A spark-chamber experiment on the peripheral production of 9245 pion pairs by 12- and 18-GeV/c incident pions is reported and analyzed in terms of a one-pion-exchange model in which the final state at the nucleon vertex contains generally one or more pions. The relevant dynamics and kinematics appropriate to this problem are reviewed, and the experimental and analysis techniques giving good resolution and detection-bias correction are discussed in some detail. From the results, fair agreement is found between the data and the one-pion-exchange calculation of the ρ0 production cross sections and of the associated missing-mass spectra. The ρ0 is found to be consistent with a single peak, and no evidence of peak splitting is observed. A search for a narrow s-wave dipion resonance is made with negative results. Normalizing to the ρ0 meson, the s-wave π+π− scattering cross section is computed from the abundant low-dipion-mass events, giving a cross section falling smoothly from 50 mb (300 MeV) to about 20 mb (600 MeV). No evidence of an s-wave resonance is found in this range of energies. Below 450 MeV, the pion-pion scattering asymmetry favors backward scattering (by 2½ standard deviations), which is consistent with a negative and falling J=T=0 phase shift. The extrapolated forward-backward asymmetry and the s-wave cross section are both consistent with a J=T=0 phase shift near|90°| at about 750 MeV.
Dipion production cross section under RHO resonance. Errors are statistical only.
Dipion production cross section under RHO resonance. Errors are statistical only.
RHO0 cross section. Errors are statistical only.
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No description provided.
We have measured η0 photoproduction at 4 GeV. We find our results to be consistent with a theoretical preduction relating this cross section to ω0 production by π mesons using a vector-dominance model; there is no evidence for a dip or change of slope at −t=0.6 as seen in π0 photoproduction.
Axis error includes +- 0.0/0.0 contribution (?////).
The cross sections for the two antiproton-proton annihilation-in-flight modes, ˉp + p → π+ + π- ˉp + p → k+ + k- were measured for fifteen laboratory antiproton beam momenta ranging from 0.72 to 2.62 GeV/c. No magnets were used to determine the charges in the final state. As a result, the angular distributions were obtained in the form [dσ/dΩ (ΘC.M.) + dσ/dΩ (π – ΘC.M.)] for 45 ≲ ΘC.M. ≲ 135°. A hodoscope-counter system was used to discriminate against events with final states having more than two particles and antiproton-proton elastic scattering events. One spark chamber was used to record the track of each of the two charged final particles. A total of about 40,000 pictures were taken. The events were analyzed by measuring the laboratory angle of the track in each chamber. The value of the square of the mass of the final particles was calculated for each event assuming the reaction ˉp + p → a pair of particles with equal masses. About 20,000 events were found to be either annihilation into π ±-pair or k ±-pair events. The two different charged meson pair modes were also distinctly separated. The average differential cross section of ˉp + p → π+ + π- varied from ~ 25 µb/sr at antiproton beam momentum 0.72 GeV/c (total energy in center-of-mass system, √s = 2.0 GeV) to ~ 2 µb/sr at beam momentum 2.62 GeV/c (√s = 2.64 GeV). The most striking feature in the angular distribution was a peak at ΘC.M. = 90° (cos ΘC.M. = 0) which increased with √s and reached a maximum at √s ~ 2.1 GeV (beam momentum ~ 1.1 GeV/c). Then it diminished and seemed to disappear completely at √s ~ 2.5 GeV (beam momentum ~ 2.13 GeV/c). A valley in the angular distribution occurred at cos ΘC.M. ≈ 0.4. The differential cross section then increased as cos ΘC.M. approached 1. The average differential cross section for ˉp + p → k+ + k- was about one third of that of the π±-pair mode throughout the energy range of this experiment. At the lower energies, the angular distribution, unlike that of the π±-pair mode, was quite isotropic. However, a peak at ΘC.M. = 90° seemed to develop at √s ~ 2.37 GeV (antiproton beam momentum ~ 1.82 GeV/c). No observable change was seen at that energy in the π±-pair cross section. The possible connection of these features with the observed meson resonances at 2.2 GeV and 2.38 GeV, and its implications, were discussed.
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No description provided.
The differential cross sections for single-π+ photoproduction from hydrogen have been measured over a range of momentum transfers from -2×10−4 to -2 (GeV/c)2, and photon energies from 5 to 16 GeV. The differential cross section increases by roughly a factor of 2 as the magnitude of the square of the momentum transfer decreases from 0.02 (GeV/c)2. The cross section falls approximately as exp(−3|t|) at large momentum transfers, with a similar momentum-transfer dependence of the cross section at all photon energies studied.
No description provided.
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Elastic differential cross sections were measured at 6 energies between 2.3 and 6 BeVc for π++p and π−+p. The behavior of the secondary peak as a function of energy and charge is shown. Evidence for considerable resonance structure is seen in the angular distributions.
No description provided.
Differential cross sections for the reaction π−p→π0n were measured at nine incident-pion kinetic energies in the interval from 500 to 1300 MeV. The negative pion beam from the bevatron was focused on a liquidhydrogen target completely surrounded by a cubic array of six steel-plate spark chambers. The spark chambers were triggered on events with neutral final states. Charge-exchange events were identified from the one-shower and two-shower events in the spark-chamber pictures. By the Monte Carlo technique, the π0 distributions were calculated from the bisector distributions of the two-shower π0 events together with the observed γ-ray distributions of the one-shower π0 events. These π0 distributions were fitted with both Legendre-polynomial expansions and power-series expansions by the method of least squares. The extrapolated forward differential cross sections are in good agreement with the dispersion calculations. The Legendre coefficients for the differential cross sections in isospin state T=12 were obtained by combining our results with available data on π±p elastic scattering. In the light of existing phase-shift solutions, the behavior of these coefficients is discussed. The D5F5 interference term that peaks near 900 MeV is verified to be in isospin state T=12 only. We report here also the total neutral cross sections and the cross sections for the production of neutral multipion final states 2π0n and 3π0n. The 4π solid angle and the calibrated energy response of the spark chambers contribute to the accuracy of the results.
No description provided.
No description provided.
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Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
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No description provided.
We have analyzed 2560 events in the final-state K O 1 K O 1 n produced in π − p interactions at 5, 7 and 12 GeV/ c . We observe the S ∗ (1070), f O and A 2 decaying into K O 1 K O 1 . Resonance parameters, cross sections, and branching ratios are given.
Cross section times branching ratio.
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