Search

Data taken with the CYGNUS detector between 1989 September and 1993 January have been used to search for 1 s bursts of ultrahigh-energy gamma rays from point sources at arbitrary locations in the northern sky. We find no evidence for such bursts. We set a theory-dependent upper limit on the rate-density of evaporating black holes of 8.5\ifmmode\times\else\texttimes\fi{}${10}^{5}$ ${\mathrm{pc}}^{\mathrm{\ensuremath{-}}3}$ ${\mathrm{yr}}^{\mathrm{\ensuremath{-}}1}$ at the 99% C.L. When the same emission spectrum is used to recalculate previous upper limits based on direct searches, this limit is the most restrictive by nearly 2 orders of magnitude.

The CYGNUS extensive air-shower experiment is described. The design criteria, construction and operation details, and performance characteristics are presented. A discussion of the data analysis techniques is given. Finally, several enhancements and improvements in the apparatus are described.

This paper describes how data from a new type of air shower detector, MILAGRO, can shed light on a variety of interesting problems in astrophysics. MILAGRO has the capability to make observations of VHE/UHE emission from the recently discovered TeV gamma‐ray source Markarian 421, an Active Galactic Nucleus (AGN). An observation of the attenuation of this signal in the range of 1–20 TeV can be used to make the first measurement of the intergalactic infrared radiation. We will also describe how MILAGRO can improve the existing limits on the density of Primordial Black Holes (PBH) by three orders of magnitude. In addition, MILAGRO will have a large aperture and continuous operation which gives it the capability to search for VHE gamma ray bursts.

Data from an extensive air shower detector of ultrahigh-energy cosmic rays shows shadowing of the cosmic-ray flux by the Moon and the Sun with significance of 4.9 standard deviations. This is the first observation of such shadowing. The effect has been used to determine that the angular resolution of the detector is 0.75{degree} {sub {minus}0.90{degree}}{sup +0.13{degree}}.

In this paper we describe a new proposed water‐Cerenkov detector called MILAGRO, for observing cosmic gamma rays over a broad energy range of 1–1000 TeV. This detector will have an angular resolution better than 0.5° and an energy threshold near 1 TeV.

The 11 ‘‘in‐phase’’ source events from the 1986 muon‐rich bursts associated with Hercules X‐1 (previously reported by this group) have been studied for indications of further anomalous behavior. The most significant effect observed resulted from an analysis of the showerfront time‐structures of these events. This analysis was then applied a priori to the rest of the source day, where an additional ∼9 signal events are expected to remain. The same effect was observed at a chance probability level of ∼0.1%.

A new method of searching for UHE point source has been developed. With a data sample of 150 million events, we have surveyed the sky for point sources over 3314 locations (1.4°

We report here the preliminary results of our observations of the sporadic X‐binary system 4U0115+63. The CYGNUS air shower array has been collecting data since April 1986. No significant excess is seen from the direction of this source, nor any correlation with its 24‐day orbital period. A 90% confidence‐level upper limit on the flux from 4U0115+63 is 2.8×10−13 cm−2 s−1 above 50 TeV. This flux limit is considerably lower than those reported by other UHE experiments. Search for periodicity at the neutron star frequency is in progress.

Data from the CYGNUS extensive air shower experiment at Los Alamos, NM has been analyzed to study the angular resolution of the array, and to search for point sources in the galaxy. Results on searches for steady emission from Cyg X‐3, Her X‐1 and the Crab nebula are presented.

A unique feature of Cygnus X-3 is that occasionally it has large radio outbursts that begin very abruptly and last for several days. Several experiments in the past have claimed to observe signals above 1 TeV correlated with these radio bursts; the most recent bursts occurred in June and July 1989. No significant signal was observed by the CYGNUS experiment over time scales longer than a day during this time; a 90%-confidence-level limit of 3.0{times}10{sup {minus}13} cm{sup {minus}2} s{sup {minus}1} is placed on the flux above 50 TeV during the period from 15 May to 31 July 1989.

A basic tenet of special relativity is that all massless particles travel at a constant, energy-independent velocity. Astrophysical data, including observation of the Crab pulsar at {similar to}100 MeV and the recent detection of the pulsar in Hercules X-1 at energies {ge}100 TeV, are used to place new experimental constraints on energy-dependent deviations from constant velocity for massless particles. Previous experiments reached energies {similar to}10 GeV; this analysis improves the previous constraints by 7 orders of magnitude.

The CYGNUS air-shower array has been used to search for emission of ultra-high-energy gamma radiation from 13 active galactic nuclei (AGNs) that were detected by EGRET. The data set spans the period 1986 April 2 to 1993 January 1. The data set has been searched for continuous emission, for emission on the time scale of 1 week, and for emission on the time scale of 1 day. No evidence for emission from any of the AGNs on any of the time scales examined was found. The 90% Confidence Level (CL) upper limit to the continuous flux from Mrk 421 above 50 TeV is 7.5×10 -14 cm -1 s -1

A daily search for emission of ultra-high-energy radiation from astrophysical point sources using the CYGNUS extensive air shower array is described. The data set spans the period from 1986 April 4 to 1992 June 22. Fifty-one astrophysical objects have been examined, including Cyg X-3, Her X-1, the Crab, a number of gamma-ray and X-ray sources from the COS B and the fourth Uhuru catalogs, and several cataclysmic variables, nearby galaxies, and radio pulsars. The observed daily number of events from the source directions are consistent with expected statistical fluctuations of the number of events from backgrounds cosmic rays

A search has been made for steady emission or ultra-high-energy radiation from individual point sources over most or the northern sky. Over 2×10 8 air showers induced by primary particles or energy greater than about 10 TeV were recorded from 1986 April until 1991 May by the CYGNUS air shower array. No statistically significant excess above the background from the isotropic flux or cosmic rays was found for any direction in the sky from 0° to 80° declination. In addition, 49 specific potential sources were examined, and none showed a statistically significant excess or events

A search has been performed for the muon-number--violating decay ..mu -->..e/sup +/e/sup +/e/sup -/. No candidate event has been found, the result yielding an upper limit for the branching ratio of B/sub mu3e/ ..e/sup +/e/sup +/e/sup -/..nu../sub e/nu-bar/sub ..mu../ events, eleven such events were observed. They agree in number and spectra with expectations based on standard electroweak theory.

An examination of 3.6\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\ensuremath{\mu}}^{+}$ decays yields an improved upper limit for the branching ratio $\frac{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma})}{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\nu}}_{e}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})}l1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ with 90% confidence.

We report a measurement of parity nonconservation in the transmission of 800-MeV longitudinally polarized protons through an unpolarized, 1-m liquid-hydrogen target. The dependence of transmission on beam properties was studied to measure and to correct for systematic errors. The measured longitudinal asymmetry in the total cross section is ${A}_{L}=[+2.4\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{statistical})\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{systematic})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$.

A search has been performed for the decays μ → eee, μ → e γ , and μ → eγγ with a sensitivity in the branching ratios at the level of 10 −10 . The experiment used a separated, 26 MeV/c μ + beam with an average intensity of 300kHz. A total of 2.2 × 10 11 muon decays were examined for the present result. The detector for the experiment Is the Crystal Box, which consists of a cylindrical drift chamber surrounded by 396 NaI(T1) crystals. A layer of scintillation counters in front of the crystals provided timing for electrons and a veto for photons. The energy resolution for electrons and photons is ≈6% (FWHM). The position resolution of the drift chamber is 350 μm leading to a vertex cut with a rejection of 10 3 for μ → eee. The timing resolution is ≈300 ps from the scintillators and ~1 ns from the crystals. No candidate for μ → eee has been found, yielding an upper limit for the branching ratio of B μ 3e −10 (90% C.L.).

We have investigated requirements for an integrating-type ion chamber that performs with signal fluctuations (noise) near the 1/√N counting statistics level. A large noise contribution occurs when the chamber collection foils intercept a beam of particles whose energy exceeds spallation production threshold. Experimental results demonstrate the source of this noise to be the production of low-energy spallation products in the plates and gas of the chamber. Delta rays also contribute to the noise, but not as severely. We have developed hydrogen-filled ion chambers with longitudinal collection plates that successfully eliminate the spallation contribution. With such chambers, noise improvement is typically a factor of 15 over chambers of conventional design.

An array of 45 NaI(Tl) crystals modules, each in 20 in. in length and hexagonal in cross section with six 3 in. sides, has been operated as a detector of 50 MeV γ-rays in a search for the decay μ + →e + γ . The calibration procedure used for this detector and the resolutions achieved in γ-ray energy, time of detection and point of impact on the detector face are described.

A search has been made for parity nonconservation in the scattering of 1.5-GeV/c (800-MeV) polarized protons from an unpolarized water target. The result for the longitudinal asymmetry is A/sub L/ = (1.7 +- 3.3 +- 1.4) x 10/sup -7/, where the second uncertainty is an estimate of systematic effects. This result is significantly smaller than the value of A/sub L/ for H/sub 2/O reported at 6 GeV/c.

An array of 49 NaI(Tl) modules each 20 inch in depth and 2.5 inch × 2.5 inch in cross section has been constructed and its properties, especially energy resolution, explored for positrons in the range 20 MeV – 18 GeV. A subsequent much larger detector, the Crystal Box, has also been constructed from 396 modules of the same cross section, but mostly 12 inch in depth, and operated as a γ-ray and positron detector in a search for rare muon decays. The calibration procedure used for the Crystal Box and its characteristic resolutions in energy, impact point and time are described.

This paper describes a kinematically complete search for the muon decay ..mu../sup +/..-->..e/sup +/..gamma... The experiment used a magnetic spectrometer outfitted with proportional chambers to measure the positron momentum vector and a large segmented NaI(Tl) array to determine the ..gamma..-ray energy and impact point. The positrons were mostly from normal muon decay while the ..gamma.. rays were mostly from internal and external bremsstrahlung. Approximately 3 x 10/sup 12/ muons were stopped in a 50-mg/cm/sup 2/ polyethylene target. The relative timing between the positron and the ..gamma.. ray was measured with a resolution of 1.9 ns full width at half maximum (FWHM) by the use of a plastic-scintillator hodoscope for the positron and by NaI(Tl) constant-fraction timing for the ..gamma.. ray. The positron energy resolution averaged over all data was 8.8% FWHM, and the ..gamma..-ray energy resolution was 8% FWHM, both at 52.8 MeV. When the ..gamma.. ray is assumed to originate at the same place in the target as the positron, the rms error in the measurement of the angle between the positron and ..gamma..-ray momentum vectors was 37 mrad. The acceptance of the apparatus for ..mu../sup +/..-->..e/sup +/..gamma.. events was (1.75 +- 0.04)%. A maximum-likelihood analysis established a 90%-confidencemore » upper limit for the branching ratio GAMMA(..mu../sup +/..-->..e/sup +/..gamma..)/GAMMA(..mu../sup +/..-->..e..nu nu..) of 1.7 x 10/sup -10/.« less

We have measured differential cross sections for both ..pi../sup +/p and ..pi../sup -/p elastic scattering at incident-pion kinetic energies of 30, 50, 70, and 90 MeV in the center-of-mass angular range between 50/sup 0/ and 150/sup 0/. The experiment detected pions scattered from a liquid-hydrogen target with multiwire proportional chambers and scintillation-counter range telescopes. The relative accuracy of each angular distribution is better than 5%, while the absolute cross sections have uncertainties of 4% to 25%. Our results for the absolute cross section for ..pi../sup +/p scattering at 30 and 90 MeV are inconsistent with previous measurements. Our ..pi../sup -/p measurements comprise the first extensive set of precision differential cross sections below 90 MeV.

This Letter reports a new experimental search for the family-number-nonconserving decay ..mu../sup +/ ..-->.. e/sup +/..gamma... There is no evidence for the presence of this decay mode. The upper limit for the branching ratio is GAMMA(..mu.. ..-->.. e..gamma..)/GAMMA(..mu.. ..-->.. enu anti nu) < 4.9 x 10/sup -11/ (90% C.L.). 13 refs., 3 figs.

The invariant cross sections for direct positron production in p-p collisions have been measured to be Ed/sup 3/sigma/dp/sup 3/= (-3 +- 2) x 10/sup -32/ and (-14 +- 12) x 10/sup -32/ cm/sup 2//sr (GeV/c)/sup 2/ at 256 and 800 MeV, respectively. These results are consistent with zero (e/sup +//..pi../sup +/approximately-less-than3 x 10/sup -6/ at 800 MeV) and are in marked contrast to results at higher energies. (AIP)

>The Mossbauer effect provides a tool to investigate the angular dependence and the polarization of individual com ponents emitted in the nuclear Zeeman effect. A discussion of the physical picture of the photon polarization in Fe/sup 57/ is followed by the general theory of elliptical polarization in the Mossbauer effect. The experimental arrangement to measure this polarization is described, and relevant results are given. (auth)

The behavior of standing wave accelerator tanks, made up of chains of resonant cavities, is investigated using a coupled resonator model. This model gives accurate predictions of the behavior of such a cavity chain, including tolerances to errors in manufacture, cavity feed distributions, and transient response. The parameters necessary in the theory, the cavity couplings, Q's, and frequencies, may easily be determined by experiment. Extension of the simple chain to a more complex chain with double periodicity and second nearest neighbor coupling is demonstrated. Advantages of operating such accelerators in the π/2 mode are shown.

The electrical behavior of long linac tanks can be represented by the behavior of a finite chain of coupled harmonic oscillators.1 A theory is given of chains of oscillators of two kinds, which is appropriate for semi-resonant or resonant coupling structures.2 The perturbation theory given previously is extended to predict the effects of errors in the coupling cells and in the main cells.2 Some advantages of ?/2 mode operation of the double chain are discussed. A new accelerating scheme is presented in which the coupling structures are resonant and the tanks are resonantly coupled. The theory, numerical calculations, and measurements on laboratory models3 all indicate that tolerances on power amplifier voltage and phase can be relaxed by as much as a factor of five.

A sthdy is made of the effect of low temperathres on the resonant emission and absorption of the 14.4 kev Mossbauer radiation from Fe/sup 5//sup 7/ in Fe metal. Analysis of irtensity changes in the hyperfine spectrum is made, in terms of the Zeeman level splittings of the ground states of both Fe/sup 5//sup 7/ absorbing nuclei and Co/sup 5//sup 7/ parent nuclei. The theory for the temperature dependence is developed in terms of the properties of the Co/sup 5// sup 7/ decay and of the subsequent gamma transitions. Experiments are carried out with a source of Co/sup 5//sup 7/ nuclei in Fe metal at temperatures between 4.5 and 0.85 deg K. The results, analyzed in terms of the theory, yield a value of the hyperfine magnetic field at the Co/sup 5//sup 7/ nuclei. Comparison of the result with other experimental values indicates that depolarization of the nuclei by the K-capture decay of Co/sup 5//sup 7/ is not evident. (auth)

When a generally radial electric field is imposed upon a mirror magnetic field configuration, the resulting system has an increased ability to contain plasma between the mirror regions. The motion of the ions consists of a drift around the axis of symmetry upon which is superimposed a spiraling motion. The guiding center motion departs from the direction of magnetic flux surfaces. An adiabatic invariant is derived for the drift component of the motion, and an expression is derived for the mirror enhancement brought about by the E x B drift. The departure of the guiding center of a particle from a flux surface and the energy balance of its secular motion are calculated by using the adiabatic invariant. (auth)

Fifty-seven ${\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{-}p$ scattering events in the energy range 10-30 Mev have been observed in a hydrogen bubble chamber. The $S$-wave scattering length $\frac{1}{3}{\ensuremath{\eta}}^{\ensuremath{-}1}(2{\ensuremath{\alpha}}_{1}+{\ensuremath{\alpha}}_{3})=0.077\ifmmode\pm\else\textpm\fi{}0.011$ is found to give the best fit to the data assuming ${\ensuremath{\alpha}}_{13}={\ensuremath{\alpha}}_{31}={\ensuremath{\alpha}}_{11}=0$, ${\ensuremath{\alpha}}_{33}=0.235{\ensuremath{\eta}}^{3}$. This result is combined with the results of other low-energy scattering experiments to give estimates of ${\ensuremath{\alpha}}_{1}$ and ${\ensuremath{\alpha}}_{3}$.

The angular distribution of pions scattered by liquid hydrogen has been studied using the collimated pion beams from the Chicago synchrocyclotron. Differential cross sections have been measured for the laboratory angles 45\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, and 135\ifmmode^\circ\else\textdegree\fi{} for positive pions of energies 78 Mev, 110 Mev, and 135 Mev, and for negative pions of 120 Mev and 144 Mev. For negative pions, separate results were obtained for the elastic scattering and for the charge exchange scattering. The scattering of positive pions and charge exchange scattering of negative pions show a larger intensity in the backward direction. The elastic scattering of negative pions is mostly forward.The results have been interpreted in terms of phase shift analysis on the assumption that the scattering is mainly due to states of isotopic spins $\frac{3}{2}$ and \textonehalf{} and angular momenta ${s}_{\frac{1}{2}}$, ${p}_{\frac{1}{2}}$ and ${p}_{\frac{3}{2}}$.The experimental results are represented quite accurately by the following phase shifts expressed in degrees for the angular momentum states in the order indicated above: at 120 Mev, phase shifts \ifmmode\pm\else\textpm\fi{}15, \ifmmode\pm\else\textpm\fi{}4, \ifmmode\pm\else\textpm\fi{}30 for isotopic spin $\frac{3}{2}$ and \ifmmode\pm\else\textpm\fi{}9, \ifmmode\pm\else\textpm\fi{}3, \ifmmode\pm\else\textpm\fi{}2 for isotopic spin \textonehalf{}; at 135 Mev, \ifmmode\pm\else\textpm\fi{}14, \ifmmode\pm\else\textpm\fi{}5, \ifmmode\pm\else\textpm\fi{}38 for isotopic spin $\frac{3}{2}$ and \ifmmode\pm\else\textpm\fi{}10, \ifmmode\pm\else\textpm\fi{}5, \ifmmode\pm\else\textpm\fi{}2 for isotopic spin \textonehalf{}.

A diagnostic experiment has been carried out on the $d\ensuremath{-}d$ reactions produced by fast magnetic compression of a deuterium plasma. A determination of the velocity spectra of protons and of tritons from the $d\ensuremath{-}d$ reaction was made by magnetic analysis and nuclear plate detection of the particles. The observed distributions are Gaussian, with widths which correspond to a deuteron temperature of 1.3 kev. Comparison of the mean proton and triton momenta indicates that no plasma drift in the (axial) direction of observation is present, nor any potential difference between the source plasma and detector greater than a few volts. These results, coupled with previous ones on the neutron yield, duration, source extent, and lack of circumferential drift argue against any of the simple, physically plausible non-Maxwellian acceleration mechanisms for the $d\ensuremath{-}d$ reactions so far proposed.

A 2.5×2.5×10‐cm hydrogen bubble chamber has been developed for experiments on the scattering of particles from the 450 Mev synchrocyclotron. Seventy‐five thousand pictures have been taken at the rate of one every two seconds and are being scanned at the rate of two thousand per day. The average track length per picture is about one gram per square centimeter. The characteristics of the bubble chamber are described and examples of the pictures are shown.

The magnetic behavior of very dilute Fe impurities in Cu has been studied as a function of temperature between 1.1° and 310°K in applied magnetic fields up to 61 kOe by means of the Mossbauer hyperfine spectra of Fe 57 . The temperature dependence of the negative internal field is explained in terms of a localized moment on Fe which is coupled to the host lattice.

A missing-mass spectrometer, employing optical spark chambers with automatic vidicon readout, was used to measure the forward differential cross section ($cos{\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\approx}0.995$) for the reaction $p+p\ensuremath{\rightarrow}d+{\ensuremath{\pi}}^{+}$ at closely spaced settings of the incident proton momentum in the range ${p}_{0}=3.4\ensuremath{-}12.3 \frac{\mathrm{GeV}}{c}$. The deuterons from the reaction were identified by time of flight, and their momentum and angle of emission measured by a reconstruction of the spark-chamber tracks. Since the incoming proton momentum was accurately known, the missing mass associated with deuteron production could be deduced. The reaction $p+p\ensuremath{\rightarrow}d+{\ensuremath{\pi}}^{+}$ was identified by the appearance of a distinct peak corresponding to the pion mass in a missing-mass plot. The data confirm the existence of a prominent peak in the forward cross section at ${E}_{\mathrm{c}.\mathrm{m}.}=3.0$ GeV and show a hitherto unreported shoulder at ${E}_{\mathrm{c}.\mathrm{m}.}=3.7$ GeV. This structure, along with the well-known sharp maximum at ${E}_{\mathrm{c}.\mathrm{m}.}=2.2$ GeV, may be understood on the basis of a one-pion-exchange model as reflecting the behavior of the $T=\frac{3}{2}$ isobars in pion-nucleon scattering. Above ${E}_{\mathrm{c}.\mathrm{m}.}=3.9$ GeV, the forward differential cross section decreases monotonically as the -2.5 power of $s$, the square of the total c.m. energy. This feature also reflects the behavior of the $\ensuremath{\pi}p$ scattering cross section. The structureless upper-energy region can also be accommodated within the framework of Regge theory. The cross section $\frac{d\ensuremath{\sigma}}{\mathrm{du}}$ extrapolated to $u=0$ varies as the -3.2 power of $s$, midway between that expected for the ${N}_{\ensuremath{\alpha}}$ and ${N}_{\ensuremath{\gamma}}$ trajectories.

Measurements are reported of the influence of the nuclear Zeeman effect and other perturbing factors upon the Mossbauer effect in Zn/sup 67/ embedded in an enriched ZnO absorber lattice at temperatures below the helium lambda transition (2.175 deg K). Ways in which the design of the experiment are affected by various perturbations are described. The resonance absorption pattern for the 93-kev line of Zn/sup 67/ as a function of the magnetic field is given including corrections for background and unresolved gamma rays of 30%. The major structural feature of the curve lies in the fact that the maximum resonance does not occur at zero field but is shifted to approximately 10 gauss. A plausible explanation for this is that chemical shifts are superimposed upon the isotopic mass effect. (B.O.G.)

The amplitude and width of the Mossbauer’s resonance in57Fe has been measured for57Fe as a very dilute impurity in metallic indium. The resonance amplitude is found to remain substantially unchanged in the temperature interval 0.35 °K/4 °K, showing that the Dehye’s temperature of In increases by less than 3 °K in this temperature range. Specific heat measurements on In had indicated a possible Debye’s temperature change of 12 °K. As the source is cooled from 300 °K to 4 °K the resonance amplitude increases by only 50% in contrast to the minimum of 500% calculated from the Debye-Waller’s factor.

Recent advances in linear accelerator technology point to the feasibility of designing and developing practical medical linacs for producing protons, neutrons, or pi mesons for the radiation therapy of cancer. Additional uses of such linacs could include radioisotope production and charged particle radiography. For widespread utilization medical linacs must exhibit reasonable cost, compactness, reliability, and simplicity of operation. Possible extensions of current accelerator technology which might provide these characteristics are discussed in connection with linac design, fabrication techniques, materials, power sources, injectors, and particle collection and delivery systems. Parameters for a medical proton linac for producing pions are listed.

In general, the pion factories have lived up to the expectations for them with respect to their performance as accelerators and their output of interesting results on the physics of particles and of the nucleus. Interest in kaon factories, seen as an extension of the pion factories, is presently very high, both as to accelerator design and as to facility and experimental program planning.

We measure a limit on a parity-nonconserving asymmetry in the $p$-Be cross section at 6 GeV/c. The result is $\frac{({\ensuremath{\sigma}}_{+}\ensuremath{-}{\ensuremath{\sigma}}_{\ensuremath{-}})}{({\ensuremath{\sigma}}_{+}+{\ensuremath{\sigma}}_{\ensuremath{-}})}=(5\ifmmode\pm\else\textpm\fi{}9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ where ${\ensuremath{\sigma}}_{+}({\ensuremath{\sigma}}_{\ensuremath{-}})$ is approximately the $p$-Be total cross section for positive (negative) beam helicity. Systematic errors are determined to be 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$.

The Mossbauer effect was observed in the 77-kev gamma-ray line of Au/sup 197/. Resonance was bound using as sources either tbe beta /sup -/ parent. Pt/ sup 197/, or Hg/sup 197/. It was found that the effect could be enhanced by placing the source atoms in a lattice which was mostly Au. The probabilities of emission of photons in no-photon processes and of resonant sbsorption from an incident beam of uniform energy spectrum were determined to be 23 plus or minus 7 and 3 plus or minus 1%, respectively. The mean life of Au/sup 197/ was determined to be 0.82 plus or minus 0.15 m mu sec. (C.J.G.)