The 685 keV excitation energy of the first excited $0^{+}$ state in ${}^{152}\mathrm{Sm}$ makes it an attractive candidate to explore expected two-phonon excitations at low energy. Multiple-step Coulomb excitation and inelastic neutron scattering studies of ${}^{152}\mathrm{Sm}$ are used to probe the $E2$ collectivity of excited $0^{+}$ states in this “soft” nucleus and the results are compared with model predictions. No candidates for two-phonon $K^{\pi }=0^{+}$quadrupole vibrational states are found. A $2^{+},K=2$ state with strong $E2$ decay to the first excited $K^{\pi }=0^{+}$ band and a probable $3^{+}$ band member are established.

We show that single-particle energies in doubly magic nuclei depend almost linearly on the coupling constants of the nuclear energy density functional. Therefore, they can be very well characterized by the linear regression coefficients, which we calculate for the coupling constants of the standard Skyrme functional. We then use these regression coefficients to refit the coupling constants to experimental values of single-particle energies. We show that the obtained rms deviations from experimental data are still quite large, of the order of 1.1 MeV. This suggests that the current standard form of the Skyrme functional cannot ensure spectroscopic-quality description of single-particle energies, and that extensions of this form are very much required.

Strongly damped reactions of ${}^{238}\mathrm{U}+{}^{238}\mathrm{U}$, ${}^{232}\mathrm{Th}+{}^{250}\mathrm{Cf}$ at $E_{\mathrm{c}.\mathrm{m}.}=680\text{−}1880$ MeV have been studied based on the improved quantum molecular dynamics model. The formation and properties of the transiently formed composite system during the reaction process are carefully studied. We find that at a certain energy region, the entrance channel potential is weakly repulsive, and the dissipation is very strong after touching configuration. These two effects delay the re-separation time for a composite system. The single-particle potential well of the transiently formed composite system has a Coulomb barrier about 15–20 MeV high at the surface, which causes the excited unbound protons still embedded in the potential well to move in a common mono-single-particle potential for a period of time and thus restrains the quick decay of the composite system. The incident-energy dependence of the lifetime of the composite system and how the lifetime correlates with the shape configuration, the momentum distribution of the composite system, and the angular distribution of primary fragments are carefully investigated. The results indicate that the longest average lifetime for the transient composite system of U+U can reach about 1200 fm/$c$ at properly selected incident energies.

Effects of strong final-state interactions in the superscaling properties of neutral-current quasielastic neutrino cross sections are investigated by using the relativistic impulse approximation as guidance. First- and second-kind scaling are analyzed for neutrino beam energies ranging from 1 to 2 GeV for the cases of ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$. Different detection angles of the outgoing nucleon are considered to sample various nucleon energy regimes. Scaling of the second kind is shown to be very robust. The validity of first-kind scaling is found to be linked to the kinematics of the process. Superscaling still prevails even in the presence of very strong final-state interactions, provided that some kinematical restrains are kept, and the conditions under which superscaling can be applied to predict neutral-current quasielastic neutrino scattering are determined.

The structure of ${}^{194}\mathrm{Ir}$ is investigated via ($n,\gamma ),(n,e^{-}),(d,p)$, and ($\overrightarrow{d},\alpha$) spectroscopy. The use of different methods leads to an almost complete level scheme up to high excitation energies including γ-decay and spin-parity assignments. A reanalysis of the formerly published ($n,\gamma$) data was triggered by our new ($d,p$) and ($\overrightarrow{d},\alpha$) transfer reactions. The experimental level scheme is compared to predictions using extended supersymmetry. Herein, the classification of states was done according to quantum numbers, excitation energies, and ($\overrightarrow{d},\alpha$) transfer strengths. A one-to-one correspondence in excitation energies was obtained for the 23 lowest lying theoretical states with similar structures for the experimental and calculated level schemes. The two-nucleon transfer strengths show remarkable agreement. A Nilsson classification is discussed as well.

We explore the effects of shear viscosity on the hydrodynamic evolution and final hadron spectra of Cu + Cu collisions at ultrarelativistic collision energies, using the newly developed (2 + 1)-dimensional viscous hydrodynamic code VISH2+1. Based on the causal Israel-Stewart formalism, this code describes the transverse evolution of longitudinally boost-invariant systems without azimuthal symmetry around the beam direction. Shear viscosity is shown to decelerate the longitudinal and accelerate the transverse hydrodynamic expansion. For fixed initial conditions, this leads to a longer quark-gluon plasma (QGP) lifetime, larger radial flow in the final state, and flatter transverse momentum spectra for the emitted hadrons compared to ideal fluid dynamic simulations. We find that the elliptic flow coefficient $v_2$ is particularly sensitive to shear viscosity: even the lowest value allowed by the AdS/CFT conjecture $\eta /s⩾1/4\pi$ suppresses $v_2$ enough to have significant consequences for the phenomenology of heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC). A comparison between our numerical results and earlier analytic estimates of viscous effects within a blast-wave model parametrization of the expanding fireball at freeze-out reveals that the full dynamical theory leads to much tighter constraints for the specific shear viscosity $\eta /s$, thereby supporting the notion that the quark-gluon plasma created at RHIC exhibits almost “perfect fluidity.”

We focus on the initial-state spatial anisotropies, originating at the thermalization stage, for central collisions in relativistic heavy-ion collisions. We propose that a plot of the root-mean-square values of the flow coefficients $\sqrt{\overline{v_n^2}}\equiv v_n^{\mathrm{rms}}$, calculated in a laboratory fixed coordinate system, for a large range of $n$ from 1 to about 30, can give nontrivial information about the initial stages of the system and its evolution. We also argue that for all wavelengths λ of the anisotropy (at the surface of the plasma region) much larger than the acoustic horizon size $H_s^{\mathrm{fr}}$ at the freeze-out stage, the resulting values of $v_n^{\mathrm{rms}}$ should be suppressed by a factor of order $2H_s^{\mathrm{fr}}/\lambda$. For noncentral collisions, these arguments naturally imply a certain amount of suppression of the elliptic flow. Further, by assuming that initial flow velocities are negligible at thermalization stage, we discuss the possibility that the resulting flow could show imprints of coherent oscillations in the plot of $v_n^{\mathrm{rms}}$ for subhorizon modes. For gold-gold collision at 200 GeV/nucleon center-of-mass energy, these features are expected to occur for $n⩾5$, with $n<4$ modes showing suppression due to being superhorizon. This has strong similarities with the physics of the anisotropies of the cosmic microwave background radiation (CMBR) resulting from inflationary density fluctuations in the universe (despite important differences such as the absence of gravity effects for the heavy-ion case). It seems possible that the statistical fluctuations due to finite multiplicity may not be able to mask such features in the flow data or at least a nontrivial overall shape of the plot of $v_n^{\mathrm{rms}}$ may be inferred. In that case, the successes of analysis of CMBR anisotropy power spectrum to get cosmological parameters can be applied for relativistic heavy-ion collisions to learn about various relevant parameters at the early stages of the evolving system.

We consider the Bose-Einstein condensation (BEC) in a relativistic pion gas. The thermodynamic limit when the system volume $V$ goes to infinity as well as the role of finite size effects are studied. At $V\to \infty$ the scaled variance for particle-number fluctuations, $\omega =\langle \Delta N^2\rangle /\langle N\rangle$, converges to finite values in the normal phase above the BEC temperature, $T>T_C$. It diverges as $\omega \propto V^{1/3}$ at the BEC line $T=T_C$, and $\omega \propto V$ at $T<T_C$ in a phase with the BE condensate. Possible experimental signals of the pion BEC in finite systems created in high-energy proton-proton collisions are discussed.

The Coulomb electron scattering on even-even nuclei and the magnetic electron scattering on odd-$A$ nuclei have been investigated in the relativistic eikonal approximation and in the plane wave Born approximation, respectively. In this article, we generalize the relativistic eikonal approximation to the parity violating electron scattering on even-even nuclei. The parity violating asymmetries at electron energy of 850 MeV are calculated for three typical cases: Ca isotopes, $N=50$ isotones, and $N=Z$ doubly magic nuclei. In calculations the proton and neutron densities are obtained from the relativistic mean-field theory. The parity violating asymmetries are analyzed by comparing both the form factors and the densities of neutrons and protons. It is found that the parity violating asymmetries are sensitive to the differences between neutron and proton densities. Our results provide useful references for the parity violating electron-nucleus scattering experiments in the future.

The ($d,{}^2$He) charge-exchange reaction on the double-β decay ($\beta \beta$) nucleus ${}^{64}\mathrm{Zn}$ has been studied at an incident energy of 183 MeV. The two protons in the ${}^1{S}_0$ state (indicated as ${}^2\mathrm{He}$) were both momentum analyzed and detected simultaneously by the BBS magnetic spectrometer and its position-sensitive detector. ${}^2\mathrm{He}$ spectra with a resolution of about 115 keV (FWHM) have been obtained allowing identification of many levels in the residual nucleus ${}^{64}\mathrm{Cu}$ with high precision. ${}^{64}\mathrm{Zn}$ is one of the rare cases undergoing a $\beta \beta$ decay in ${\beta }^{+}$ direction. In the experiment presented here, Gamow-Teller (GT${}^{+}$) transition strengths have been extracted. Together with the GT${}^{-}$ transition strengths from ${}^{64}\mathrm{Ni}$(${}^3\mathrm{He}$,$t$) data to the same intermediate nucleus ${}^{64}\mathrm{Cu}$, the nuclear matrix elements of the $\beta \beta$ decay of ${}^{64}\mathrm{Zn}$ have been evaluated. Finally, the GT${}^{\pm }$ distributions are compared with shell-model calculations and a critical assessment is given of the various residual interactions presently employed for the $\mathit{pf}$ shell.

Using a shell model which is capable of describing the spectra of upper $g_{9/2}$-shell nuclei close to the $N=Z$ line, we study the structure of two isomeric states $7^{+}$ and ${21}^{+}$ in the odd-odd $N=Z$ nucleus ${}^{94}\mathrm{Ag}$. It is found that both isomeric states exhibit a large collectivity. The $7^{+}$ state is oblately deformed, and is suggested to be a shape isomer in nature. The ${21}^{+}$ state becomes isomeric because of level inversion of the ${19}^{+}$ and ${21}^{+}$ states due to core excitations across the $N=Z=50$ shell gap. Calculation of spectroscopic quadrupole moment indicates clearly an enhancement in these states due to the core excitations. However, the present shell model calculation that produces the ${19}^{+}-{21}^{+}$ level inversion cannot accept the large-deformation picture of Mukha et al. [Nature (London) 439, 298 (2006)].

The complex scaled hyperspherical adiabatic expansion method is used to compute momentum and energy distributions of the three α particles emerging from the decay of low-lying ${}^{12}\mathrm{C}$ resonances. The large distance continuum properties of the wave functions are crucial and must be accurately calculated. We discuss separately decays of natural-parity states: two $0^{+}$, one $1^{-}$, three $2^{+}$, one $3^{-}$, two $4^{+}$, one $6^{+}$, and one of each of unnatural parity $1^{+},2^{-},3^{+},4^{-}$. The lowest natural-parity state of each $J^{\pi }$ decays predominantly sequentially via the ${}^8\mathrm{Be}$ ground state, whereas other states, including unnatural-parity states, predominantly decay directly to the continuum. We present Dalitz plots and systematic detailed momentum correlations of the emerging α particles.

A continued fraction approximation is used to calculate the Random Phase Approximation (RPA) response function of nuclear matter. The convergence of the approximation is assessed by comparing it with the numerically exact response function obtained with a typical effective finite-range interaction used in nuclear physics. It is shown that just the first order term of the expansion can give reliable results at densities up to the saturation density value.

The total cross section and angular distributions for the reaction ${}^4\mathrm{He}(\gamma ,{\pi }^0)$ from a cryogenic liquid helium target have been measured within 25 MeV of threshold using tagged photons and a large acceptance ${\pi }^0$ spectrometer at the Saskatchewan Accelerator Laboratory. The reduced isovector amplitude $p_3^{(+)}$ has been determined from the total cross-section measurement using a distorted-wave impulse approximation analysis. Refinements from earlier analytical methods, specifically an improved background event rejection scheme and a corrective tagged photon energy calibration analysis, have also yielded an improved estimate on the $p_3^{(+)}$ amplitude for the ${}^{12}\mathrm{C}(\gamma ,{\pi }^0)$ reaction explored previously.

I consider Compton scattering off the nucleon in the presence of $T$ violation. I construct the Compton tensor that possesses these features and consider low-energy expansion of the corresponding amplitudes. It allows separation of the Born contribution that depends only on the static properties of the nucleon, such as the electric charge, the mass, the magnetic moment, and the electric dipole moment. I introduce new structure constants, the $T$-odd nucleon polarizabilities that parametrize the unknown non-Born part. These constants describe the response of the $T$-violating content of the nucleon to the external quasistatic electromagnetic field. As an estimate, I provide a heavy-baryon ChPT calculation for these new polarizabilities and discuss the implications for the experiment.

Gamma-ray angular distribution measurements following the ${}^{\mathrm{nat}}$Ni($n,n^{\text{'}}\gamma$) reaction were carried out at 1.6 and 1.8 MeV neutron energies. Through the Doppler-shift attenuation method, the lifetime of the $2_1^{+}$ state in ${}^{58}\mathrm{Ni}$ is determined as $\tau =1.{00}_{-0.10}^{+0.15}$ ps, which yields a $B(E2;2_1^{+}\to 0_1^{+})$ value of $9.4_{-1.2}^{+1.0}$ W.u. From previous measurements and this work, average values of $\tau =0.94(3)$ ps and $B(E2;2_1^{+}\to 0_1^{+})=10.0(4)$ W.u. are recommended as standards for normalization. In addition, a longer lifetime of $\tau =1.{30}_{-0.20}^{+0.30}$ ps has been determined for the $2_1^{+}$ state in ${}^{60}\mathrm{Ni}$, which yields an $E2$ strength of $10.7_{-2.5}^{+1.7}$ W.u. Our results support an enhancement of proton-core excitations and related quadrupole and pairing strengths in the light Ni isotopes, in agreement with mean-field and shell-model calculations.

Direct neutron capture reactions play an important role in nuclear astrophysics and applied physics. Since for most unstable short-lived nuclei it is not possible to measure the $(n,\gamma )$ cross sections, $(d,p)$ reactions have been used as an alternative indirect tool. We analyze simultaneously ${}^{48}\mathrm{Ca}(d,p){}^{49}\mathrm{Ca}$ reactions at deuteron energies of $2,13,19,$ and 56 MeV and the thermal $(n,\gamma )$ reaction at 25 meV. We include results for the ground state and the first excited state of ${}^{49}\mathrm{Ca}$. From the low-energy $(d,p)$ reaction, the neutron asymptotic normalization coefficient (ANC) is determined. Using this ANC, we extract the spectroscopic factor (SF) from the higher energy $(d,p)$ data and the $(n,\gamma )$ data. The SF obtained through the 56-MeV $(d,p)$ data are less accurate but consistent with those from the thermal capture. We show that to have a similar dependence on the single-particle parameters as in the $(n,\gamma )$, the $(d,p)$ reaction should be measured at 30 MeV.

From an SU(2)$\otimes$SU(2) chiral quark potential model incorporating spontaneous chiral symmetry breaking the asymptotic $\pi$ and $\sigma$ exchange pieces of the $\mathit{NN}$ potential are generated. From them the $\pi \mathit{NN}$ and $\sigma \mathit{NN}$ coupling constants can be extracted. The generalization to SU(3)$\otimes$SU(3) allows for a determination of $\pi B_8{B}_8$ and $\sigma B_8{B}_8$ coupling constants according to exact SU(3) hadron symmetry. The implementation of the values of the couplings at $Q^2=0$ provided by QCD sum rules and/or phenomenology makes also feasible the extraction of the meson-baryon-baryon form factors. In this manner a quite complete knowledge of the couplings may be attained.

A strong enhancement of the photon strength function at low γ-ray energies was recently reported for several Mo isotopes. To study this enhancement further we have measured the spectra of two-step γ cascades following thermal neutron capture in ${}^{95}\mathrm{Mo}$. These spectra were compared with simulations of the γ decay of ${}^{96}\mathrm{Mo}$ performed with the aid of the dicebox algorithm. Simulations with a large number of model combinations of photon strength functions for $E1,M1,$ and $E2$ radiation are not consistent with the strong enhancement observed in the ${}^{96}\mathrm{Mo}$(${}^3\mathrm{He}$,${}^3\mathrm{He}$${}^{\text{'}}\gamma$)${}^{96}\mathrm{Mo}$ and ${}^{97}\mathrm{Mo}$(${}^3\mathrm{He}$,$\alpha \gamma )$${}^{96}\mathrm{Mo}$ reactions. Predictions based on a combination of $E1,M1,$ and $E2$ photon strength functions with no enhancement of the photon strength functions at low γ-ray energies are in good agreement with the two-step γ cascade data.

We investigate the effects of $\beta \text{−}\gamma$ mixing using branching ratios between the $2_{\gamma }^{+}$ level and the ground state band in well-deformed nuclei. We find that the deviations from the well-known Alaga rules vary as a function of the energy separation between the $2_{\gamma }^{+}$ and $2_{\beta }^{+}$ levels. For nuclei where these two intrinsic excitations are nearly degenerate, we find two classes of behavior. For one of those, the systematics can be reproduced in a simple bandmixing formalism but only with an anomalously strong interaction strength between the $2_{\gamma }^{+}$ and $2_{\beta }^{+}$ levels, on the order of tens of keV. This result is supported by $X(E0/E2;2_{\gamma }^{+}\to 2_1^{+}$) values that are large for these nuclei (where measured), indicating significant $K=0$ components in the $2_{\gamma }^{+}$ levels. In the other class, there is virtually no mixing. These nuclei have previously been associated with near-SU(3) structure.