The effects of systematic errors in elastic scattering differential cross-section data upon the assessment of quality fits to that data have been studied. First, to estimate the probability of any unknown systematic errors, select, typical, sets of data have been processed using the method of generalized cross validation; a method based upon the premise that any data set should satisfy an optimal smoothness criterion. Specified systematic errors should also be taken into account when high quality fits to data are sought. We have considered such effects due to the finite angular resolution associated with the data in some quite exceptional, heavy ion scattering data sets. Allowing angle shifting of the measured values gave new data sets that are very smooth. Furthermore, when such allowances for systematic errors are so taken into account, reasonable, but not necessarily statistically significant, fits to the original data sets can become so. Therefore, they can be plausible candidates for the ‘‘physical’’ descriptions of the scattering processes. In another case, the S function that provided a statistically significant fit to data, upon allowance for angle variation, became overdetermined. A far simpler S function form could then be found to describe the scattering process. The S functions so obtained have been used in a fixed energy inverse scattering study to specify effective, local, Schrödinger potentials for the collisions. An error analysis has been performed on the results to specify confidence levels for those interactions. © 1996 The American Physical Society.

A generalized kinetic equation of Lennard-Balescu type is derived with retardation effects. By explicit consideration of the density-density fluctuations we give the contribution of fluctuations to the spreading width of giant resonances besides the collisional part. For small frequencies and long wavelengths, approximate formulas for the damping of giant resonances are derived. The density fluctuations couple the equation of state to the damping rate and give rise to an overall enhancement factor. This density and temperature dependent factor can reproduce the experimental values of the damping. Inside the spinodal region the factor turns out to be negative, indicating unstable modes. Explicit comparisons are made with the experimental values of giant monopole and dipole resonances. It is shown that the experimental widths can be described assuming finite nuclei since surface effects are important for the influence on density fluctuations. The recently reported saturation of the dipole width with increasing energy is explained as a transition between zero and first sound. Within this treatment we find an overcritical range of fluctuations, above which the nucleus is destroyed and no collective behavior is possible at all. © 1996 The American Physical Society.

The strength of transverse flow is examined as a function of transverse momentum ${\mathit{p}}_{\mathit{t}}$ using a simple, transversely moving thermal model and a more realistic, relativistic transport model. It is shown that the ${\mathit{p}}_{\mathit{t}}$ dependence reveals useful information about the collective flow that is complementary to that obtained from the standard in-plane transverse momentum analysis. Interesting features of using the ${\mathit{p}}_{\mathit{t}}$ dependence to study the equation of state of the superdense hadronic matter formed in relativistic heavy-ion collisions are demonstrated. © 1996 The American Physical Society.

The suppression of the J/Ψ production is attributed to shadowing in the initial state parton distributions in nuclei due to multiquark cluster formation and to the dissociation of the final cc¯ state in the nuclear medium. The model agrees with the hadron-nucleus and nucleus-nucleus collision data and predicts enhancement of the effect at the Relativistic Heavy Ion Collider energies. Nuclear transparency at these energies is also considered and found to increase the suppression. © 1996 The American Physical Society.

We have studied the phase diagram and evolution of a strangelet in equilibrium with a finite hadronic gas. Significant finite size modifications of the phase diagram are found and their parameter dependences are studied. With the inclusion of finite size effects we have also been able to obtain the detailed properties of the cold strangelet emerging in the final stage of the isentropic expansion of a finite strange fireball in high energy heavy-ion collisions. © 1996 The American Physical Society.

We present a realistic expanding source model with nine parameters that are necessary and sufficient to describe the main physics occurring during hydrodynamical freeze-out of the excited hadronic matter produced in relativistic heavy-ion collisions. As a first test of the model, we compare it to data from central Si + Au collisions at ${\mathit{p}}_{\mathrm{lab}}$/A=14.6 GeV/c measured in experiment E-802 at the Brookhaven Alternating Gradient Synchrotron. An overall ${\mathrm{\chi }}^2$ per degree of freedom of 1.055 is achieved for a fit to 1416 data points involving invariant ${\mathrm{\pi }}^{+}$, ${\mathrm{\pi }}^{\mathrm{-}}$, ${\mathit{K}}^{+}$, and ${\mathit{K}}^{\mathrm{-}}$ one-particle multiplicity distributions and ${\mathrm{\pi }}^{+}$ and ${\mathit{K}}^{+}$ two-particle correlations. The 99%-confidence region of parameter space is identified, leading to one-dimensional error estimates on the nine fitted parameters and other calculated physical quantities. Three of the most important results are the freeze-out temperature, longitudinal proper time, and baryon density along the symmetry axis. For these we find values of 92.9 ± 4.4 MeV, 8.2 ± 2.2 fm/c, and 0.${0222}_{\mathrm{-}0.0069}^{+0.0096\mathrm{}}$ ${\mathrm{fm}}^{\mathrm{-}3}$, respectively. © 1996 The American Physical Society.

We calculate the p¯ background in the upper atmosphere which results when primary cosmic rays interact with air nuclei. Since the p¯ yield from p-nucleus and nucleus-nucleus interactions is not directly known from experiments, we derive these quantities by using a Monte Carlo simulation which is theoretically based on the dual parton model and which had been successfully applied to the description of hadron production in high energy collisions. Results on the calculated atmospheric p¯ background indicate a larger p¯ background than earlier estimates predicted, particularly at low energies. © 1996 The American Physical Society.

The Ioffe current constants for the proton are evaluated using a Poincaré invariant solution of the three-body Dirac equation, for the (1/$2^{+}$${)}^3$ positive parity configuration. Results are also compared to the QCD sum rule predictions and with the random instanton liquid model. © 1996 The American Physical Society.

We discuss spin-dependent, deep-inelastic scattering from nuclei within a covariant framework. In the relativistic impulse approximation this is described in terms of the amplitude for forward, virtual-photon scattering from an off-mass-shell nucleon. The general structure of the off-shell nucleon hadronic tensor is derived, and the leading behavior of the off-shell nucleon structure functions computed in the Bjorken limit. The formalism, which is valid for nucleons bound inside nuclei with spin 1/2 or 1, is applied to the case of the deuteron. © 1996 The American Physical Society.

We investigate the low-energy behavior of the four-point Green’s function ${\mathrm{\Gamma }}^{\mathrm{\mu }\nu }$ describing virtual Compton scattering off the nucleon. Using Lorentz invariance, gauge invariance, and crossing symmetry, we derive the leading terms of an expansion of the operator in the four-momenta q and ${\mathit{q}}^{\prime }$ of the initial and final photon, respectively. The model-independent result is expressed in terms of the electromagnetic form factors of the free nucleon, i.e., on-shell information which one obtains from electron-nucleon scattering experiments. Model-dependent terms appear in the operator at O(${\mathit{q}}_{\mathrm{\alpha }}$${\mathit{q}}_{\mathrm{\beta }}^{\prime }$), whereas the orders O(${\mathit{q}}_{\mathrm{\alpha }}$${\mathit{q}}_{\mathrm{\beta }}$) and O(${\mathit{q}}_{\mathrm{\alpha }}^{\prime }$${\mathit{q}}_{\mathrm{\beta }}^{\prime }$) are contained in the low-energy theorem for ${\mathrm{\Gamma }}^{\mathrm{\mu }\nu }$, i.e., no new parameters appear. We discuss the leading terms of the matrix element and comment on the use of on-shell equivalent electromagnetic vertices in the calculation of ‘‘Born terms’’ for virtual Compton scattering. © 1996 The American Physical Society.

The influence of the nuclear medium upon the internal structure of a composite nucleon is examined. The interaction with the medium is assumed to depend on the relative distances between the quarks in the nucleon consistent with the notion of color neutrality, and to be proportional to the nucleon density. In the resulting description the nucleon in matter is a superposition of the ground state (free nucleon) and radial excitations. The effects of the nuclear medium on the electromagnetic and weak nucleon form factors and the nucleon structure function are computed using a light-front constituent quark model. Further experimental consequences are examined by considering the electromagnetic nuclear response functions. The effects of color neutrality supply small but significant corrections to predictions of observables. © 1996 The American Physical Society.

Neutrino trapping effects on the properties of dense stellar matter in nonstrange supranuclear regime are studied with the purpose of applying to supernovae dynamical evolution. The hadronic and leptonic compositions of stellar matter are obtained in the framework of the relativistic mean-field theory coupled with the β-equilibrium condition, and maintaining the charge neutrality of the stellar medium. It is shown that the matter composition depends dramatically upon the confined electronic-leptonic fraction. The softness of the equation of state and the lowering of the nuclear incompressibility values, when compared with the situation in which neutrino confinement is not considered, are the remarkable results. © 1996 The American Physical Society.

The inelastic neutron scattering reaction has been employed to search for a 2485-keV γ ray which has been reported as a deexciting transition from one of the higher-spin members of the two-phonon octupole quartet in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Although other states of similar spin and excitation energy are observed, no evidence for a 2485-keV γ ray is obtained in either γ-ray singles or γ-γ coincidence measurements. © 1996 The American Physical Society.

Neutron-rich, odd-Z nuclei ${}_{}{}^{145}{}_{}{}^{}\mathrm{La}$ and ${}_{}{}^{147}{}_{}{}^{}\mathrm{La}$ populated in spontaneous fission of ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ were studied using the EUROGAM array. The experiment indicates the presence of similar octupole correlations in the studied La isotopes as found in the barium core nuclei. Alternating-parity structures were found in ${}_{}{}^{145}{}_{}{}^{}\mathrm{La}$, indicating enhanced octupole correlations, as observed in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$, while in ${}_{}{}^{147}{}_{}{}^{}\mathrm{La}$ octupole effects are weakened by alignment phenomena, as seen in the core nucleus ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$. © 1996 The American Physical Society.

The isotope ${}_{}{}^{190}{}_{}{}^{}\mathrm{Po}$ was produced in the ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$${(}^{48}$Ti,2n) reaction and its α-decay energy and half-life were measured to be 7.49(4) MeV and 2.$0_{\mathrm{-}1.0}^{+0.5\mathrm{}}$ ms, respectively. These data compare as follows with preliminary values reported by Quint et al.: ${\mathit{E}}_{\mathrm{\alpha }}$=7482(20) keV and a ${\mathit{T}}_{1/2}$=9.$6_{\mathrm{-}4.4}^{+47\mathrm{}}$ ms. While the two energies agree, the half-lives differ by a factor of almost 5. The earlier data yield an α reduced width which is much smaller than those of neighboring nuclides; our ${}_{}{}^{190}{}_{}{}^{}\mathrm{Po}$ energy and half-life result in a width that fits the overall α-decay-rate systematics in the mass region above the Z=82 closed shell. © 1996 The American Physical Society.

It has recently been proved from measurements of the spin-transfer coefficients ${\mathit{D}}_{\mathit{xx}}$ and ${\mathit{D}}_{\mathit{zz}}$ that there is a small but nonvanishing ΔS=0 component ${\mathrm{\sigma }}_0$ in the inclusive p(p,n)Nπ differential reaction cross section σ in the forward direction. It is shown that the dominant part of the measured ${\mathrm{\sigma }}_0$ at forward neutron angles can be explained in terms of the projectile Δ excitation mechanism. An estimate is further made of contributions to ${\mathrm{\sigma }}_0$ from s-wave rescattering processes. It is found that the s-wave rescattering contribution is much smaller than the contribution coming from the projectile Δ excitation mechanism. The addition of an s-wave rescattering contribution to the dominant part, however, improves the fit to the data. © 1996 The American Physical Society.

We consider several topics concerning static magnetic dipole and electric quadrupole moments (μ and Q) as signatures of the onset of nuclear collectivity. Having previously noted that in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$ there is an abrupt change of sign in Q of yrast states with ${\mathit{J}}^{\mathrm{\pi }}$=${10}^{+}$,${12}^{+}$, and ${14}^{+}$ relative to lower J states, we discuss whether these states are oblate or prolate. We next show that configuration mixing leads to much larger changes in Q than in μ. We then look for other bands of interest in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$. Finally we discuss the Jolos–von Brentano relationship which relates Q of $2_1^{+}$ states to B(E2)’s for transitions from and to the $2_1^{+}$ states. © 1996 The American Physical Society.

Resonant inelastic proton scattering experiments were carried out to investigate the $\gamma$ decay of the $1^{-}$ state at an excitation energy of around 3.5 MeV in the $N=82\mathrm{}$ nuclei ${}_{}{}^{142}{}_{}{}^{}\mathrm{Nd}$ and ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$. $\gamma$-ray branching ratios were determined from $\gamma$-proton coincidences in both nuclei. The newly observed $\gamma$ decay of the dipole excitation at 3225 keV in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ to the one-phonon states, in particular the ($1^{-}$ → $3_1^{-}$) $E2\mathrm{}$ transition to the octupole phonon state, is the first direct proof of the two-phonon character of the 1${}_{}{}^{-}{}_{}{}^{}\mathrm{state}$ in any $N=82\mathrm{}$ nucleus.

A decoupled rotational band with an average dynamical moment of inertia ${\mathcal{I}}^{\mathrm{}\left(2\right)\mathrm{}}\sim 55$ ${\mathit{ħ}}^2$/MeV has been observed to high spin in $N=71\mathrm{}$ ${}_{}{}^{129}{}_{}{}^{}\mathrm{Ce}$. The measured quadrupole moment of $Q_0=6.3\mathrm{}\left(4\right)\mathrm{}$ eb is as large as that of the superdeformed band in ${}_{}{}^{131}{}_{}{}^{}\mathrm{Ce}$. The large deformation and decoupled character of the band suggests that the odd neutron occupies either the $\frac{h_{\frac{9}{2}}}{f_{\frac{7}{2}}}\mathrm{}\left[541\right]\mathrm{}\frac{1}{2^{-}}$ orbital or the $i_{\frac{13}{2}}\mathrm{}\left[660\right]\mathrm{}\frac{1}{2^{+}}$ intruder orbital. This is the first example of a superdeformed band extending to high spin below $N=73\mathrm{}$, a neutron number that has long been considered as the boundary for superdeformation in the $A\sim 130$ mass region.