A partial-wave analysis has been performed of the diffractively produced low-mass ( K ̄ 0 π − π 0 ) system in the reaction K − p → ( K ̄ 0 π − π 0 ) p at 10 and 16 GeV/ c . Thus information complementary to that derived from the K − p → (K − π + π − )p) channel is obtained. The presence of the K ϱ decay mode, besides the dominant K ∗ (890)π mode, for the state J P = 1 + , is confirmed. It is also confirmed that for this 1 + state the assumption of factorization of the amplitude into “production” and “decay” does not hold: the two decay modes K ∗ π and K ϱ have different polarisation properties (helicity is approximately conserved in the t -channel for the first, in the s -channel for the second). The assumption that the ( K ̄ 0 π − π 0 ) system has isospin I = 1 2 has been tested and found to hold. From the cross sections for the various J P states, assuming I = 1 2 , the cross sections for the (K − π + π − ) system are predicted and compared with the experimental ones. In general, agreement is found.
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A partial-wave analysis has been performed on the (K − π − π + ) system produced in the reaction K − p → K − π − π + p at 10 and 16 GeV/ c . In the Q mass region it is found that the two dominant states, K ∗ π and Kπ, both in 1 + S wave, are produced with different polarisations, helicity being approximately conserved in the t -channel for K ∗ π and in the s -channel for Kπ. This is in contradiction with the assumption that the amplitude can be factorised into “production” and “decay” parts, and hence that the two amplitudes are fully coherent. The phase variation of the two states do not indicate simple resonance behaviour. It is concluded that the Q-mass enhancement is composite.
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The differential cross section d σ d t′ for the charge-exchange process π + p → π 0 ( π + p) at 8, 16 and 23 GeV/ c is presented for several regions of the π + p effective mass. It is found that the dip at t ′ ≈ 0.6 (GeV/ c ) 2 which is observed in the Δ(1236) mass band becomes a less pronounced structure in the higher mass regions. However, while the slope of the d σ d t′ distributions in the near-forward direction decreases strongly with increasing π + p mass, there is no evidence that the observed structure moves to higher values of t ′ as the π + p mass increases. These results are consistent with a Regge-exchange picture where the position of the dip is determined by the exchanged trajectory, but are inconsistent with a simple geometrical picture.
TP DEPENDENCE FOR FOUR <PI+ P> MASS INTERVALS.
We have investigated the pp elastic scattering at the CERN Intersecting Storage Rings (ISR). We report results for centre-of-mass scattering angles between 30 and 100 mrad and for centre-of-mass energies of 23.5,30.7, 44.9 and 53 GeV. The elastic differential cross-section shows a diffraction-like shape with a sharp minimum at about t = −1.4 GeV 2 .
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A sample of 43000 two-prong events obtained at a momomentum of 11.7 GeV/c is used to determine the cross-sections of the fitted channels, and to study the reaction π+p→π+pπ0. We investigate in particular the quasi-two-body channels π0Δ++ and ρ+p.
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New results are presented on the reaction π+p→η0Δ++ between 1.2 and 2.67 GeVc. The data above 2 GeVc, when combined with some existing data, give evidence for a dip in the t distribution near t=−1.5 (GeVc).2 This dip, and other features of the data, are adequately described by an A2 Regge-pole model. The effective A2 trajectory is calculated and found to disagree with that obtained from the reaction π−p→η0n.
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