Preliminary data on transverse energy “flow” and event asymmetries reported by the E877(814) Collaborations are compared to ARC (a relativistic cascade) model calculations for Au+Au at full AGS Brookhaven (Alternating Gradient Synchroton) beam energy. ARC triple differential cross sections for protons and pions are presented. Proton flow is produced in ARC, with the maximum $〈P_x〉\sim 120$ MeV/$c$. For central events $〈P_x〉$ for the pions is near zero, consistent with experiment. The comparison with data provides a constraint on the size of flow at the highest energy available, to be put beside that at Bevalac energy. This sets the stage for examining flow at intermediate energies, now being measured by E895, for signs of baryon rich plasma.

We present a study of the ${}^4$He charge distribution based on realistic nucleonic wave functions and incorporation of quark substructure. Any central depression of the proton point density seen in modern four-body calculations is too small by itself to lead to a correct description of the charge distribution of ${}^4$He if folded with a fixed proton size parameter, as is usually done. We utilize six-quark structures calculated in the chromodielectric model for $N$-$N$ interactions to find a “swelling” of the proton size as the internucleon distance decreases. This swelling is a result of the short-range dynamics in the $N$-$N$ system. Using the independent pair approximation, the corresponding charge distribution of the proton is folded with the two-nucleon distribution generated from Green’s function Monte Carlo calculations of the ${}^4$He nucleonic wave function. We obtain a reasonably good fit to the experimental charge distribution of ${}^4$He. Meson-exchange currents have not been included.

Based upon recent studies on quark condensates, we investigate strange quark matter at zero temperature and find that the mass parametrization popularly used for $u/d$ quarks with the mass-density-dependent model is just a first-order approximation to a more general formula, whereas the corresponding formula for $s$ quarks has to be modified, which leads to the result that the strangeness fraction in strange quark matter can exceed $u/d$ fraction. This strangeness excess may have a negative influence on the search for strangelets in ultrarelativistic heavy ion collisions.

Due to the internal structure of the nucleon, we should expect, in general, that the effective meson nucleon parameters may change in nuclear medium. We study such changes by using a chiral confining model of the nucleon. We use density-dependent masses for all mesons except the pion. Within a Dirac-Brueckner analysis, based on the relativistic covariant structure of the $\mathrm{NN}$ amplitude, we show that the effect of such a density dependence in the $\mathrm{NN}$ interaction on the saturation properties of nuclear matter, while not large, is quite significant. Due to the density dependence of the $g_{\sigma \mathrm{NN}},$ as predicted by the chiral confining model, we find, in particular, a looping behavior of the binding energy at saturation as a function of the saturation density. A simple model is described, which exhibits looping and which is shown to be mainly caused by the presence of a peak in the density dependence of the medium modified $\sigma N$ coupling constant at low density. The effect of density dependence of the coupling constants and the meson masses tends to improve the results for $E/A$ and density of nuclear matter at saturation. From the present study we see that the relationship between binding energy and saturation density may not be as universal as found in nonrelativistic studies and that more model dependence is exhibited once medium modifications of the basic nuclear interactions are considered.

We have studied the deuteron breakup in the $p(d,2p)n$ reaction at $T_d$=2.0 GeV. In this experiment, the vector analyzing power $A_Y,$ the tensor analyzing power $A_{\mathrm{YY}},$ and the polarization of the forward scattered proton are measured close to the quasifree $\mathrm{pp}$ scattering kinematics. These observables are presented as a function of the neutron momentum ranging from 0.04 to 0.45 GeV/$c$ in the rest frame of the deuteron. Marked deviations from the impulse approximation using conventional deuteron wave functions are observed. Corrections due to the multiple scattering, the final state interaction, and the $\Delta$ excitation are calculated in a model where the spin-isospin structure of the elementary amplitudes is treated rigorously. With this model, a reasonable account of the measured polarization observables is obtained. The global agreement with all observables is, however, not good enough that we can reliably discriminate between conventional wave functions.

We analyze the nucleon matrix element of the strange quark vector current in a nucleon-model-independent dispersive approach with input from the current world data set for the isoscalar electromagnetic form factors. The update of Jaffe’s minimal three-pole Ansatz for the spectral functions yields a 40% larger (Sachs) strangeness radius ${(r}_s^2{)}_{\mathrm{Sachs}}=0.20\mathrm{}\hspace{0.5em}{\mathrm{fm}}^2$ and a by 20% reduced magnitude of the strangeness magnetic moment ${\mu }_s=-0.26$. In the pole approximation these values are shown to be upper bounds. After extending the Ansatz in order to implement the asymptotic QCD momentum dependence (which the three-pole form factors cannot reproduce), we find the magnitude of the three-pole results reduced by up to a factor of 2.5. The signs of the leading moments originate primarily from the large $\phi$-meson couplings and are generic in the pole approximation.

The coherent and incoherent channels of the neutrinoless muon to electron conversion in nuclei, ${\mu }^{-}\mathrm{}(A,Z)\mathrm{}\to e^{-}{\mathrm{}(A,Z)\mathrm{}}^{*}$, are studied throughout the periodic table. The relevant nuclear matrix elements are computed by explicitly constructing all possible final nuclear states in the context of the quasiparticle random phase approximation. The obtained results are discussed in view of the existing at PSI and TRIUMF experimental data for ${}^{48}\mathrm{Ti}$ and ${}^{208}\mathrm{Pb}$ and compared with results obtained by (i) shell model sum-rule techniques, (ii) nuclear matter mapped into nuclei via a local density approximation, and (iii) earlier similar calculations.

We perform nuclear shell model calculations of the neutralino-nucleus cross section for several nuclei in the $A=127\mathrm{}$ region. Each of the four nuclei considered is a primary target in a direct dark matter detection experiment. The calculations are valid for all relevant values of the momentum transfer. Our calculations are performed in the ${3s2d1g}_{7/2}{1h}_{11/2}$ model space using extremely large bases, allowing us to include all relevant correlations. We also study the dependence of the nuclear response upon the assumed nuclear Hamiltonian and find it to be small. We find good agreement with the observed magnetic moment as well as other obervables for the four nuclei considered: ${}^{127}$I, ${}^{129,131}$Xe, and ${}^{125}$Te.

The ${}^{19}$F$(\alpha$,${}^2$He)${}^{21}$F reaction was investigated at 55 MeV incident energy. The transferred angular momenta of prominent transitions excited were determined from a distorted wave Born analysis of the angular distributions. Tentative spin assignments for the observed levels are extracted from shell-model calculations with the “unified” $\mathrm{sd}$-space interaction based on the very good reproduction of the excitation energies and the predicted large two-neutron transfer spectroscopic factors.

The Ioffe current constants for the proton and Roper resonance are evaluated using a linear confining potential model parametrized to reproduce the proton magnetic moment, spin, and energy. The three-body Dirac equation, for the ${(1/2\mathrm{}}^{+}{)}^3$ positive parity configuration, is solved in hypercentral approximation. Quark masses of the order of 9 MeV are needed to reproduce the proton magnetic moment. When the proton rms charge radius and magnetic moment are reproduced, the Roper has an Ioffe coupling constant about 25% larger than the proton.

The possibility of observing a bright interior in the nucleus “viewed” by intermediate energy alpha particles ${(E}_{\alpha }$=172.5 MeV), as a probe for the ${}^{58}$Ni nucleus, previously predicted by applying only a first-order noneikonal correction and one simple optical model potential was confirmed. The first-, second-, and third-order noneikonal corrections to the Glauber model were incorporated in three arbitrary different nominal optical potentials and the effects of switching (off/on) the Coulomb potential were studied. The role of corrections in the effective potentials and also the results of calculations of the imaginary part of the phase shift functions for the different optical potentials used were discussed.

Experimental data on strongly energy-damped yields from the ${}^{28}\mathrm{Si}{+}^{16}$O reaction at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=39.1\mathrm{}$ and 50.5 MeV are analyzed in the context of fission from the ${}^{44}$Ti compound system. Several features of this system, including the presence of resonantlike structures in the elastic- and inelastic-scattering excitation functions, the observation of large cross sections for strongly damped yields, and the recognition that there are relatively few channels open for reactions involving the near-grazing partial waves, have been taken to infer a deep-inelastic as opposed to fission origin of the strongly damped yields. We test this claim by comparing the predictions of the transition-state model for fission to the experimental results. The statistical model is found to adequately describe the experimental results at the higher energy. The fully energy-damped inelastic yields at 39.1 MeV, however, are found to be far in excess of expectations based on the fission model. This result is in sharp contrast to what has been observed in the nearby ${}^{24}\mathrm{Mg}{+}^{16}$O system.

The energy and the width of resonance states are determined by analytic continuation of bound-state energies as a function of the coupling constant (potential strength). The advantage of the method is that the existing techniques for calculation of bound states can be applied, without any modifications, to determine the position of resonances. Various numerical examples show the applicability of the method for three-body systems, including the excited states of the ${}^6$He and ${}^6$Li.

The quark-meson coupling (QMC) model is applied to a study of the mass of the $\rho$-meson in helium and carbon nuclei. The average mass of a $\rho$-meson formed in ${}^{3,4}$He and ${}^{12}$C is expected to be around 730, 690, and 720 MeV, respectively.

Using the QCD sum-rule approach, we show that the flavor-nonsinglet $H$ dibaryon states with $J^{\pi }{=1\mathrm{}}^{+},\hspace{0.5em}{J}^{\pi }{=0\mathrm{}}^{+},\hspace{0.5em}I=1\mathrm{}$ (27 plet) are nearly degenerate with the $J^{\pi }{=0\mathrm{}}^{+},\hspace{0.5em}I=0\mathrm{}$ singlet $H_0$ dibaryon, which has been predicted to be stable against strong decay, but has not been observed. Our calculation, which does not require an instanton correction, suggests that the $H_0$ is slightly heavier than these flavor-nonsinglet $H$’s over a wide range of the parameter space. If the singlet $H_0$ mass lies above the $\Lambda \Lambda$ threshold (2231 MeV), then the strong interaction breakup to $\Lambda \Lambda$ would produce a very broad resonance in the $\Lambda \Lambda$ invariant mass spectrum which would be very difficult to observe. On the other hand, if these flavor-nonsinglet $J=0\mathrm{}$ and 1 $H$ dibaryons are also above the $\Lambda \Lambda$ threshold, but below the ${\Xi }^{0}n$ breakup threshold (2254 MeV), then because the direct, strong interaction decay to the $\Lambda \Lambda$ channel is forbidden, these flavor-nonsinglet states might be more amenable to experimental observation. The present results allow a possible reconciliation between the reported observation of $\Lambda \Lambda$ hypernuclei, which argue against a stable $H_0$, and the possible existence of $H$ dibaryons in general.

We investigate the consequences of anharmonic terms in the vibrational spectrum of giant dipole resonances for the double Coulomb excitation of such modes in relativistic heavy-ion collisions. It is found that apparent discrepancies between the results of two separate experiments can be put in harmony assuming minor departures from the harmonic limit because of the special features of the reaction mechanism.

We have updated our multipole analyses to incorporate new data from the low-energy and $\Delta$ resonance regions. We note a slight decrease in our estimate of the $\Delta$ photodecay amplitudes. This agrees with results found in Compton scattering. Our values are also in good agreement with another previous determination. We have reexamined our determinations of the $E2/M1\mathrm{}$ ratio at the resonance energy and at the pole. We find an $E2/M1\mathrm{}$ ratio (at the pole) which is in good agreement with the recent Mainz value.

We comment on a recent paper by Wieser et al. [Phys. Rev. C 54, 1930 (1996)]. The authors have performed a single-energy analysis of ${\pi }^{+}p$ scattering data at 68.3 MeV, finding a value for the $S_{31}$ phase shift about 1${}^{\mathrm{o}}$ smaller than found in the Karlsruhe-Helsinki partial-wave analysis. The authors use this result to argue for a dispersion relation analysis using recently measured data, so that their effect on the $\pi \mathrm{NN}$ coupling constant ${(f}^2)$ and $\Sigma$ amplitude can be determined. We note that these tasks were accomplished prior to the submission of the above paper. We clarify the effect of this analyzing power data on $f^2$ and the $\Sigma$ amplitude.

We critically discuss the recently developed quantum-mechanical equivalent photon spectrum by Benesh et al. [Phys. Rev. C 54, 1404 (1996)]. We point out that the key point, the strong absorption in heavy ion collisions, is not treated adequately. Conclusions drawn from such a spectrum are invalid. Equivalent-photon spectra appropriate for heavy ions have been given before in quantal, as well as semiclassical versions, and were found to be very satisfactory.

Shortcomings of a momentum-space treatment of strong absorption, as discussed in the preceding Comment, are only of concern at low projectile energies, $\gamma <1.5\mathrm{}$. At intermediate and high energies, for which the quantum-mechanical equivalent-photon spectrum is intended, the quantum-mechanical cross sections are reduced relative to the semiclassical results whether one treats strong effects via a momentum-space or an impact-parameter (spatial) cutoff. At these energies the origin of the discrepancy between the predictions of fully quantum-mechanical and the semiclassical calculations cannot be traced to differences in the treatment of strong-interaction effects. Rather, they arise from quantum effects neglected in the semiclassical calculations.