Comparative study ofρ0,ω,K*0(890), andK¯*0(890)production by charge-exchange reactions

Abstract
We present cross sections and density-matrix elements from a high-statistics study of the reactions πpρ0n, KpK¯*0(890)n, and K+nK*0(890)p, at 3, 4, and 6 GeV/c and four-momentum transfer squared to the recoil nucleon t<~0.9 GeV2. The experiment was carried out at the Argonne Zero Gradient Synchrotron using the effective-mass spectrometer. In the same experiment, we have measured the ρω interference cross sections by comparison of the two reactions πpππ+n and π+nπ+πp, to which the interference terms contribute with opposite signs. We examine the systematics of ρ0 production: In the s channel we find little shrinkage with energy of the helicity-0 cross sections, which are presumably dominated by π exchange; the helicity-1 cross sections exhibit considerable shrinkage for unnatural-parity exchange, and antishrinkage for natural-parity exchange. The K*0 and K¯*0 production observables exhibit significant differences, especially in the helicity-1 states. These differences are due to interference between even- and odd-G-parity exchange amplitudes and they are related by SU(3) symmetry to ρω interference effects and to the ρ0 and ω production observables. It is shown that exchange-degeneracy-breaking effects satisfy SU(3) symmetry and can be explained qualitatively in the frame-work of SU(3)-symmetric, strongly absorbed Regge-pole models. The results of our amplitude analysis are compared with previous phenomenological analyses and model predictions.