Juan Antonio Rubio

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.

Inclusive production of non-strange mesons in pp annihilations

Abstract A study of the inclusive production of π − , η , ϱ 0 , ω ad f mesons in p p annihilation at 0.7 GeV/ c is presented. Topological and channel cross sections are determined. Longitudinal and transversal momentum distributions of non-strange mesons are studied. It is deduced that nearly 48% of all negative pions arise from the decay of η , ϱ 0 , ω and f mesons.

Inclusive production of K∗±(892) and KS0 in pp annihilations at 0.76 GeV/c

The production of K∗±(892) and KS0 are studied in pp annihilations at 0.76 GeV/c. Longitudinal and transverse momentum distributions are presented. The ratio σ(K∗+)σdir(K0) is found to be 0.09 ± 0.09, where σdir(K0) refers to kaons which do not arise from decay of the resonances. The ratio of strange to non-strange directly produced vector mesons is Kdir∗+ϱdir0 = 0.054 ± 0.005, compared to the corresponding ratio for the pseudoscalar mesons Kdir0πdir− = 0.021 ± 0.003. It is deduced that (50±5)% of all KS0 are indirectly produced through the decay of the meson resonances and consequently (50±5)% are directly produced.

φ and ω meson production in pp annihilations at 0.70–0.76 GeV/c and the OZI rule

Abstract The production of the φ and ω mesons has been studied in the reactions p p → φ(ω)π + π − and p p → φ(ω) ϱ 0 at 0.70–0.76 GeV /c . The c.m. angular distribution of the φ meson in the reaction p p → φπ + π − is found to be consistent with isotropy. The corresponding distribution for ω is not. the ratio σ( p p → φπ + π − ) σ( p p → ωπ + π − ) is (10 ± 2.4) · 10 −3 , which leads to a value of (19 ± 5) · 10−3 when corrected for the phase-space factor. Implications of this result for the OZI rule are discussed.

Properties of pp annihilations into strange particles at 702 and 757 MeV/c

Abstract p p annihilations, leading to the production of at least one neutral K meson in the final state, have been studied in the incident momentum region of 700–760 MeV/ c . Topological cross sections and cross sections for the various exclusive final states are presented. Detailed analyses of the different final states have been carried out to study the importance of resonance production and of quasi two-body and quasi three-body processes. A detailed study of the K K π system in the four-body final states shows that the F 1 meson is a spurious effect due to systematic biases. In the momentum range investigated, the C = +1 final states are strongly suppressed.

Study of the D(1285) and E(1420) resonances produced in pp annihilations at 700–760 MeV/c

In this paper we have investigated the properties of the D(1285) and E(1420) meson resonances using the five-body annihilation channels pp → KKπππ obtained in a large statistics experiment (28 events/μb). The analysis favours the 1+ spin-parity assignment for the D(1285) meson. The dominant decay mode of the D(1285) into KKπ is found to be δ(970)π. The situation concerning the E(1420) meson remains confused although not inconsistent with previous analyses. Partial cross sections on resonance production are also presented.

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}