We use the $d=2\mathrm{}$ Ising model as a concrete example to show that truncation of the derivative matrix $T$ to a subspace $S$ of short-range interactions needs some justification, since each row of $T$ contains arbitrarily large elements in the long-range sector. We point out that despite this a small parameter justifying truncation may exist, we show how to find it, and we perturbatively correct the errors due to truncation, all without leaving $S$. The bulk of our analysis carries over to other Monte Carlo renormalization-group studies, particularly the $d=3\mathrm{}$ Ising model.

The prompt neutrino (${\nu }_e+{\overline{\nu }}_e$) flux produced by the interaction of 400-GeV protons with targets of beryllium, copper, and tungsten has been measured in a beam-dump experiment at Fermilab. With the assumption that these neutrinos arise from charm decay, the cross section for charm production by protons on nuclei varies as $A^{\alpha }$, where $\alpha =0.75\mathrm{}\pm 0.05$. No significant variation of $\alpha$ with neutrino energy is observed.

Initial results are presented from an experiment designed to test the dynamics of large-angle exclusive scattering. Cross sections are given for two reactions near 90° c.m., ${\pi }^{-}p\to {\pi }^{-}p\left(\mathrm{elastic}\right)$ and ${\pi }^{-}p\to {\rho }^{-}p$, where $t=-8.9\mathrm{}$ Ge${\mathrm{V}}^2$/${\mathit{c}}^2$ for 9.9-GeV/c incident pions. The ratio of $\frac{{\rho }^{-}p}{\mathrm{elastic}}$ is large, $\frac{2}{3}$, and remarkably similar to measurements for small-angle scattering.

The exclusive process ${\pi }^{-}p\to {\rho }^{-}p$ has been measured at 90° c.m. with an incident pion momentum of 9.9 GeV/c. We present data on the angular dependence of the decay ${\rho }^{-}\to {\pi }^{-}{\pi }^0$. We observe a strong azimuthal dependence in the decay in the c.m. helicity frame of the $\rho$. Such an azimuthal dependence is not compatible with SU(6) valence-quark perturbation calculations.

It is shown that the interacting field theory of bosonic closed strings in the light-cone formulation is invariant under a class of complex space-time coordinate transformations.

A high-statistics measurement has been made of the process $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ at $\sqrt{s}=29\mathrm{}$ GeV with the MAC detector at the SLAC storage ring PEP. The electroweak forward-backward charge asymmetry for a sample of approximately 16 000 events was measured to be $A_{\mu \mu }=-0.063\mathrm{}\pm 0.008\pm 0.002$. The ratio of the cross section to the lowest-order QED cross section was measured to be $R_{\mu \mu }=1.01\mathrm{}\pm 0.01\pm 0.03$. From these results the weak neutral axial-vector and vector couplings are determined to be $g_A^e{g}_A^{\mu }=0.25\mathrm{}\pm 0.03\pm 0.01$ and $g_V^e{g}_V^{\mu }=-0.02\mathrm{}\pm 0.03\pm 0.09$.

The reactions $\overline{p}p\to {\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ have been studied at 390, 490, 590, 690, and 780 MeV/c. An enhancement of about 150 μb has been observed in the cross sections of both reactions at the same beam momentum of 490 MeV/c. If this structure is interpreted as a meson resonance, it has a mass of 1940 ± 20 MeV and a width of less than 40 MeV.

A new relativistic baryon-wave-function model is obtained by the requirement that it describe three valence quarks with the usual constituent masses and the universal hadronic scale (≈ 1 fm) and contract in the nonrelativistic limit into the usual harmonic-oscillator model. It provides a parameter-free prediction for baryon magnetic moments, which gives very good agreement for the hyperon data but reveals a significant discrepancy for the nucleon. This result contradicts the usual static-quark-model calculations and may suggest the relative importance of the nonvalence part of the nucleon wave function.

Pairs of $\tau$ leptons produced at $\sqrt{s}=3.77\mathrm{}$ GeV have been studied in $e\mu$, $\mathrm{ee}$, and $\mu \mu$ final states. The leptonic branching ratios have been measured to be $B(\tau \to e\nu \nu )=(18.2\mathrm{}\pm 0.7\pm 0.5)\%$ and $B(\tau \to \mu \nu \nu )=(18.0\mathrm{}\pm 1.0\pm 0.6)\%$. Limits have been set for the two-body decays $\tau \to \mathrm{eG}$ and $\tau \to \mu G$, where $G$ is a light Goldstone boson.

In the presence of arbitrary background gauge, gravitational, and antisymmetric tensor fields, the heterotic string may be described by a two-dimensional local field theory. It is conjectured, and verified to a certain approximation, that the conditions on the background fields for this model to have vanishing $\beta$ function are identical to the equations of motion for the massless fields. In particular, the appearance of the Chern-Simons three-forms in the classical equations of motion is shown to be related to the chiral anomaly in two-dimensional gauge theories.

A superconducting inductive monopole detector consisting of six independent high-order planar gradiometers placed on the six faces of a 15×15×60-${\mathrm{cm}}^3$ rectangular parallelepiped was operated from November 1983 to February 1985. This detector had a fully coincident-detection area of 0.1 ${\mathrm{m}}^2$. No monopoles were detected during an accumulated 9100 h of observation time, setting an upper limit of 5.5×${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ (90% C.L.) for the cosmic-ray monopole flux.

A Langevin method is proposed for simulation of full QCD including dynamical quark loops. It is shown that the method works well once a proper discretization of the fictitious time is made. A realistic simulation with this method is perfectly feasible on vector computers presently available.

The experimentally observed structure of the $E2\mathrm{}$ transitions in the quasicontinuum for ${}_{}{}^{168}{}_{}{}^{}\mathrm{Yb}$ is analyzed. The valley ridge structure along the $E_{\gamma 1}=E_{\gamma 2}$ diagonal in $\gamma$-energy correlation spectra has been reproduced by a model simulation in which a spreading of the rotational decay strength ${\Gamma }_{\mathrm{rot}}$ is introduced in regions of nuclear excitation energy $U>\mathrm{}{U}_0$ where the density of bands with slightly differing moments of inertia and alignment is high. The values of ${\Gamma }_{\mathrm{rot}}$ and $U_0$ vary from 75 to 110 keV and from 1.25 to 1.0 MeV, respectively, in the energy range $780<\mathrm{}{E}_{\gamma }<1160\mathrm{}$ keV.

Forward-angle differential cross sections at low energies (≤80 MeV) are reported for pion single charge exchange to the isobaric analog state for nuclei from ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ to ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$. A minimum in the 0° excitation function near 50 MeV persists for all of the measured nuclei and reflects the analogous minimum in the ${\pi }^{-}p\to {\pi }^{0}n$ cross section that is caused by a nearly perfect cancellation of the $s$- and $p$-wave $\pi$-nucleon amplitudes. The persistence of this feature in these nuclei indicates a strong suppression of the net effect of the medium and constrains the interplay of the medium effects.

The effect of neutron-proton symmetry breaking on the distribution of $M1\mathrm{}$ and $M3\mathrm{}$ strength in the SU(3) limit of the interacting-boson model (IBA-2) is studied. A possible alternative choice for the Majorana force is investigated, with a structure that resembles more closely that which is calculated in microscopic theories. It is found that the specific choice for the Majorana interaction has important consequences for the magnetic strength distribution function. This implies that a determination of this in deformed nuclei will impose strong constraints on the hitherto largely unknown Majorana force in the IBA-2 Hamiltonian.

Muonic x-ray spectra of $\mu {}_{}{}^3{}_{}{}^{}\mathrm{He}$ from $d\mu d$ and $p\mu d$ fusion have been measured for the first time. Intensity ratios $\frac{\mu {}_{}{}^3{}_{}{}^{}\mathrm{He}(3\mathrm{}\to 1)}{\mu {}_{}{}^3{}_{}{}^{}\mathrm{He}(2\mathrm{}\to 1)}$ were found to be 0.13±0.02 and 0.053±0.007 in the cases of $d\mu d$ and $p\mu d$ fusion, respectively. The population of excited $\mu {}_{}{}^3{}_{}{}^{}\mathrm{He}$ states from $p\mu d\to \mu {}_{}{}^3{}_{}{}^{}\mathrm{He}+\gamma$ was measured with the help of the $\gamma$ rays.

In charge-transfer collisions of 4-keV ${\mathrm{Ne}}^{8+}$ recoil ions with Na, we have observed 434-nm photons emitted in the $n=9\mathrm{} \mathrm{to} 8$ transition in ${\mathrm{Ne}}^{7+}$. We find this radiation to be strongly polarized, with a degree of polarization $P=0.32\mathrm{}\pm 0.02$. This result is in accord with a recent calculation of Salin indicating that electron capture into slow, highly charged ions preferentially populates the $m=0, \pm 1$ magnetic substates.

We demonstrate that recombination pumping following rapid radiative cooling of an overstripped selenium plasma can quantitatively account for the observed gains of the $J=2\mathrm{} \mathrm{to} 1$ Se xxv transitions in the recent successful Livermore x-ray-laser experiments. The absence of gain in the $J=0\mathrm{} \mathrm{to} 1$ transition, hitherto unexplained, is fully consistent with this scenario.

Experimental measurements on the long-time evolution of strong Langmuir turbulence in a beam-plasma system reveal a picture of periodic, short bursts of Langmuir wave collapse instead of the existence of long-lived solitons. The remnants of density cavities from burnout cavitons are observed to curtail wave growth periodically, creating time intervals of low wave activity between successive cycles of wave collapse, and establishing three regimes of wave evolution.

Static and dynamic scaling behaviors of electrical conductivity and dielectric constant are obtained near the percolation transition in an oil-continuous microemulsion. Conductivity data are in agreement with a dynamic percolation picture and inconsistent with the static percolation expected from a bicontinuous structure. The dielectric constant, on the other hand, is found to be insensitive to the dynamical process.