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  1. Measurement of the Ke2+ Branching Ratio

    Bowen, D. R. ; Mann, A. K. ; McFarlane, W. K. ; ... - Physical Review
    The Ke2+ branching ratio has been measured in a spark-chamber and counter experiment at the Princeton-Pennsylvania accelerator. A 𝐾+ beam which yielded an average of 500 stopped, identified 𝐾+ mesons per second was used. Particles which left the stopping region approximately at right angles to the incident beam passed through a series of six thin-plate chambers situated in a 7.5-kG magnetic field which permitted measurement of the particle momentum with a standard deviation of 1.9%. Positrons were identified by a threshold gas Čerenkov counter placed behind the magnetic field. A thick-plate spark chamber was placed behind the Čerenkov counter tomore » permit observation of a particle emerging from that counter and measurement of the particle's total range. The time interval between the 𝐾+ stop and decay was recorded for each event. Discrimination against background events, arising principally from the Kμ2+ decay mode, was provided by selection criteria on momentum, range, the time between the 𝐾+ stop and decay, and by a requirement that the measured position of the track at the entrance to the thick-plate chamber match the extrapolated momentum chamber track. After applying these criteria, we obtain a total of seven events in the momentum interval 242-252 MeV/c in which positrons from Ke2+ should fall, with 2.8 of these events estimated to be background. This gives a Ke2+ branching ratio of ($$2.1^{+1.8}_{−1.3}$$)×10−5, in agreement with the prediction of 𝑉 −𝐴 theory, which, including a radiative correction, is 1.44×10−5.« less

  2. Survey of Radioactive Content of Food Grown on Brazilian Areas of High Natural Radioactivity

    Franca, E. Penna ; Ribeiro, C. Costa ; Teitakowski, M. ; ... - Health Physics
    Two types of high background regions have been studied in Brazil-the monazite sand region along the Atlantic coast and the zone of volcanic intrusives in the inland state of Minas Gerais. In both regions, there are groups of people living on variable fields of radiation ranging from 0.03 to 1.0 mR/h. The most representative towns and villages in these areas are being intensively studied in order to investigate possible long-term consequences to human beings exposed to continuous levels of radiation. Food produced in the areas has been extensively sampled and assayed for its radioactive content. Total alpha counting, fast alphamore » pair coincidence counting, radiochemical analysis of 226Ra 228Ra and 228Th as well as gamma and alpha spectrometry have been employed. In villages in the monazite sand areas, only small quantities of food are produced, all for local consumption. Practically every kind of vegetable and fruit grown in this area has been assayed. The total alpha activities found range from 4 to 260 pCi/kg of fresh weight. The percent of these foods in the local diet is quite small. Therefore, present work centers on the effects of external radiation. The situation is quite different in the volcanic intrusive region around Araxa. The radioactive minerals there are associated with apatite, a natural fertilizer. The local production of beans, vegetables, manioc and fruits is appreciable, and a large fraction of it is locally consumed. In some isolated farms and villages the inhabitants subsist principally on the foods they grow. The levels of total alpha activities found in local foods present wide ranges: beans 71–800; vegetables 3–1990; citrous fruits 2–2000 pCi/kg fresh weight. Ratios of 226Ra/228Ra are quite variable. A systematic sampling is being conducted there to determine the range of levels in the most important crops cultivated in different areas, the differences in values found in various foods grown on the same soils, and the importance of highly contaminated food on the total local crops. Attempts are being made to estimate daily intakes of radium in some of the isolated and highly contaminated farms. Indirect measurements of intake were also made by analysis of urine and feces.« less

  3. Air shower observation between 5200m and 3260m altitude

    Sitte, Kurt ; Kofsky, Irving L. ; Stierwalt, Don L. ; ... - Nuovo Cimento
    In a study of the development of extensive air showers in the atmosphere, a hodoscope experiment was carried out at three mountain stations: Chacaltaya (5,200m), Mt. Evans (4,300m), and Echo Lake (3,260m). Six trays containing a total of 80 counters were used to determine the size and the lateral distribution of the showers. Four other trays with 54 counters and four liquid scintillators served to measure the transition effect of the shower electrons in lead, and thus to determine the age of the showers. The events could then be grouped and analyzed according to both age and size. The lateralmore » distribution of showers of different age (as determined from the transition effect), both near the core and at larger distances, showed very little variation with altitude and with age. Near the core it is flatter than outside, and the flattening extends at all altitudes over an equal distance. Apparently this phenomenon is due to the continuous effect of the nucleonic component. The attenuation of the shower rate, at fixed geometry, is practically constant between 5,200 and 3,260m, the attenuation mean free path between Mt. Evans and Chacaltaya for the youngest showers being (155±12) g/cm2 against an average of about 140 g/cm2. The attenuation of the particle numbers in showers of equal frequency was over the whole range exponential with a mean free path of about 125 g/cm2. The interaction mean free path of the shower primaries, determined from a comparison of the rates of showers of equal size and age at the three stations, was (87±7) g/cm2. This suggests that the shower primaries, in the energy region concerned (about 1015 ev), are predominantly protons.« less

  4. Proton-Proton Scattering at 437 Mev

    Sutton, R. B. ; Fields, T. H. ; Fox, J. G. ; ... - Physical Review
    This paper is a detailed account of measurements, already briefly reported, of the angular distribution of proton-proton scattering at 437 Mev. A description is given of the external proton beam: its collimation, angular spread, energy spectrum, and intensity. The counters, electronics, and targets are described. Two scattering arrangements were used. In one the polyethylene-carbon subtraction method with coincidence detection of the scattered and recoil protons was employed. In the other a counter telescope detected the protons emerging at a given angle from a liquid hydrogen target; at the larger angles but not at the smaller the scattered pairs could alsomore » be detected by coincidences between the telescope and another counter. At the smaller angles, when coincidence counting could not be used to insure detection of elastic p – p scattering, precautions were taken to absorb the particles produced in inelastic p – p collisions. Finally, the results are that the differential cross section for elastic proton-proton scattering rises smoothly from its value at 90° c.m. to a value about 20 percent higher at 17° c.m. The value at 90° c.m. is 3.49 ± 0.17 mb/sterad.« less

  5. Structure and Composition of Air Shower Cores

    Kasnitz, Harold L. ; Sitte, Kurt - Physical Review
    Extensive air showers were observed with an arrangement in which details of their structure and composition could be studied with the help of a large cloud chamber and a 102-counter hodoscope, while extension trays permitted a classification of the showers in three groups according to their initial energy, and a selection favoring events with cores striking near the central cloud chamber-hodoscope set. The electron density distribution is found to be flatter than the Molière structure function, and despite the different shower ages in the three energy groups, to be nearly the same for all the showers recorded. A structure functionmore » φ⁡(r)∝r-0.76 to r-0.85 in the immediate neighborhood of the core fits the data best. An attempt to correlate the very dense local cascades started by high-energy electrons or photons with the expected multiple cores representing the high multiplicity of the nuclear interaction initiating the shower failed; the structure of the groups of local cascades observed does not appear to vary with the shower energy. The penetrating component contains N particles interacting in the lead plates of the chamber with a mean free path of approximately 165 g/cm2, and consisting of neutrons (41±8 percent) and charged particles. The total abundance of penetrating particles near the core does not differ appreciably from that found by various authors in experiments not as strongly biased in favor of the detection of shower cores. The abundance ratios of N particles to μ mesons, and of penetrating particles to electrons, show only slight variations with the shower age and demonstrate that the nucleonic cascade reaches its maximum somewhat later than the electron cascade.« less

  6. Development of Air Showers in the Atmosphere

    Sitte, Kurt ; Stierwalt, Don L. ; Kofsky, Irving L. - Physical Review
    An experiment was carried out at Mt. Evans, Colorado (altitude 4300 m) to study the development of extensive air showers in the atmosphere. Showers with cores striking near a cloud-chamber-hodoscope arrangement were selected, and the differential energy spectrum of the shower particles determined by observing their transition effect in six ½-in. lead plates with a 68-counter hodoscope. Each shower can be assigned an age classification on the basis of this energy spectrum. The lateral structure function between 2 m and 8 m from the core was obtained from measurements of the particle densities at four extension trays containing 50 countersmore » with a total area of 1.34 m2. It was found from the hodoscope data that the lateral structure function of the showers of various ages does not agree well with the predictions of the single-particle cascade theory. The observed structure function for showers at and beyond the cascade maximum is less steep than expected near the axis; this is consistent with multiple production of shower-producing particles in the primary collision. It was also found that the lateral distribution of showers past the cascade maximum varies only slowly with age; this tendency is predicted in a general way by the cascade theory, but only at a much later stage of development than observed and with quite a different slope of the distribution curve. The interpretation of this effect as the result of a "rejuvenation" of the shower by the continuous transfer of energy from the nucleonic cascade to the electron cascade is therefore more likely.« less

  7. The Scattering of 40-Mev Positive Pions by Hydrogen

    Perry, J. P. ; Angell, C. E. - Physical Review
    In this work, differential scattering cross sections of hydrogen for 40 ± 3-Mev positive pions have been measured at laboratory angles of 45, 60, 90, 120, and 140 degrees.
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