\mathrm{C}}_{60}$ increases due to the attractive effective potential well generated by the fullerene. The $2s$ state in the isolated Be atom turns into a $3s$ state in the joint potential. This new state has higher energy and slightly larger amplitude at the Be nucleus than the previous $2s$ state. Moreover the $3s$ wave function has an additional node that appeared at a distance $r\simeq 5a_B$ from the center. The node imitates repulsion between the Be electron and the fullerene wall because the electron has zero probability to occupy this region. Such an imitation of the repulsion by means of the node in an attractive potential has a direct physical analogy in the theory of $\alpha$-$\alpha$ and $N-N$ nuclear interactions.

Fusion evaporation cross sections for the ${}^{27}\mathrm{Al}+{}^{45}\mathrm{Sc}$ ($Q=9.63$ MeV) system are measured down to about 300 nb. Deviations from standard coupled-channels calculations were observed in this system at the lowest energies. The steep fall-off of the fusion cross sections can be reproduced by calculations using a shallow potential model, which was originally developed to explain the hindrance behavior of heavy-ion fusion in medium-mass systems with negative $Q$ values. Comparisons of the hindrance behavior between the present experiment and other systems, for example, ${}^{28}\mathrm{Si}+{}^{30}\mathrm{Si}$ ($Q=14.3$ MeV) and ${}^{36}\mathrm{S}+{}^{48}\mathrm{Ca}$ ($Q=7.55$ MeV) are presented.

Motivated by the renewed interest in the surrogate nuclear reactions approach, an indirect method for determining compound-nuclear reaction cross sections, the prospects for determining ($n,\gamma$) cross sections for deformed rare-earth and actinide nuclei are investigated. A nuclear reaction model is employed to simulate physical quantities that are typically measured in surrogate experiments and used to assess the validity of the Weisskopf-Ewing and ratio approximations, which are typically employed in the analysis of surrogate reactions. The expected accuracy of ($n,\gamma$) cross sections extracted from typical surrogate measurements is discussed and limitations of the approximate methods are illustrated. Suggestions for moving beyond presently employed approximations are made.

The recent experimental data on Coulomb breakup of the nucleus ${}^{31}\mathrm{Ne}$ are interpreted in terms of deformation. The measured large one-neutron removal cross section indicates that the ground state of ${}^{31}\mathrm{Ne}$ is either an $s$ halo or a $p$ halo. The data can be most easily interpreted as the spin of the ground state being 3/$2^{-}$ coming from either the Nilsson level [$330 1/2$] or the Nilsson level [$321 3/2$] depending on the neutron separation energy $S_n$. However, the possibility of $1/2^{+}$ coming from [$200 1/2$] is not excluded. It is suggested that if the large ambiguity in the measured value of $S_n$ of ${}^{31}\mathrm{Ne}$, $0.29\pm 1.64$ MeV, can be reduced by an order of magnitude, say to be $\pm 100$ keV, one may get a clear picture of the spin-parity of the halo ground state.

Measurements of neutron-deuteron ($n$-$d$) analyzing power $A_y(\theta )$ at $E_n=19.0$ MeV are reported at 16 angles from ${\theta }_{\mathrm{c}.\mathrm{m}.}=46.7$ to ${152.0}^{°}$. The objective of the experiment is to better characterize the discrepancies between $n$-$d$ data and the predictions of three-nucleon calculations for neutron energies above 16.0 MeV. The experiment used a shielded neutron source, which produced polarized neutrons via the ${}^2\mathrm{H}$($\mathrm{d⃗}$,$\mathrm{n⃗}$)${}^3\mathrm{He}$ reaction, a deuterated liquid scintillator center detector (CD) and liquid-scintillator neutron side detectors. A coincidence between the CD and the side detectors isolated the elastic-scattering events. The CD pulse height spectrum associated with each side detector was sorted by using pulse-shape discrimination, time-of-flight techniques, and by removing accidental coincidences. A Monte Carlo computer simulation of the experiment accounted for effects due to finite geometry, multiple scattering, and CD edge effects. The resulting high-precision data (with absolute uncertainties ranging from 0.0022 to 0.0132) have a somewhat lower discrepancy with the predictions of three-body calculations, as compared to those found at lower energies.

The neutrinoless double-$\beta$ ($0\nu \beta \beta$) decay process could provide crucial information to determine the absolute scale of neutrino masses, and it is the only one that can establish whether a neutrino is a Dirac or a Majorana particle. A key ingredient for extracting the absolute neutrino masses from $0\nu \beta \beta$ decay experiments is a precise knowledge of the nuclear matrix elements (NMEs) describing the half-life of this process. We developed a shell model approach for computing the $0\nu \beta \beta$ decay NME, and we used it to analyze the $0\nu \beta \beta$ mode of ${}^{48}\mathrm{Ca}$. The dependence of the NME on the short-range correlation parameters, on the average energy of the intermediate states, on the finite-size cutoff parameters, and on the effective interaction used for many-body calculations is discussed.

We propose to investigate the properties of nuclear matter by measuring the elastic scattering of $J/\psi$ on nuclei with a high precision. $J/\psi$ mesons are produced from photons emitted in high-energy electron-proton or electron-nucleus scattering in the low-$x$ region. Their scattering on nucleons or nuclei is predominantly mediated by gluonic forces. The measurement could be performed at the future ENC, EIC, or LHeC facility.