[en] In the summer of 1980, a balloon-borne cosmic ray experiment reported the detection of 14 low energy antiprotons during an 18 hour flight. This measurement represented an antiproton intensity two orders of magnitude greater than that predicted by conventional theories. This surprising result triggered a flurry of papers theorizing the origin of these particles, including the prediction of domains of primary antimatter, and evidence for supersymmetric particle annihilation. Not until the summer of 1987 was a follow up experiment (PBAR) performed. The PBAR detector has both better resolution and a larger dynamic range in energy than the previous detector. It measured the energy spectrum of antiprotons in the 0.1-1.5 GeV kinetic energy range. The present work describes the instrument, the experiment, and the results. Our analysis of the PBAR data reveals no antiprotons in the energy range of 0.13-0.64 GeV and only one antiproton candidate for energies between 0.64 and 1.5 GeV. The numbers of protons detected to data in these energy bins are 75,000 and 6,400 respectively. This result is in disagreement with the 1980 findings and rules out some of the exotic theories of antiproton production

[en] The Indiana University High Energy Physics Group, Task C has been actively involved in the MACRO experiment at Gran Sasso during the current contract year. MACRO is a large US-Italian Monopole, Astrophysics, and Cosmic Ray Observatory being built under the Gran Sasso Mountain outside of Rome. Indiana University is in charge of the US software effort. We have been performing extensive Monte Carlo design and data analysis calculations. We are also doing development work on the MACRO liquid scintillator. We are setting up a Quality Assurance liquid scintillator laboratory in Frascati, Italy. We are producing vertical scintillator tank endplates and calibration boats in our machine shop

[en] The Indiana University High Energy Physics Group, Task C has been actively involved in the MACRO experiment at Gran Sasso during the current contract year. MACRO is a large US-Italian Monopole, Astrophysics, and Cosmic Ray Observatory being built under the Gran Sasso Mountain outside of Rome. Indiana University is in charge of organizing the United States software effort. We have contributed to the online event display software and the data analysis software. We are also doing development work on the MACRO liquid scintillator. We have set up a Liquid Scintillator Quality Assurance Laboratory in Frascati, Italy. We are producing vertical scintillator tank end plates and calibration boats in our machine shop. We have preliminary data from a test run of one MACRO supermodule. 14 figs

[en] The experiment MACRO (Monopole, Astrophysics, and Cosmic Ray Observatory), located in the Gran Sasso Laboratory in Italy, will use approximately one million liters of liquid scintillator and will last for five to ten years. We have developed a simple test for the MACRO experiment that determines the concentration of pseudocumene in its scintillator. This test has general applicability for a content analysis of volatile components in any liquid scintillator. (orig.)

[en] This paper reports the results of an investigation into the nature of background events in proportional counters sensitive to x-ray photons of energy <150 keV. Even with the use of thick shields composed of high atomic number material, a significant flux background in the detector's energy region can result from multiple Compton scattering in the mass surrounding the active region of the detector. The authors emphasize the importance of the selection of detector components in the reduction of the background by more than an order of magnitude. Experimental results are shown to agree qualitatively with Monte Carlo simulations

[en] We describe a prototype water Cherenkov counter which has been built and tested with relativistic cosmic ray muons. An analysis of the expected photoelectron yield is described. The predicted result of 315±31 photoelectrons is compared with the experimental result of 272±30 photoelectrons. We find that over 70% of the Cherenkov photons detected have wavelengths less than 400 nm. (orig.)

[en] We have built a position sensitive wire chamber and tested it with X-rays and cosmic ray muons. Using a fill gas of 62% CF₄ and 38% CO₂, we have achieved resolutions of 38 μm for 1 keV X-rays, 42 μm for normally incident cosmic ray muons in the absence of a magnetic field, and 46 μm for cosmic rays incident at the gas's Lorentz angle for a 0.8 T magnetic field. For throughgoing charged particles, the degradation in position resolution with angle away from the optimum incident angle has been found to be 11 μm/ (added in quadrature). ((orig.))

[en] Kinematics predicts the severe suppression of low-energy (<1 GeV) secondary antiprotons in the Galactic cosmic rays. Thus the observation several years ago of a finite flux of low-energy antiprotons could not be explained with existing models of cosmic ray propagation, which led to a plethora of theoretical speculation. We have recently flown a balloon-borne instrument to measure the energy spectrum of cosmic-ray anti p's, and have found no antiprotons in the energy interval 200-640 MeV (corrected to the top of the atmosphere). This yields an upper limit to the anti p/p ratio of 5.5x10^-5 (90% confidence level), well below and hence contradicting the earlier result. (orig.)

[en] We describe the PBAR balloon-borne magnet spectrometer flown on August 13-14, 1987 to measure the abundance of cosmic ray antiprotons in the energy interval 100-1580 MeV at the top of the atmosphere. The limits first reported have been improved to an overall limit of anti p/p<2.0x10^-5 (85% CL). We summarize the overall design and performance of the PBAR spectrometer, which had the unique ability to establish the mass of each singly charged cosmic ray, as well as to reject spurious antimatter candidates caused by hard scatterings within the instrument. (orig.)

[en] We present a new measurement of atmospheric muons made during an ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio μ⁺/μ^- as a function of atmospheric depth in the momentum interval 0.3-0.9 GeV/c is presented. The differential μ^- intensities in the 0.3-50 GeV/c range and for atmospheric depths between 4-960 g/cm² are also presented. We compare these results with other measurements and model predictions. We find that our charge ratio is ∼1.1 for all atmospheric depths and is consistent, within errors, with other measurements and the model predictions. We find that our measured μ^- intensities are also consistent with other measurements, and with the model predictions, except at shallow atmospheric depths