Three-dimensional magnetic confinement of neutrons is reported. Neutrons are loaded into an Ioffe-type superconducting magnetic trap through inelastic scattering of cold neutrons with ${}^4\mathrm{He}.$ Scattered neutrons with sufficiently low energy and in the appropriate spin state are confined by the magnetic field until they decay. The electron resulting from neutron decay produces scintillations in the liquid helium bath that results in a pulse of extreme ultraviolet light. This light is frequency downconverted to the visible and detected. Results are presented in which $500\pm 155$ neutrons are magnetically trapped in each loading cycle, consistent with theoretical predictions. The lifetime of the observed signal, ${660}_{-170}^{+290\mathrm{}}\hspace{0.5em}\mathrm{s},$ is consistent with the neutron beta-decay lifetime.

The ${}^6{\mathrm{L}\mathrm{i}(}^6\mathrm{Li},\alpha \alpha {)}^4\mathrm{He}$ three-body reaction has been studied in a kinematically complete experiment at $E_{6_{\mathrm{Li}}}=6\mathrm{}\mathrm{MeV},$ from which indirect information on the ${}^2{\mathrm{H}(}^6\mathrm{Li},\alpha {)}^4\mathrm{He}$ two-body reaction at $13<~E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~750\mathrm{}\mathrm{keV}$ has been extracted by applying the Trojan horse method. The method used a recent improved formulation. The derived astrophysical $S\left(E\right)\mathrm{}$ factor for the two-body process is compared with that obtained from direct experiments.

A new approach has been used to explain the experimental data for the ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}$ system over a wide energy range in the laboratory system from 32.0 MeV to 126.7 MeV. This new coupled-channel-based approach involves replacing the usual first-derivative coupling potential by a new, second-derivative coupling potential. This paper first shows and discusses the limitation of the standard coupled-channel theory in the case where one of the nuclei in the reaction is strongly deformed. Then, this new approach is shown to improve consistently the agreement with the experimental data: the elastic scattering and single-$2^{+}$ and mutual-$2^{+}$ excitation inelastic scattering data as well as their $90°$ elastic and inelastic excitation functions with little energy-dependent potentials. This new approach makes major improvement on all the previous coupled-channel calculations for this system.

The giant-resonance region in ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$ has been studied using the reactions ${}^{48}\mathrm{Ca}{(p,p}^{\prime }{n}_0{)}^{47}\mathrm{Ca},$ ${}^{40}\mathrm{Ca}{(p,p}^{\prime }{p}_0{)}^{39}\mathrm{K},$ and ${}^{40}\mathrm{Ca}{(p,p}^{\prime }{\alpha }_0{)}^{36}\mathrm{Ar}$ for an incident proton energy $E_p=100\mathrm{}\hspace{0.5em}\mathrm{MeV}.$ Knockout cross sections for these reactions were calculated within the distorted wave impulse approximation formalism using parameters fixed from previous investigations. The results quantitatively account for the data at higher excitation energies while the knockout contributions underneath the main resonance strength are small.

High-spin states in the doubly odd $N=75\mathrm{}$ nuclei ${}^{136}\mathrm{Pm}$ and ${}^{138}\mathrm{Eu}$ were populated following the ${}^{116}\mathrm{Sn}{(}^{24}\mathrm{Mg},p3n)$ and ${}^{106}\mathrm{Cd}{(}^{35}\mathrm{Cl},2pn)$ reactions, respectively. A new $\Delta I=1\mathrm{}$ band is reported in ${}^{138}\mathrm{Eu}$ and new data are presented for the recently reported band in ${}^{136}\mathrm{Pm}.$ Polarization and angular correlation measurements have been performed to establish the relative spin and parity assignments for these bands. Both bands have been assigned the same $\pi h_{11/2}\otimes \nu h_{11/2}$ structure as the yrast band and are suggested as candidates for chiral twin bands.

Parton energy loss inside a dense medium leads to the suppression of large $p_T$ hadrons and can also cause azimuthal anisotropy of hadron spectra at large transverse momentum in noncentral high-energy heavy-ion collisions. Such azimuthal anisotropy is studied qualitatively in a parton model for heavy-ion collisions at RHIC energies. The coefficient $v_2{(p}_T)$ of the elliptic anisotropy at large $p_T$ is found to be very sensitive to parton energy loss. It decreases slowly with $p_T$ contrary to its low $p_T$ behavior where $v_2$ increases very rapidly with $p_T.$ The turning point signals the onset of contributions of hard processes and the magnitude of parton energy loss. The centrality dependence of $v_2{(p}_T)$ is shown to be sensitive to both size and density dependence of the parton energy loss and the latter can also be studied via variation of the colliding energy. The anisotropy coefficient $v_2/\varepsilon$ normalized by the spatial ellipticity $\varepsilon$ is found to decrease significantly toward semiperipheral collisions, differing from the hydrodynamic results for low $p_T$ hadrons. Constrained by the existing WA98 experimental data at the SPS energy on parton energy loss, both hadron spectra suppression and azimuthal anisotropy at high $p_T$ are predicted to vanish for $b>\mathrm{}7\mathrm{}–8$ fm in Au+Au collisions at $\sqrt{s}=130\mathrm{}-200$ GeV when the hadron rapidity density per unit area of the initial overlapped region is less than what is achieved in the central Pb+Pb collisions at the SPS energy.

The renormalization of the weak charge-changing hadronic current as a function of the reaction energy release is studied at the nucleonic level. We have calculated the average quenching factors for each type of current (vector, axial vector, and induced pseudoscalar). The obtained quenching in the axial vector part is, at zero momentum transfer, 19% for the $1s0d$ shell and 23% in the $1p0f$ shell. We have extended the calculations also to heavier systems such as ${}^{56}\mathrm{Ni}$ and ${}^{100}\mathrm{Sn},$ where we obtain stronger quenchings, 44% and 59%, respectively. Gamow-Teller-type transitions are discussed, along with the higher-order matrix elements. The quenching factors are constant up to roughly 60 MeV momentum transfer. Therefore the use of energy-independent quenching factors in beta decay is justified. We also found that going beyond the zeroth and first order operators (in inverse nucleon mass) does not give any substantial contribution. The extracted renormalization to the ratio $C_P{/C}_A$ at $q=100\mathrm{}$ MeV is $-3.5\%,$ $-7.1\%,$ $-28.6\%,$ and $+8.7\%$ for mass 16, 40, 56, and 100, respectively.

We compare the effects of several form factor recipes in fits to pseudoscalar meson photoproduction data. The specific examples of pion and kaon photoproduction are used to illustrate how different choices can alter the results of such analyses.

We report the first calculations of cross sections for the radiative capture reactions ${}^3\mathrm{H}(\alpha ,\gamma {)}^7\mathrm{Li}$ and ${}^3\mathrm{He}(\alpha ,\gamma {)}^7\mathrm{Be}$ below 2 MeV that use wave functions derived from realistic nucleon-nucleon interactions by the variational Monte Carlo technique. After examining several small corrections to the dominant $E1\mathrm{}$ operator, we find energy dependences for the low-energy S factors that agree reasonably with experimental measurements. There is no contradiction with the previous theoretical understanding of these processes, but the zero-energy derivative of the ${}^3\mathrm{H}(\alpha ,\gamma {)}^7\mathrm{Li}$ S factor is smaller than that in most models. While this method can, in principle, predict cross section normalizations, the normalizations of our results are mostly too low.

The cross section asymmetry $\Sigma$ has been measured for the photoproduction of $\pi °$ mesons off protons, using polarized photons in the energy range $E_{\gamma }=0.5\mathrm{}–1.1\mathrm{GeV}.$ The center-of-mass angular coverage is ${\theta }_{\pi }^{*}=85\mathrm{}°–125°$ with energy and angle steps of 25 MeV and $5°,$ respectively. The obtained $\Sigma$ data, which cover the second and third resonance regions, are compared with existing experimental data and recent phenomenological analyses. The influence of these measurements on such analyses is also considered.

Fragmentation of a nuclear system by tunneling is discussed in a molecular dynamics simulation coupled with an imaginary time method. In this way we obtain information on the fragmenting systems at low densities and temperatures. These conditions cannot be reached normally (i.e., above the barrier) in nucleus-nucleus or nucleon-nucleus collisions. The price to pay is the small probability of fragmentation by tunneling but we obtain observables which can be a clear signature of such phenomena.

We compute the magnetic quadrupole strength function in heavy spherical and deformed nuclei in proton-neutron random-phase approximation using a separable Hamiltonian that couples magnetic and electric channels and adopting a technique that avoids the diagonalization of the eigenvalue matrix. We intend to check if the different sensitivity of the spin dipole and orbital responses to the multipole terms of the Hamiltonian leads to an energy separation of the two modes sufficient for the identification of the twist mode. We explore also the possibility of a K splitting induced by deformation, in analogy to the electric giant dipole resonance, also briefly studied for the sake of completeness.

The region of light actinides $(Z\sim 88,N\sim 134),$ which is thought to exhibit signs of stable octupole deformation, offers a real challenge for nuclear structure models. We study the even-even Ra-Th nuclei in the framework of the $\mathrm{spdf}$ interacting boson model and we find that while the properties of the low-lying states can be understood without stable octupole deformation, higher spin states $\left(J\gtrsim 12ħ\right)$ in some of these nuclei (e.g., ${}^{226}\mathrm{Ra})$ suggest that octupole deformation develops with increasing spin. We also discuss how octupole deformation can arise in the rotational (dynamical symmetry) limit.

In this paper we present the β-level mixing resonance (β-LMR) method as a tool to measure the initial spin-orientation of exotic nuclear beams produced and oriented in a fragmentation reaction. Understanding this spin-orientation process is the key to allow studies of nuclear moments of nuclear states far from stability. The $\beta -\mathrm{LMR}$ method is a unique tool, sensitive to both the spin-polarization and the spin-alignment component in the selected ensemble of fragment spins. In the paper we describe the formalism to extract this information from the experimental data and report on a first test experiment.

Two conceptually different hyperspherical harmonics expansions are used for the calculation of the total ${}^4\mathrm{He}$ photoabsorption cross section. Besides the well-known method of correlated hyperspherical harmonics, the recently introduced effective interaction approach for the hyperspherical formalism is applied. Semirealistic NN potentials are employed and final-state interaction is fully taken into account via the Lorentz integral transform method. The results show that the effective interaction leads to a very good convergence, while the correlation method exhibits a less rapid convergence in the giant dipole resonance region. The rather strong discrepancy with the experimental photodisintegration cross sections is confirmed by the present calculations.

We show that it is possible to empirically partition the differential cross section for $p\overrightarrow{p}\mathrm{pp}{\pi }^0$ into initial singlet and triplet differential cross sections in a model independent way which can be implemented using the existing technological capabilities at the PINTEX facility. We also show that the differential cross section for $\overrightarrow{p}\overrightarrow{p}\to \mathrm{pp}{\pi }^0$ can be expressed as a weighted sum of a set of initial singlet and triplet differential cross sections together with a contribution arising from the initial singlet-triplet correlations for any arbitrary beam polarization $\mathbf{P}\mathrm{}\left(b\right)\mathrm{}$ and target polarization $\mathbf{P}\mathrm{}\left(t\right)\mathrm{}$ either collinear or noncollinear.

We analyze the recently obtained new data on the partial cross sections and parallel momentum distributions for transitions to ground as well as excited states of the ${}^{16}\mathrm{C}$ core, in the one-neutron removal reaction ${}^{197}\mathrm{Au}{(}^{17}\mathrm{C}{,}^{16}\mathrm{C}\gamma )X$ at the beam energy of 61 MeV/nucleon. The Coulomb and nuclear breakup components of the one-neutron removal cross sections have been calculated within a finite range distorted wave Born approximation theory and an eikonal model, respectively. The nuclear contributions dominate the partial cross sections for the core excited states. By adding the nuclear and Coulomb cross sections together, a reasonable agreement is obtained with the data for these states. The shapes of the experimental parallel momentum distributions of the core states are described well by the theory.

We present a general analysis of polarization phenomena for three-body processes (in noncoplanar kinematics), in terms of a P- and T-odd acoplanarity parameter. The spin structure of the matrix element and the polarization phenomena contain new contributions, with respect to binary processes, which can be conveniently expressed as functions of this parameter. We apply this formalism to the reaction $p+\overrightarrow{\alpha }p+{\pi }^0+\alpha ,$ in view of characterizing the different mechanisms involved and studying the excitation of the Roper resonance. We find that the polarization transfer coefficient $D_{\mathrm{nn}},$ where $\overrightarrow{n}$ is normal to the proton scattering plane, is especially sensitive to the spin of the exchanged particle.

Using the reaction ${}^{58}\mathrm{Ni}{(}^{50}\mathrm{Cr},\alpha$ $2p)$ and the coincidence recoil distance Doppler shift technique, we determined picosecond lifetimes of high-spin states in ${}^{102}\mathrm{Cd}.$ The positive-parity yrast and yrare cascades evidence the competition and interplay of the two proton holes in the $g_{9/2}$ orbit and four neutrons in the $d_{5/2},$ $g_{7/2},$ and $h_{11/2}$ orbits, outside the $Z=N=50\mathrm{}$ ${}^{100}\mathrm{Sn}$ core. At positive parity, this interplay leads to multiplets of states in the spin range $6^{+}–{10}^{+},$ some of which are connected by very weak $E2\mathrm{}$ transitions. At higher spins, spin-aligned proton holes and neutrons lead to magnetic rotation. Energies and transition strengths when compared with the predictions of several shell model calculations reveal the high sensitivity on the model parameters.

The equation of state (EOS) of finite nuclei is constructed in the relativistic Thomas-Fermi theory using the nonlinear $\sigma -\omega -\rho$ model. The caloric curves are calculated by confining the nuclei in the freeze-out volume taken to be a sphere of size about 4–8 times the normal nuclear volume. The results obtained from the relativistic theory are not significantly different from those obtained earlier in a nonrelativistic framework. The nature of the EOS and the peaked structure of the specific heat $C_v$ obtained from the caloric curves show clear signals of a liquid-gas phase transition in finite nuclei. The temperature evolution of the Gibbs potential and the entropy at constant pressure indicate that the characteristics of the transition are not too different from the first-order one.