J. C. Street

INTERACTIONS OF 1.3-Bev NEGATIVE PIONS IN NITROGEN

Seventy-four inelastic pion-nitrogen interactions were studied using a diffusion cloud chamber provided with a magnetic field. Distributions have been made of the momenta, emission angles, and charges of the various nuclear and mesonic fragments, including a number of neutral pions and a hyperon, from these interactions. It is found that the induced excitation of the nitrogen nucleus can lead to a breakdown into from two to seven charged nuclear fragments. Evidence for multiple pion scattering within single nuclei is discussed. (auth)

ENERGY SPECTRUM OF CHARGED PIONS FROM 2.2-Bev PROTONS ON Be

Nuclear emulsions were exposed to the radiations produced by 2.2-Bev protons incident upon an internal Be target in the Brooknaven Cosmotron. Particles were identified and their energies determined by grain counts and multiple scattering measurements. Approximately 1OO pion tracks were studied at each of three laboratory angles, 12 deg , 18 deg , and 36 deg with respect to the direction of the incident beam. Assuming a simple nucleon-nucleon interaction in the target, these data correspond to spectra ncar 30, 50, and 9O deg in the center-of-mass system of two nucleons. Over this 30 to 9O deg angular range, the portion of the spectrum near 100 Mev is roughly isotropic, while in the 200- to 300-Mev range it is strongly anisotropic. A comparison of these and other results with recent calculations based on the isobar model reveal certain basic inconsistencies. The observed angular distributions appear qualitatively to be more in agreement with those to be expected from the statistical theory modified to include the final-state particle interactions and the conservation of angular momentum. (auth)

An Example of the Beta-Decay of the Light Meson

vacuum in a 0.5-inch quartz tube with the result that a mass (~8.0 g) of extremely luminescent sma11 crystals was produced. The crystals are about one or two mi11imeters on a side. When the quartz tube containing the crystals was placed close to a photo-multiplier, very large pulses were observed from radium gamma-rays. These pulses were larger than those observed with a clear piece of naphthalene (5.8 g) of comparable size. Of course, this NaI sample is completely unaffected by atmospheric conditions and is quite convenient for normal handling. A comparison of results is shown in Figs. 1 and 2. Figure 1 sho~s oscilloscope pictures of 1 /30-second random exposures taken under identical circumstances with the NaI sample and with naphthalene. The source was 0.1-mi11icurie radium at 16 cm, filtered by 3/32-inch brass. Figure 2 shows a diHerential bias curve taken under identical conditions for the two materials. From the rise times of the pulses in NaI there is some evidence that the light flashes are emitted in about one inicrosecond or less. All v ork reported has been carried on at room temperature. Further work in progress is designed to prodiice large single crystals of this and other alkali halides with thalliiim impurities. A neutron counter iising a lithium halide seems to be a reasonable possibility. In tests made by placing crystals of NaI, KI, and naphthalene on photographic plates {Eastman 103-0) much greater light output was observed from NaI and KI than from naphthalene samples of comparable size. Apparently, naphthalene is not an. efficient phosphor. A sample of NaI in a quartz tube gave measurable lilackening of a photographic plate when the combination was exposed for thirty minutes to the gamma-rays of 1.8 millicuries of radium at a meter distance. A more complete description of these results is being prepared. The author wishes to thank Professors J. A. Wheeler and R. Sherr for interesting discussions, and Professors M. G. White and H. W. Fulbright for loan of equipment used in these tests.