Amplitude analysis of reaction K+n↑→K+π-p at 5.98 GeV/c

We present a model-independent amplitude analysis of the reaction K+n↑→K+π-p at 5.98 GeV/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 t [-t≤1.0 (GeV/c)2] in the K*0 mass region, and their dependence on K+π- invariant mass below 1000 MeV for momentum transfers -t=0.2--0.4 (GeV/c)2. The analysis is performed in both t-channel and 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 J=0 (S wave) and J=1 (P wave). The two solutions differ mainly in the contributions of the 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 P-wave moduli show unexpected structures within the K*0 mass range which provide new information on K*0 production. The mass dependence of solution 2 suggests the possible existence of a scalar state I=1/2 0+ (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