Although the observation of wobbling was once thought to be possibly confined to lutetium isotopes in $N\approx 94$ nuclei, the identification of this exotic collective mode in ${}^{167}$Ta has raised the question of the role of the proton Fermi surface with regard to this phenomenon. To investigate this issue, an experiment was performed to populate high-spin states in the $N=94$ nucleus ${}^{169}$Re. The heavy-ion reaction ${}^{55}\mathrm{Mn}+{}^{118}\mathrm{Sn}$ was used in conjunction with Gammasphere to detect the emitted $\gamma$ rays. More than 130 new transitions were added to the ${}^{169}$Re level scheme, including the first identification of the $\pi i_{13/2}$ rotational sequence in this nucleus. This configuration is the structure on which all known wobbling sequences are based, but no wobbling band was observed, likely owing to the fact that the $\pi i_{13/2}$ sequence is located at a relatively high energy in comparison with the other structures found in ${}^{169}$Re. Nine decay sequences are now established in this nucleus and are described within the context of the cranked shell model. In addition, significant extension of the level scheme of the odd-odd ${}^{170}$Re nucleus was possible and a discussion of the residual interactions for the $\pi h_{9/2}\nu i_{13/2}$ and $\pi i_{13/2}\nu i_{13/2}$ configurations in this region is given as well.

We report measurements of the exclusive electroproduction of $K^{+}\Lambda$ and $K^{+}{\Sigma }^0$ final states from an unpolarized proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions ${\sigma }_U$, ${\sigma }_{LT}$, ${\sigma }_{TT}$, and ${\sigma }_{L{T}^{\prime }}$ were extracted from the $\Phi$-dependent differential cross sections acquired with a longitudinally polarized 5.499 GeV electron beam. The data span a broad range of momentum transfers $Q^2$ from 1.4 to 3.9 GeV${}^2$, invariant energy $W$ from threshold to 2.6 GeV, and nearly the full center-of-mass angular range of the kaon. The separated structure functions provide an unprecedented data sample, which, in conjunction with other meson photo- and electroproduction data, will help to constrain the higher-level analyses being performed to search for missing baryon resonances.

A collective model is proposed to describe the chiral rotation and vibration and applied to a system with one $h_{11/2}$ proton particle and one $h_{11/2}$ neutron hole coupled to a triaxial rigid rotor. The collective Hamiltonian is constructed from the potential energy and mass parameter obtained in the tilted axis cranking approach. By diagonalizing the collective Hamiltonian with a box boundary condition, it is found that for the chiral rotation, the partner states become more degenerate with the increase of the cranking frequency, and for the chiral vibrations, their important roles for the collective excitation are revealed at the beginning of the chiral rotation region.

Background: One-nucleon removal reactions at or above the Fermi energy are important tools to explore the single-particle structure of exotic nuclei. Experimental data must be compared with calculations to extract structure information, evaluate correlation effects in nuclei, or determine reaction rates for nuclear astrophysics. However, there is insufficient knowledge to calculate the cross sections for these reactions accurately.

Purpose: We evaluate the contributions of the final-state interaction (FSI) and of the medium modifications of the nucleon-nucleon interactions and obtain the shapes and magnitudes of the momentum distributions. Such effects have been often neglected in the literature.

Method: Calculations for reactions at energies of 35–1000 MeV/nucleon are reported and compared to published data. For consistency, the state-of-the-art eikonal method for stripping and diffraction dissociation is used.

Results: We find that the two effects are important and their relative contributions vary with the energy and with the atomic and mass number of the projectile involved.

Conclusions: These two often neglected effects modify considerably the one-nucleon-removal cross sections. As expected, the effects are largest at lower energies, around 50 MeV/nucleon, and on heavy targets.

The conditions for the development of a Kelvin-Helmholtz instability (KHI) for the quark-gluon plasma (QGP) flow in a peripheral heavy ion collision is investigated. The projectile and target side particles are separated by an energetically motivated hypothetical surface, characterized with a phenomenological surface tension. In such a view, a classical potential flow approximation is considered and the onset of the KHI is studied. The growth rate of the instability is computed as a function of phenomenological parameters characteristic for the QGP fluid: viscosity, surface tension, and flow layer thickness.

The effect of multiple scatterings on the propagation of hard partonic jets in a dense nuclear medium is studied in the framework of deep-inelastic scattering (DIS) off a large nucleus. Power counting arguments based on the Glauber improved soft collinear effective theory are used to identify the class of leading power corrections to the process of a single parton traversing the extended medium without emission. It turns out that the effect of longitudinal drag and diffusion (often referred to as straggling) is as important as transverse scattering, when relying solely on power counting arguments. With the inclusion of momentum exchanges in both transverse and longitudinal directions between the traversing hard parton and the constituents of the medium, we derive a differential equation for the time (or distance) evolution of the hard parton momentum distribution. Keeping up to the second order in a momentum gradient expansion, this equation describes in-medium evolution of hard jets which experience longitudinal drag and diffusion plus the transverse broadening caused by multiple scatterings from the medium.

The relativistic correction of the anti de Sitter space/conformal field theory implied potential model for a quarkonium state is examined. For the typical range of the coupling strength appropriate to heavy-ion collisions, we find the correction is significant in size for $J/\Psi$.

Recent observation of pulsar PSR J1614-2230 with a mass of about two solar masses poses a severe constraint on the equations of state (EOSs) of matter describing stars under extreme conditions. Neutron stars (NSs) can reach the mass limit set by PSR J1614-2230, but stars having hyperons or quark stars (QSs) having boson condensates, with softer EOSs, can barely reach such limit and are ruled out. QSs with pure strange matter cannot attain such high mass unless the effect of strong coupling constants or color superconductivity are considered. In this work I calculate the upper mass limit for a hybrid star (HS) having a quark-hadron mixed phase. The hadronic matter (having hyperons) EOS is described by relativistic mean field theory and the quark matter EOS is modeled according to the Massachusetts Institute of Technology bag model. The intermediate mixed phase is constructed using the Glendenning prescription. A HS with a mixed phase cannot reach the mass limit set by PSR J1614-2230 unless one assumes a density-dependent bag constant. However, for such case the mixed-phase region is small. The maximum mass of a mixed hybrid star obtained with such a mixed-phase region is $2.01M_{\odot }$. A stiffer hadronic EOS can raise the maximum mass of a mixed HS to $2.1$ $M_{\odot }$.

The $\beta$ decay of ${}^{53,54}$Ni, ${}^{52,53}$Co, ${}^{51}$Fe, and ${}^{50}$Mn was investigated via the fragmentation of a ${}^{58}$Ni primary beam with an energy of 68.6 MeV/u. The proton-$\gamma$ coincidences of ${}^{53}$Ni $\beta$-delayed proton emission were observed. Based on the analysis of the proton-$\gamma$ coincidence events, it was inferred that the previous assignment of the excitation energy for the isobaric analog state in ${}^{53}$Co may be problematic. The half-lives of these nuclei were obtained, in which the uncertainty of ${}^{52}$Co half-life was reduced by a factor of 3. The half-lives were evaluated and used as inputs of nucleosynthesis calculations of the rapid proton-capture process in an x-ray burst.

A complete and improved calculation of phase space factors (PSF) for $2\nu {\beta }^{+}{\beta }^{+}$ and $0\nu {\beta }^{+}{\beta }^{+}$ decay, as well as for the competing modes $2\nu \mathrm{EC}{\beta }^{+}$, $0\nu \mathrm{EC}{\beta }^{+}$, and $2\nu \mathrm{ECEC}$, is presented. The calculation makes use of exact Dirac wave functions with finite nuclear size and electron screening and includes life-times, single and summed positron spectra, and angular positron correlations.

We show that fluctuations of the fireball shape in the longitudinal direction generate nontrivial rapidity correlations that depend not only on the rapidity difference, $y_1-y_2$, but also on the rapidity sum, $y_1+y_2$. This is explicitly demonstrated in a simple wounded nucleon model, and the general case is also discussed. It is argued that rapidity fluctuations are large compared to normal statistical fluctuations. We show how to extract different components of the fluctuating fireball shape from the measured two-particle rapidity correlation function. The experimental possibility of studying the longitudinal initial conditions in heavy-ion and proton-proton collisions is emphasized.

We study $J/\Psi$ absorption in high-multiplicity proton-proton (pp) collisions at $\sqrt{s_{NN}}=7$TeV. We predict a modification of the $J/\Psi$ yield within the ultrarelativistic quantum molecular dynamics (UrQMD) transport model approach, where explicit interactions of the $J/\Psi$ with the surrounding comovers and a prehadronic phase with adjusted cross sections and $J/\Psi$ melting is included. We present the analog of the nuclear modification factor in pp collisions at various charged particle multiplicities. It turns out that $J/\Psi$ mesons may be suppressed towards higher particle multiplicities in pp collisions at LHC energies.

A nonconventional mechanism for the basic $2\pi$-fusion reaction $pn\to d+{\left(\pi \pi \right)}_0$ in the energy region $T_p=1.0$–$1.4$ GeV is suggested. The mechanism is aimed at providing a consistent explanation for the comprehensive experimental studies of this reaction in an exclusive setting done recently by the WASA-at-COSY Collaboration. The basic assumption of the model proposed is the production of the $I\left(J^P\right)=0\left(3^{+}\right)$ dibaryon resonance $D_{03}$ in the $pn$ collision. The interference of two decay channels of this resonance—$D_{03}\to d+\sigma \to d+{\left(\pi \pi \right)}_0$ and $D_{03}\to D_{12}+\pi \to d+{\left(\pi \pi \right)}_0$—is shown to give a strong near-threshold enhancement in the $\pi \pi$ invariant mass spectrum, which is well known as the Abashian-Booth-Crowe (ABC) effect. The $\sigma$-meson parameters found to reproduce the ABC enhancement are in a general agreement with models which predict the chiral symmetry restoration at high excitation energy and/or high density of matter, although they are essentially less than those accepted for the free $\sigma$ meson. So, this result might be considered as an indication of partial chiral symmetry restoration in dense and excited quark matter.

We study the spin response of cold dense neutron matter in the limit of zero momentum transfer and show that the frequency dependence of the long-wavelength spin response is well constrained by sum rules and the asymptotic behavior of the two-particle response at high frequency. The sum rules are calculated using an auxiliary field diffusion Monte Carlo technique and the high-frequency two-particle response is calculated for several nucleon-nucleon potentials. At nuclear saturation density, the sum rules suggest that the strength of the spin response peaks at $\omega \simeq$ 40–60 MeV, decays rapidly for $\omega \ge 100$ MeV, and has a sizable strength below 40 MeV. This strength at relatively low energy may lead to enhanced neutrino production rates in dense neutron-rich matter at temperatures of relevance to core-collapse supernova.

We have performed large-scale shell-model calculations of the half-lives and neutron-branching probabilities of the $r$-process waiting-point nuclei at the magic neutron numbers $N=50$, 82, and 126. The calculations include contributions from allowed Gamow-Teller and first-forbidden transitions. We find good agreement with the measured half-lives for the $N=50$ nuclei with charge numbers $Z=28$–32 and for the $N=82$ nuclei ${}^{129}$Ag and ${}^{130}$Cd. The contribution of forbidden transitions reduce the half-lives of the $N=126$ waiting-point nuclei significantly, while they have only a small effect on the half-lives of the $N=50$ and 82 $r$-process nuclei.

With high-statistics data coming from both the Relativistic Heavy Ion Collider and the Large Hadrom Collider, the experimentally available selection of hard tomographic probes for the medium created in ultrarelativistic heavy-ion ($A$-$A$) collisions is rapidly expanding. Jet-hadron (jet-h) correlation measurements as introduced by the STAR collaboration are a promising avenue to study the structure of highly modified jets in a differential way since the away side correlation can be measured down to very low transverse momenta ($P_T$) in an essentially hydrodynamical regime. At the same time, the geometry bias introduced by the trigger condition ensures that the away-side shower has propagated a long distance in the medium. The aim of this paper is to provide a theoretical overview of the observable, discuss similarities and differences to other correlation observables such as hadron-hadron (h-h) and photon-hadron ($\gamma$-h) correlations, and provide recommendations for future measurements.

We have performed shell-model calculations for the nucleus ${}^{137}$Xe, which was recently studied experimentally using the ${}^{136}$Xe($d,p$) reaction in inverse kinematics. The main aim of our study has been to investigate the single-neutron properties of the observed states, focusing attention on the spectroscopic factors. We have employed a realistic low-momentum two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential that has already proved quite successful in describing the spectroscopic properties of nuclei in the ${}^{132}$Sn region. Comparison shows that our calculations reproduce very well the experimental excitation energies and yield spectroscopic factors that come close to those extracted from the data.

One of the useful and practical methods for solving quantum-mechanical many-body systems is to recast the full problem into a form of the effective interaction acting within a model space of tractable size. Many of the effective-interaction theories in nuclear physics have been formulated by use of the so-called $\widehat{Q}$ box introduced by Kuo et al. It has been one of the central problems how to calculate the $\widehat{Q}$ box accurately and efficiently. We first show that, introducing new basis states, the Hamiltonian is transformed to a block-tridiagonal form in terms of submatrices with small dimension. With this transformed Hamiltonian, we next prove that the $\widehat{Q}$ box can be expressed in two ways: One is in the form of a continued fraction and the other is a simple series expansion up to second order with respect to renormalized vertices and propagators. This procedure ensures derivation of an exact $\widehat{Q}$ box, if the calculation converges as the dimension of the Hilbert space tends to infinity. The $\widehat{Q}$ box given in this study corresponds to a nonperturbative solution for the energy-dependent effective interaction which is often referred to as the Bloch-Horowitz or the Feshbach form. By applying the $\widehat{Z}$-box approach based on the $\widehat{Q}$ box proposed previously, we introduce a graphical method for solving the eigenvalue problem of the Hamiltonian. The present approach has a possibility of resolving many of the difficulties encountered in the effective-interaction theory.