Adhikari has pointed out that the coupled reaction channels many-body scattering equations can be interpreted as a projected version of a formally exact set of dynamical equations. This provides a new basis for calculating the corrections due to three-body breakup processes. To establish a convenient framework for such analyses, we recast the formalism into transition operator equation form. We observe that the integral equations that result are not independent of each other. This defect is remedied by a formal decoupling procedure. The resulting equations are antisymmetrized and projected onto a finite basis.

NUCLEAR REACTIONS Exact version CRC transition operator equations, decoupling, antisymmetrization, projection.

High spin states in ${}_{}{}^{79}{}_{}{}^{}\mathrm{Kr}$ and ${}_{}{}^{81}{}_{}{}^{}\mathrm{Kr}$ have been investigated via the ${}_{}{}^{76,78}{}_{}{}^{}\mathrm{Se}(\alpha , n){}_{}{}^{79,81}{}_{}{}^{}\mathrm{Kr}$ reactions using in-beam gamma-ray spectroscopy techniques. The decay schemes and decay properties for levels up to ∼3 MeV in excitation energy could be deduced from gamma ray yield data, obtained at bombarding energies between 10 and 18 MeV, $\gamma -\gamma$ coincidence and angular distribution measurements. Rotational-like band structures are observed in ${}_{}{}^{79}{}_{}{}^{}\mathrm{Kr}$ which are less apparent in ${}_{}{}^{81}{}_{}{}^{}\mathrm{Kr}$. Both nuclei show the presence of high-spin cascades based on the lowest ${\frac{9}{2}}^{+}$ excited level.

NUCLEAR REACTIONS ${}_{}{}^{76,78}{}_{}{}^{}\mathrm{Se}(\alpha , n){}_{}{}^{79,81}{}_{}{}^{}\mathrm{Kr}$, $E=10-18\mathrm{}$ MeV; measured $E_{\gamma }$, $n-\gamma$, $\gamma -\gamma$ coincidences, gamma ray angular distributions; ${}_{}{}^{79}{}_{}{}^{}\mathrm{Kr}$ and ${}_{}{}^{81}{}_{}{}^{}\mathrm{Kr}$ deduced levels, $J^{\pi }$; enriched targets, Ge(Li) detectors.

Cross sections and analyzing powers are presented for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\overrightarrow{p}, p){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic scattering at 122 and 160 MeV. The data cover a large angular range (up to ${\theta }_{\mathrm{lab}}=154\mathrm{}°$) and extend to lower energies an earlier, similar measurement at 200 MeV. The complete data set is analyzed in the framework of the optical model. Besides the standard Woods-Saxon potential, nonstandard radial shapes for the central and the spin-orbit potentials are investigated. Although the number of free parameters for the nonstandard potential is substantially reduced from the standard potential, it provides an improved fit to the data and a description of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(p, p){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ scattering with a simple monotonic energy dependence in the region 100-200 MeV. The characteristic features of the nonstandard potential are reproduced by microscopic theories.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\overrightarrow{p}, p)$, $E_p=122, 160$ MeV, ${\theta }_{\mathrm{lab}}=6\mathrm{}°-154\mathrm{}°$; measured $\sigma \left(\theta \right)$ and $A\left(\theta \right)$; optical-model analysis, including data at 200 MeV, nonstandard potential shapes, energy dependence of optical potential.

We measured protons and alpha particles emitted from the giant electric dipole resonance of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ using tagged photons; discrete final states in the residual nuclei were resolved. The proton decay was found to be dominated by the ground state branch. Comparisons with Hauser-Feshbach calculations and spectroscopic factors from nucleon pickup reactions indicate that most proton decay channels have a significant, nonstatistical component. The alpha decay channels appear to be statistical.

NUCLEAR REACTIONS ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}(\gamma , p){}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}(\gamma , \alpha ){}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, $E_{\gamma }=15.6-22.5\mathrm{}$ MeV, $\delta E_{\gamma }=150-200\mathrm{}$ keV; measured partial cross sections.

Elastic and inelastic differential cross sections of protons scattered from ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ were measured for incident proton energies of 20.0, 25.0, 30.4, 34.9, 39.9, and 44.9 MeV. Angular distributions from 10° to 170° in the laboratory were obtained for seven states of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, namely: $0^{+}$ (0.00 MeV), $2^{+}$ (1.37 MeV), the sum of $4^{+}$ (4.12 MeV) and $2^{+}$ (4.24 MeV), $3^{+}$ (5.24 MeV), $4^{+}$ (6.01 MeV), and $0^{+}$ (6.43 MeV). These data, along with data from the literature in the energy range 17-185 MeV, were analyzed using optical model and coupled channels calculations. Using a rotational model, with triaxial deformation limited to terms in $Y_{2,2}$ and $Y_{2,-2}$, reasonable agreement with the data was obtained for all states except for the $3^{+}$ (5.24 MeV) and $4^{+}$ (6.01 MeV) states. The inclusion of terms of $Y_{4,2}$ and $Y_{4,-2}$ in the model improved the agreement with these two states considerably; but the $3^{+}$ (5.24 MeV) experimental data are still not accurately reproduced.

NUCLEAR REACTIONS ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(p, p^{\prime }){}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, $T=20.0, 25.0, 30.4, 34.9, 39.9, 44.9$ MeV; measured $\sigma \left(\theta \right)$, $\theta =10\mathrm{}°-170\mathrm{}°$ lab; $E_x=0.00, 1.37, 4.12+4.24, 5.24, 6.01, \mathrm{and} 6.43$ MeV; enriched target; optical model and coupled channels analyses.

A new graphical derivation is given of the nested Rosenberg equations which reveals the simple structural reasons for their validity. The graphical techniques are shown to apply in other contexts in nuclear reaction theory.

NUCLEAR REACTIONS Rosenberg equations, almost connected graphs.

We have studied the $E_x=14.36\mathrm{}$ MeV $6^{-}$, $T=1\mathrm{}$ resonance in the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}(p, \gamma )$ reaction with the result that ${\Gamma }_{p_0}=\Gamma =4.0\mathrm{}\pm 0.2$ keV, from which we infer a (${d_{\frac{5}{2}}}^{-1\mathrm{}}, f_{\frac{7}{2}}$) parentage ${{\delta }_1}^2\approx 0.7$. We also obtain $B\left(M1\mathrm{}\right)=2.8\mathrm{}\pm 0.4 {{\mu }_N}^2 or 0.19\pm 0.03$ of the pure single particle (${d_{\frac{5}{2}}}^{-1\mathrm{}}, f_{\frac{7}{2}}$) value for the $6^{-}$, 1→$6^{-}$, 0 $M1\mathrm{}$ $\gamma$ decay. ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({}_{}{}^3{}_{}{}^{}\mathrm{He}, d)$ results for stripping to the $6^{-}$, 1 and the $6^{-}$, 0 (11.58 MeV) levels indicate $\frac{S_0\mathrm{}\left(p\right)\mathrm{}}{S_1\mathrm{}\left(p\right)\mathrm{}}=1.1\mathrm{}\pm 0.1$ and hence that the $6^{-}$, 0 level has a (${d_{\frac{5}{2}}}^{-1\mathrm{}}, f_{\frac{7}{2}}$) parentage comparable to the $6^{-}$, 1 level, contrary to inferences based on inelastic proton and pion scattering data. We discuss the hindrance of the $M1\mathrm{}$ decay and the previously measured inelastic electron, proton, and pion excitation strengths relative to the expectations of a one-particle-one-hole model.

NUCLEAR REACTIONS ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}(p, \gamma ){}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ measured $\sigma \mathrm{}\left(E\right)\mathrm{}$ for $J^{\pi }$; $T=6^{-}$; 1 resonance at $E_x=14.36\mathrm{}$ MeV. Deduced $\Gamma$, ${\Gamma }_{p_0}$, and ${\Gamma }_{\gamma }$. ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({}_{}{}^3{}_{}{}^{}\mathrm{He}, d){}_{}{}^{28}{}_{}{}^{}\mathrm{Si}_{}^{*}{}_{}{}^{}$ measured $\sigma \left(\theta \right)$ for transitions to the $6^{-}$; 1 (14.36 MeV) and $6^{-}$; 1 (11.58 MeV) states for $E\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)=40\mathrm{} \mathrm{and} 60$ MeV. Deduced $S$ factors from DWBA analysis and from ${\Gamma }_{p_0}$. Deduced (${d_{\frac{5}{2}}}^{-1\mathrm{}}, f_{\frac{7}{2}}$) particle-hole intensity for $6^{-}$; $T$ states. Compared these results together with inelastic electron, proton, and pion scattering results with a simple particle-hole model.

Photoneutron angular distributions were measured by time-of-flight techniques for the reaction ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}(\gamma , n_0){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ over the region of excitation energy from 15 to 25 MeV. Ground state cross sections were obtained by stepping the bremsstrahlung end point over the energy region of interest in 2 MeV intervals. By fitting the spectral data to a series of Legendre polynomials, angular distribution coefficients were extracted and interpreted on the basis of a simple single particle model. It appears that a large fraction of the photoabsorption strength leading to decays via the ground state channel is due to the formation of $J^{\pi }={\frac{3}{2}}^{+}$, $T=\frac{1}{2}$ states in ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ which decay by $d$-wave neutron emission. The data support an approximation of purely electric dipole absorption in the region measured. Some small amount of $s$-wave neutron emission interfering with the dominant $p_{\frac{1}{2}}\to d_{\frac{3}{2}}$ transition is consistent with an observed value for the $\frac{a_2}{a_0}$ coefficient of -0.7±0.2. The ($\gamma , n_0$) cross section integrated between threshold and 30 MeV is estimated to represent about one-third of the total strength in the neutron channel. A state identified at 17.3 MeV is consistent in energy and composition with a theoretical prediction based on a shell model calculation using a residual interaction with a Soper mixture of exchange forces.

NUCLEAR REACTIONS ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}(\gamma , n_0)$, $E_{\gamma }=15-25\mathrm{}$ MeV; measured differential cross sections as function of angle; extracted Legendre coefficients; estimated $\frac{s}{d}$ matrix-element ratio in dipole approximation.

We propose a separable representation of the nuclear part of the proton-proton interaction in angular-momentum states $l=0, 1, \mathrm{and} 2$. This representation yields an accurate fit to all experimental data currently accepted for elastic proton-proton scattering. The form factors of the separable potentials are represented by simple functions in momentum space (and also in configuration space). This makes it possible to treat the Coulomb distortion of the nuclear interaction exactly and to derive the corresponding proton-proton transition matrix in closed analytic form. Our model thus provides an adequate and convenient starting point for rigorous calculations on few-body systems with charges.

NUCLEAR REACTIONS Separable potential proposed for $p-p$ system; Coulomb distortion of nuclear interaction treated exactly; closed analytic formulas for transition matrix given.

We have evaluated expressions for $E1\mathrm{}$ and $M1\mathrm{}$ virtual photon spectra for relativistic electron scattering in second order Born approximation and included the effects of finite nuclear size and charge. The scattering amplitude can be evaluated analytically provided the elastic and inelastic form factors contain only poles. We have observed that the virtual photon spectrum is insensitive to details of both form factors over a wide range of electron energy and depends only on the nuclear rms radius and transition radius. The integral over the physical momentum transfer is performed numerically. We have evaluated spectra for electric dipole and magnetic dipole radiation for electron energies in the range 10-200 MeV and compared with distorted wave calculations. Except for low energy and high $Z$, our results compare well. A range-of-validity plot is given for each multipole, distinguishing regions of electron energy and mass number where the second order calculation is adequate and also those where the first order term alone would be sufficient and where the conventional long wavelength limit is applicable. Comparison with data on the excitation of the 16.3 MeV isobaric analog state in ${}_{40}{}^{90}{}_{}{}^{}\mathrm{Zr}$ yields excellent agreement with no adjustable parameters.

NUCLEAR REACTIONS Inelastic electron scattering, virtual photon method, second order Born approximation.

The reorientation effect in Coulomb excitation has been used to measure in ${}_{}{}^{162,164,166,168,170}{}_{}{}^{}\mathrm{Er}$ the static quadrupole moments $Q_{{2^{+}}^{\prime }}$ of $2^{+}$′ $\gamma$-vibrational states; and the branching ratio $B_{\gamma }$ for the decay of the $2^{+}$′ state to the $0^{+}$ ground state and the first $2^{+}$ state. Both particle-$\gamma$ coincidence and particle spectroscopy experiments were carried out to extract these quantities, using 12.5 MeV $\alpha$ and 48 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ beams with enriched targets. The evaluation was based on the semiclassical Winther-deBoer code and corrected for quantum mechanical effects. The measured values of $Q_{{2^{+}}^{\prime }}$ agree well with the predictions of the rotation-vibration model, asymmetric rotor model, and, for ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$, the interacting boson approximation. For $B_{\gamma }$, all of the above models predict the increasing trend with increasing mass number seen in the measurements, but are unable to correctly predict the absolute magnitudes.

NUCLEAR REACTIONS ${}_{}{}^{162,164,166,168,170}{}_{}{}^{}\mathrm{Er}(\alpha , {\alpha }^{\prime }\gamma )$, $E=12.5\mathrm{}$ MeV, ${}_{}{}^{162,164,166,168,170}{}_{}{}^{}\mathrm{Er}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, {}_{}{}^{16}{}_{}{}^{}\mathrm{O}_{}^{\prime }{}_{}{}^{}\gamma )$, ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$′), $E=48\mathrm{}$ MeV; measured particle-$\gamma$ coincidence $\sigma$, inelastic $\sigma$; deduced $Q_{{2^{+}}^{\prime }}$, $B_{\gamma }$. Enriched metal targets. Ge(Li) and silicon surface-barrier detectors. Coupled channel semiclassical and quantum mechanical analysis.

Elastic and Raman scattering of 8.5 to 11.4 MeV $\gamma$-ray photons are investigated between charge numbers of 73 and 92. The experimental elastic scattering cross sections show large deviations from calculations based on available giant dipole resonance photoabsorption cross sections and on lowest order Delbrück amplitudes. The elastic differential cross sections measured at $Z=83\mathrm{} \mathrm{and} 90$ confirm the indications of a Coulomb correction effect in Delbrück scattering previously obtained for $Z=92\mathrm{}$ only. By a systematic analysis, quantitative information on the Coulomb correction effect in Delbrück scattering and on scaling factors for the giant dipole resonance photoabsorption cross sections is obtained.

NUCLEAR REACTIONS ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ ($\gamma , \gamma$), ($\gamma , {\gamma }^{\prime }$), $E=8.5-11.4\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$, elastic scattering, nuclear Raman scattering, Coulomb correction effect in Delbrück scattering.

We consider the physical effects responsible for the momentum distribution parallel to the beam of nuclides arising from projectile fragmentation. A simple model relates the widths of these distributions to separation energies and an absorptive cutoff radius rather than Fermi momentum. A one-parameter successful treatment of these widths is explored. Coulomb distortions are found to dramatically influence the observed widths at low bombarding energies, leading to a reduction of width with decreasing energy. A simple model for isotope yields from fragmentation reactions is presented and compared with high energy data.

NUCLEAR REACTIONS Projectile fragmentation of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, $E=2\mathrm{}$ GeV/nucleon and $E=10-20\mathrm{}$ MeV/nucleon; parallel momentum distribution width; isotope yields.

The total reaction cross section ${\sigma }_R$ for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been determined between 8.5 and 14 MeV (c.m.) from elastic data using the optical theorem. It exhibits the well-known ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ resonances as pronounced structures. Elastic partial widths have been deduced from ${\sigma }_R$ for all resonances. Some of them represent a large fraction of the single particle width. This is a strong hint that the corresponding resonances have the structure of a dinuclear molecule.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$,${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$), ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$,${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$), $E=8.5-15\mathrm{}$ MeV (c.m.), $\Delta E=85\mathrm{}$ keV; measured $\sigma (\theta , E)$, deduced total reaction cross section and quasimolecular resonances and their elastic widths.

Energy and angular correlations of $\alpha$ particles in coincidence with deeply inelastic ejectiles from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ collisions at 6 and 9 MeV/nucleon reveal $\alpha$ emission processes which cannot be explained by sequential emission from the fragments.

NUCLEAR REACTIONS ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, \mathrm{HI}\alpha )$, $E=6, 9$ MeV/nucleon; energy and angular correlation for HI $\alpha$ coincidences measured; deduced reaction mechanism.

The angular-momentum distributions of both fragments in low-energy heavy-ion collisions are calculated in a nonequilibrium-statistical model. The distribution functions are obtained analytically via moment expansion on the basis of a transport equation. They include the correlations between the two fragments. In conjunction with a phenomenological model for the description of the relative motion we compute fragment angular-momentum distributions as a function of energy loss and compare with experimental data.

NUCLEAR REACTIONS Deeply inelastic heavy-ion collisions. Calculated angular-momentum distributions of both fragments. Comparison with $\gamma$-multiplicity data.

The $g$ factor of the (${10}^{+}$) isomeric level [${\tau }_{\frac{1}{2}}=357\mathrm{}\left(4\right)\mathrm{}$ nsec, $E=6.527\mathrm{}$ MeV] in ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ has been measured to high precision as $g=0.7281\mathrm{}\left(10\right)\mathrm{}$. Possible corrections due to the paramagnetic nature of the Fe atom were avoided by utilizing the strong internal field in Fe metal for the measurement.

NUCLEAR REACTIONS ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}[{}_{}{}^{12}{}_{}{}^{}\mathrm{C}, 2n, p]{}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}\left({10}^{+}\right)$, pulsed beam $W(\theta , t, H)$ deduced $g\left({10}^{+}\right)$.

The Coulomb effects on slow pions formed in heavy ion collisions are investigated here by Monte Carlo methods. The trajectory calculations differ from some earlier theoretical work in that pions are considered to be absorbed if they pass within 0.8 radius of a spectator nuclear center. Absorption in the fireball is implicit in the treatment. The source function (i.e., ${\pi }^0$ cross section without shadowing) is also more detailed in that we use a linear combination of thermalized and unthermalized terms based on two-fireball and row-on-row models. The numerical calculations are mainly applied to the system ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$+${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ at $\frac{E}{A}=655\mathrm{}$ MeV and resulting $\frac{{\pi }^{-}}{{\pi }^{+}}$ ratios and spectra are in satisfactory agreement with experimental results for ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$+NaF at this energy.

NUCLEAR REACTIONS Theory of Coulomb distortion of pion spectra by heavy-ion reactions. ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}(\mathrm{NaF}, {\pi }^{\pm })X$, $\frac{E}{A}=655\mathrm{}$ MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}({}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}, {\pi }^{\pm })X$, $\frac{E}{A}=1.05\mathrm{}$ GeV, Monte Carlo trajectories, row-on-row model, thermalized and nonthermalized (nascent) pions, $\frac{{\pi }^{-}}{{\pi }^{+}}$ ratio.

Relativistic heavy ion collisions are studied here taking into account the hard scattering model of Schmidt and Blankenbecler along with a dynamical derivation of the inclusive distribution for $\mathrm{pp}\to \pi x$, $\mathrm{pp}\to \mathrm{Kx}$, and $\mathrm{pp}\to \overline{p}x$ and $\mathrm{pp}\to \mathrm{px}$ proposed in an earlier paper. This scheme takes into account scale breaking and it is found that both $A$ and $B$ dependence occur in such processes as $\mathrm{AB}\to {\pi }^{-}x$, $\mathrm{AB}\to K^{-}x$, and $\mathrm{AB}\to \overline{p}x$ and $\mathrm{AB}\to \mathrm{px}$ in the forward region. In the backward region the independent $N-N$ collision model is also found satisfactory when the structural rearrangement factor is incorporated in the vertex function. It is found that although in the forward region scale breaking is not appreciable, it becomes quite significant in the backward region. The $x$ distributions in the forward region as well as in the backward region have been computed on the basis of this independent $N-N$ collision model. The results are found to be in very good agreement for inclusive pion production.

NUCLEAR REACTIONS Relativistic nucleus-nucleus collision. Independent $N-N$ collision model. Inclusive distributions. Scale breaking. Forward region, backward region.

Angular distributions of relativistic $\alpha$ particles produced from Fe emulsion and Ar emulsion at about $2A$ GeV and Fe emulsion at $0.9A$ GeV have been studied. The angular distribution falls in either one or the other of two separate classes with different characteristics; hot for tail or cold for peak zones, and thus, a single Boltzmann distribution cannot fit the fragmentation peak and the tail simultaneously. Two zones are characterized by separate Boltzmann distributions in the projectile rest frame and the associated temperatures differ by a factor of 4 or more. The $\alpha$ particles with large angular distributions especially cannot be explained by a model which is based on the fragmentation from a clean-cut participants-spectator picture. Experimental results in the "hot" events give some direct evidence for the transfer of large "transverse" momenta in these collisions.

NUCLEAR REACTIONS $\mathrm{Ar}\mathrm{or} \left(\mathrm{Fe}\right)+\mathrm{em}\to \alpha +x$, $E=1A \mathrm{GeV} \mathrm{and} 2A \mathrm{GeV}$. Angular distribution of $\alpha$ particle, Fermi momentum and Maxwell-Boltzmann parametrization.