We have measured the production and decay angular distributions of the reaction π + p→ π O Δ ++ at 13.1 GeV/ c incident momentum. For − t > 0.1 (GeV/ c ) 2 the data is well described by M1 ϱ-exchange models, the best results being obtained from a weak cut model with a wrong signature nonsense zero. For − t < 0.1 (GeV/c) 2 there is evidence for the existence of other exchange mechanisms.
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Small angle elastic scattering events have been observed at the CERN Intersecting Storage Rings. Directions of both particles as well as the collision vertex are reconstructed with the help of four sets of spark chambers, two for each of the two arms. The elastic nature of the events is demonstrated by a collinearity requirement. We find values for the (diffraction) slope parameter in disagreement with the simple linear extrapolation of lower energy (Surpukov) data.
NUMBER OF EVENTS 87364.
NUMBER OF EVENTS 8305.
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Polarization and differential cross-section data for elastic scattering of positive pions on protons between 0.82 and 2.74 GeV/ c are presented. A dip in the polarization, at constant u ≈ −0.65 GeV 2 , is observed. The data are compared with published phase-shift analyses.
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Results are presented on elastic scattering of 10.1 GeV/ c K − mesons on protons, based on a sample of 16 261 kinematically-fitted bubble-chamber events. The differential cross section is given over the | t |- range of 0.06 to 2.5 GeV 2 and is fitted with the expressions a e bt , A e Bt + Ct 2 and ( P e Qt + Re St ) over various intervals of t . The results are compared with those of other experiments at nearby energies. Upper limits of | α | < 0.28 and σ B < 0.4 μ b (both at a 90% confidence level) are given for the ratio of real to imaginary part of the forward-scattering amplitude and the backward-elastic-scattering cross section, respectively.
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ERROR INCLUDES STATISTICAL ERROR AND ERROR IN TOTAL CROSS SECTION USED FOR NORMALIZATION. EXTRAPOLATION OF D(SIG)/DT TO T=0 PROVIDES ABOUT 0.5 PCT UNCERTAINTY.
NO BACKWARD EVENTS OBSERVED. LARGEST ANGLE EVENT SEEN WAS AT 64 DEG (-T = 2.33 GEV**2).
Differential cross sections and polarizations have been measured for the reaction π − p → K 0 Λ and π − p → K 0 Σ 0 at 3.9 GeV/ c π − momentum. Comparison of these data with those of the related reactions K − n → π − Λ and K − p → π − Σ + (at approximately the same c.m. energy) indicate that simple Regge-pole models involving only K ∗ (890) and K ∗ (1420) exchange are unable to describe all the features of the data. On the other hand, comparison of the π − p → K 0 Σ 0 data with that of π + p → K + Σ + shows that the data are consistent with absence of exotic strange-meson exchange.
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Data on p p annihilations at rest into K 1 0 K 1 0 ω 0 and K + K − ω 0 are discuss New measurements for the mass, the width and the branching ratio of the ω 0 are presented. Evidence for quasi two-body annihilations p p → ϕπ, p ̄ p → S ∗ π is discussed.
PRODUCTION RATE FOR ANNIHILATION AT REST.
The reaction K + p → K ∗o (892) Δ ++ (1236) has been studied at 3 GeV/ c in both a hydrogen and a deuterium bubble chamber experiment. The production mechanism is described by a Regge-type model using π- and B-exchange. The joint decay distributions are analysed in various frames and compared with quark-model predictions.
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At 3 GeV/ c , the total and differential cross sections of the reactions K − n → Y π − have been determined for nine S = −1 baryonic states. Backward peaks associated with a dip near u = −0.2 are observed in many cases. They have been interpreted, for the isospin-zero Y-states, in terms of a proton-exchange mechanism. The backward peaks in the reactions K − n → Λπ − and K − n → Σ o π − have been more quantitatively related to the backward π N → N π differential cross sections at the same energy. This comparison leads to the conclusion, that the first reaction is dominated by nucleon exchange, whereas the second one requires a more complex exchange mechanism.
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We present an analysis of the K ππ system produced in 10 GeV/ c K + p interactions. We show that the low-mass enchancement between 1.2 and 1.4 GeV/ c 2 on the K ππ mass spectrum is predominantly 1 + throughout, give the relative amplitudes for the decay of this system into K ∗ (890) π and K ρ , and offer new evidence for the presence of two 1 + resonances in this mass region.
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DIFFERENTIAL CROSS SECTION FOR THREE MASS BANDS IN Q-REGION. NORMALIZATION UNCERTAIN - NO UNITS FOR D(SIG)/DT GIVEN ON FIGURE. NUMERICAL VALUES TAKEN FROM THE COMPILATION LST7V2 FOX 72B. ERRORS ADDED AS 1/SQRT(EVENTS).
We present results of measurements of the differential cross sections for the following elastic-scattering reactions: (i) π + p at 5.2 and 7.0 GeV/ c in the range −1 < u < 0.02 (GeV/ c ) 2 , (ii) π − p at 7.0 GeV/ c in the range −0.7 < u < 0.05 (GeV/ c ) 2 , (iii) K + p at 5.2 and 7.0 GeV/ c in the ranges −1 < t < −0.01 (GeV/ c ) 2 and −1 < u < 0 (GeV/ c ) 2 , and K − p at 7.0 GeV/ c in the range −1 < u < 0 (GeV/ c ) 2 .
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SIDE GEOMETRY.
Forum