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No description provided.
No description provided.
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A beam of ∼200-Mev π+ mesons was defined inside the vacuum chamber of the Nevis Cyclotron. Nuclear emulsions were exposed to a flux of about 104 mesons/cm2. The plates were scanned for pion-hydrogen scatterings and 103 such events were observed in two interaction energies, 151±7 Mev and 188±8 Mev. We obtain total cross sections of 152±31 and 159±34×10−27 cm2, respectively. The data suggest that the angular distribution changes from backwards peaked to almost symmetric over this energy interval. Our observations are not in agreement with the hypothesis of a P32-wave resonance in this energy region. The best fit to the combined results includes a D-wave contribution of -5.4°, although satisfactory agreement may be obtained with only S and P waves.
Axis error includes +- 0.0/0.0 contribution (?////Due to flux, scanning efficiency, doubtful and background events, and thesmall uncertainty in the density of hydrogen in the emulsion).
Axis error includes +- 0.0/0.0 contribution (?////Due to flux, scanning efficiency, doubtful and background events, and thesmall uncertainty in the density of hydrogen in the emulsion).
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No description provided.
Transmission measurements in good and poor geometry have been performed at the Brookhaven Cosmotron to measure the total and absorption cross sections of several nuclei for neutrons in the Bev energy range. The neutrons are produced by bombarding a Be target with 2.2-Bev protons. The neutron detector requires the incident particle to pass an anticoincidence counter and produce in an aluminum radiator a charged particle that will traverse a fourfold scintillation telescope containing 6 in. of lead. Contribution of neutrons below 800 Mev are believed small. The angular distribution of neutrons from the target is sharply peaked forward with a half-width of 6°. The integral angular distributions of diffraction scattered neutrons from C, Cu, and Pb are measured by varying the detector geometry. The angular half-width of these distributions indicates a mean effective neutron energy of 1.4±0.2 Bev. The total cross sections σH and σD−σH are measured by attenuation differences in good geometry of CH2-C and D2O-H2O, with the result: σH=42.4±1.8 mb, σD−σH=42.2±1.8 mb. The cross sections of eight elements from Be to U are measured in good and poor geometry, and the following values of the total and absorption cross sections are deduced (in units of millibrans): Experimental errors are about 3 percent in σtotal and 5 percent in σabsorption. An interpretation of these cross sections is given in terms of optical model parameters for two extreme nuclear density distributions: uniform (radius R) and Gaussian [ρ=ρ0exp−(ra)2]. The absorption cross-section data are well fitted with R=1.28A13 or a=0.32+0.62A13 in units of 10−13 cm. A nuclear density distribution intermediate between uniform and Gaussian will make the present results consistent with the recent electromagnetic radii.
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The total proton-proton cross section (excluding Coulomb scattering) has been measured at energies from 410 Mev up to 2.6 Bev, using external beams from the Cosmotron. Fast counting equipment was used to measure the attenuation of the beams through polyethylene, carbon, and liquid H2 absorbers. At each energy E, σp−p(E, Ω) was measured as a function of the solid angle Ω subtended by the rear counter at the center of the absorber. The total cross section σp−p was obtained by a least squares straight line extrapolation to Ω=0. The measured σp−p as a function of energy rises sharply from 26.5 mb at 410 Mev to 47.8 mb at 830 Mev and then remains approximately constant out to 1.4 Bev, above which energy it decreases gradually to about 42 mb at 2.6 Bev. Using the same equipment and procedure, we have also measured the D2O-H2O difference cross section, called "σp−n," for protons over the same energy range. From a comparison of "σp−n," and σp−p, with the n−p and n−d measurements of Coor et al. at 1.4 Bev, it is apparent that one nucleon is "shielded" by the other in the deuteron. This effect is not present at energies below 410 Mev. Comparing the measured p−p and "p−n" (corrected) cross sections with the results of other high-energy experiments, one may infer the following conclusions: (1) The sharp rise in σp−p from 400 to 800 Mev results from increasing single pion production, which may proceed through the T=32, J=32 excited nucleon state. (2) Above 1 Bev the inelastic (meson production) p−p cross section appears to be approximately saturated at 27-29 mb. (3) The rise in cross section for n−p interaction in the T=0 state, associated with the rise in double pion production, implies that double meson production also proceeds through the T=32 nucleon state. (4) The probable equality of σp−d and σn−d at 1.4 Bev implies the validity of charge symmetry at this energy.
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No description provided.
Interactions initiated by 3-Bev protons of the Brookhaven Cosmotron were studied by photoemulsion technique. With appropriate criteria, 115 events are attributed to interactions of the incident beam protons with hydrogen nuclei (∼55%) and with bound protons of other nuclei (∼45%). A detailed analysis allowed the subdivision of the 115 events in categories, according to the number of π mesons (N>~0) produced in the collision. The ratio of elastic scattering to the total number of events was estimated to be σelσtotal=0.20−0.07+0.04. The observed cross section for pure elastic scattering is σel=8.9±1.0 mb. The percentages of single, double, triple, and quadruple π-meson production are respectively: 34−20+22; 35.6−23+20; 9.6−4+6; ∼1.0+3.5. Among the 20 most probable cases of single π-meson production—the estimated ratio of π+ to π0 is σπ+σπ0=5.3−1.4+0.3. The experimental results are not in agreement with the Fermi statistical-model theory (in particular the lower limit for the experimental ratio of triple to single production is given by σ3σ1>∼110 in contrast with the predicted ratio σ3σ1=167) but are not inconsistent with the Peaslee excited-state-model theory.
No description provided.
212 interactions of 2.75-Bev protons have been observed in a hydrogen-filled diffusion cloud chamber. The data indicate an elastic cross section of 15 millibarns, with about 9 millibarns cross section for single pion production, 13 millibarns for double, and 4 for triple. There is one example of quadruple pion production. One definite example of the production of heavy unstable particles was observed, and two doubtful cases. The median elastic scattering angle was 19° in the c.m. system. Angle and momentum distributions for inelastic events are consistent with those observed at lower energies.
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A strong-focusing momentum channel has been arranged to form a beam from antiprotons produced by 6.0-Bev protons striking an internal target of the Bevatron. The channel consists of five 4-inch-diameter magnetic quadrupole lenses and two deflecting magnets adjusted to give a ±5% momentum interval. The antiprotons were selected from a large background of mesons by a scintillation counter telescope with a time-of-flight coincidence circuit having a resolution of ±2×10−9 second. This system allowed detection of approximately 400 antiprotons per hour. With a liquid hydrogen attenuator, the total antiproton-proton cross section at four different energies, 190, 300, 500, and 700 Mev, has been observed to be 135, 104, 97, and 94 mb, respectively. Also, the total cross sections for antiprotons incident on Be and C have been measured at two energies. The inelastic cross sections for carbon have been measured by observing the pulse heights produced by the interactions in a target of liquid scintillator. To measure the inelastic cross section for a high-Z element, lead wafers were immersed in the liquid scintillator, and to select inelastic events the pulse heights were measured.
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No description provided.
No description provided.
No description provided.
Elastic π+−p scattering at 1.1 Bev and elastic p−p scattering at 582 Mev have been measured using a propane bubble chamber. On the basis of 661 identified π+−p elastic scatterings found in the scanning of 1.726×106 cm of pion track, the total elastic cross section is found to be 12.3±1.2 mb. The differential cross section is rather isotropic at large angles and exhibits a strong peak for small forward scattering angles. If the forward peak is interpreted as diffraction scattering according to the optical model, the data are best fitted by a proton with a π+−p interaction radius, R=(0.99−0.11+0.13)×10−13 cm and an opacity, O=0.70−0.07+0.06. The total cross section for p−p elastic scattering at 582 Mev was found to be 24.2±1.6 mb on the basis of 2442 elastic scatterings observed in the scanning of 3.000×106 cm of proton track. Both differential and total p−p cross sections are in excellent agreement with the results of counter experiments in this energy region.
No description provided.
No description provided.
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