Recently developed renormalization-group techniques are used to study the tetracritical (or bicritical) point of quenched mixed magnetic crystals (e.g., $A_p{B}_{1-p}$, where $A$ and $B$ have ferromagnetic and antiferromagnetic phase transitions). The tetracritical (bicritical) exponents are possibly given by the $n=0\mathrm{}$ value of their $\epsilon$ expansions. In particular, the crossover exponent $\varphi$, describing the shape of the $p-T$ phase diagram near the tetracritical point, is exactly equal to 1. This explains various experiments.

Ultrafine particles of Ni${\mathrm{Fe}}_2$${\mathrm{O}}_4$ coated with organic molecules show a behavior consistent with extremely strong pinning of the ferrite surface spins. The low-temperature magnetization is only ∼75% saturated in fields of 200 kOe, and Mössbauer spectra show that the spins remain at large angles with respect to the direction of an applied field of 68.5 kOe. Uncoated ultrafine Ni${\mathrm{Fe}}_2$${\mathrm{O}}_4$ particles do not show this behavior.

The measured distributions in invariant mass $W$ of the recoiling hadron systems in neutrino- and antineutrino-nucleon inelastic collisions are observed to be significantly different after taking into account the opposite helicities of neutrinos and antineutrinos. These distributions indicate the onset of a new phenomenon in the antineutrino data beginning at an incident energy of about 30 GeV, which appears as an excess of events with $W>\mathrm{}4\mathrm{}$ GeV/${\mathit{c}}^2$.

We have measured single-particle inclusive spectra of ${\pi }^{+}$ and ${\pi }^{-}$ mesons produced at 2.5° (lab) in the collision of 1.05-4.2-GeV protons, 1.05- and 2.10-GeV/nucleon deuterons and $\alpha$ particles, and 2.10-GeV/nucleon ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nuclei with various targets at an angle of 2.5° (lab). The negative-pion spectra show scaling behavior. The results are compared to a simple model in which individual nucleons in the projectile interact with the target to produce pions.

Independent evidence is presented for the decay of the recently discovered particle $\psi \mathrm{}\left(3105\right)\mathrm{}$ into electron-positron pairs and new evidence is presented for the decay of this particle into muon pairs. Measurements of the rate of the reaction $e^{+}{e}^{-}\to \gamma \gamma$ at center-of-mass energies in the vicinity of 3105 MeV are also reported.

We have measured the multiplicities of pions produced in the collisions of $\pi$ mesons with neon nuclei at bombarding momenta of 10.5 and 200 GeV/c. The diffractive production of pions is clearly separable. If one excludes the diffractive part, the pion multiplicity obeys the same Koba-Nielsen-Olesen scaling as found previously for ${\pi }^{-}-p$ collisions. This fact would seem to indicate the validity of an energy-flux or collective-variable description of the production process. A surprisingly large number of energetic protons (> 1 GeV/c lab momentum) are found to be produced in $\pi$-Ne collisions.

I analyze the experimental data on the recently observed heavy resonance $J$ assuming that it is a spin-one particle. The results of this analysis are used to discuss $\mu -e$ universality, parity-nonconserving effects, and production cross sections by high-energy (≥20 GeV) photons and electrons.

We explore the possibility that the new particles $\psi$ and ${\psi }^{\prime }$ are color gluons and propose characteristic tests of such a possibility.

The conjecture of a possible narrow $D$-wave resonance of the $\Omega \overline{\Omega }$ system is extended to general baryon-antibaryon systems. On the basis of the well-known $\mathrm{NN}$ forces one finds that $B\overline{B}$ systems bound by pion forces are more likely to produce narrow resonances. In particular one may expect narrow resonances below the $N\overline{N}$, $\Lambda \overline{\Lambda }$, and perhaps even the $\Xi \overline{\Xi }$ thresholds. A narrow $B\overline{B}$ resonance may serve in a second step (similar to the $\alpha$ particle) to explain the narrow $\psi$ and ${\psi }^{\prime }$.

We examine some experimental consequences of the "charmonium" picture, in which the boson resonances at 3.1 and 3.7 GeV are interpreted as bound triplet-$s$ states of a charmed quark-antiquark pair. We investigate the radiative decays of the observed resonances into other charmonium states.

We present a series of new measurements of orientation and alignment in the beamtilted-foil source designed to test the final surface electrostatic-interaction theory proposed by Eck. We find that the predictions of the model in its simplest form are not borne out by the data.

Centroid shift analysis of time spectra show that mean lifetimes range from 106 psec in Fe to 415 psec in Cs and have a systematic dependence on atomic number.

High-resolution measurements of the thermal-expansion coefficient of pressurized ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ($5 \mathrm{bar}<~P<~29 \mathrm{bar}$) near $T_{\lambda }$ ($2\times {10}^{-5\mathrm{}}\lesssim \mathrm{}\left|t\right|\mathrm{}\lesssim 0.07$; $t\equiv \frac{T}{T_{\lambda }}-1\mathrm{}$) by a new technique yielded a universal (pressure-independent) critical exponent $\alpha ={\alpha }^{\prime }=-0.026\mathrm{}\pm 0.004$, a universal amplitude ratio $\frac{A}{A^{\prime }}=1.11\mathrm{}\pm 0.02$ for the leading singularity, and a universal ratio $\frac{D}{D^{\prime }}=1.27\mathrm{}\pm 0.2$ for the amplitudes of the confluent singularity. These results agree with renormalization-group theory, but are in part contrary to previous experiments.

The effects of applied magnetic field up to 1.2 T have been observed on nuclear spin ordering in solid He. For B 0.4 T the transition is sharp and is depressed in temperatture by the field. For $B>~0.42$ the ordering region is broadened and moves to significantly higher temperatures with increasing fields.

The crystal distortions commonly observed in the layered transition-metal dichalcogenides have been attributed to a Fermi-surface instability, i.e., a charge-density wave. I find that the temperatures of these distortions correlate with the ionicity of the metal-chalcogen bond. This results suggests that these distortion temperatures can be specified without knowing the details of the Fermi surface.

We present the temperature dependence of the proton spin-lattice relaxation rates (${T_1}^{-1\mathrm{}}$) for pure tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) and its deuterated analogs TTF(${\mathrm{D}}_4$)-TCNQ and TTF-TCNQ(${\mathrm{D}}_4$). In the metallic region, the relaxation is Korringa-like, characteristic of metals without strong electron-electron Coulomb correlations.

Photoelectron energy distributions for solid Ne, Ar, Kr, and Xe have been measured for $8 \mathrm{eV}<~\hslash \omega <~30 \mathrm{eV}$ by use of synchrotron radiation. From these we obtained the total width and structure of the valence bands. Our data demonstrate that almost all available band-structure calculations fail to predict quantitatively features other than the spin-orbit splitting. Photoelectron energy distributions for Xe in Ar and Xe in Ne support this viewpoint.

We report the results of a parameter-free, self-consistent, wave-mechanical calculation of the properties of H, Li, and O chemisorbed on a metal surface. Comparison is made with available experimental results on dipole moments, adsorption energies, and state densities.

Isotope shifts of the $2p\to 1s$ muonic transition energies in ${}_{}{}^{54,56,58}{}_{}{}^{}\mathrm{Fe}$ have been measured. The results indicate that the charge radii of these isotopes vary approximately as $A^{\frac{1}{3}}$. Whereas spherical Hartree-Fock calculations can account for less than one third of the observed isotope shifts, deformed Hartree-Fock results reproduce two thirds of the observed shifts. It is suggested that the remaining discrepancy is primarily due to neglected neutron-proton residual interactions.

A search for events with no final-state muon, as expected in the neutral-current interactions ${\nu }_{\mu }\left({\overline{\nu }}_{\mu }\right)+N\to {\nu }_{\mu }\left({\overline{\nu }}_{\mu }\right)+\mathrm{hadrons}$, has been carried out by using the California Institute of Technology-Fermilab neutrino detector and narrow-band neutrino beam. A clear signal of events with no apparent final-state muon has been observed. Furthermore, missing energy in the final state for these events provides strong evidence for the existence of a final-state $\nu$.