A measurement of the ratio of the magnetic form factor of the neutron to that of the proton has been carried out by comparing large- and small-angle elastic electron-deuteron scattering at constant four-momentum transfers. The experimental result for the average value of the ratio in the range of momentum transfers from 1.6 f−1 to 2.25 f−1 is F2nFp=(0.91±0.05)±0.07; the first error is a standard deviation arising from experimental uncertainties, and the second from theoretical uncertainties in the analysis. Measurements of the ratio of the nucleon isotopic scalar form factors have also been obtained from this experiment. The average value of F2sF1s for the same range of momentum transfers has been found to be (+0.06±0.09) ±0.13. The small-angle scattering data have been used to determine the charge form factor of the deuteron in the range of momentum transfers from 0.98 f−1 to 2.8 f−1. The results are consistent with a repulsive-core model of the deuteron.
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We have studied the process p¯p into π+X− using wire spark chambers. The data cover the angular range of cosθp¯π+* between 0.96 and 1.0 at several incident momenta between 1 and 2 GeVc. The reaction p¯p→π+ρ− was observed with (dσdΩ)* of the order of 100 μb/sr at several momenta.
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From a bubble chamber exposure in an antiproton beam at 5.7 GeV/ c yielding 13 events/μb, the final states p ̄ p → Y 1 ∗+ (1385)Λ, Y 1 ∗+ (1385)Σ + , Y 1 ∗+ (1385) Y 1 ∗+ (1385) have been isolated. We have measured the total cross section, d σ /d t , and the complete density matrix of the Y ∗ for these processes. Upper limits have been set to the forbidden reactions p ̄ p → Y 1 ∗− (1385)Σ − , Y 1 ∗− (1385) Y 1 ∗− (1385) .
VALUE OF PRODUCTION CROSS-SECTION IN TEXT HALVED AS INCLUDED CHARGE CONJUGATE REACTION.
VALUE OF PRODUCTION CROSS-SECTION IN TEXT HALVED AS INCLUDED CHARGE CONJUGATE REACTION.
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Data are presented which firmly establish the existence of the double charge exchange reaction p p → Σ − Σ − at 3.6 GeV/ c . The forward cross section was found to be (5.9 ± 1.1) μb and the ratio of the “forbidden” to “allowed” forward cross section is R = σ( Σ − Σ − σ( Σ + Σ + ) = 0.09 ± 0.02 .
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Pions from the reaction γ + p → π + + n were analysed in the backward direction by a magnetic spectrometer. The photon energy region of 0.394 GeV to 1.397 GeV was covered by 19 different momentum settings. Data reduction resulted in 74 measured differential cross sections with statistical uncertainties typically from 4% to 8%. The systematic uncertainty was estimated to be ±5%. The data are compared to other recent experiments and predictions of phenomenological analyses.
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From 63 760 four pronged events we have selected 10 960 events of the p p π + π − final state. We have studied baryon resonances production and the associated production of Δ(1236) Δ (1236) isobars. We find (48.5 ± 2.6)% of Δ ++ Δ ++ and (4.5 ± 0.5)% of Δ 0 Δ 0 . Study of the various mass spectra shows that they are essentially described by the introduction of Δ ++ ( Δ ++ ) production. Introduction of the strong t dependence of the Δ ++ ( Δ ++ ) changes this description only slightly. A study of the interaction radius of the p π system reveals a best value of r = 1.6 ± 0.4 fm. Bumps observed in the p π + π − + c.c. system at 1450 and 1690 MeV when treated as resonances give rates of (4.0 ± 0.4)% and (4.5 ± 0.4)% respectively. We arrive at the conclusion that the reaction p p → p p π + π − at 5.7 GeV/ c proceeds almost entirely via the production of baryon resonances.
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A comparison of K±p and p±p elastic scattering is made for incident energy 50 to 175 GeV. Average values of 0.19±0.04 and 0.11±0.02 GeV2 were found for the invariant-momentum-transfer values of the Kp and pp crossover points, respectively.
KP AND PP CROSSOVER POINTS AT -T = 0.19 +- 0.04 AND 0.11 +- 0.02 GEV**2 (AVERAGE VALUES) RESPECTIVELY.
The differential cross sections for the elastic scattering of π+, π−, K+, K−, p, and p¯ on protons have been measured in the t interval -0.04 to -0.75 GeV2 at five momenta: 50, 70, 100, 140, and 175 GeV/c. The t distributions have been parametrized by the quadratic exponential form dσdt=Aexp(B|t|+C|t|2) and the energy dependence has been described in terms of a single-pole Regge model. The pp and K+p diffraction peaks are found to shrink with α′∼0.20 and ∼0.15 GeV−2, respectively. The p¯p diffraction peak is antishrinking while π±p and K−p are relatively energy-independent. Total elastic cross sections are calculated by integrating the differential cross sections. The rapid decline in σel observed at low energies has stopped and all six reactions approach relatively constant values of σel. The ratio of σelσtot approaches a constant value for all six reactions by 100 GeV, consistent with the predictions of the geometric-scaling hypothesis. This ratio is ∼0.18 for pp and p¯p, and ∼0.12-0.14 for π±p and K±p. A crossover is observed between K+p and K−p scattering at |t|∼0.19 GeV2, and between pp and p¯p at |t|∼0.11 GeV2. Inversion of the cross sections into impact-parameter space shows that protons are quite transparent to mesons even in head-on collisions. The probability for a meson to pass through a proton head-on without interaction inelastically is ∼20% while it is only ∼6% for an incident proton or antiproton. Finally, the results are compared with various quark-model predictions.
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We report on the measurement of the reaction e+e−→e+e− with a large—solid-angle electromagnetic shower detector at center-of-mass energies s=13 and 17 GeV. Comparison of our results with predictions of quantum electrodynamics shows excellent agreement in both the angular distribution and energy dependence. Values of cutoff parameters are also given.
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