Comparison of the reactions K ±p→Q ±p at incident momentum 8.25 GeV/ c

Abstract

In this paper a comparison of the general features of the reactions K ±p→Q ±p (1) at incident momentum 8.25 GeV/ c is presented. The relevant data derive from events yielding four-constraint fits to the reactions K ±p→K ± π + π −p in exposures of the CERN 2m HBC to RF-separated K + and K − beams. The (K ππ) effective mass distributions, production angular distributions in the Q region (1.2⩽ M(K ππ)⩽1.5 GeV) and corresponding decay angular distributions are exhibited, and background effects due to N ∗ and Δ production are systematically studied. In particular, it is found that the distributions d σ/d t′ and d σ/d t for reactions (1) are adequately described by exponential functions over the interval 0.05–0.35 GeV 2, and exhibit a cross-over effect for momentum transfer squared −0.1 GeV 2. For both reactions a flattening of d σ/d t′ for t′ < 0.05 GeV 2 is observed. By studying the Chew-Low plots and the effects of the different cuts it was found that this flattening cannot be attributed to amplitudes with net s-channel helicity flip different from zero, at least at these energies.