At the Bonn 2.5 GeV synchrotron the polarization of the Λ 0 was measured at 40° and 90° for three energies. The kaon was detected with a strong focussing magnetic spectrometer and separated from other particles with the help of a differential liquid Čerenkov counter. The polarization was determined by means of the angular distribution of the decay proton which was measured with a combination of sonic spark chambers and a scintillation counter hodoscope. The typical statistical errors are about 13%. The systematic errors add up to 8%.
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A strong negative transverse polarization P z is found for forward produced lambdas observed in 10 and 16 GeV/ c K − p interactions. This indicates that exchanges of natural spin-parity are dominant in the production process. Using the polarization results, the d σ d u′ distributions for natural and unnatural spin-parity exchanges are derived. For unnatural exchanges, a dip is observed at u ′≅0.3 GeV 2 , which can be explained as a nonsense-wrong-signature zero of the N β trajectory. The value of P z for forward producted lambdas is constant with energy. This is in agreement with the triple-Regge model prediction, as is the fact that P z is constant as a function of M 2 s . The two non-transverse polarization components, P x and P y , have been measured and are found to be consistent with zero for all x values, unlike P z .
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Single-pion production in p p interactions at 9.1 GeV/ c is analysed and cross sections are given. The p lab dependence of the isospin amplitudes is determined by a fit to the world data. The data are also compared with the predictions of a reggeized Deck model. The results and the N π N amplitudes are compared with the results at other energies and with the corresponding N π N amplitudes.
MEASUREMENTS FROM OTHER EXPERIMENTS DOWN TO PLAB = 1 GEV ALSO QUOTED.
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Cross sections have been determined for the inclusive production of vector (ϱ 0 , ω, K ∗ ) and tensor (f, A 2 ± ) mesons in p p reactions at 9.1 GeV/c for both annihilation and non-annihilation processes. Distributions in the Feynman variable x and transverse momentum squared, p T 2 , have been examined for the ϱ 0 , ω and f mesons. The slopes for p T 2 appear to be exponential and decrease with increasing particle mass for both annihilation and non-annihilation reactions, furthermore the slopes have consistently higher values for non-annihilation reactions. Comparisons with other data indicate that the ratio ϱ 0 / π − is independent of antiproton momentum in annihilation processes.
NON-ANNIHILATION EVENTS.
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We present results on inclusive Δ ++ (1236) production in 100 GeV/ c p p interactions. In the region | t | < 1 GeV 2 we find a cross section of 1.29 ± 0.15 mb. Comparisons with pp interactions at high energies show Δ ++ production in pp and p p interactions to be very similar. The decay angular distributions of the Δ ++ are consistent with production predominantly through pion-exchange and the properties of the system recoiling from the Δ ++ are similar to those of real π + p interactions. However, the p π + background is found to show qualitatively similar behaviour. In contrast to the indications of Δ ++ production through pion exchange we also find evidence that events proceeding through diffraction dissociation are more likely to contain Δ ++ than other events. We present results on the forward production of Δ ++ in association with Δ ++ and protons.
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At the CERN intersecting storage ring the inclusive differential cross section [dσdσ]y=1 has been measured for f0, g0, K*0(1420), and K¯*0(1420) production: We obtain 0.58±0.05 mb, 0.09±0.05 mb, 38±15 μb, and 26±13 μb, respectively. The corresponding total inclusive cross sections are estimated to be 2.62±0.26 mb, 0.40±0.22 mb, 154±60 μb, and 107±52 μb, respectively. The magnitude of the K* cross section implies a cross section of approximately 5 μb for production of a charmed DD¯ pair.
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The polarization of the Σ+ has been measured for the line-reversed reactions π+p→K+Σ+ and K−p→π−Σ+ at 7 and 11.6 GeV/c using the SLAC Hybrid Facility. Since the Σ+ decay is observed in the bubble chamber, the trigger of the flash lamps on a fast K+(π−) did not bias the polarization measurements. We find that the Σ+ polarizations from the two reactions have opposite signs but similar magnitudes and are in much better agreement with the predictions of weak exchange degeneracy than previous lower-energy comparisons.
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Polarization of the scattered Λ has been measured in the reaction Λ+p→Λ+p. A total of 90 000 elastic events was recorded. Polarization was observed which decreased in magnitude with increasing momentum. For 0.1<~|t|<~0.4 GeV2 the polarization is P=−0.21±0.07 for p=110 GeV/c and is +0.01±0.04 at p=320 GeV/c. Results for 860 Λ¯−p elastic scatterings are also presented.
90000 ELASTIC EVENTS.
860 ELASTIC EVENTS.
Results on the protron structure function, F2, are presented for 0.3<q2<80.0 GeV2 and 10<ν<200 GeV. The results support the conclusions of earlier work at 97 and 147 GeV that scaling is violated. A new value for R=σSσT=0.44±0.25 has been obtained using all the Fermilab proton measurements.
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Measurements of inclusive scattering in the target-fragmentation region are extended to higher incident energy. The combined data set shows departures from an approach to the asymptotic scaling limit as A+Bs−12 that are significant even at the highest energies. When these departures are taken into account, the data approach a limit that is consistent with equal cross sections induced by particles and antiparticles and with Pomeron factorization. The corrections to A+Bs−12 are so large that detailed tests of Mueller-Regge relationships are not conclusive.
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