C. Louedec

Study of the Kππ system produced in K−p → KππN reactions at 14.3 GeV/c

We have studied the Kππ system in the 14.3 GeV/c reactions K−p → K−π+π−p, K−p → K0π−π0 and K−p → K0π+π−n. The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (Kππ) ∼ 1.75 GeV. The reaction cross sections are compared to K−p data at other energies. We discuss the Kππ mass dependence of the diffractive production slope. Evidence is presented for a Q−p versus Q+p differential cross section cross-over around |t| = 0.17 GeV2. A t-channel isospin analysis for the KN → K∗(890)πN channels in the Q-region shows that the I = 1 exchange amplitude is ⋍ 10% of the dominant I = 0 exchange amplitude. The Kππ decay distributions indicate a predominant JP = 1+ state in the Q-region, and an important JP = 2− contribution in the L-region. We find neither s-channel nor t-channel helicity conservation at the meson vertex in the Q- or L-regions. The Kπ angular correlation moments within the Kππ diffractive system are characteristic of Kπ elastic scattering, suggesting a π-exchange Deck-type production mechanism. There is evidence for a Kf0 and κπ contribution (where κ is the JP(Kπ) = 0+ state) to the diffractive Kππ system. A fit to the K−π+π− and K0π−π0 Dalitz-plot distributions for the Q-re gion indicates that the ratio of Kϱ to K∗π decay amplitudes decreases with increasing Kππ mass.

Inclusive production of charged and neutral sigma hyperons in K−p interactions at 14.3 GeV/c

Abstract Inclusive production of Σ + , Σ − and Σ 0 hyperons in K − p interactions at 14.3 GeV/ c has been studied and compared to Λ production. Cross sections are presented as a function of longitudinal and transverse momenta and compared to the pp → Σ + + anything data.

K−π− elastic scattering cross section measured in 14.3 GeV/c K−p interactions

Results are presented on a measurement of the I = 3/2 Kπ elastic scattering cross section by applying the Chew-Low extrapolation method in the reaction K−p → K−π−Δ++at14.3GeV/c. The magnitude of σ(K−π− → K−π−) is found to be about 3 mb at threshold and slowly falling with energy to about 1.5 mb at 2.8 GeV. The off-mass-shell moments of the differential elastic cross section are given. The absolute value of δ30 is found to be increasing slowly from 0° to 20° between threshold and 1.2 GeV.

Inclusive production of Y∗ resonances in K−p interactions at 14.3 GeV/c

The inclusive production of Σ+(1385), Σ−(1385), Λ(1405) and Λ(1523) in K−p interactions at 14.3 GeV/c is studied. Cross sections are presented and the x dependence of the invariant cross sections is discussed. The density matrices for production of the spin-32 resonances at small momentum transfer to the target are consistent with spin-0 exchange.

Inclusive pion and eta production in K−p interactions at 14.3 GeV/c

Abstract The inclusive cross sections for π − , π 0 , π + and η production in K − p interactions at 14.3 GeV/ c are calculated. The invariant cross section distributions are presented and compared in the whole phase space for π + and π 0 , and in the backward c.m. region for π − . In the fragmentation regions, the charged pion production is analysed in terms of the triple-Regge model.

Evidence for double dissociation in K-p interactions at 14.3 GeV/c

We have studied the reaction K-p → K-π+π-π+π-p at 14.3 GeV/c to search for evidence of the double dissociation process K-p → QN12∗. In the channel K-p → K∗0 (890)π1-π2-Δ++ (1236) there is evidence for simultaneous production of low-mass enhancements in the K∗0π1- and Δ++(1236)π2- subsystems which correspond to the Q → K∗ (890)π and N12∗ → Δπ decay modes. In this particular final state the double fragmentation system is produced with a cross section of the order of a few microbarns. Our data are consistent with the factorizable pomeron exchange model of double diffractive dissociation.