We analyze the second Fourier coefficient $v_2$ of the pion azimuthal distribution in noncentral heavy-ion collisions in a relativistic hydrodynamic model. The exact treatment of the decay kinematics of resonances leads to almost vanishing azimuthal anisotropy of pions near the midrapidity, while the matter elliptic flow is in plane at freeze-out. In addition, we reproduce the rapidity dependence of $v_2$ for pions measured in noncentral $\mathrm{Pb}+\mathrm{Pb}$ collisions at $158A\mathrm{GeV}$. This suggests that resonance particles as well as stable particles constitute the in-plane flow and are important ingredients for the understanding of the observed pion flow.

Directed flow measurements for $\Lambda$ hyperons are presented and compared to those for protons produced in the same $\mathrm{Au}+\mathrm{Au}$ collisions (2A, 4A, and 6A GeV; $b<\mathrm{}5-6\mathrm{fm}$). The measurements indicate that $\Lambda$ hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for $\Lambda$s] has been predicted in calculations which include the influence of the $\Lambda$-nucleon potential. The experimental flow ratio $\Lambda /p$ is in qualitative agreement with expectations ( $\sim 2/3$) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.

The high $p_T>3\mathrm{}\mathrm{GeV}$ azimuthal asymmetry, $v_2\left(p_T\right)$, in noncentral nuclear collisions at RHIC is shown to be a sensitive measure of the initial parton density distribution of the produced quark-gluon plasma. A generalization of the Gyulassy-Lévai-Vitev non-Abelian energy loss formalism including Bjorken $(1+1)\mathrm{D}$ expansion as well as important kinematic constraints is used.

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central $\mathrm{Pb}+\mathrm{Pb}$ collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.

An excitation function of proton rapidity distributions for different centralities is reported from AGS Experiment E917 for $\mathrm{Au}+\mathrm{Au}$ collisions at 6, 8, and 10.8 GeV/nucleon. The rapidity distributions from peripheral collisions have a valley at midrapidity which smoothly change to distributions that display a broad peak at midrapidity for central collisions. The mean rapidity loss increases with increasing beam energy, whereas the fraction of protons consistent with isotropic emission from a stationary source at midrapidity decreases with increasing beam energy. The data suggest that the stopping is substantially less than complete at these energies.

The dependence of $K^{+}$ production on the nuclear equation of state is investigated in heavy-ion collisions. An increase of the excitation function of $K^{+}$ multiplicities obtained in heavy $(\mathrm{Au}+\mathrm{Au})$ over light $(\mathrm{C}+\mathrm{C})$ systems when going far below threshold which has been observed by the KaoS Collaboration strongly favors a soft equation of state. This observation holds despite the influence of an in-medium kaon potential predicted by effective chiral models which is necessary to reproduce the experimental $K^{+}$ yields.

We analyzed the spectrum of the ${}^{187}\mathrm{Re}$ beta decay, obtained with a cryogenic microcalorimeter, searching for heavy neutrinos in the mass range 50–1000 eV. No evidence has been found for them and the upper limits on the mixing angle with a zero-mass neutrino are reported. Upper limits of $9\times {10}^{-3\mathrm{}}$ at $1000\mathrm{eV}{/c}^2$, $1.2\times {10}^{-2\mathrm{}}$ at $500\mathrm{eV}{/c}^2$, $4.4\times {10}^{-2\mathrm{}}$ at $200\mathrm{eV}{/c}^2$, and 0.116 at $100\mathrm{eV}{/c}^2$ at $95\%$ C.L. have been obtained. These upper limits are a factor of 2 to 4 lower than the current limits reported in the literature.

We report on the first measurement of a hypernuclear $\gamma$-transition probability. $\gamma$ rays emitted in the $E2\mathrm{}(5/2^{+}\to 1/2^{+})$ transition of ${}_{\Lambda }^7\mathrm{Li}$ were detected by a large-acceptance germanium detector array (Hyperball), and the lifetime of the parent state ( $5/2^{+}$) was determined by the Doppler shift attenuation method. The obtained result, ${5.8}_{-0.7\mathrm{}}^{+0.9\mathrm{}}\pm 0.7\mathrm{ps}$, was then converted into the reduced transition probability [ $B\left(E2\mathrm{}\right)$] to be $B({E2;5/2\mathrm{}}^{+}\to {1/2}^{+})=3.6\mathrm{}\pm {0.5}_{-0.4\mathrm{}}^{+0.5\mathrm{}}{e}^2{\mathrm{fm}}^4$. Compared with the $B\left(E2\mathrm{}\right)$ of the corresponding $E2\mathrm{}(3^{+}\to 1^{+})$ transition in the ${}^6\mathrm{Li}$ nucleus, our result gives evidence that the size of the ${}^6\mathrm{Li}$ core in ${}_{\Lambda }^7\mathrm{Li}$ is smaller than the ${}^6\mathrm{Li}$ nucleus in the free space.

We describe a reaction mechanism which is consistent with all available experimental information of high energy three-body breakup processes. The dominating channels are removal of one of the three halo particles leaving the other two either undisturbed or absorbed. We compare with the commonly used deceptive assumption of a decay through two-body resonance states. Our predictions can be tested by measuring neutron-neutron invariant mass spectra.

The initial gluon multiplicity per unit area per unit rapidity, $\mathrm{dN}/L^2/d\eta$, in high energy nuclear collisions, is equal to $f_N\left(g^2\mu L\right)(g^2\mu {)}^2/g^2$, with ${\mu }^2$ proportional to the gluon density per unit area of the colliding nuclei. For an SU(2) gauge theory, we compute $f_N\left(g^2\mu L\right)=0.14\mathrm{}\pm 0.01$ for a wide range in $g^2\mu L$. Extrapolating to SU(3), we predict $\mathrm{dN}/L^2/d\eta$ for values of $g^2\mu L$ relevant to the Relativistic Heavy Ion Collider and the Large Hadron Collider. We compute the initial gluon transverse momentum distribution, $\mathrm{dN}/L^2/d^2{k}_{\perp }$, and show it to be well behaved at low $k_{\perp }$.

Proton decay from odd-odd deformed nuclei is a long-standing unsolved problem. We present for the first time an exact solution using single particle Nilsson resonances. The lifetime is found to depend strongly on the single particle level occupied by the unpaired neutron, allowing a clear assignment of its Nilsson level. The emitters ${}^{112}\mathrm{Cs}$, ${}^{140}\mathrm{Ho}$, ${}^{150}\mathrm{Lu}$, and ${}^{150}{\mathrm{Lu}}^m$ are considered. The agreement with the experimental data is very good with deformations $0.1<\mathrm{}\beta <0.19\mathrm{}$ for ${}^{112}\mathrm{Cs}$ and $-0.17<\beta <-0.16\mathrm{}$ for the ground and isomeric states of ${}^{150}\mathrm{Lu}$. In the case of ${}^{140}\mathrm{Ho}$, two ranges of deformation $0.16<\mathrm{}\beta <0.28\mathrm{}$ and $0.28<\mathrm{}\beta <0.38\mathrm{}$ according to the neutron single particle level can describe the experimental half-life.

Two excited well-deformed bands have been observed in the semi-magic nucleus ${}^{58}\mathrm{Ni}$. One of the bands was observed to partially decay by emission of a prompt discrete $\alpha$ particle that feeds the 2949 keV $6^{+}$ spherical yrast state in the daughter nucleus ${}^{54}\mathrm{Fe}$. This constitutes the first observation of prompt $\alpha$ emission from states lying in the deformed secondary minimum of the nuclear potential. $\gamma$-ray linking transitions via several parallel paths establish the spin, parity, and excitation energy of this deformed band in ${}^{58}\mathrm{Ni}$.

Presently, the world data for superallowed $\beta$ decay leads to a result in disagreement (at the $98\%$ confidence level) with the predictions of the minimal standard model for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. Precise data for the superallowed $0^{+}\to 0^{+}$ $\beta$ decay of ${}^{74}\mathrm{Rb}$ would provide a critical test of the nucleus-dependent isospin symmetry-breaking corrections that must be calculated for these superallowed Fermi $\beta$ decays. The present work reports the first precise measurement of the half-life for ${}^{74}\mathrm{Rb}$ ( $t_{1/2}=64.761\mathrm{}\pm 0.031\mathrm{ms}$). The data were obtained at the radioactive beam facility (ISAC) at TRIUMF using a beam of $\sim 4000$ ${}^{74}\mathrm{Rb}$ ions ${\mathrm{s}}^{-1\mathrm{}}$.

Rotational bands feeding the ground state and the isomeric state in the proton emitter ${}^{141}\mathrm{Ho}$ were observed using the recoil-decay tagging method. This constitutes direct evidence that ${}^{141}\mathrm{Ho}$ is deformed. A quadrupole deformation of ${\beta }_2=0.25\mathrm{}\left(4\right)$ was deduced for the ground state from the extracted dynamic moment of inertia. Based on observed band crossings and signature splittings the $7/2^{-}\left[523\right]$ and $1/2^{+}\left[411\right]$ configurations were proposed for the ground state and the isomeric state, respectively. Comparison with particle-rotor calculations for ${\beta }_2=0.25\mathrm{}$ indicates, however, that ${}^{141}\mathrm{Ho}$ may have significant hexadecapole deformation and could be triaxial in the $7/2^{-}\left[523\right]$ ground state.

The transition from spherical to deformed shapes is studied in terms of large-scale shell-model calculations for Ba isotopes as a function of valence nucleon number with fixed single-particle space and Hamiltonian. A new version of the Monte Carlo shell model is introduced so as to incorporate pairing correlations efficiently, by utilizing condensed pair bases. The energy levels and electromagnetic matrix elements are described in agreement with experiments throughout the transitional region. The orbital $M1\mathrm{}$ sum rule is calculated as a measure of the deformation evolution, and the $Q$-phonon picture is shown to be reasonable from spherical to deformed nuclei.

Developments in spin-polarized internal targets for storage rings have permitted measurements of 197 MeV polarized protons scattering from vector polarized deuterons. This work presents measurements of the polarization observables $A_y$, ${\mathrm{iT}}_{11}$, and $C_{y,y}$ in proton-deuteron elastic scattering. When compared to calculations with and without three-nucleon forces, the measurements provide further evidence that three-nucleon forces make a contribution to the observables. This work indicates that three-body forces derived from static nuclear properties appear to be crucial to the description of dynamical properties.

New sideband partners of the yrast bands built on the $\pi h_{11/2}\nu h_{11/2}$ configuration were identified in ${}_{55}\mathrm{Cs}$, ${}_{57}\mathrm{La}$, and ${}_{61}\mathrm{Pm}$ $N=75\mathrm{}$ isotones of ${}^{134}\mathrm{Pr}$. These bands form with ${}^{134}\mathrm{Pr}$ unique doublet-band systematics suggesting a common basis. Aplanar solutions of 3D tilted axis cranking calculations for triaxial shapes define left- and right-handed chiral systems out of the three angular momenta provided by the valence particles and the core rotation, which leads to spontaneous chiral symmetry breaking and the doublet bands. Small energy differences between the doublet bands suggest collective chiral vibrations.

Using an isospin-dependent quantum molecular dynamics, nuclear stopping in intermediate heavy ion collisions has been studied. The calculation has been done for colliding systems with different neutron-proton ratios in beam energy ranging from 15 MeV/ $u$ to 150 MeV/ $u$. It is found that, in the energy region from above Fermi energy to 150 MeV/ $u$, nuclear stopping is very sensitive to the isospin dependence of in-medium nucleon-nucleon cross section, but insensitive to symmetry potential. From this investigation, we propose that nuclear stopping can be used as a new probe to extract the information on the isospin dependence of in-medium nucleon-nucleon cross section in intermediate energy heavy ion collisions.

The two-neutron halo nucleus ${}^{14}\mathrm{Be}$ has been investigated in a kinematically complete measurement of the fragments ( ${}^{12}\mathrm{Be}$ and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large $\nu ({2s}_{1/2}{)}^2$ admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation.

The spectroscopic quadrupole moment of the high-spin, high- $K$ five-quasiparticle isomer ( $K^{\pi }={\frac{35}{2}}^{-}$, $T_{1/2}=750\mathrm{}\left(80\right)$ ns, $E_i=3349\mathrm{}$ keV) in ${}^{179}\mathrm{W}$ has been determined using the level mixing spectroscopy method. A value $Q_s=4.00\mathrm{}{(}_{-1.06\mathrm{}}^{+0.83\mathrm{}})e\mathrm{b}$ was derived, which corresponds to an intrinsic quadrupole moment $Q_0=4.73\mathrm{}{(}_{-1.25\mathrm{}}^{+0.98\mathrm{}})e\mathrm{b}$ and to a quadrupole deformation ${\beta }_2=0.185\mathrm{}{(}_{-0.049\mathrm{}}^{+0.038\mathrm{}})$. These values differ significantly from the deduced ground-state quadrupole moments and are in disagreement with the current theoretical predictions in this mass region.