We present data on dimuon-production rates from neutrinos and antineutrinos in the energy range 45-205 GeV. The measurements were made using the Fermilab narrow-band beam. At higher energies (≳100 GeV), the dimuon-production rates relative to single-muon production for events within our kinematic cuts are about 1%. The numbers are consistent with calculations of Glashow-Iliopoulos-Maiani (four-quark) models and do not require the introduction of additional quarks.

Neutron-proton population ratios for quasielastic and inelastic processes in the reactions of 761-MeV ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$, 769-MeV ${}_{}{}^{132}{}_{}{}^{}\mathrm{Xe}$, and 795-MeV ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ ions with thick ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ targets were determined radiochemically. Completely relaxed $\frac{N}{Z}$ ratios are observed for damped collisions involving the transfer of $\Delta Z>~1$ charge units. The limiting condition $\Delta Z\approx 1$ corresponds to a characteristic time of the order of ${10}^{-22\mathrm{}}$ sec which indicates the absence of dissipative forces in the equilibration of the charge-asymmetry mode.

The (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $n$) reaction was studied at an incident beam energy of 33.3 MeV for targets of ${}_{}{}^{204}{}_{}{}^{}\mathrm{Hg}$ and ${}_{}{}^{204,206,208}{}_{}{}^{}\mathrm{Pb}$. A $0^{+}$ state at 4.1 ± 0.1 MeV in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ was excited with 70% of the cross section of the ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}({}_{}{}^3{}_{}{}^{}\mathrm{He},n){}_{}{}^{208}{}_{}{}^{}\mathrm{Po}\left(\mathrm{ground}\mathrm{state}\right)$ transition. This state lies at the predicted excitation energy of the proton-pairing vibration when particle-hole interactions are included.

Experiments aimed at testing for the existence of yrast traps are reported. A search for delayed $\gamma$ radiation of lifetimes longer than ∼ 10 ns and of high multiplicity has been performed by producing more than 100 compound nuclei between Ba and Pb in bombardments with ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$, ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, and ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$ projectiles. An island of high-spin isomers is found to exist in the region $64\lesssim Z\lesssim 71$ and $N\lesssim 82$.

Configuration mixing is investigated in a relativistic theory for states in Bi which dominate the effects of weak parity nonconservation. The corrections to the parity-nonconserving electric dipole and parity-conserving magnetic dipole transition matrix elements between the lowest two states are computed and found to be less than 4%. Such effects do not remove the discrepancy between atomic experiments and the Weinberg-Salam theory.

When an oscillating electric field is applied along a plasma density gradient, an enhanced field is resonantly excited where the electron plasma frequency approximately equals the frequency of the applied field. The measured, time-averaged distribution function of the electrons accelerated by the enhanced field in a plasma-filled capacitor includes a high-energy component that agrees with calculations.

Lines of critical points which emerge from the two-dimensional planar model's multicritical point are analyzed. These lines seem to be in the same universality class as both the Ashkin-Teller and the eight-vertex (8V) models' critical lines, with the multicritical point being isomorphic with the 8V model at both the points $tanh2\lambda =\frac{\sqrt{2}}{2} \mathrm{and} -1\mathrm{}$. Expansions of critical indices about these values of $\lambda$ are performed. If this analysis is right, then this work permits the evaluation of a whole class of interesting correlation functions at the critical point of the $F$ model and that of the four-state Potts model.

We have measured the inclusive production of massive dimuons ($7<~M_{\mu \mu }<~11$ ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$) by 200-, 300-, and 400-GeV protons incident on Cu in order to check whether the dimensionless cross section ${M_{\mu \mu }}^3{\left[\frac{d\sigma }{d{M}_{\mu \mu }\mathrm{dy}}\right]}_{y=0\mathrm{}}$ is a function of $\frac{{M_{\mu \mu }}^2}{s}$ alone, where $s$ is the square of the c.m. energy. The results support the scaling hypothesis.

The cascade-gluon model is used to show that the observed enhancement at 9.5 GeV can be interpreted as due to the production, and subsequent cascade decay into ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ states, of at least two and most likely three sets of $C=+$ bound states of quarks $Q$ of mass $m_Q\simeq 5$ GeV and charge $-\frac{1}{3}e$.

A comparison of neutron-capture $\gamma$-ray spectra in neighboring $s$- and $p$-wave-capture states in a ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ target shows two sharp departures from what is normally expected from a compound-nucleus process. The spectra are highly correlated, with $r=+{0.84}_{-0.10\mathrm{}}^{+0.16\mathrm{}}$, and $E1\mathrm{}$ and $M1\mathrm{}$ strengths are comparable. The $E1\mathrm{}$ strength can be explained by the $E1\mathrm{}$ giant resonance; it is consistent with the Axel prediction for a $A^{\frac{8}{3}}$ dependence. $M1\mathrm{}$ strengths agree with single-particle estimates, in sharp contrast to heavy nuclides.

Data for the analyzing power $A_y\left(\theta \right)$ for $n-p$ scattering at 16.9 MeV have been measured for the range from 50 to 145° (c.m.). Eleven values are reported to an accuracy of about ±0.002, the highest overall precision ever obtained in any fast-neutron polarization experiment. Predictions based on phase-shift sets obtained from global analyses of nucleon-nucleon scattering disagree significantly with the new data. The data are sufficiently precise to show a dependence on the $f$-wave spin-orbit phase parameter.

Broad structures have been observed in the incompletely relaxed part of the energy spectra of fragments emitted in the symmetrical reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ + ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 284 MeV and ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ + ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ at 450 MeV. Excitation energies of these structures, angular distributions, and ($Z, N$) distributions leading to multiplicities for nucleon emission have been measured. They can be interpreted as being due to a predominantly direct reaction process, possibly proceeding through the excitation of highly collective high-energy modes in the region of giant resonances.

The coupled monopole and $\beta$ and $\gamma$ quadrupole $T=0\mathrm{}$ vibrations in $\mathrm{sd}$-shell nuclei are studied within the generator-coordinate method, together with a scaling assumption. In contrast to heavier deformed nuclei, the splitting due to the nuclear deformation appears as the dominant mechanism in the spreading of the $E2\mathrm{}$ strength. The available experimental data support our analysis.

Sharp fluctuations in the coefficients describing the angular distribution and analyzing power in the reaction ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}(p_{\mathrm{pol}}, {\gamma }_0){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ are observed near $E_{\gamma }=21\mathrm{}$ MeV. These correspond to structure in the total cross section. All these structures can be fitted by introducing a narrow secondary doorway state interfering with the primary giant dipole resonance of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$.

We have made simultaneous determination of the rotational and translational temperatures of $\mathrm{OH}\left({}_{}{}^2{}_{}{}^{}\Pi \right)$ in a water-vapor discharge. These temperatures were determined by measuring the strength and line shape of the absorption lines in the ${}_{}{}^2{}_{}{}^{}\Pi \mathrm{}(v=0\mathrm{})\mathrm{}\to {}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}\mathrm{}(v=0\mathrm{})\mathrm{}$ transitions of OH using a cw tunable laser. It was found that the rotational distribution was thermalized, but the corresponding rotational temperature was much lower than the translational temperature. Possible implications of these results are discussed.

Interferometric measurements of plasmas produced by C${\mathrm{O}}_2$-laser pulses at intensities of ${10}^{14}$ W ${\mathrm{cm}}^{-2\mathrm{}}$ provide direct evidence for density-profile modification due to radiation pressure.

The energy distribution of a relativistic electron beam which has interacted with a plasma was investigated. The beam parameters were 550 keV, 500 A, and 20 ns (full width at half-maximum). From the broadening of the energy spectrum by interaction with the plasma we calculated the axial-wave electric field of the electrostatic beam-plasma instability to be $E\approx 1.8\times {10}^6$ V/m. This is in reasonable agreement with values predicted from theory.

I identified the topology and main physical characteristics of plasma modes that can be driven unstable by the periodically unfavorable magnetic-field curvature, along a given field line in a magnetic confinement configuration. The relevant analysis has been carried out in order to explain the results of numerical fluid codes recently developed and to connect them with those obtained by a nonfluid (kinetic) analysis of microinstabilities in regimes of thermonuclear interest.

We studied ballooning instabilities in tokamaks of arbitrary cross section and finite shear. These azimuthally localized, ideal magnetohydrodynamic modes have large toroidal-mode numbers, but finite variation along the field and across the flux surfaces. Stability is determined by solving a second-order ordinary differential equation on each flux surface, subject to the proper boundary conditions. Qualitative agreement is achieved with the Princeton pest stability code.

We calculate by renormalized field theory, up to two-loop order, the bicritical dynamic exponents of stochastic models appropriate for describing spin-flop bicritical points. In the presence of reversible mode-coupling terms, two-loop contributions establish bicritical dynamic scaling in the restricted sense and invalidate recent predictions based on mode-coupling arguments. In case of a purely relaxational model, total bicritical dynamic scaling is found to second order in $\epsilon =4-d$.