The hyperfine structures of the 33715.27 ${\mathrm{cm}}^{-1}$ and 33706.47 ${\mathrm{cm}}^{-1}$ transitions from the ground state of singly ionized Ta have been measured by collinear laser spectroscopy. The structures were found to contain a large second order contribution. From fitting the observed hyperfine components for both ${}^{181}\mathrm{Ta}$ and the ${}^{180}\mathrm{Ta}$ naturally occurring isomer it was possible to determine the first and second order hyperfine structure coefficients. As no model independent determination of the nuclear spin of the ${}^{180}\mathrm{Ta}$ isomer has been performed, fitting was attempted for a range of spins. A clear chi-squared minimum is obtained for a nuclear spin of 9, in agreement with model dependent measurements.

Using simple parametrizations of the thermodynamic freeze-out parameters extracted from the data over a wide beam-energy range, we reexpress the hadronic freeze-out line in terms of the underlying dynamic quantities, the net baryon density ${\rho }_B$ and the energy density ɛ, which are subject to local conservation laws. This analysis reveals that ${\rho }_B$ exhibits a maximum as the collision energy is decreased. This maximum freeze-out density has $\mu =400–500$ MeV, which is above the critical value, and it is reached for a fixed-target bombarding energy of 20–30 GeV/nucleon.

We present a phenomenological approach (EPOS), based on the parton model, but going much beyond by incorporating elastic and inelastic parton ladder splitting. Based on this model, we try to understand proton-proton and deuteron-gold ($d\mathrm{Au}$) collisions, in particular the rapidity dependence of transverse momentum results in $d\mathrm{Au}$ from all four experiments conducted on the BNL Relativistic Heavy Ion Collider.

The charged hadron multiplicity fluctuations are considered in the canonical ensemble. The microscopic correlator method is extended to include three conserved charges: baryon number, electric charge, and strangeness. The analytical formulas are presented that allow us to include resonance decay contributions to correlations and fluctuations. We make the predictions for the scaled variances of negative, positive, and all charged hadrons in the most central Pb+Pb (Au+Au) collisions for different collision energies from SIS and AGS to SPS and RHIC.

In $2+1$ dimensions, we simulated the hydrodynamic evolution of quark-gluon plasma (QGP) fluid with dissipation due to shear viscosity. Comparison of the evolution of ideal and viscous fluids, both initialized under the same conditions, e.g., same equilibration time, energy density and velocity profile, reveals that the dissipative fluid evolves slowly, cooling at a slower rate. Cooling slows even more at higher viscosities. The fluid velocities, however, evolve faster in a dissipative fluid than in an ideal fluid. The transverse expansion is also enhanced in dissipative evolution. For the same decoupling temperature, the freeze-out surface for a dissipative fluid is more extended than that for an ideal fluid. Dissipation produces entropy as a result of which particle production is increased. Particle production is increased as a result of the (i) the extension of the freeze-out surface and (ii) the change of the equilibrium distribution function to a nonequilibrium one, the latter effect being prominent at large transverse momentum. Compared to ideal fluid, transverse momentum distribution of pion production is considerably enhanced. Enhancement is greater at high $p_T$ than at low $p_T$. Pion production also increases with viscosity; the greater the viscosity, the greater the pion production. Dissipation also modifies the elliptic flow, which is reduced in viscous dynamics. Also, contrary to ideal dynamics where elliptic flow continues to increase with transverse momentum, in viscous dynamics elliptic flow tends to saturate at large transverse momentum. The analysis suggests that the initial conditions of the hot, dense matter produced in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), as extracted from ideal fluid analysis, can be changed significantly if the QGP fluid is viscous.

The thermal cross section and resonance integral were measured for radiative neutron capture by radioactive ${}^{148}\mathrm{Gd}$. The deduced values are $\sigma =9600\pm 900$ b and $I=28,200\pm 2300$. We also deduced upper limits for the n,p and n, α cross sections, respectively, 0.25 b and 13 b. The γ-ray spectrum from the decay of ${}^{149}\mathrm{Gd}$ was studied in singles mode at high resolution to verify the previously determined energies and intensities. From the latter measurements, new transitions are proposed and upper limits are deduced for previously reported transitions.

Excited states in ${}^{249}\mathrm{Fm}$ were populated via the α decay of ${}^{253}\mathrm{No}$ and the subsequent decay was observed with the GABRIELA detection system installed at the focal plane of the VASSILISSA recoil separator. The energies, spins, and parities of these states could be established through combined $\alpha ,\gamma$, and conversion-electron spectroscopy. The first members of the ground-state rotational band were identified. Their excitation energies as well as the observation of a cross-over $E2$ transition confirm the assignment of $7/2^{+}\left[624\right]$ for the ground state of ${}^{249}\mathrm{Fm}$. Two excited states were also observed and their decay properties suggest that they correspond to the particle excitation $9/2^{-}\left[734\right]$ and hole excitation $5/2^{+}\left[622\right]$. The analysis suggests that the 279-keV transition de-exciting the $9/2^{-}$ state has anomalous $E1$ conversion coefficients.

An overwhelming fraction of photons from relativistic heavy-ion collisions has its origin in the decay of ${\pi }^0$ and η mesons. We calculate the azimuthal asymmetry of the decay photons for several azimuthally asymmetric pion distributions. We find that the $k_T$ dependence of the elliptic flow parameter $v_2$ for the decay photons closely follows the elliptic flow parameter $v_2^{{\pi }^0}$ evaluated at $p_T\approx k_T+\delta$, where $\delta \approx 0.1\text{−}0.2$ GeV, for typical pion distributions measured in nucleus-nucleus collisions at relativistic energies. Similar results are obtained for photons from the $2\text{−}\gamma$ decay of η mesons. Assuming that the flow of ${\pi }^0$ is similar to those for ${\pi }^{+}$ and ${\pi }^{-}$ for which independent measurements would be generally available, this ansatz can help in identifying additional sources for photons. Taken along with quark number scaling suggested by the recombination model, it may help to estimate $v_2$ of the parton distributions in terms of azimuthal asymmetry of the decay photons at large $k_T$.

Isospin and density waves in neutral neutron-proton-electron ($\mathit{npe}$) matter are studied within a relativistic mean-field hadron model at finite temperature with the inclusion of the electromagnetic field. The dispersion relation is calculated and the collective modes are obtained. The unstable modes are discussed and the spinodals, which separate the stable from the unstable regions, are shown for different values of the momentum transfer at various temperatures. The critical temperatures are compared with the ones obtained in a system without electrons. The largest critical temperature, 12.39 MeV, occurs for a proton fraction $y_p=0.47$. For $y_p=0.3$ we get $T_{\mathrm{cr}}=5$ MeV and for $y_p>0.495$ $T_{\mathrm{cr}}\lesssim 8$ MeV. It is shown that at finite temperature the distillation effect in asymmetric matter is not so efficient and that electron effects are particularly important for small momentum transfers.

We use the quasiparticle random-phase approximation with a few Skyrme density functionals to calculate strength functions in the $J^{\pi }=0^{+},1^{-},$ and $2^{+}$ channels for even Ca, Ni, and Sn isotopes from the proton drip line to the neutron drip line. We show where and how low-lying strength begins to appear as $N$ increases. We also exhibit partial energy-weighted sums of the transition strength as functions of $N$ for all nuclei calculated and transition densities for many of the interesting peaks. We find that low-energy strength increases with $N$ in all multipoles, but with distinctive features in each. The low-lying $0^{+}$ strength at large $N$ barely involves protons at all, with the strength coming primarily from a single two-quasineutron configuration with very large spatial extent. The low-lying $1^{-}$ strength is different, with protons contributing to the transition density in the nuclear interior together with neutrons at large radii and with somewhat more collectivity in the heavier isotopes. The low-lying $2^{+}$ transition strength goes largely to more localized and frequently more collective states. In all channels the correlation between strength and collectivity is much weaker than in stable nuclei. The three Skyrme interactions we test produce similar results, differing most significantly in their predictions for the location of the neutron drip line, the boundaries of deformed regions, energies of and transition strengths to the lowest $2^{+}$ states between closed shells, and isovector energy-weighted sum rules.

The direct interaction of superintense laser fields in the optical frequency domain with nuclei is studied. As main observable, we consider the nuclear dynamic (AC) Stark shift of low-lying nuclear states due to the off-resonant excitation by the laser field. We include the case of accelerated nuclei to be able to control the frequency and the intensity of the laser field in the nuclear rest frame over a wide range of parameters. We find that AC-Stark shifts of the same order as in typical quantum optical systems relative to the respective transition frequencies are feasible with state-of-the-art or near-future laser field intensities and moderate acceleration of the target nuclei. Along with this shift, but only at intensities above the critical field strength, we find laser-induced modifications to the proton root-mean-square radii and to the proton density distribution. We thus expect direct laser-nucleus interaction to become of relevance together with other super-intense light-matter interaction processes such as pair creation.

The external-field quantum chromodynamics (QCD) sum rules method is used to evaluate the coupling constants of the vector mesons ρ and ω to the nucleon and the $\Lambda ,\Sigma$, and Ξ baryons. It is shown that these coupling constants as calculated from QCD sum rules are consistent with SU(3)-flavor relations. By assuming ideal mixing, this leads to a determination of the $F/(F+D)$ ratio of the vector-meson octet: we find ${\alpha }_v=1$ and ${\alpha }_m=0.18$ for the vector and the magnetic $F/(F+D)$ ratios, respectively. The sensitivity of the results to the unknown vacuum susceptibility ζ is discussed. The coupling constants with SU(3)-breaking effects taken into account are also calculated.

Semiclassical theories such as the Thomas-Fermi and Wigner-Kirkwood methods give a good description of the smooth average part of the total energy of a Fermi gas in some external potential when the chemical potential is varied. However, in systems with a fixed number of particles $N$, these methods overbind the actual average of the quantum energy as $N$ is varied. We describe a theory that accounts for this effect. Numerical illustrations are discussed for fermions trapped in a harmonic oscillator potential and in a hard-wall cavity, and for self-consistent calculations of atomic nuclei. In the latter case, the influence of deformations on the average behavior of the energy is also considered.

Electron capture and β decay play important roles in the evolution of presupernovae stars and their eventual core collapse. These rates are normally predicted through shell-model calculations. Experimentally determined strength distributions from charge-exchange reactions are needed to test modern shell-model calculations. We report on the measurement of the Gamow-Teller strength distribution in ${}^{58}\mathrm{Co}$ from the ${}^{58}\mathrm{Ni}$($t$,${}^3\mathrm{He}$) reaction with a secondary triton beam of an intensity of $~{10}^6$ pps at 115 MeV/nucleon and a resolution of $~250$ keV. Previous measurements with the ${}^{58}\mathrm{Ni}$$(n,p)$ and the ${}^{58}\mathrm{Ni}$($d$,${}^2\mathrm{He}$) reactions were inconsistent with each other. Our results support the latter. We also compare the results to predictions of large-scale shell-model calculations using the KB3G and GXPF1 interactions and investigate the impact of differences between the various experiments and theories in terms of the weak rates in the stellar environment. Finally, the systematic uncertainties in the normalization of the strength distribution extracted from ${}^{58}\mathrm{Ni}$(${}^3\mathrm{He}$, $t$) are described and turn out to be nonnegligible due to large interferences between the $\Delta L=0,\Delta S=1$ Gamow-Teller amplitude and the $\Delta L=2,\Delta S=1$ amplitude.

It is shown that the boost-invariant and cylindrically asymmetric hydrodynamic equations for baryon-free matter may be reduced to only two coupled partial differential equations. In the case where the system exhibits the crossover phase transition, the standard numerical methods may be applied to solve these equations and the proposed scheme allows for a very convenient analysis of the cylindrically asymmetric hydrodynamic expansion.

Hard pQCD processes taking place in ultrarelativistic heavy-ion collisions are a well-calibrated probe. It is believed that the interaction with the surrounding medium of outgoing partons from a hard vertex is capable of revealing details of the medium. We demonstrate that correlation measurements of hard photon-hadron back-to-back coincidences are a tool suitable for extracting such tomographic information. Introducing the concept of averaged energy loss probability distributions, we first argue that almost no information about details of the medium evolution is reflected in the nuclear suppression factor $R_{\mathit{AA}}$. Thus, a wide variety of jet quenching scenarios and geometries are compatible with the measured data. This problem can be overcome by a γ-hadron correlation measurement. We show that averaged probability distributions for quarks are accessible experimentally, and we sketch an analysis procedure capable of distinguishing different energy loss scenarios leading to the same nuclear suppression factor.

The photoproduction reaction $\gamma N\to KK\Xi$ is investigated based on a relativistic meson-exchange model of hadronic interactions. The production amplitude is calculated in the tree-level approximation from relevant effective Lagrangians, whose (coupling constant) parameters are mostly fixed from the empirical data and/or quark models together with SU(3) symmetry considerations. Gauge invariance of the resulting amplitude is maintained by introducing the contact currents by extending the gauge-invariant approach of Haberzettl for one-meson photoproduction to two-meson photoproduction. The role of the intermediate low-lying hyperons and of the intermediate higher-mass hyperon resonances are analyzed in detail. In particular, the basic features of the production of ${\Xi }^{-}(1318)$ in $\gamma p\to K^{+}{K}^{+}{\Xi }^{-}$ and their possible manifestations in the forthcoming experimental data are discussed.

The atomic masses of the neutron-rich krypton isotopes ${}^{84,86-95}\mathrm{Kr}$ have been determined with the tandem Penning trap mass spectrometer ISOLTRAP with uncertainties ranging from 20 to 220 ppb. The masses of the short-lived isotopes ${}^{94}\mathrm{Kr}$ and ${}^{95}\mathrm{Kr}$ were measured for the first time. The masses of the radioactive nuclides ${}^{89}\mathrm{Kr}$ and ${}^{91}\mathrm{Kr}$ disagree by 4 and 6 standard deviations, respectively, from the present Atomic-Mass Evaluation database. The resulting modification of the mass surface with respect to the two-neutron separation energies as well as implications for mass models and stellar nucleosynthesis are discussed.

A systematic analysis of α(${}^4\mathrm{He}$)-nucleus elastic scattering is made by using a microscopic optical model potential obtained by the double folding of the complex nucleon-nucleon ($\mathit{NN}$) effective interaction based on the $G$-matrix theory. We adopt the so-called JLM interaction as the complex $\mathit{NN}$ interaction and test its applicability to the ${}^4\mathrm{He}$ elastic scattering by ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, ${}^{28}\mathrm{Si}$, and ${}^{40}\mathrm{Ca}$ over a wide range of incident energy and scattering angle. The experimental cross sections for incident energies ranging from $E_{\mathrm{lab}}=40$ to 240 MeV are well reproduced by the double folding potential up to backward angles. Although modification of the real and imaginary potential strength by about 25% and 35%, respectively, on average is necessary to reproduce the data, the renormalization factors are found to be almost constant with respect to the incident energy and target mass number.