A total of 1589 two-prong events were observed in an exposure of the Brookhaven National Laboratory 14-in. bubble chamber at the Cosmotron. The fit to the elastic angular distribution requires terms through cos4θc.m.. The ratio of the inelastic cross sections σ(π−p→π−π+n)σ(π−p→π−π0p) is 3.75±0.46. The π−p→π−π+n reaction is dominated by formation of the π−n isobar and an enhancement in the di-pion mass spectrum previously reported by Kirz. The π−p→π−π0p reaction shows no structure in the effective-mass spectra.
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The interactions of 775 MeV (kinetic energy) π−-mesons in a hydrogen bubble chamber have been studied. Total and partial crosssections have been determined with the following results: σ (total) = (39.0±1.6) mb, σ (elastic)=(14.8±0.7) mb, σ (π− + p → all neutrals) = (9.0 ± 0.5) mb, σ (π− + p = π− + π+ + n) = (9.8 ± 0.5) mb, and σ (π− + p = π− + p + π0) = (4.8 ± 0.3) mb. The elastic-scattering angular distribution has been fitted with a Legendre polynomial series terminated at the fifth order. Various angular and effective-mass distributions of single-π production are presented and discussed in terms of the Olsson-Yodh and O.P.E. models.
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A 14-in. liquid-hydrogen-filled bubble chamber in a 17.5-kG magnetic field was exposed to a beam of negative pions produced by the Cosmotron at Brookhaven National Laboratory. About 26 000 pictures were taken and examined for the following final states: (1) elastic scattering (π−p); (2) π+ production (π−π+n); (3) π0 production (π−π0p); (4) neutrals. Values for the cross sections for these processes are σ(elastic)=17.56±0.43 mb, σ(π+)=7.14±0.23 mb, σ(π0)=4.65±0.17 mb. The elastic-scattering angular dependence in the c.m. system is fitted by a power-series expansion in cosθ and gives the following coefficients: a0=0.27±0.02, a1=1.48±0.11, a2=3.86±0.22, a3=−0.29±0.53, a4=−0.65±0.28, a5=1.69±0.52 (units: mb/sr). Cross sections for multiple-pion production were also measured: σ(π−π+π0n)=0.33±0.04 mb, σ(π−π+π−p)=0.08±0.02 mb. The total neutral cross section was σ(neutrals)=11.78±0.43 mb; the total charged events cross section was σ(charged)=29.76±0.69 mb; and the total cross section was σ(total)=41.54±0.82 mb. For single-pion production events, two-body mass distributions and angular distributions were compared with the predictions of the Olsson-Yodh isobar model.
Axis error includes +- 0.0/0.0 contribution (?////STATISTICAL YIELD DOMINATES).
Measurements have been made of the total cross sections σ(p−p) and σ(p−d) over the laboratory momentum range 1.1 to 8 GeV/c, with relative errors of 0.1%. The absolute accuracies of these cross sections are limited to 0.3% by lack of information which will allow the Coulomb-nuclear interference to be calculated accurately. Values of the total cross sections σ(p−n) and σ(I=0) are deduced by assuming the Glauber correction. Structure is observed in σ(p−p) near a mass value of 2.75 GeV/c2; its interpretation is discussed. σ(I=0) rises rapidly in the range 2.3 to 2.9 GeV/c2, and this is attributed to the onset of strong inelastic scattering.
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The differential cross section for elastic scattering of positive pions on protons has been measured at a nominal incident-meson kinetic energy of 250 MeV. The angular range covered in the center of mass by the 13 data was 14.9° to 160°. The fractional rms errors were typically 1.5%. A liquid-hydrogen target was bombarded by a beam of 2.5×106 mesons/sec. The scattered pions were detected by a counter telescope. Recoil protons were eliminated by means of a Čerenkov counter. A phase-shift analysis was performed combining the above-mentioned data with the recoil-proton polarization measurements taken recently with the help of a polarized proton target. Only one acceptable SPD Fermi-type phase-shift set was found. When F waves were included, a total of three possible phase-shift solutions emerged from the analysis. However, arguments based on the data could still be made to eliminate all but one phase-shift set. On the other hand, the remaining phase-shift set, similar in type to the SPD solution, suffers from the disadvantage of large rms errors assigned to its small phase shifts.
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Interactions of 781-MeV π+ mesons with protons were investigated using the Brookhaven National Laboratory 14-in. hydrogen bubble chamber. A total of 2305 events was observed. The data were normalized to a total cross section of 22.2 mb, giving partial cross sections σ(π+p→π+p)=9.5±0.5 mb, σ(π+p→π+pπ0)=9.3±0.5 mb, σ(π+p→π+π+n)=2.15±0.17 mb, and a multiple-pion-production cross section of 1.15±0.17 mb. The elastic angular distribution was obtained and is dσdω=(0.25±0.03)+(0.90±0.11)cosθc.m.+(2.57±0.24)cos2θc.m.+(0.19±0.22)cos3θc.m.−(1.73±0.34)cos4c.m.. The kinetic-energy and angular distributions of the outgoing particles in single-pion production are given. The data are compared with other experiments in this energy region and their relevance to the shoulder in the π+p total cross section near 830 MeV is discussed.
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Interactions of 2.08−BeVc positive pions with protons have been studied using the 20-in. hydrogen bubble chamber and the alternating gradient synchrotron at Brookhaven National Laboratory. Using 3000 elastic and 8000 inelastic events, the partial cross sections for elastic scattering and for meson production have been measured. The ρ+, ρ0, ω0, and η0 resonances are produced strongly and emerge predominantly in the forward direction in the center-of-mass system, suggesting a peripheral mechanism for their production. The possibility of explaining these reactions by specific particle-exchange models is investigated. More than 75% of the ρ0, ω0, and η0 are produced with the N33* (1238) isobar. The N* (1688) is produced in about one-third of the π+π+N final states. Cross sections for production of ρ+p, π+pω, N33*ω, π+pη, N33*η, π+pρ0, N33*ρ0, N15*π+, and N33*π0, are given. A1, B, φ, and X mesons are not observed.
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In an exposure of the Brookhaven National Laboratory 20-in. hydrogen bubble chamber to a separated π+ beam at π+ momenta of 2.35 BeV/c (center-of-mass energy E*=2.30 BeV), 2.62 BeV/c (E*=2.41 BeV), and 2.90 BeV/c (E*=2.52 BeV), we have observed production of the ω0, ρ0, and η0 mesons. The production of the ω0, ρ0, and η0 is often accompanied by simultaneous production of the N*++. The momentum transfer in ω0 and ρ0 production is characteristic of peripheral collisions and suggests a single-particle exchange for the production mechanism. The decay distributions for the ω0, ρ0, and the ρ+ demonstrate the importance of modifying the single-particle-exchange model to include absorptive effects. An upper limit on the two-π decay of the ω0 is set at 2%. The width of the η0 is found to be less than 10 MeV. Elastic-scattering distributions are presented.
No description provided.
A bubble-chamber experiment in which the reaction π−+p→π+π+N was studied at a beam momentum of 2.14 BeV/c yielded 1533 and 2234 events of the final states π−π0p and π−π+n, respectively. These events are dominated by the formation of the ρ resonance, which is produced mostly in the forward direction. Both the production and decay angular distributions of the ρ− agree very well with the predictions of the one-pion exchange theory modified by absorption effects. The decay angular distribution of the ρ0 shows the well-known forward-backward asymmetry. This effect is interpretable as the result of the interference between the ρ0 and an isospin-zero s-wave π−π resonance. The production of the ρ0, in addition to its forward peak, shows a weak backward peak. Partial cross sections of various final states are also presented.
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The elastic scattering of K+ mesons on protons is studied at 3.5 and 5 GeV/c. The total elastic cross-sections are found to be (4.36±0.36) mb and (3.82±0.41) mb respectively. The differential elastic cross-sections, which exhibit characteristic diffraction peaks, are fitted by dσ/dt=(dσ/dt)0eαt, giving α=(3.85±0.12) and (4.70±0.21) (GeV/c)−2 for the two momenta respectively, with |t|⪝0.65 (GeV/c)2. The results are compared to those at neighbouring energies, giving some support to the presence of a real part of the forward scattering amplitude. The diffraction peak shows definite shrinking with increasing momenta. The data are examined in the light of models for high-energy scattering.
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