Future Colliders

Abstract:

The total and differential cross sections of the reactions K^-p → π⁰Λ (1520), ηΛ(1520) and η′ Λ(1520) have been measured. Prominent forward peaks are onserved in all three reactions. The first reaction shows also a backward peak. The spin density matrix elements of the Λ(1520) in this reaction are determined. For forward production the results show a remarkable alignment of the Λ(1520) corresponding to an M2 transition in the model of Stodolsky-Sakurai for 3 2^- baryon production. © 1979.

Abstract:

A partial-wave analysis and an isospin analysis are presented of the (Kππ)^- systems produced in the reactions K^-p→K^-π^-π⁺ and K^-p→K⁰π^-π^-p u sing the high-statistics bubble-chamber data at 4.2 GeV/c. The energy dependence of J^P = 1⁺ waves is investigated in a comparison with results at higher energy. The dominant 1⁺0+ (K^*π) with its maximum in the Q2 (1.4 GeV) region is an almost pure I = 1 2 state. The energy dependence of 1⁺0+ (K^*π) at low masses is consistent with pomeron exchange while at higher masses (including the Q2 region) other natural exchanges are involved. The 1^*1+ (Kρ{variant}) has its maximum at about 1.3 GeV. The relative phase between these two 1⁺ states is consistent with Q1-Q2 contribution to the 1⁺ state. Properties of the Q resonances are obtained in a fit of a two-resonance model to the 1⁺ date. There is no clear evidence for the 0^- resonance seen at SLAC. © 1979.

Abstract:

We have studied the production and decay of the D(1285) meson in the reaction K^-p→ ΛD at an incident K^- momentum of 4.2 GeV/c. The cross section for this reaction is 11 ± 3 μb and the branching ratios D→ KKπ/D → ηππ and D → 4π/D → ηππ are found to be 0.42 ± 0.15 and 0.7 ± 0.5, respectively. The proportion of D → ηπ⁺π^- going through the intermediate δ^±π^∓ states is 0.72 ± 0.15. Forward and backward exchange mechanisms are found to contribute in the ratio 3 : 2. © 1979.

Abstract:

An additive diquark model is proposed to relate the forward cross sections of meson-baryon quasi-two-body reactions. The model consists of a quark-diquark structure for baryons combined with additivity of quark-(di)quark amplitudes. Good agreement is found between this model, which contains only one free parameter, and a large body of experimental data for charge-exchange and strangeness-exchange meson-baryon two-body reactions. This is in contrast to the SU(6)-symmetric additive quark model which disagrees violently with the data. © 1979 The American Physical Society.