Systematic calculations on the $\alpha$-decay half-lives of heavy and superheavy nuclei are performed within a deformed version of the cluster model, using the modified two-potential approach. The deformed Woods-Saxon potential is employed to calculate the $\alpha$-decay width through a deformed barrier. For comparison the calculated $\alpha$-decay half-lives in the empirical relations are also presented. The present study is initially restricted to even-even nuclei in the heavy mass region with $N>126$. Then the study is extended to the recently observed heaviest nuclei, including synthesized superheavy elements and isotopes. The $\alpha$-decay half-lives obtained are found to be in good agreement with the experimental data.

Low-lying collective states in ${}^{126}\mathrm{Xe}$ have been investigated via the ${}^{12}\mathrm{C}$(${}^{126}\mathrm{Xe}$,${}^{126}\mathrm{Xe}$${}^{*}$) projectile Coulomb excitation reaction at 399 MeV. The $\gamma$ decays were detected with the Gammasphere array. Coulomb excitation cross sections relative to the $2_1^{+}$ state were obtained. Twenty-two absolute $E2$ transition strengths have been deduced. An $\mathit{sd}$– interacting boson model (IBM-1) fit agrees well with the new experimental data. This makes a quantitative test of O(6)-symmetry breaking in ${}^{126}\mathrm{Xe}$ possible. The measured absolute $B(E2)$ values indicate a preservation of O(5) symmetry, while the O(6) symmetry is broken. The evolution of O(6)-symmetry breaking and of O(5)-symmetry conservation in the ${}^{124,126,128}\mathrm{Xe}$ isotopic chain is discussed.

The monopole excitations ($0_{\mathrm{g}.\mathrm{s}.}^{+}$ $\to$ $0_{\mathrm{ex}}^{+}$) of light neutron-excess systems ${}^{12}\mathrm{Be}$ $=\alpha +\alpha +4N$ are investigated by the generalized two-center cluster model. We analyze the mechanism of an enhancement of the monopole strength in connection to structures of adiabatic energy surfaces as a function of an $\alpha$-$\alpha$ distance. The crossing of two adiabatic energy surfaces, which have different intrinsic configurations, increases the monopole strength. Furthermore, we find that the monopole strength is strongly enhanced by a smooth connection in the adiabatic energy surface from the ground $0^{+}$ state to the excited $0^{+}$ state. A comparison of the calculated strength with the respective single particle limit is also discussed.

Nuclear level density and $\gamma$-ray strength functions of ${}^{121,122}\mathrm{Sn}$ below the neutron separation energy are extracted with the Oslo method using the (${}^3\mathrm{He}$,${}^3\mathrm{He}$${}^{\text{'}}\gamma$) and (${}^3\mathrm{He}$,$\alpha \gamma$) reactions. The level densities of ${}^{121,122}\mathrm{Sn}$ display steplike structures, interpreted as signatures of neutron pair breaking. An enhancement in both strength functions, compared to standard models for radiative strength, is observed in our measurements for $E_{\gamma }\gtrsim 5.2$ MeV. This enhancement is compatible with pygmy resonances centered at $\approx 8.4(1)$ and $\approx 8.6(2)$ MeV, respectively, and with integrated strengths corresponding to $\approx 1.8_{-5}^{+1}\%$ of the classical Thomas-Reiche-Kuhn sum rule. Similar resonances were also seen in ${}^{116-119}\mathrm{Sn}$. Experimental neutron-capture cross reactions are well reproduced by our pygmy resonance predictions, while standard strength models are less successful. The evolution as a function of neutron number of the pygmy resonance in ${}^{116-122}\mathrm{Sn}$ is described as a clear increase of centroid energy from 8.0(1) to 8.6(2) MeV, but with no observable difference in integrated strengths.

We study the nucleus-nucleus total reaction cross sections for stable nuclei, in the energy region from $30A$ MeV to about $1A$ GeV, and find them to be in proportion to $(\sqrt{{\sigma }_{\mathit{pp}}^{\mathrm{tot}}{Z}_1^{2/3}+{\sigma }_{\mathit{pn}}^{\mathrm{tot}}{N}_1^{2/3}}+\sqrt{{\sigma }_{\mathit{pp}}^{\mathrm{tot}}{Z}_2^{2/3}+{\sigma }_{\mathit{pn}}^{\mathrm{tot}}{N}_2^{2/3}}\hspace{0.5em}){}^2$ in the mass range 8 to 100. Also, we find a parameter-free relation that enables us to predict a total reaction cross section for any nucleus-nucleus within $10\%$ uncertainty at most, using the experimental value of the total reaction cross section of a given nucleus-nucleus. The power of the relation is demonstrated by several examples. The energy dependence of the nuclear interaction radius is deduced; it is found to be almost constant in the energy range from about $200A$ MeV to about $1A$ GeV; in this energy range and for nuclei with $N=Z$, $R_I(A)=(1.14\pm 0.02)A^{1/3}$ fm.

A relativistic distorted-wave impulse approximation formalism is presented for the calculation of quasielastic proton-nucleus scattering. It is shown that the double differential cross section may be written as a contraction between the hadronic tensor (describing the projectile and ejectile) and the polarization tensor (describing the nuclear target) and that this mathematical structure also holds for the case where distortions are included. The eikonal approximation is used to introduce distortions in the wave functions, and the nuclear response is described using a Fermi gas model. The highly oscillatory nine-dimensional integrand contained in the expression for the double differential cross section is computed using a novel technique based on combining traditional Gaussian integration methods with the powerful fitting functions in the matlab programming language. This work has successfully calculated the distorted-wave quasielastic differential cross section for proton-nucleus scattering within a fully relativistic framework. It is found that the distortions lead to a reduction in the double differential cross section and have a negligible effect on the computed spin observables.

By extending our previous isobar model to the $K^0\Lambda$ isospin channel, we investigate the properties of the $K^0\Lambda$ photo- and electroproduction at energies near threshold. It is found that the pseudovector coupling yields significantly larger cross sections. Variation of the $K_1$ coupling constants has significant effect only on the pseudovector model. The electromagnetic form factor of the neutral kaon $K^0$ is found to have a sizable effect on the longitudinal cross section of the $K^0\Lambda$ electroproduction near the threshold.

Recent simulations of classical novae on oxygen-neon white-dwarf stars indicate that the isotopic ratio ${}^{32}\mathrm{S}$/${}^{33}\mathrm{S}$ has the potential to be a remarkable indicator of presolar grains of nova origin. The ${}^{33}\mathrm{S}$$(p,\gamma ){}^{34}$Cl reaction influences this ratio directly by destroying ${}^{33}\mathrm{S}$ in novae. Additionally, $\beta$-delayed $\gamma$ rays from the metastable state of ${}^{34}\mathrm{Cl}$ ($t_{1/2}=32$ min) have been suggested to be potential nova observables. We have measured the branches for known ${}^{33}\mathrm{S}$$(p,\gamma ){}^{34}$Cl resonances that are activated at temperatures relevant to oxygen-neon novae. We provide the first reliable uncertainties on these branches and the first upper limits for several previously unmeasured branches.

Weakly populated band structures have been established in ${}^{156}\mathrm{Er}$ at low to medium spins, following the ${}^{114}\mathrm{Cd}$(${}^{48}\mathrm{Ca}$,$6n\gamma$) reaction at 215 MeV. High-fold $\gamma$-ray coincidence data were recorded in a high-statistics experiment with the Gammasphere spectrometer. Bands built on the second $0^{+}$ and $2^{+}$ ($\gamma$-vibrational) states have been established. A large energy staggering between the even- and odd-spin members of the $\gamma$-vibrational band suggests a $\gamma$-soft nature of this nucleus. An additional band is discussed as being based on a rotationally aligned $(\nu h_{9/2},f_{7/2}){}^2$ structure, coexisting with the systematically observed, more favorable $(\nu i_{13/2}){}^2$ aligned structure seen in this mass region.

The Feynman-Metropolis-Teller treatment of compressed atoms is extended to the relativistic regimes. Each atomic configuration is confined by a Wigner-Seitz cell and is characterized by a positive electron Fermi energy. The nonrelativistic treatment assumes a pointlike nucleus and infinite values of the electron Fermi energy can be attained. In the relativistic treatment there exists a limiting configuration, reached when the Wigner-Seitz cell radius equals the radius of the nucleus, with a maximum value of the electron Fermi energy $(E_e^F){}_{\max }$, here expressed analytically in the ultrarelativistic approximation. The corrections given by the relativistic Thomas-Fermi-Dirac exchange term are also evaluated and shown to be generally small and negligible in the relativistic high-density regime. The dependence of the relativistic electron Fermi energies by compression for selected nuclei are compared and contrasted to the nonrelativistic ones and to the ones obtained in the uniform approximation. The relativistic Feynman-Metropolis-Teller approach here presented overcomes some difficulties in the Salpeter approximation generally adopted for compressed matter in physics and astrophysics. The treatment is then extrapolated to compressed nuclear matter cores of stellar dimensions with $A\simeq (m_{\mathrm{Planck}}/m_n){}^3~{10}^{57}$ or $M_{\mathrm{core}}~M_{\odot }$. A new family of equilibrium configurations exists for selected values of the electron Fermi energy varying in the range $0<E_e^F⩽(E_e^F){}_{\max }$. Such configurations fulfill global but not local charge neutrality. They have electric fields on the core surface, increasing for decreasing values of the electron Fermi energy reaching values much larger than the critical value $E_c=m_e^2{c}^3/(e\hslash )$ for $E_e^F=0$. We compare and contrast our results with the ones of Thomas-Fermi model in strange stars.

We consider bottom-up holographic models for quantum chromodynamics (QCD) that are constrained by the ultraviolet (UV) cutoff. Such models are supposed to exclusively describe the low-energy sector of QCD. The introduction of the UV cutoff in the soft-wall model is shown to result in a model with qualitatively different predictions. The ensuing model seems able to incorporate the constituent quark mass. We also demonstrate that in order to reproduce the results of the usual soft-wall model for the vector and higher-spin mesons in the presence of the UV cutoff, one can consider the flat bulk space with a modified dilaton background.

Gamma-ray transitions in ${}^{235}\mathrm{U}$ were measured using the ($\gamma ,{\gamma }^{\text{'}}$) reaction below 3 MeV. The nuclear-resonance-fluorescence experiment was carried out at the High-Intensity $\gamma$-ray Source facility using nearly monoenergetic and circularly polarized photon beams. More than 20 transitions corresponding to deexcitations to the ground state and low-lying levels in ${}^{235}\mathrm{U}$ were observed. The integrated cross sections to the excited levels and intensities of branching transitions were deduced. The experimental results are compared with predictions from a quasiparticle random-phase approximation in a deformed basis.

Using a reasonable but simple model, properties of $2^{+}$ states in ${}^{12}\mathrm{Be}$ and ${}^{12}\mathrm{O}$ are calculated and compared with results of experiments.

I compare the first viscous hydrodynamic prediction for integrated elliptic flow in Pb-Pb collisions at the Large Hadron Collider with the first data released by the ALICE Collaboration. These new data are found to be consistent with hydrodynamic extrapolations of the Relativistic Heavy-Ion Collider data with no change in medium parameters (e.g., average viscosity). I also discuss how, in general, a precise comparison of data to theoretical calculations requires an understanding of some subtleties of the measurement—most notably the cut on transverse momentum of the particles used and the differing sensitivities to flow fluctuations and nonflow effects of the various measurement methods.

We show that flavor-diagonal and off-diagonal susceptibilities of light quarks at vanishing chemical potential can be calculated consistently assuming the baryon density and isospin density dependence of QCD to be expressed by a vector-isoscalar and a vector-isovector coupling, respectively. At the mean-field level, their expression depends only on the effective medium-dependent couplings and quark thermodynamic potential. The strength of the couplings can be then estimated from the model using lattice QCD data as an input.

Limits on ${\beta }^{+}$EC and ECEC processes in ${}^{112}\mathrm{Sn}$ have been obtained using a 380 cm${}^3$ HPGe detector and an external source consisting of 100 g enriched tin (94.32% of ${}^{112}\mathrm{Sn}$). A limit with 90% C.L. on the ${}^{112}\mathrm{Sn}$ half-life of $1.3\times {10}^{21}$ yr for the ECEC(0$\nu$) transition to the $0_3^{+}$ excited state in ${}^{112}\mathrm{Cd}$ (1871 keV) has been established. This transition has been discussed in the context of a possible enhancement of the decay rate. The limits on other ${\beta }^{+}$EC and ECEC processes in ${}^{112}\mathrm{Sn}$ have also been obtained on the level of $(0.1-1.6)\times {10}^{21}$ yr at the 90% C.L.

The process of electron-positron annihilation into a pair of ${\pi }^0$ and $\omega$ mesons is considered in the framework of the SU(2)$\times$SU(2) Nambu–Jona-Lasinio model. Contributions of intermediate photons, $\rho (770)$ and ${\rho }^{\text{'}}(1450)$ vector mesons are taken into account. It is shown that the bulk of the cross section at energies below 2 GeV is provided by the process with intermediate ${\rho }^{\text{'}}(1450)$ state. The contribution due to single photon and $\rho (770)$ exchange is in agreement with the vector meson dominance model. Numerical results are compared with experimental data.

We compute the potential between a $q\mathrm{q̄}$ color-singlet state for $\mathcal{N}=4$ SUSY with gauge group SU(N) at finite temperature $T$, large distances $\mathit{rT}\gg 1$, and weak coupling $g$. As a first step, we only consider the electric modes and compute the Debye mass $m_D$, where we find that each of the $8(N^2-1)$ bosonic degrees of freedom contributes to $m_D^2$ (on average) with $\frac{N}{N^2-1}\frac{1}{6}{g}^2{T}^2$, while each of the $8(N^2-1)$ fermionic degrees of freedom contributes (on average) with $\frac{N}{N^2-1}\frac{1}{12}{g}^2{T}^2$, yielding $m_D^2=2{\mathit{Ng}}^2{T}^2$. Then, motivated by results obtained in the literature from both the weak-coupling results in QCD and the large-coupling investigations of $\mathcal{N}=4$ SUSY through AdS/CFT, we attempt to include magnetic mode corrections. Our results illustrate that, for this particular computation, $\mathcal{N}=4$ SUSY is in striking qualitative agreement with QCD.

We study the role of colliding geometry on the balance energy ($E_{\text{bal}}$) of mass-asymmetric systems by varying the mass asymmetry ($\eta$ $=$$A_T-A_p$/$A_T+A_P$, where $A_T$ and $A_P$ are the masses of the target and projectile, respectively) from 0.1 to 0.7, over the mass range 40–240 and on the mass dependence of the balance energy. Our findings reveal that colliding geometry has a significant effect on the $E_{\text{bal}}$ of asymmetric systems. We find that, as we go from central collisions to peripheral ones, the effect of mass asymmetry on $E_{\text{bal}}$ increases throughout the mass range. Interestingly, we find that for every fixed system mass ($A_{\text{tot}}$) the effect of the impact parameter variation is almost uniform throughout the mass-asymmetry range. For each $\eta$, $E_{\text{bal}}$ follows a power-law behavior ($\propto$$A^{\tau }$) at all colliding geometries.

The coupled Langevin equations in two-dimensional collective space are used to study the dynamics of nuclear neck growth. Special attention is paid to the effects of coupling between neck and radial degrees of freedom on the evolution from dinucleus to mononuleus. The dynamic model is applied for the study of neck evolution of the mass asymmetric system ${}^{50}\mathrm{Ti}$ $+$ ${}^{249}\mathrm{Cf}$. In order to estimate the effects of the coupling, we use the equations in the coupled and uncoupled cases. Our results show that the coupling between neck and radial motions reduces the neck growth velocity and delays the transition from dinuclear to mononuclear regimes. In addition, by solving these dynamic equations we get the probability distributions of radial degree of freedom at the injection point $s_{\mathrm{in}}$ in the asymmetric fission valley. In this way, $s_{\mathrm{in}}$ is no longer an adjustable parameter in the fusion-by-diffusion model. The distributions obtained are located at positions very close to $s=0$. Moreover, the coupling significantly reduces the fluctuation in the $s_{\mathrm{in}}$ space. Our results show that the quasifissionlike events are unlikely to take place during the transition period for the mass asymmetric systems. Based on the $s_{\mathrm{in}}$ distribution obtained, the evaporation residue (ER) cross sections for $3n$ and $4n$ evaporation channels in the ${}^{50}\mathrm{Ti}$ $+$ ${}^{249}\mathrm{Cf}$ reaction leading to formation of ${}^{296}120$ and ${}^{295}120$ isotopes are calculated. The maximum ER cross sections in $3n$ and $4n$ channels with the $s_{\mathrm{in}}$ distributions are equal to $0.1$ and $0.065$ pb, respectively, which are more than two times larger than those obtained by the fusion-by-diffusion model with the $s_{\mathrm{in}}=0$ assumption.