The elliptical flow of fragments is studied for different systems at incident energies between 50 and 1000 MeV/nucleon using the isospin-dependent quantum molecular dynamics (IQMD) model. Our findings reveal that elliptical flow shows a transition from positive (in-plane) to negative (out-of-plane) values in the midrapidity region at a certain incident energy known as the transition energy. This transition energy is found to depend on the model ingredients, size of the fragments, and composite mass of the reacting system as well as on the impact parameter of the reaction. A reasonable agreement is observed for the excitation function of elliptical flow between the data and our calculations. Interestingly, the transition energy is found to exhibit a power-law mass dependence.

Symmetry properties of densities and mean fields appearing in the nuclear density functional theory with pairing are studied. We consider energy functionals that depend only on local densities and their derivatives. The most important self-consistent symmetries are discussed: spherical, axial, space-inversion, and mirror symmetries. In each case, the consequences of breaking or conserving the time-reversal and/or proton-neutron symmetries are discussed and summarized in a tabulated form, useful in practical applications. Particular attention is paid to the case of broken proton-neutron symmetry, especially in the context of isoscalar pairing. We demonstrate that isoscalar pairing fields have geometrical properties markedly different from those of the usual isovector pairing fields and their theoretical treatment requires great care.

The cross sections for $(n,x)$ reactions with Lu, Tb, and Ta isotopes were measured at $(d,t)$ neutron energies around 14 MeV with the activation technique using metal foils of natural composition. Additionally, tantalum samples were irradiated with $(d,d)$ neutrons and filtered neutron beams. To ensure an acceptable precision of the results all major sources of uncertainties were taken into account. Calculations of efficiency and correction factors were performed with the Monte Carlo technique. The cross section results obtained for the ${}^{175}\mathrm{Lu}$$(n,\alpha )$${}^{172}\mathrm{Tm}$ reaction at $(d,t)$ neutron energies are reported for the first time. ${}^{181}\mathrm{Ta}$$(n,\gamma )$${}^{182}\mathrm{Ta}$${}^{m2}$ reaction cross sections were also measured for the first time at 1.9, 58.7, and 144.3 keV and at 2.85 MeV. The earlier evaluated cross section upper estimate for the nuclear reaction ${}^{159}\mathrm{Tb}$$(n,n^{\text{'}}\alpha )$${}^{155}\mathrm{Eu}$ is reported in this article to be one order lower. Some other cross sections were obtained with higher precision. Theoretical calculations of excitation functions were performed with the TALYS-1.0 code and compared with the experimental cross section values.

The suppression of high-transverse-momentum ($P_T$) hadron production in ultrarelativistic heavy-ion (A-A) collisions as compared to the scaled expectation from proton-proton (p-p) collisions expressed as the nuclear modification factor $R_{\mathrm{AA}}$ is experimentally well established and can be traced back to interactions between the hard parton shower and the soft bulk matter. Intuition suggests that the medium modification should cease to be important when the hard scale of parton production is much larger than the typical momentum scale in the medium (e.g., the temperature $T$) and that consequently $R_{\mathrm{AA}}(P_T)\to 1$ for $P_T\gg T$. However, $R_{\mathrm{AA}}$ is not a “simple” observable but rather results from many different mechanisms that influence what happens when $P_T$ increases. In particular, $R_{\mathrm{AA}}$ does not necessarily approach unity even if the hadron momentum is probed at the kinematic limit of the reaction. The aim of this work is to identify and discuss such mechanisms, to present different model expectations of what one would find if one could measure suppression to the kinematic limit for hard hadron production, and to predict the $P_T$ dependence at both Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC).

We derive an analytical form for flow background to jet-like azimuthal correlations in a cluster approach. We argue that the elliptic flow parameter to use in a jet-correlation background is that from a two-particle method excluding nonflow correlation unrelated to the reaction plane, but including cross-terms between cluster correlation and cluster flow. We verify our result with Monte Carlo simulations. We discuss implications of our findings in the context of jet-like correlations from STAR and PHENIX.

Lifetimes of excited states in ${}^{182}\mathrm{Hg}$ were extracted from recoil-gated $\gamma$-ray spectra and recoil-gated $\gamma \gamma$-coincidence matrices using the recoil distance Doppler-shift method. States were populated using the ${}^{96}\mathrm{Mo}$(${}^{88}\mathrm{Sr}$,$2n$)${}^{182}\mathrm{Hg}$ fusion-evaporation reaction. Measured lifetimes allowed transition probabilities, transition quadrupole moments, quadrupole deformation parameters, and transition dipole moments to be deduced for the band formed by the odd-spin yrast states. The experimental results confirm the low degree of octupole collectivity in this mass region.

Fission fragment mass distribution has been determined in the ${}^{238}\mathrm{U}$(${}^{18}\mathrm{O}$,$f$) reaction from the on-line measurement of individual even-even fragment yields by analyzing the $\gamma$-$\gamma$ matrix. Fine structure dips corresponding to fragment shell closures at $Z=50$ and $N=82$ are observed, indicating the effect of nuclear structure in the dynamical evolution of fissioning nucleus. The present results may suggest a new feature of shape inhibition of closed shell nuclei at the scission point.

The role $j_{15/2}$ neutron orbitals play in the transuranic region of actinides has been studied by exploring $\gamma$-ray transitions between yrast states in ${}^{235}\mathrm{Np}$, populated utilizing the nucleon-transfer reaction ${}^{237}\mathrm{Np}$(${}^{116}\mathrm{Sn}$,${}^{118}\mathrm{Sn}$). Two rotational sequences, presumably the two signatures of the ground-state band, have been delineated to high spin for the first time, with the $\alpha =+1/2$ and $\alpha =-1/2$ signature partners reaching $49/2^{+}\hslash$ (tentatively $53/2^{+}\hslash$) and $47/2^{+}\hslash$ (tentatively $51/2^{+}\hslash$), respectively. Definite isotopic assignments for these in-band transitions were established through $\gamma$-ray cross correlations between ${}^{235}\mathrm{Np}$ and ${}^{118}\mathrm{Sn}$ and events where at least three $\gamma$ rays corresponding to neptunium-like particles were detected. These transitions reveal clear upbends in the aligned angular momentum and kinematic moment of inertia plots; such a phenomenon could indicate a strong interaction between an aligned $\nu j_{15/2}$ configuration crossing the ground-state band in ${}^{235}\mathrm{Np}$, which is based on a $\pi i_{13/2}$ orbital. However, the lack of any signature splitting over the observed frequency range of the ${}^{235}\mathrm{Np}$ rotational sequences cannot remove the possibility of a $\pi h_{9/2}$ assignment for the observed band. The role of the $\nu j_{15/2}$ and $\pi i_{13/2}$ alignment mechanisms in the deformed U-Pu region is discussed in light of the current spectroscopic data and in the context of the cranked-shell model.

In this article we present a new calculation of the cascade of $K^{-}p$ and $K^{-}d$ atoms by the Monte Carlo method. Energy dependence of the collisional cascade processes is taken into account. The x-ray yields due to the radiative transition during the cascade are also calculated. We compare our results with the previous calculations by others and by KEK and DEAR experimental data for $K^{-}p$ atoms. We have also investigated the kinetic energy distribution of $K^{-}p$ atoms and the role of Coulomb transition on x-ray yields. Finally, the Doppler broadening contribution on the measured width of x-ray spectra are determined. In order to study the strong interaction in low energies, our results for x-ray yields from $K^{-}p$ and $K^{-}d$ atoms can be compared with the forthcoming SIDDHARTA collaboration results.

In nuclear fusion and fission, fluctuation and dissipation arise because of the coupling of collective degrees of freedom with internal excitations. Close to the barrier, quantum, statistical, and non-Markovian effects are expected to be important. In this work, a new approach based on quantum Monte Carlo addressing this problem is presented. The exact dynamics of a system coupled to an environment is replaced by a set of stochastic evolutions of the system density. The quantum Monte Carlo method is applied to systems with quadratic potentials. In all ranges of temperature and coupling, the stochastic method matches the exact evolution, showing that non-Markovian effects can be simulated accurately. A comparison with other theories, such as Nakajima-Zwanzig or time-convolutionless, shows that only the latter can be competitive if the expansion in terms of coupling constant is made at least to fourth order. A systematic study of the inverted parabola case is made at different temperatures and coupling constants. The asymptotic passing probability is estimated by different approaches including the Markovian limit. Large differences with an exact result are seen in the latter case or when only second order in the coupling strength is considered, as is generally assumed in nuclear transport models. In contrast, if fourth order in the coupling or quantum Monte Carlo method is used, a perfect agreement is obtained.

Time-odd mean fields (nuclear magnetism) are analyzed in the framework of covariant density functional theory (CDFT) by blocking the single-particle states with a fixed signature. It is shown that they always provide additional binding to the binding energies of odd-mass nuclei. This additional binding only weakly depends on the relativistic mean-field parametrization, reflecting good localization of the properties of time-odd mean fields in CDFT. The underlying microscopic mechanism is discussed in detail. Time-odd mean fields affect odd-even mass differences. However, our analysis suggests that the modifications of the strength of pairing correlations required to compensate for their effects are modest. In contrast, time-odd mean fields have a profound effect on the properties of odd-proton nuclei in the vicinity of the proton drip line. Their presence can modify the half-lives of proton emitters (by many orders of magnitude in light nuclei) and considerably affect the possibilities of their experimental observation.

Virtual Compton scattering off the nucleon (VCS) is studied in the regime of low energy of the outgoing real photon. This regime allows one to directly access the generalized polarizabilities of the nucleon in a VCS experiment. In the derivation of the low energy theorem for VCS that exists in the literature, the low energy limit taken for virtual initial photons does not match on that for real photons, when one approaches the initial photon’s mass shell. While this problem has for a long time been attributed to the nonanalyticity of the Compton amplitude with respect to the photon virtuality, I demonstrate that it is merely due to an ill-defined low energy limit for VCS, on one hand, and to a particular way of constructing the VCS amplitude, used in the literature, on the other. I provide a uniform description of low energy Compton scattering with real and virtual photons by defining a Lorentz-covariant operator sub-basis for Compton scattering in that regime, which has six independent structures. Correspondingly, six new generalized polarizabilities are introduced in the Breit frame. These polarizabilities are defined as continuous functions of the photon virtuality and at the real photon point match onto the nucleon polarizabilities known from real Compton scattering.

The solutions analytically derived by W. Glöckle, J. Golak, R. Skibiński, and H. Witala [Phys. Rev. C 79, 044003 (2009)] for the three-dimensional wave function and on-shell $t$ matrix in the case of scattering on a sharply cut-off Coulomb potential appear to be fallacious if finite values of a cut-off radius are concerned. And the analysis carried out for an infinite cut-off radius limit is incomplete.

The results by W. Glöckle et al. [Phys. Rev. C 79, 044003 (2009)] are shown to be consistent with the screening and renormalization theory, and they do not invalidate previous numerical calculations of physical observables.

${}^{171,173}\mathrm{Yb}(d,p\gamma )$ reactions are measured, with the goal of extracting the neutron capture cross-section ratio as a function of the neutron energy using the external surrogate ratio method. The cross-section ratios obtained are compared to the known neutron capture cross sections. Although the Weisskopf-Ewing limit is demonstrated not to apply for these low neutron energies, a prescription for deducing surrogate cross sections is presented. The surrogate cross-section ratios deduced from the ${}^{171,173}\mathrm{Yb}(d,p\gamma )$ measurements agree with the neutron capture results within 15%.

We calculate the nucleon-nucleon scattering amplitudes in the ${}^1{S}_0$ and ${}^3{S}_1-{}^3{D}_1$ channels at next-to-next-to-leading order starting from a recently proposed nonrelativistic chiral effective theory, which includes dibaryon fields as fundamental degrees of freedom. We restrict ourselves to center-of-mass energies ($E$) smaller than the pion mass ($m_{\pi }$) and further divide the calculation into two relative momentum ($p$) regions, a high-energy one $p~m_{\pi }\gg \delta m_i$, $\delta m_i$ being the dibaryon residual masses, and low-energy one $p\lesssim \delta m_i$. We first match to a lower energy effective theory in which we calculate the amplitudes in the high-energy region. We further match this effective theory to the so-called pionless effective theory in the low-energy region and carry out the calculations in the latter. Dimensional regularization and minimal subtraction scheme are used throughout. For ${}^1{S}_0$ channel a good description of the phase shift data is obtained for $E\lesssim 50$ MeV. For the ${}^3{S}_1-{}^3{D}_1$ channel, the ${}^3{S}_1$ phase shift data is only well described up to $E\lesssim 20$ MeV.

We construct a density-dependent, Class III, charge-symmetry-violating (CSV) potential due to mixing of the $\rho -\omega$ meson with off-shell corrections. Here, in addition to the usual vacuum contribution, the matter-induced mixing of $\rho -\omega$ is also included. It is observed that the contribution of the density-dependent CSV potential is comparable to that of the vacuum contribution.

Wavelet analysis is applied as a tool for the examination of magnetic dipole ($M1$) strength distributions in $\mathit{pf}$-shell nuclei by the extraction of wavelet scales. Results from the analysis of theoretical $M1$ strength distributions calculated with the KB3G interaction are compared to experimental data from ($e,e^{\text{'}}$) experiments and good agreement of the deduced wavelet scales is observed. This provides further insight into the nature of the scales from the model results. The influence of the number of Lanczos iterations on the development and stability of scales and the role of the model space in terms of the truncation level are studied. Moreover, differences in the scales of spin and orbital parts of the $M1$ strength are investigated, as is the use of different effective interactions (KB3G, GXPF1, and FPD6).

A new method of measuring fission fragment mass and energy distributions as a function of incident neutron energy in the range from below 0.1 eV to 1 keV has been developed. The method involves placing a double-sided Frisch-gridded fission chamber in Rensselaer Polytechnic Institute’s lead slowing-down spectrometer (LSDS). The high neutron flux of the LSDS allows for the measurement of the energy-dependent, neutron-induced fission cross sections simultaneously with the mass and kinetic energy of the fission fragments of various small samples. The samples may be isotopes that are not available in large quantities (submicrograms) or with small fission cross sections (microbarns). The fission chamber consists of two anodes shielded by Frisch grids on either side of a single cathode. The sample is located in the center of the cathode and is made by depositing small amounts of actinides on very thin films. The chamber was successfully tested and calibrated using $0.41\pm 0.04$ ng of ${}^{252}\mathrm{Cf}$ and the resulting mass distributions were compared to those of previous work. As a proof of concept, the chamber was placed in the LSDS to measure the neutron-induced fission cross section and fragment mass and energy distributions of $25.3\pm 0.5\hspace{0.5em}\mu$g of ${}^{235}\mathrm{U}$. Changes in the mass distributions as a function of incident neutron energy are evident and are examined using the multimodal fission mode model.

The pentaquark is studied in a simple model of confinement in which the quarks and the antiquark are linked by flux tubes of minimal cumulated length and the Coulomb-like interaction, the spin-dependent terms, and the antisymmetrization constraints are neglected. The ground state is found to be stable against spontaneous dissociation into a meson and a baryon, both in the case of five equal-mass constituents and for a static quark or antiquark surrounded by four equal masses.