Amplitude analysis of reaction K+n

Abstract

We present a model-independent amplitude analysis of the reaction {ital K}{sup +}{ital n}{sub {up arrow}}{r arrow}{ital K}{sup +}{pi}{sup {minus}}{ital p} at 5.98 GeV/{ital c} using Saclay data obtained with a transversely polarized deuteron target at the CERN Proton Synchrotron. The analysis makes use of the data in two sets of binnings to examine the dependence of amplitudes on momentum transfer {ital t} ({minus}{ital t}{le}1.0 (GeV/{ital c}){sup 2}) in the {ital K}{sup *0} mass region, and their dependence on {ital K}{sup +}{pi}{sup {minus}} invariant mass below 1000 MeV for momentum transfers {minus}{ital t}=0.2--0.4 (GeV/{ital c}){sup 2}. The analysis is performed in both {ital t}-channel and {ital s}-channel helicity frames of the dimeson state. The data yield two solutions for 8 moduli and 6 cosines of relative phases of nucleon transversity amplitudes with dimeson spins {ital J}=0 ({ital S} wave) and {ital J}=1 ({ital P} wave). The two solutions differ mainly in the contributions of the {ital S} wave. Both solutions require nonzero nucleon helicity-flip amplitudes. The differences in the moduli of the amplitudes with a recoil nucleon transversity up'' and down'' reveal the essential role of nucleon spin in the pion production process. The {ital P}-wave moduli show unexpected structures withinmore » the {ital K}{sup *0} mass range which provide new information on {ital K}{sup *0} production. The mass dependence of solution 2 suggests the possible existence of a scalar state {ital I}=1/2 0{sup +} (887) with a width of about 20 MeV. We comment on its possible constituent structure. Our results emphasize the need for a systematic study of pion production on the level of amplitudes in a new generation of dedicated experiments with spin at the recently proposed advanced hadron facilities.« less