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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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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Measurements of the differential cross section for the process γ+p→π0+p have been made at eight pion center-of-mass angles in the range 51-135° and for incident photon energies from approximately 600-1200 MeV. The bremsstrahlung photon beam used was obtained from the California Institute of Technology electron synchrotron. Both the recoil proton and one γ ray from the decay of the π0 were detected. The incident photon energy was determined by measuring the laboratory angle and time of flight of the recoil proton. The angular distributions obtained indicate that the third pion-nucleon resonance is predominantly a D(52) resonance excited by a magnetic quadrupole transition. It can also be concluded that any contribution to the π0 photoproduction cross section from a virtual vector-meson exchange process is probably negligible in the region of the second and third pion-nucleon resonances.
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This article reports the results of a spark-chamber measurement of the reactions K−+p→K¯0+neutrals and K−+p→Λ0+neutrals with an incident kaon momentum of 7.7 GeV/c. The production cross sections for these reactions are measured to be 800±50 μb and 188±18 μb, respectively. The cross-section distributions d2σdPIIdP⊥ in the center-of-mass system with large momentum transfer are discussed in terms of a fireball model of production.
Axis error includes +- 0.0/0.0 contribution (?////NEUTRAL DECAY MODES, ETC).
Differential cross sections have been measured for π − p elastic scattering at laboratory momenta in the range 1.2 to 3.0 GeV/ c for the c.m. range 0.97 > cos θ ∗ > −0.98 . The corresponding mass range is 1.78 to 2.56 GeV/ c 2 . The data was obtained from a counter experiment in which the scattered pions and protons were detected in coincidence by arrays of scintillation counters.
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We have measured the reactions π±p→π±p and π+p→K+Σ+ at 5.0 GeV/c in the region 2.2<−t<3.5 (GeV/c)2. We find the minimum cross section of the dip at −t=2.8 (GeV/c)2 in π+p elastic scattering to be 0.16 ± 0.05 μb/GeV2. The π−p differential cross section exhibits similar structure, while the π+p→K+Σ+ channel shows a steady decline in cross section as |t| increases. The polarization of the Σ+ remains large and positive to at least −t=2.8 (GeV/c)2.
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We present data on the reaction K+p→K+p at large angles. Between the forward diffraction peak and the backward peak the cross section is independent of four-momentum transfer but varies with incident momentum.
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Differential cross sections for π±p, K±p, pp, and p¯p elastic scattering were measured at 3, 3.65, 5, and 6 GeVc for momentum transfers from 0.03 to 1.5 GeV2 using the Argonne effective mass spectrometer. Particular attention was paid to the relative particle-antiparticle normalization. The crossover points are consistent with no energy dependence, average values being 0.14 ± 0.03, 1.190 ± 0.005, and 0.160 ± 0.007 GeV2 for π's, K's, and protons, respectively.
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We have measured the differential cross sections for the associated-production reactions π−p→K0Λ0 and π−p→K0Σ0 at 3, 4, 5, and 6 GeV/c, with a total of over 40 000 events. We find that both reactions have exponential forward peaks for −t≲0.4 (GeV/c)2, with no indication of forward-direction flattening or turnover; the slopes of the forward peaks show little if any variation with momentum; and the two cross sections are equal within experimental error from −t=1.2 (GeV/c)2 out to at least −t=2.0 (GeV/c)2.
INTERCEPT AND SLOPE FROM FIT TO D(SIG)/DT (PRESUMABLY FOR -TP < ABOUT 0.4 GEV**2).
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