The final-state distribution of ${\mathrm{HeT}}^{+}$ resulting from the β decay of molecular tritium has been investigated with particular emphasis on its reliability in connection with the interpretation of the tritium neutrino-mass experiments. This investigation concentrates on two aspects. First, the reliability within the sudden approximation is examined. This includes the extension of previously calculated final-state distributions to a larger range of energy transfer, i.e., to an excitation energy of 800 eV, the investigation of the effect of nuclear motion on the continuous electronic spectrum, and the use of improved basis sets. Second, the molecular transition-probability spectrum (including electronic bound and continuous states) has been calculated for the first time in a beyond sudden-impulse approximation. It is concluded that the concomitant corrections are too small to explain the problems of recent experiments difficulties to extract the neutrino mass out of the β spectrum of ${\mathrm{T}}_2.$

Frame dependence of parton cascade results is studied for different schemes of performing cascade simulations. We show that different schemes do not always agree and results may have strong frame dependence. When the interaction range is on the order of mean free path and the collisions are done in the two parton center-of-mass frame, the results are not sensitive to the global frame in which the collisions are ordered. Effects of different differential cross sections are also discussed.

We explore the correspondence between classical gluon radiation and quantum radiation in a coherent state for gluons produced in ultrarelativistic nuclear collisions. The expectation value of the invariant momentum distribution of gluons in the coherent state is found to agree with the gluon number distribution obtained classically from the solution of the Yang-Mills equations. A criterion for the applicability of the coherent state formalism to the problem of radiation in ultrarelativistic nucleus-nucleus collisions is discussed. This criterion is found to be fulfilled for midrapidity gluons with perturbative transverse momenta larger than $\sim 1$–2 GeV and produced in collisions between valence partons.

We discuss the evolution of the mixed phase at RHIC and SPS within boost-invariant hydrodynamics. In addition to the hydrodynamical expansion, we also consider evaporation of particles off the surface of the fluid. The back reaction of this evaporation process on the dynamics of the fluid shortens the lifetime of the mixed phase. In our model this lifetime of the mixed phase is $<~12\hspace{0.5em}\mathrm{fm}/c$ in Au+Au at RHIC and $<~8\hspace{0.5em}\mathrm{fm}/c$ in Pb+Pb at SPS, even in the limit of vanishing transverse expansion velocity. Strong separation of strangeness occurs, especially in events (or at rapidities) with relatively high initial net baryon and strangeness number, enhancing the multiplicity of multiply strange nuclear clusters. If antiquarks and antibaryons reach saturation in the course of the pure QGP or mixed phase, we find that at RHIC the ratio of antideuterons to deuterons may exceed $0.3$ and even $\overline{{}^4\mathrm{He}}{/}^4\mathrm{He}>0.1\mathrm{}$. In S+Au at SPS we find only $\overline{N}/N\approx 0.1$. As a result of fluctuations, at RHIC even a negative baryon number at midrapidity is possible in individual events, so that the antibaryon and antibaryon-cluster yields exceed those of the corresponding baryons and clusters.

We recapitulate a thermodynamically consistent excluded volume hadron gas model and examine its differences with other “thermal models” used in the literature. Preliminary experimental data for particle number ratios in the collisions of $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ at the BNL AGS $(11A\mathrm{GeV}/c)$ and $\mathrm{P}\mathrm{b}+\mathrm{P}\mathrm{b}$ at the CERN SPS $(160A\mathrm{GeV}/c)$ are analyzed. For equal values of the hadron hard-core parameters the excluded volume model gives essentially the ideal gas predictions for the particle number ratios, which is similar to other thermal models. We observe, however, the systematic excess of experimental pion abundances compared to the ideal gas results. This effect can be explained in our model by a smaller pion hard-core volume compared to those of other hadrons. The absolute values for particle number and energy densities at the chemical freezeout are predicted with a simultaneous fit to all these AGS and SPS particle number ratios.

The classical Yang-Mills radiation computed in the McLerran-Venugopalan model is shown to be equivalent to the gluon bremsstrahlung distribution to lowest ${(g}^6)$ order in pQCD. The classical distribution is also shown to match smoothly onto the conventional pQCD minijet distribution at a scale $k_{\perp }^2\sim \chi$, characteristic of the initial parton transverse density of the system. The atomic number and energy dependence of $\chi$ is computed from available structure function information. The limits of applicability of the classical Yang-Mills description of nuclear collisions at RHIC and LHC energies are discussed.

The ORELA experiment on the neutron charge radius has been reevaluated. The neutron transmission of liquid thorogenic ${}^{208}\mathrm{Pb}$ with the neutron time-of-flight method in the neutron energy range from 0.08 to 800 eV was measured. Additional studies on condensed matter effects for liquid Bi and liquid Pb have provided more accurate corrections resulting in smaller systematic uncertainties for the neutron-electron scattering length $b_{\mathrm{ne}}.$ We have also reevaluated the transmission data on liquid Bi of Melkonian and co-workers. We have obtained values of $b_{\mathrm{ne}}=(-1.33\pm 0.027\pm 0.03)\times {10}^{-3}\mathrm{fm}$ for ${}^{208}\mathrm{Pb}$ and $b_{\mathrm{ne}}=(-1.44\pm 0.033\pm 0.06)\times {10}^{-3}\mathrm{fm}$ for ${}^{209}\mathrm{Bi}$ where for both results the two uncertainties denote the statistical and the systematic uncertainty, respectively. The results for ${}^{208}\mathrm{Pb}$ and ${}^{209}\mathrm{Bi}$ were found to be in good agreement.

Polarization observables for strange particle threshold production in the processes $N+N\to K+Y+N$ (where $Y$ is a Λ or a Σ) are studied. The spin structure of the corresponding matrix elements is derived, assuming $S$-wave production. Using the $P$ invariance of the strong interaction and the Pauli principle, it is shown that these reactions can be described in terms of two (in the case of $\mathrm{pp}$ collisions) or three (in the case of $\mathrm{np}$-collisions) independent complex amplitudes. This results in a specific behavior for polarization observables which is described. Polarization observables are calculated in the $S$- and $P$-wave approximations. In the case of collinear kinematics, relationships between spin correlation coefficients and the spin structure of the nucleon are explained.

We develop arguments for “mapping” the effective chiral Lagrangian whose parameters are given by “Brown-Rho” (BR) scaling to a Landau Fermi-liquid fixed-point theory for nuclear matter in describing fluctuations in various flavor (e.g., strangeness) directions. We use for this purpose the effective Lagrangian used by Furnstahl, Tang, and Serot that incorporates the trace anomaly of QCD in terms of a light-quark (quarkonium) degree of freedom with the heavy (gluonium) degree of freedom integrated out. The large anomalous dimension $d_{\mathrm{an}}\approx 5/3$ for the scalar field found by Furnstahl et al. to be needed for a correct description of nuclear matter is interpreted as an indication for a strong-coupling regime and the ground state given by the BR-scaled parameters is suggested as the background around which fluctuations can be rendered weak so that mean-field approximation is reliable. We construct a simple model with BR-scaled parameters that provides a satisfactory description of the properties of matter at normal nuclear matter density. Given this, fluctuations around the BR-scaled background are dominated by tree diagrams. Our reasoning relies heavily on recent developments in the study of nucleon and kaon properties in normal and dense nuclear matter, e.g., nucleon and kaon flows in heavy-ion processes, kaonic atoms, and kaon condensation in dense compact-star matter.

We report variational calculations of symmetric nuclear matter and pure neutron matter, using the new Argonne $v_{18}$ two-nucleon and Urbana IX three-nucleon interactions. At the equilibrium density of 0.16 ${\mathrm{fm}}^{-3}$ the two-nucleon densities in symmetric nuclear matter exhibit a short-range spin-isospin structure similar to that found in light nuclei. We also find that both symmetric nuclear matter and pure neutron matter undergo transitions to phases with pion condensation at densities of 0.32 ${\mathrm{fm}}^{-3}$ and 0.2 ${\mathrm{fm}}^{-3}$, respectively. Neither transtion occurs with the Urbana $v_{14}$ two-nucleon interaction, while only the transition in neutron matter occurs with the Argonne $v_{14}$ two-nucleon interaction. The three-nucleon interaction is required for the transition to occur in symmetric nuclear matter, whereas the transition in pure neutron matter occurs even in its absence. The behavior of the isovector spin-longitudinal response and the pion excess in the vicinity of the transition, and the model dependence of the transition are discussed.

In order to include pionic degrees of freedom in the description of nuclear many-body systems, the chiral $\sigma$ model in the nonlinear representation is investigated. The renormalizability of the model, which is obtained from the linear $\sigma$ model by a field transformation, is studied in the context of the equivalence theorem. It is shown that in any expansion scheme which is based on self-consistent mean scalar fields, the nonlinear $\sigma$ model should be considered as unrenormalizable (even if the $\sigma$ mass is kept finite), and new counterterms have to be introduced in each order. The resulting equation of state in the one-loop (Hartree) approximation is calculated, and the corresponding pion-nucleus optical potential is discussed.

A relativistic description of polarized deep-inelastic lepton scattering from polarized nuclei is presented. It is based on front form dynamics. Convolution formulas for the nuclear spin structure functions $g_1^A$ and $g_2^A$ are derived. They require the front form spin distributions of nuclei and the nucleonic spin structure functions. The description is applied to the deuteron and the trinucleon bound states. The numerical calculations show that relativistic effects arising from the consistent quantum mechanical treatment of spin are small. Simple approximations to the convolution formulas for $g_1^A$ and $g_2^A$ are justified. The approximative convolution formulas allow the subtraction of nuclear effects from measured spin structure functions and therefore the experimental determination of the neutron spin structure functions. Polarized ${}^3$He turns out to be a rather reliable effective neutron spin target for deep-inelastic scattering of polarized leptons. The differences between descriptions based on front form and on instant form dynamics are also discussed.

We report on an experiment to search for the decay of two-phonon octupole vibrational states in ${}^{208}\mathrm{Pb}$ with GAMMASPHERE. A beam of ${}^{154}\mathrm{Sm}$ at a bombarding energy of 1 GeV was used to excite ${}^{208}\mathrm{Pb}$ via quasielastic as well as via deep-inelastic processes. To be independent of the lifetime of the two-phonon state a thin target was used, requiring the measurement of the position of the scattered particles to correct for the Doppler shift of the emitted γ rays. Scattered particles were detected by a silicon-strip detector covering forward angles. We did not observe any discrete γ transition in the expected energy range of 2–3 MeV down to a limit of 20% and 4% of the intensity in the $5^{-}\to 3^{-}$ transition for quasielastic and deep-inelastic processes, respectively.

We present γ-ray energies and intensities of 34 new weak transitions in the electron-capture decay of ${}^{194}\mathrm{Au}.$ These γ rays were detected in singles experiments with high-purity Ge and anti-Compton detectors, and in γ-γ coincidence experiments, with the HERA array of Ge detectors. Their placements in the decay scheme confirm levels in ${}^{194}\mathrm{Pt}$ at 1373.9 and 1737.3 keV observed in the electron-capture decay of ${}^{194}\mathrm{Au}.$

The level structures of ${}^{217}\mathrm{Po}$ and ${}^{213}\mathrm{Pb}$ have been studied following the alpha decay of ${}^{221}\mathrm{Rn}$ and ${}^{217}\mathrm{Po}.$ The ground state band of ${}^{217}\mathrm{Po}$ can be interpreted as arising from the mixed $1/2(-0.1;0.5;-2)+3/2(-0;0.6)$ reflection asymmetric orbital with considerable $i_{11/2}$ shell model character. The $<10\mathrm{}\sec$ half-life of the ${}^{217}\mathrm{Po}$ leads to a hindrance factor $<8\mathrm{}$ for the alpha decay to ${}^{213}\mathrm{Pb}$ and suggests the surprising result that the previously proposed ${}^{213}\mathrm{Pb}$ ground state has the configuration $i_{11/2}.$ This anomaly has been discussed.

In view of the semiclassical treatment, the Berry phase is shown to be responsible for the decoupling phenomena in the $K=1/2\mathrm{}$ nuclear rotational bands.

We examine the question of the gauge invariance of electromagnetic form factors calculated within the cloudy bag model. One of the assumptions of the model is that electromagnetic form factors are most accurately evaluated in the Breit frame. This feature is used to show that gauge invariance is respected in this frame.

The coherence length of superfluid neutron matter is calculated from the microscopic BCS wave function of a Cooper pair in momentum space making use of recent nucleon-nucleon potential models and including polarization (RPA) effects. We find as our main result that the coherence length is proportional to the Fermi momentum to pairing gap ratio, in good agreement with simple estimates used in the literature, with a nearly interaction independent constant of proportionality. Our calculations can be applied to the problem of inhomogeneous superfluidity of hadronic matter in the crust of a neutron star.

Three superdeformed bands have been observed in ${}^{191}$Au using the EUROGAM II multidetector array. The previously known yrast superdeformed band has been extended up to very high rotational frequencies and two new excited bands have been assigned to this nucleus. These bands behave as signature partners and display characteristics which suggest they could be based either on the $\pi$ [532]3/2 orbital alone or on that orbital plus the $\pi$ [530]1/2 orbital, which become the $\left[\widetilde{431}\right]$3/2,1/2 doublet in the pseudospin formalism.