a Study of the Strange Meson Spectrum as Observed in the Reaction Negative Kaon Proton to Neutral Kaon Positive Pion Negative Pion Neutron at 11 Gev/c
The results of a high statistics study of the reaction K('-)p (--->) (')K('0) (pi)('+)(pi)('-)n are presented. The data derive from a 4 event/nanobarn exposure of the LASS (Large Aperture Superconducting Solenoid) spectrometer to an 11 GeV/c K('-) beam. The (')K('0) (pi)('+)(pi)(' -)n event sample consists of 34,000 events with (')K('0) (pi)('+)(pi)('-) invariant masses less than 2.4 GeV/c('2) and (VBAR)t'(VBAR) (LESSTHEQ) 0.3 (GeV/c)('2). The forward-produced (')K('0) (pi)('+)(pi)('-) events arise predominantly through the production and subsequent strong decay of natural spin-parity strange meson states (J('P) = 1('-), 2('+), ...). Their production can be understood in the context of an exchange model, while their decay into the (')K('0) (pi)('+)(pi)('-) final state proceeds through intermediate two-body states such as K*(892)(' -)(pi)('+), (')K('0)(rho)(770)('0), K*(1430)('-)(pi)('+), and (')K('0)f(1270)('0). A partial wave analysis employing the three-body isobar model successfully describes all of the features of the data. The J('P) = 1('+), 2('+), and 3('-) partial waves show resonant behavior that is attributed to the production and decay of the 1('+) Q(1400), the 2('+) K*(1430), and the 3('-) K*(1780). The structure in the 1('-) amplitudes can be understood as arising from two vector states, one at (TURN)1.42 GeV/c('2) coupling only to K*(pi) and the other at (TURN)1.73 decaying to both K*(pi) and K(rho). The J('P) = 4('+) waves, required above a mass of 2.0 GeV/c('2), show structures that may arise from the production of the 4('+) K*(2060). There is a second enhancement in the J('P) = 2('+) waves at (TURN)2.0 GeV/c('2) that may be evidence for a new resonant state. The t' dependences of the 2('+), 3('-), and the higher mass 1('-) partial waves are steep, whereas the t' dependence of the 1('-) amplitude at low mass is shallow. This indicates that the lower mass 1('-) state, unlike the other natural spin-parity resonances, does not couple strongly to the K(pi) system. The observed properties of these resonant states can be used to test and further develop models of the strange meson spectrum. The implications of these data for the most successful of these, the non-relativistic quark model, are discussed.
- Pub Date:
- ELEMENTARY PARTICLES;
- PARTIAL WAVE ANALYSIS;
- Physics: Elementary Particles and High Energy