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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A sample of 2657 proton-proton scattering events at 1.48 BeV has been analyzed. The elastic cross section is 19.86 mb, and the elastic scattering is consistent with a simple opaque-disk optical model with R=0.91 F and 1−a=0.864. The dominant feature of the inelastic scattering is the production of the (3/2, 3/2) isobar. The reaction p+p→p+n+π+ is interpreted satisfactorily in terms of the one-pion-exchange model.
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The cross section for the reaction [...] was measured at the Caltech synchrotron. The [...] was detected by measuring its decay gamma rays with two lead glass, total absorption Cherenkov counters. The results are three angular distributions at k = 911, 1180, and 1390 MeV, at forward angles from 3 degrees to 90 degrees. The deuteron/proton ratio differs significantly from 2.0, but final state effects from the use of a deuteron target make impossible quantitative conclusions about the neutron cross section.
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Cross section angular distributions for [...] photoproduction from hydrogen were measured for 28 laboratory photon energies from 574 to 1211 MeV. At most energies, the [...] center of mass angle was varied from 60[degrees] to 170[degrees] in steps of 10[degrees]. A magnetic spectrometer was used to measure the momentum and angle of the recoil proton. A scintillation counter hodoscope with lead convertors was used to detect the presence of at least one of the [...] decay gamma rays. For a majority of the measurements the [...] rates were separated from a contamination of pi pair rates using the difference in their distribution among the gamma counters. For the remainder of the measurements, charged pi pairs were eliminated using veto counters in front of the gamma counters. Internal inconsistency and comparison with other experiments indicate that the veto data are 10 to 15% low near 90[degrees] in the region of 750 MeV. The remainder of the data show good internal consistency and fair agreement with data of other experiments. The results show a peak at 140[degrees] near 1050 MeV which had been expected but not previously measured. Comparison of the backward angle data with that from experiments measuring cross sections very near 180[degrees] indicates either an inconsistency between experiments or a rapid drop in the cross section near 180[degrees] in the region around 800 MeV.
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We have performed an experiment to study the reaction π−+p→η+n near threshold, preliminary to a forthcoming measurement of charge asymmetry in η-meson decay. The η was identified by the velocity of the associated neutron. We detected neutrons produced in the forward hemisphere in the center-of-mass system corresponding to the most energetic neutrons in the laboratory. Data were taken at π− momenta between 670 and 805 MeVc. The four neutron detectors made it possible to detect neutrons at angles of 0° to 21° from the incident pion beam. We present backward differential cross sections for both pion charge exchange and η production calculated from the data. We looked for η′ at pion momenta of 1.5 BeVc and observed none. We obtained σ(π−p→nη′)≤60 μb.
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Results are presented on measurements of elastic proton-proton scattering at 19.2 and 21.1 GeV/ c in the angular region where previously structure had been observed at lower energies.
'1'. '2'. '3'.
Results are presented from an experiment in which high-energy deuterons, produced by proton-proton interactions at 21.1 GeV/ c incident momentum, were detected over a range of angles from 12.5 mrad to 60 mrad in the laboratory system. From the momentum spectra of the deuterons, the final states D + π + and D + ϱ + have been identified. The angular distribution for these reactions are presented and compared with previous data at lower energies.
The statistical errors are presented.
The statistical errors are presented.
The statistical errors are presented. The data are from previous publications.
Experimental results are presented on the excitation of the nucleon isobars N ∗ (1518) and N ∗ (1688) in proton-proton collisions at an incident momentum of 19.2 GeV/ c and in the range of four-momentum squared 0.6 ⩽7 z . sfnc ; t | ⩽ 5.8 GeV 2 .
Axis error includes +- 0.0/0.0 contribution (?////Due to the method used in estimating the area under the peak).
Axis error includes +- 0.0/0.0 contribution (?////Due to the method used in estimating the area under the peak).
Axis error includes +- 0.0/0.0 contribution (?////Due to the method used in estimating the area under the peak).
A systematic search for exotic states produced in K − d interactions at 3 GeV/ c is reported. From the analysis of the mass spectra of strange mesons, non-strange mesons, hyperons with S = −1 and S = −2, upper limits for the production cross sections of exotic resonances may be placed at one or two orders of magnitude smaller than for the production of normal resonances of same strangeness and baryon number.
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The results of the experiment searching for quarks with charge − 1 3 and 2 3 produced by 70 GeV protons on an aluminium target at zero angle are reported. For the selection of quarks the system of spectrometric scintillation counters, time-of-flight spectrometer, gas Cerenkov threshold counter and magnetic spectrometer with spark chambers were used. In the range of masses available at the IHEP accelerator, quarks were not found. The upper limit estimation of the differential cross-section for quark production with mass ⩽ 5 GeV /c 2− and charge −1 3 is 7×10 −38 cm 2 / ster GeV /c (with 90% confidence level). The total cross-section for quark production with charge −1 3 and mass 4.5–5 GeV /c 2 does not exceed 3×10 −39 cm 2 .
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