I. Sjögren

Observation and quantum numbers determination of the E(1420) meson in π−p interactions at 3.95 GeV/c

In a high statistics (90 events/μb) bubble chamber experiment, the reactions π−p→Ks0K±π∓n have been studied at 3.95 GeV/c. A significant enhancement is observed in the (KKπ) system which we attribute to the production of the E(1420) meson. For its mass, M, and width, Λ, we find M=1426±6 MeV and Γ=40±15 MeV. The E(1420) quantum numbers are determined to be IGJP=0+1+ with a branching ratio E→K∗ K+c.cE→[δπ+(K∗ K+ c.c.)]=0.86±0.12, where δ→KK. The cross section for the reaction π−p→En, with E→K0K±π±, is 8.2±1.0 μb. Forward and backward productions are observed in the approximate ratio 2:1. The SU(3) assignment of the E(1420) meson is discussed.

Study of hypercharge exchange reactions of the type 0−1/2+→2+1/2+ at 4GeV/c

AbstractResults are presented for the quasi two-body hypercharge exchange reactions of the type 0−1/2+→2+1/2+:

Study of the reactionsπ−p→K0∑0(1385) andπ−p→K+∑−(1385) at 3.95 GeV/c

\begin{gathered} \pi ^ - p \to K^0 (1420)(\Lambda ,\sum ^0 ), \hfill \\ K^ - p \to f^0 (1270)(\Lambda ,\sum ^0 ), \hfill \\ K^ - p \to f\prime (1515)(\Lambda ,\sum ^0 ), \hfill \\ \end{gathered}

E. Meson observation in π−p interactions at 3.95 GeV/c

using data from two high statistics bubble chamber experiments. The total and differential cross sections are presented and compared with those obtained for the corresponding vector meson reactions and with simple phenomenological ideas.

A partial wave analysis of the (Kππ) system in the reaction π−p→(K+π−π0)Λ at 3.95 GeV/c

Q-meson production is studied in the hypercharge exchange reaction π-p → (Kππ)Λ at 3.95 GeV/c by selecting events witht(π- →Kππ)>1.2GeV2. An enhancement with a mass of 1294±10 MeV and a width of 66±15 MeV is observed in the (Kππ) mass distribution. A spin-parity analysis of the (Kππ) decay Dalitz plot shows the enhancement to be in theJP=1+S(Kϱ) wave and is therefore attributed toQ1-meson production. No evidence is found for the decayQ1→K0ω but limited statistics allow only placing an upper limit of 30% for the decay ratioKω/Kϱ0. TheQ1 production cross section fort(π- →Kππ)>1.2GeV2 is 8±1.3 μb. No evidence is found for the process π-p→Q2Λ withQ2→K*π for which the partial wave analysis gives an upper cross section limit of 2.5 μb at the 95% confidence level.

Study of theKs0Ks0 system produced in the reactionπ−p→Ks0Ks0n at 3.95 GeV/c

The reactionsπ−p→K0∑0(1385) andπ−p→K+∑−(1385) are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to approximately 90 events/μb. The total and differential cross sections and the density matrix elements of the Σ(1385) are presented. The results are compared with those obtained for the related processesπpp→K+∑+(1385) and\(K^ - p \to \pi ^ \mp \sum ^ \pm (1385)\) in this energy range. Evidence is presented for the existence of production mechanisms with exotic exchanges in thet channel.

Study of the Reactions

The reactionπ−p→Ks0Ks0n is studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to 90 ev/μb. We measure the cross section of the reactionπ+π−→Ks0Ks0n in theS*(990) region and find an elasticityη00≃0.6. The isotopic spin and production properties of theS wave in the 1.3 GeV region are discussed.

\pi^- p \to K^0 \Sigma^0(1385)

Evidence for the E meson production in the reactions π−p→K0K±π n (σ = (8.2±1.0)μb) is presented. The mass and width of the meson are M = (1426±6)MeV and Γ = 40±15 MeV. Our analysis shows that the quantum numbers are, most likely, IGJP = 0+1+. The favoured decay mode is E→K*K+ c.c.