S. de Unamuno

Measurement of the branching ratios of multi-pion final states in pp annihilation at 1.6 GeV/c

Abstract The final results on the pionic annihilation of 1.6 GeV/ c antiprotons on free protons in the heavy liquid bubble chamber Gargamelle are presented here. Branching ratios of the various channels (including multi-π 0 channels) as well as multiplicity distributions for charged and neutral pions are given which are for the most part compatible with the prediction of the isospin statistical model.

Heavy liquid chamber analysis of ηO → 3π and ηO → γγ decay-modes

Abstract From 199 η O → 3 π O → 6 γ , 526 η O → π + π − π O and 401 η O → γγ events with all γ-rays reconstructed in a heavy liquid bubble chamber, we obtain direct and independent measurements of the branching ratios: R 1 = Γ ( η O → 3 π O )/ Γ ( η O → π + π - π O ) = 1.50 -0.29 +0.15 and R 2 = Γ ( η O → γγ )/ Γ ( η O → π + π - π O ) = 1.72 ± 0.25. We also study the Dalitz-plots for the modes η O → 3π O and η O → π + π - π O , and find no significant variation of the amplitude of the decay η O → 3 π O .

An experimental study of the production of neutral pions in p̄p annihilations at 1.6 GeV/c

Abstract The heavy liquid bubble chamber Garamelle has been used to study the rate of production of neutral pions in the pionic annihilation of 1.6 GeV/ c antiprotons on free protons. Preliminary results are presented on the relative cross-sections for most channels together with the mean π 0 multiplicity and the first moments for annihilation into 0-prongs, 2-prongs, 4-prongs and 6-prongs.

A study of the charge exchange process K+n → Kop at 10 GeV/c

We present a study of the charge exchange reaction K+n → Kop using 10 GeV/c interactions on nuclei. The differential cross section is compared with that of the reaction K−p → Kon. The total cross section is estimated to be 76 ± 13 μ b per nucleon which agrees with the SU3 prediction.

Coherent production of 3 charged pions analysed by means of the longitudinal phase space plot

Abstract We present a study of π + π + π − system produced by 11.7 GeV c π + -nuclei interactions by means of longitudinal phase space analysis. This method has allowed a selection of events produced coherently on nuclei with a reduced background.

An upper limit to the cross section for the reaction νμe-→νμe- at SPS energies

Abstract Candidates for the purely leptonic process ν μ e − → ν μ e − have been searched for in the bubble chamber Gargamelle exposed to the CERN-SPS antineutrino wide-band beam. No single e − , of energy greater than 1 GeV, was found in a total of 230 000 pictures, corresponding to 7400 charged current events. This leads to an upper limit for the observed cross section of σ obs −42 ( E ν − GeV ) cm 2 (90% C.L.). Interpretation of this value in terms of the standard W Weinberg-Salam model yields an upper limit to the mixing parameter sin 2 θ W

A study of 10 GeV/c K+-nucleus coherent interactions and the Q+-nucleon cross-section

Abstract We have studied coherent production of K ππ , Kπππ and Kππππ systems using 10 GeV/ c K + interactions of nuclei. In the K + π + π − channel we observe the Q + enhancement. The Q + -nucleon interaction cross-section is estimated to be 20 ± 8 mb.

An analysis of the K+π+π− system produced in 10 GeV/c K+ coherent interactions on nuclei

The coherent production process K+-nucleus→K+π+π−-nucleus has been analysed at 10 GeV/c, in a heavy liquid bubble chamber. Evidence for a coherent process is obtained from the momentum transfer distribution; the cross section is 2.12 ± 0.36 mb per nucleus. The K+π+π−, mass distribution of the coherent events shows abundant production of the so-called Q+ state, with a cross section of 1.70 ± 0.30 mb per nucleus. A Dalitz plot analysis of the K+π+π− system indicates JP=1+ for the Q+ with a high probability. The predominant decay is K∗π with some contribution of Kϱ. The density matrix elements for Q+ -production have been studied.

Interpretation of the nucleon structure functions measured in the Gargamelle SPS Neutrino/Antineutrino experiment

Abstract The non-singlet part of the nucleon structure functions measured in the Q 2 range 0.5 to 50 (GeV/ c ) 2 is compared to leading and next-to-leading order QCD predictions. The possible contributions of higher twist and target mass effects are also evaluated.