About 10 000 two-prong events of 8.1 GeV/ c proton-proton interactions in the CERN 2 m. bubble chamber have been analyzed. We study elastic scattering and single-pion production reactions. We give cross sections for isobar production. We attempt to interpret the general features of the pp→pn π + reaction by the Deck mechanism. We compare the production and the decay of δ ++ (1236) with absorption or π Regge trajectory exchange models.
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The cross section for γp→π−Δ++(1236), measured at 5, 8, 11, and 16 GeV from nearzero momentum transfer to -1 GeV2 (-2 GeV2 at 16 GeV), rises from small t to a maximum near −t=mπ2, then falls as e12t out to −t≈0.2 GeV2, after which it becomes roughly equal in slope and magnitude to the single π+ photoproduction cross section (e3t). At fixed t, the cross section varies as k−2, where k is the laboratory photon energy. The results do not agree well with the simple vector-dominance model.
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We have investigated the photoproduction process γ+p→π++n over a wide range of energies and u values at the Stanford Linear Accelerator Center (SLAC) accelerator. We also have investigated γ+p→π−+N*++ at one value of u and γ+p→K++Λ0, Σ0 at one u value and three energies. Our results for dσdu for the photoproduction of π+ mesons from hydrogen are roughly α2π of the corresponding cross sections for the elastic scattering of π− mesons from hydrogen. The u dependence of our cross sections is not dominated by nucleon exchange as it is in the case of π+p elastic scattering.
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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 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.
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Two groups of measurements have been made on the elastic scattering of electrons by deuterium; in each case we observed the recoil deuteron instead of the scattered electron. In the first case the spectrometer was set at 45° so that magnetic scattering was unimportant (about 10%) and we deduced the electric form factors of the deuteron. In the second case deuterons were observed at 0°, allowing us to measure directly the magnetic form factor of the deuteron. Form factors of the neutron were deduced from these measurements for the transfer values q2=3, 4, and 5 (F−2). Preliminary results were given in a first paper. Here we also include a description of the experimental setup and discuss relativistic and exchange-current corrections.
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We present results on elastic electron-deuteron experiments performed at Orsay. The range of momentum transfers is 0.6 to 2 F−2. Two kinds of measurements have been taken detecting the scattered electron: one with a solid CD2 target, the other with a liquid target. The data are analyzed with the nonrelativistic theory, which gives slightly positive neutron form factors and a magnetic neutron form factor nearly equal to the magnetic proton form factor.
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Approximately 60 000 events have been collected in a spark chamber experiment at the CERN Proton Synchrotron which studied elastic diffraction scattering of π--p and p-p at incident momenta of 8.5, 12.4 and 18.4 GeV/c and of π+-p at 8.5 and 12.4 GeV/c. Magnetic analysis of the incoming and diffraction scattered particle, together with measurement of all angles, permitted each event to be determined as elastic subject to three constraints, so that the inelastic background was rejected with. high efficiency, even at the larger momentum, transfers. Much of the data have been processed by the CERN Automatic Flying-Spot DigitizerHPD. A detailed description of the experimental technique and of the methods of analysis is given. The results, together with data from lower energies, confirm the remarkable energy-independence of the shape of the pion-proton diffraction scattering peak up to |t| = 1.5 (GeV/c)2, wheret is the square of the four-momentum transfer, over a range of pion energies from 2 to 18 GeV. Proton-proton scattering does however appear to show a shrinking diffraction peak. In general, the data agree with other experiments using both counter and bubble chamber techniques, but some differences do appear. During the experiment, data were taken which set an upper limit of 2·102 μb/(GeV/c)2 on the differential elastic cross-section dσ/dt over a range of |t| from 20.9 to 23.4 (GeV/c)2 at 13.4 GeV/c incident pion momentum.
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