On the basis of the analytical study of the ladder Schwinger-Dyson equation of the technifermion self-energy we find crucial constraints on the running coupling constants in technicolor theories for the flavor-changing neutral currents to be dynamically suppressed. It is unlikely that the slowly varying coupling constants in the asymptotically free technicolor theory can solve the flavor-changing neutral-current problem. Fixed-point theories may be the only viable possibility.

The idea that fermions acquire their masses via a universal seesaw mechanism can provide a plausible explanation for the mass hier- archy ${\mathrm{m}}_{\mathrm{e}}$,u,d≃${10}^{\mathrm{-}4}$${\mathrm{M}}_{\mathrm{W}}$. A minimal SU(3${)}_{\mathrm{C}}$⊗SU(2${)}_{\mathrm{L}}$ ⊗SU(2${)}_{\mathrm{R}}$⊗U(1${)}_{\mathrm{B}\mathrm{-}\mathrm{L}}$ grand unifiable realization is presented. Whereas the fermionic representation is enlarged to include SU(2${)}_{\mathrm{L}}$⊗SU(2${)}_{\mathrm{R}}$ singlets, the Higgs system contains none of the conventional scalars of left-right-symmetric models. An alternative way to account for the superlightness of neutrinos emerges.

By consideration of the conversion of photons into axions in the presence of a classical background magnetic field, the possibility of creating artificial sources of ‘‘invisible’’ axions with a laboratory experiment is stressed. With, in particular, a high-power laser, the attainable axion current density seems to be as high as that expected from the natural astrophysical sources, provided that the axion mass is not much larger than ${10}^{\mathrm{-}5}$ eV.

We have carried out a numerical simulation in SU(3) lattice gauge theory with four flavors of low-mass staggered fermions at zero baryon-number density in the vicinity of the high-temperature phase transition on 6×${10}^3$ and 6×${10}^2$×20 lattices. Static screening masses (static susceptibilities) were measured in several color-singlet channels with quark valence qq¯ and qqq. Clear evidence for a hadronic screening spectrum is found, suggesting the presence of hadronic plasma modes. The spectral multiplets, extrapolated to zero quark mass, are consistent with a restoration of the SU(N)⊗SU(N) chiral symmetry.

It is shown that the parton branching distribution $P_{\mathrm{mn}}$ of m quarks and n gluons does not obey exact Kobu-Nielsen-Olesen scaling. When the quark evolution is neglected the probability distribution becomes wider as energy increases in agreement with experimental data. In this model it is predicted that the widening of the probability distribution will stop at Fermilab Tevatron Collider energies (1600–2000 GeV). Also given are theoretical predictions for the multiplicities and moments for Tevatron Collider energies.

We have used the measured yield of leptons near the end point of the momentum spectrum from semileptonic B decay to obtain an upper limit on Γ(b→ulν)/Γ(b→clν) and a corresponding limit on ‖$V_{\mathrm{ub}}$‖/‖$V_{\mathrm{cb}}$‖.

The τ decay modes with multiple neutral mesons in the final states have been studied with the Mark II detector at the SLAC storage ring PEP. The branching ratio for the decay mode ${\tau }^{\mathrm{-}}$→${\pi }^{\mathrm{-}}$2${\pi }^0$${\nu }_{\tau }$ is found to be consistent with the theoretical expectation. However, the branching ratio for ${\tau }^{\mathrm{-}}$→${\pi }^{\mathrm{-}}$3${\pi }^0$${\nu }_{\tau }$ is found to be inconsistent with the theoretical prediction unless there are other decay modes with multiple neutral mesons in the final states.

Data accumulated with a high-precision vertex drift chamber operating in the MAC detector at the SLAC storage ring PEP are used for a precise measurement of the lifetime of the τ lepton. We measure decay lengths of a sample of reconstructed three-prong decay vertices, and impact parameters of a separate sample of decay tracks. Combining these results, we find that ${\tau }_{\tau }$=0.309±0.019 ps, in agreement with the prediction from the measured leptonic branching ratio and τ-μ universality.

Neutrinoless double-β decay would require two new phenomena, of which one is lepton-number nonconservation. Among several candidates for the other are nonzero neutrino mass and the emission of a Goldstone boson, such as the majoron. For the former possibility our Ge-detector array now sets a limit for the $0^{+}$→$0^{+}$ transition in ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ of $T_{1/2}$>5×${10}^{23}$ yr from the fluctuation in the background or almost a factor of 2 longer by maximum likelihood at the 68% confidence level (C.L.). For the latter process we have a 90%-C.L. limit of 1.4×${10}^{21}$ yr, a result in disagreement with a recent possible observation of majoron emission.

Conditions for the applicability of, and possible corrections to, the Dirac equation in a broad variety of nuclear processes are derived in the framework of the additive constituent-quark model. In particular, we find that in small–momentum-transfer scattering of composite nucleons from spin- and isospin-zero nuclei, Z diagrams on the level of individual quarks reproduce those resulting from pointlike nucleons, in the approximation that constituent quarks carry equal fractions of the nucleon momentum. Deviations from the Dirac equation, on the other hand, may occur in interactions of nucleons with nuclei of nonzero spin or isospin.

Data on inclusive electron scattering from A=4, 12, 27, 56, 197 nuclei at large momentum transfer are presented and analyzed in terms of y scaling. We find that the data do scale for y<0 (x>1), and we study the convergence of the scaling function with the momentum transfer $Q^2$ and A.

The distribution of magnetic dipole transition strength in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ has been measured at excitations between 8.1 and 10.5 MeV with highly polarized tagged photons. A total M1 strength of Jg${\mathrm{\Gamma }}_0^2$(M1)/ Γ${=37.7\mathrm{}}_{\mathrm{-}4.0}^{+5.1\mathrm{}}$ eV was found to be broadly distributed throughout the region. This strength can account for the giant M1 resonance predicted in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. A substantial amount of E1 transition strength was also identified. This E1 strength has important implications for the interpretation of forward-angle (p,p’) scattering and its use in identifying M1 transitions in heavier nuclei.

The assumption that the distribution of reduced partial-width amplitudes is multivariate Gaussian is tested by separate measurement of width and amplitude correlations. The data are transformed to a representation in which the amplitude correlation is zero, and the width correlation is compared directly with the predicted value of zero. The average width correlation for 21 data set is r${\mathrm{¯}}_{\mathrm{w}}$=-0.01, providing the most direct and assumption-free verification that the global amplitude distribution is multivariate Gaussian. The significance of this result for current studies of quantum chaos is discussed.

Gamow-Teller (GT) strength has been extracted from cross sections for the reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$(n,p${)\mathrm{}}^{54}$Mn at 0°, 2.5°, 5°, 8°, and 12°, and for an incident energy of 298 MeV. This determination of the ${\beta }^{+}$ GT strength $S_{+}$ allows for the first time a full test of the Ikeda sum rule. These data also show that the best available shell-model calculations overestimate this strength by a factor of 2. This result is significant in models of supernovae since electron capture in (fp)-shell nuclei, which is proportional to $S_{+}$, depletes the relativistic electron gas in precollapse stars.

We study the quantum relativistic Coulomb-excitation process including recoil effects in the plane-wave Born approximation. It is shown that there exists an interplay between quantum and relativistic recoil effects in certain kinematical regions which cannot be accounted for in the conventional theories. This specific feature is shown to modify the angular distribution of Coulomb-induced fission fragmentation in an essential manner. In contrast with usual treatments we find that our results compare favorably with recent data.

In a one-component low-pressure gas, velocity-selective excitation can produce a drift due to state-dependent molecule-surface interaction. The first observation of this effect is reported for rovibrationally excited ${\mathrm{CH}}_3$F colliding with quartz. Experiments involving different rotational sublevels within the ${\nu }_3$ vibrational band indicate a strong dependence of the effect upon rotational quantum number.

A new operational regime has been observed in neutral-beam–heated JFT-2M limiter discharges. This regime is characterized by confinement times close to those of Ohmic and divertor H-mode (good confinement mode) discharges. The properties of these discharges are similar to the divertor H mode. The incremental energy-confinement time due to the heating is found to be independent of the plasma density up to the maximum density.

We introduce a mechanism to model irreversible aggregation of clusters at high concentration and investigate it by Monte Carlo simulations. Depending on the cluster diffusivity the aggregates are surface fractals, volume fractals, or nonfractal objects. Our results are compared with experiments on colloidal aggregation where, depending on concentration, either volume or surface fractals are observed. The model also provides a new, kinetic interpretation of random percolation.

The photovoltaic phenomena in the fast mixed conductor LiAl (β phase) having a semimetallic band structure are presented for the first time. Photovoltage on the order of ${10}^{\mathrm{-}6}$ V is produced with a relaxation time of ∼90 sec by illumination at 290 K. The phenomena make a reversible process by turning on and off the light. The photovoltaic effect is described in terms of a photoenhanced Li internal diffusion.

Measurements of the attenuation of zero sound in superfluid ${}_{}{}^3{}_{}{}^{}\mathit{B}$ show coupling to a collective mode in applied magnetic fields at frequencies ν∼2Δ(T), which is identified as the J${=1\mathrm{}}^{\mathrm{-}}$ mode. The attenuation as a function of reduced temperature in zero magnetic field is subtracted from that measured in magnetic fields up to 80 mT to reveal both the $J_z$=+1 and $J_z$=-1 components. The measured G factor is in good agreement with theory. The $J_z$=+1 resonance occurs in the pair excitation continuum and subtracts from the total attenuation, resulting in an antipeak.