The ratio of the cross sections for photoproduction of neutral pions from neutrons to that from protons has been obtained at average photon energies of 750, 875, and 1050 mev at a pion CM angle of 60° and at average photon energies of 875 and 1050 mev at a pion CM angle of 90°. The experimental technique required simultaneous detection of both the pions and the nucleons. Pions were detected by three scintillation counters. Lead plates of 2.4 radiation lengths and 1.2 radiation lengths were placed in front of the second and third counters. Neutral pions were identified by the absence of output in the first counter and the large outputs in the second and third counters. Nucleons were detected in two scintillation counters. The second of the two counters is 11” thick and has approximately 20% efficiency of detecting neutrons. Neutrons were identified by the absence of output in the first counter. The energy of the incident photons was determined by synchrotron subtraction. Since the statistical accuracy of synchrotron subtraction is poor, a system of three fast coincidence circuits was used as a time-of-flight instrument to reduce the number of events initiated by low energy photons. The statistical errors assigned to the ratio range between 15-30%. The results of this experiment agree with the results of Bingham within statistical errors, but show a general tendency for the σ^(no)/ σ^o ratio to lower. The ratio of σ^(no)/ σ^o obtained in this experiment ranges between 0.4 and 0.8. The cross sections for neutral pion photoproduction from neutrons are derived from the σ^(no)/ σ^o ratio and the Caltech data on neutral pion photoproduction from hydrogen.
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The differential cross section for elastic scattering of 3.63−GeVc π− mesons on protons was studied with a hydrogen bubble chamber, the emphasis being on large-angle scattering. From 90 to 180° in the barycentric system, the cross section is roughly flat with an average value of 2.7±1.0 μb/sr. Near and at 180°, there may be a slight peak of magnitude 10±6 μb/sr. But if such a peak exists, it is only one-third to one-fourth the size of the 180° peak found in 4.0 GeVc π++p elastic scattering. In addition to comparison with other π−+p and π++p large-angle elastic-scattering measurements, this measurement is compared with large-angle p+p elastic scattering. In the forward hemisphere a small peak or a plateau exists at cos θ*=+0.60. This appears to be a second diffraction maximum such as has been found in lower-energy π+p elastic scattering. A survey of indications of such a second diffraction maximum in other π+p measurements shows that it always occurs in the vicinity of −t=1.2 (GeVc)2, where t is the square of the four-momentum transfer. As the incident momentum increases, the relative size of this second maximum decreases.
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Momentum spectra for forward Σ− production on beryllium by protons of momentum 25.8 and 29.4 GeVc are presented. Data for the two primary proton momenta are compared for scaling behavior in the invariant cross section. In addition, the observed single-particle momentum distributions are compared with single-particle spectra from other inclusive reactions initiated by protons.
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The neutron polarization asymmetry in neutron-deuteron scattering has been measured from 44.5° to 160° (c.m.) neutron angle. The results display quantitatively the same structure as proton-deuteron polarization data, but discrepancies appear for angles corresponding to those near the minimum of the differential cross section. In this region the polarization is considerably more negative than in the proton-deuteron case, and both are more negative than current theoretical predictions.
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An investigation has been performed of some properties of Σ(1660) produced in the reaction K−p→Σ+(1660)π− at 2.87 GeV/c incident K− momentum. The decay modes observed for this state include Λ(1405)π and Σπ. The spin and parity are measured to be JP=32−. The differential cross section of the Λ(1405)π decay mode is sharply peaked in the forward direction, falling exponentially with a slope of 5.6 ± 0.7 (GeV/c)−2, while the slope for the Σ0π+ decay mode is 2.1 ± 0.4 (GeV/c)−2. The difference in the ratio of backward to total events for the two decay modes also suggests that two Σ(1660)'s exist.
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Momentum spectra for forward Σ− and Ξ− production by protons on beryllium are presented. Σ− production data for two primary proton momenta are compared to test scaling of the invariant cross section. In addition, the observed single-particle momentum distributions are compared with single-particle spectra from other inclusive reactions initiated by protons.
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We report on a search for Ξ* production in the mass range 1.5-2.0 GeV / c2 in K−n interactions at 2.87 GeV / c. Upper limits on Ξ* production cross sections, as well as reaction cross sections for those final states in which Ξ*'s may be observed, are presented. In particular, an upper limit of 5.4 μb is placed on production of an isospin-−32 Ξ*−−.
CROSS SECTIONS ARE QUOTED FOR THE SAME FINAL STATE DERIVED FROM DIFFERENT TOPOLOGIES.
UPPER LIMITS AT 90 PCT CONFIDENCE LEVEL FOR RESONANCE ABOVE SMOOTH BACKGROUND.
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Data on correlations between momentum analysed protons, pions or K mesons, and charged particles produced in pp collisions at the CERN ISR are presented. The charged particles were detected in a ∼4 π scintillation counter hodoscope. The pseudo-rapidity distributions are well described by production within the limits of cylindrical phase space, with negative kaons and antiprotons yielding narrower distributions than protons, pions and positive kaons. The azimuthal distributions show symmetry around the t -channel axis in the rest frame of the recoiling mass M x in pp → aX (a = detected proton, pion, positive kaon).
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In a streamer-chamber experiment at the Stanford Linear Accelerator Center, we observed hadron production in inelastic collisions of 14-GeV positive muons in a liquid hydrogen target. We report on the experiment, the analysis, and the resulting cross sections for hadronic prongs as well as the charged-hadron multiplicity distributions.
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