A. Borg

Inclusive K∗−(890) and K∗0(890) production in 14.3 GeV/c K−p interactions

Results on the inclusive reactions K−p → K∗−(890) + X+ and K−p → K∗0 (890) + X0 at 14.3 GeV/c are presented. A comparison is made with previous data and with the reaction K−p → K0 + X at 14.3 GeV/c. Predictions of a triple-Regge model for the variation of the unnatural and natural parity exchanges with the mass of the X system are examined. The experimental values of the structure functions are compared with those calculated from a quark model.

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.

Partial-wave analysis of the Q region in the reactions K−p → K−π+π−p and K−p → K0π−π0p at 14.3 GeV/c

We have studied the reactions K−p → K−π+π−p and K−p → K0π−π0p at 14.3 GeV/c using respectively 15 992 and 3723 events. Partial-wave analysis of the region 1.0 < m(Kππ) < 1.7 GeV have been made using a modified version of the method developed at the University of Illinois. n nWe have measured the cross section as a function of mass for each spin-parity state of the Kππ system. Results from the two reactions are in excellent agreement and indicate an overall isospin of 12. n nWe find that the Q enhancement is predominantly JP = 1+ but that the partial-wave substates have very different branching ratios into Kϱ and K∗π, the K∗π component of the 1+ state being similar to the 1+ state of the 3π system produced in the reaction πp → (3π)p.

Some 0−12+ and 0−32+ final states in K−p reactions at 14.3 GeV/c

We present data on K−p reactions leading to the final states K0n, π0Λ, ηΛ, ηΛ, π−Σ+, K0Δ0(1230), and π−Σ+ (1385) from a bubble chamber experiment at 14.3 GeV/c K− lab momentum. Total and differential cross sections, Λ and Σ∓ polarisations in π0Λ and π−Σ+ final states as well as the Σ+(1385) density matrix elements are given.

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.

K−p elastic scattering at 14.3 GeV/c

Results are presented on elastic scattering of 10.1 GeV/c K− mesons on protons, based on a sample of 16 261 kinematically-fitted bubble-chamber events. The differential cross section is given over the |t|- range of 0.06 to 2.5 GeV2 and is fitted with the expressions a ebt, A eBt+Ct2 and (P eQt+ReSt) over various intervals of t. The results are compared with those of other experiments at nearby energies. Upper limits of |α| < 0.28 and σB < 0.4 μb (both at a 90% confidence level) are given for the ratio of real to imaginary part of the forward-scattering amplitude and the backward-elastic-scattering cross section, respectively.

Lambda polarization in the reaction K−p → Λ + anything at 14.3 GeV/c

New results on inclusive lambda polarization in K−p interactions at 14.3 GeV/c are presented. At the kaon fragmentation vertex, the polarization is compared to that from inclusive experiments at lower momenta and to that from two-body reactions with a Λ. As predicted by the triple-Regge model with Nα (or Nγ) exchange, the polarization is found to be independent of s and MX2/s. In particular it has the same value as that found in the two-body reactions.

Some three-body final states in K−p reactions at 14.3 GeV/c

We present experimental results on a number of K−p reactions at 14.3 GeV/c that have three bodies in the final state. The final states are K−ωp, K−πp, Λπ+π−, ΛK+K−, Λpp, K∗−ωp, Λ(1520)K+K− and Λ(1520) pp. Whenever, with one exception explained by the Zweig rule, there is a K− or a proton in the final state, there is a diffractive-like threshold enhancement in the mass spectrum of the two recoiling particles. These enhancements account for a large fraction of the events in all but the Λπ+π− final state, where they cannot occur, and which is dominated by resonance production. We find evidence for the Q1(1300) decaying into K−ω.

Double diffractive dissociation in the reaction K−p → K− π+ π− nπ+ at 14.3 GeV/c and pomeron factorisation

We present evidence for the double dissociation process K−p → QN12∗ → (K∗0π−)(nπ+) at 14.3 GeV/c. The cross section for this process is of the order of 10 μb. The production differential cross section is steep (for near-threshold excitation masses), as typical of diffractive processes, and exhibits a strong correlation between the production slope and the masses of the dissociated systems. The spin-parity composition and states of the two dissociation systems closely resemble those found in single dissociation, indicating that a common diffraction-like mechanism is responsible for both processes. The mass variations of the differential cross-section slope, the decay angular correlations and the total cross section of the double dissociation component are consistent with the predictions of a factorisable pomeron exchange model.

Inclusive γ production in K− p interactions at 14.3 GeV/c

Abstract Results are presented on γ production in K− p interactions at 14.3 GeV/c. The analysis is based on 2 541 fitted e+e− pairs in a hydrogen bubble chamber. The inclusive cross section for γ production is found to be (54.5 ± 1.8) mb. The average number of γs per inelastic event is 2.93 ± 0.12; it exhibits no strong dependence on charged multiplicity. From the PL and PT2 invariant distributions of the γ, a simple function describing the π° invariant distribution is determined.