Cloud-Chamber Study of the Production and Decay of Strange Particles

Out of 1242 decay events observed in a magnetic cloud chamber array triggered on penetrating showers, a total of 54 associated V-particle pairs has been obtained. All the associations observed are consistent with the "strangeness" selection rules. A statistical analysis of the numbers of double and single events has been used to obtain rough estimates of the fractions of neutral K particles and neutral hyperons which decay by "invisible" modes, and of the relative frequencies of occurrence of various production processes. The main uncertainties in the resulting values are discussed in detail

Cloud-Chamber Investigation of Charged V Particles

An analysis of 84 charged V events obtained during two years of operation of a vertical magnetic cloud-chamber array is presented. The particular features of interest which are studied in detail are the distribution of P*, the momentum of the charged secondary in the rest system of the primary, and the possible existence of a component of short lifetime (i.e., τ<5×10^-10 sec). The P* distribution from 19 slow, accurately measurable positive events is shown to imply that the large majority of these events arise from one or more two-body decays from primaries of mass approximately equal to that of the τ meson. One case turns out to be inconsistent with this interpretation, and is presumed to represent a three-body decay. The P* distribution from 6 slow, accurately measurable negative events is consistent with a single two-body decay having a P* value of about 200 Mev/c. This suggests the existence of a negative counterpart to the well-known θ0 particle, though the statistics are much too poor to permit any strong conclusion. The lifetime analysis provides strong evidence for the existence of a negative component of lifetime equal to or less than (1.3±0.6)×10^-10 sec. The transverse momentum distribution for these short-lived events is shown to suggest a two-body decay with a P* value of 201±12 Mev/c

Theoretical Transmission Spectra During Extrasolar Giant Planet Transits

The recent transit observation of HD 209458 b - an extrasolar planet orbiting a sun-like star - confirmed that it is a gas giant and determined that its orbital inclination is 85 degrees. This inclination makes possible investigations of the planet atmosphere. In this paper we discuss the planet transmission spectra during a transit. The basic tenet of the method is that the planet atmosphere absorption features will be superimposed on the stellar flux as the stellar flux passes through the planet atmosphere above the limb. The ratio of the planet's transparent atmosphere area to the star area is small, approximately 10^{-3} to 10^{-4}; for this method to work very strong planet spectral features are necessary. We use our models of close-in extrasolar giant planets to estimate promising absorption signatures: the alkali metal lines, in particular the Na I and K I resonance doublets, and the He I $2^3S$ - $2^3P$ triplet line at 1083.0 nm. If successful, observations will constrain the line-of-sight temperature, pressure, and density. The most important point is that observations will constrain the cloud depth, which in turn will distinguish between different atmosphere models. We also discuss the potential of this method for EGPs at different orbital distances and orbiting non-solar-type stars.Comment: revised to agree with accepted paper, ApJ, in press. 12 page

Cloud-Chamber Study of Negative Strange Particles

A detailed analysis of the decays in flight of negative K mesons and hyperons, obtained with the 48-in. cloud chambers in Pasadena, is presented. The principal results are the following: 1. Two new fully measurable τ^− events add to the already strong evidence for the existence of this particle. 2. K^− events with a single charged secondary are shown to be most consistent with the K_(π^2) and K_(μ^2) decay modes. 3. An analysis of 7 Caltech Ξ^− events is shown to lead to a Q value of 65±3 Mev, and a 50% confidence lower limit to the lifetime of 4.6 × 10^(−10) sec. A rough upper limit to the lifetime of 2 × 10^(−8) sec, based on the predictions of the strangeness theory, is obtained. Angular correlations among the Ξ^− secondaries are studied, but the statistics are insufficient to permit any significant conclusion. An additional event which is most easily interpreted as a Ξ^− decay is discussed. 4. The V^− events which are neither K^− nor Ξ^− are shown to have a lifetime less than or equal to (1.52^+(0.38)_(−0.25))×10^(−10) sec and a P^* value, based on their transverse momentum distribution, of 197±7 Mev/c. These values correspond satisfactorily with the presently known properties of the Σ^−hyperon. 5. It is estimated from a comparison of the numbers of identified Ξ−'s and V^−'s that the fraction of Λ^0 particles which decay into charged secondaries is greater than 0.40^(+0.15)_(−0.11), and can, insofar as the present data are concerned, be as high as unity. All errors quoted in the above results are 50% confidence limits

Cloud Chamber Investigation of Anomalous θ^0 Particles

Eighteen anomalous θ^0, (θ^0_(anom)), decay events observed in the California Institute of Technology magnet cloud chambers have been analyzed. Many of these decays are dynamically inconsistent with the τ^0→π^++π^−+π^0 scheme, but most are consistent with the decay processes: θ^0_(anom)→π^++π^−+γ, π^±+μ^∓+ν, and π^±+e^∓+ν. However, at least one event is inconsistent with each decay scheme. From the locations of the decays in the cloud chamber, the lifetime is found to be significantly longer than that of the normal θ^0 particle, called here the θ^0_(π2) particle. Other differences in the behavior of the θ0anom and θ^0_(π2) particles were also observed in the (a) momentum distributions, (b) origin locations, (c) relative numbers of θ^0_(anom) and θ^0_(π2) particles traveling upward, and (d) the types of V particles produced in association with the θ^0_(anom) and θ^0_(π2). It is concluded that not all the θ^0_(anom) decays can result from alternate decay modes of the θ^0_(π2). Moreover, many decays can be neither τ^0 decays nor alternate decays of the θ^0_(π2). The characteristics of the θ^0_2 particle proposed by Gell-Mann and Pais are consistent with those of the θ^0_(anom) particle, with the possible exception of the observed types of associations. An estimate was made of the relative number of θ^0_(anom) to θ^0_(π2) particles observed to decay in the cloud chamber. If all θ^0_(anom) decays are assumed to arise from decays of the θ^0_2 particle, then a lower limit for the θ^0_2 lifetime is found to be about 10^(−9) sec

Physical Properties of Near-Earth Asteroid 2011 MD

We report on observations of near-Earth asteroid 2011 MD with the Spitzer Space Telescope. We have spent 19.9 h of observing time with channel 2 (4.5 {\mu}m) of the Infrared Array Camera and detected the target within the 2{\sigma} positional uncertainty ellipse. Using an asteroid thermophysical model and a model of nongravitational forces acting upon the object we constrain the physical properties of 2011 MD, based on the measured flux density and available astrometry data. We estimate 2011 MD to be 6 (+4/-2) m in diameter with a geometric albedo of 0.3 (+0.4/-0.2) (uncertainties are 1{\sigma}). We find the asteroid's most probable bulk density to be 1.1 (+0.7/-0.5) g cm^{-3}, which implies a total mass of (50-350) t and a macroporosity of >=65%, assuming a material bulk density typical of non-primitive meteorite materials. A high degree of macroporosity suggests 2011 MD to be a rubble-pile asteroid, the rotation of which is more likely to be retrograde than prograde.Comment: 20 pages, 4 figure

Spitzer/MIPS Limits on Asteroidal Dust in the Pulsar Planetary System PSR B1257+1

With the MIPS camera on Spitzer, we have searched for far-infrared emission from dust in the planetary system orbiting pulsar PSR 1257+12. With accuracies of 0.05 mJy at 24 um and 1.5 mJy at 70 um, photometric measurements find no evidence for emission at these wavelengths. These observations place new upper limits on the luminosity of dust with temperatures between 20 and 1000 K. They are particularly sensitive to dust temperatures of 100-200 K, for which they limit the dust luminosity to below $3 \times 10^{-5}$ of the pulsar's spin-down luminosity, three orders of magnitude better than previous limits. Despite these improved constraints on dust emission, an asteroid belt similar to the Solar System's cannot be ruled out

Optical Guidance System /OGS/ for rendezvous and docking Final report

Optical guidance system for Apollo rendezvous and dockin