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At this conference everyone was looking forward to the first results from PETRA, the new e+estorage ring at DESY, which started operating only a few months before. Data have been taken at 13 GeV, 17 GeV and, ve­ ry recently, at 27.4 GeV. The total ha­ dronic cross-section has been measur­ ed by three different groups and, within the large experimental uncertainties, they consistently find no evidence for any “step” which could indicate the appearence of a threshold for the pro­ duction of a new quark. The hadronic jets that are assumed to arise from the fragmentation of the quark pairs that are produced, have been studied in detail. The measured properties of these jets (thrust, sphericity, etc.) are well explained by assuming that five quarks (u, d, s, c and b) are involved, and the authors claim that the inclu­ sion of a sixth quark (t) of electric charge 2/3 and large mass, would pro­ duce a much poorer fit. Contrary to the hopes of many physicists, no evi­ dence has been found for the produc­ tion of tt pairs up to energies of 27.4 GeV. The existence of this sixth quark is required in the standard WeinbergSalam model of the weak and elec­ tromagnetic interactions, in order to complete a third generation of elemen­ tary fermions, together with the bquark and the -lepton, but there are no firm predictions on its mass. A slight excess of events with large sphericity has been found, which could be interpreted as being due to gluon radiation, while a few events with a three-jet configuration have been re­ ported, in qualitative agreement with the expectations from quantum chro­ modynamics. Beautiful results have been obtain­ ed from the study of the hadronic jets on the Y (9.4) resonance. The pattern of the hadronic energy flow looks very different from that off resonance and the distributions in several variables (thrust, sphericity, triplicity, etc.) are inconsistent with a pure phase-space effect. Instead, all these distributions are well fitted by assuming that the Y particle decays into three gluons, giving rise to three hadronic jets. The­ se results are quite impressive since the decay of the Y into three gluons is a rather unique prediction of quantum chromodynamics. With regard to the charmonium fa­ mily, the previously reported  c (2820) bound state has not been seen in a more accurate experiment, recently performed at SPEAR (SLAC). The recent data on the neutral cur­ rent weak interactions are all in nice agreement with the “standard”, or “minimal” , Weinberg-Salam model for the unification of the weak and electromagnetic interactions (hereafter denoted by W-S). The high statistics and good precision which have been achieved in the experiments with the CERN neutrino beams, have given a significant improvement in the deter­ mination of the only parameter in W-S (the Weinberg angle). New data have been reported from a difficult experi­ ment performed at SLAC on the parity violation in the deep inelastic scatter­ ing of polarized electrons from deute­ rium, which are perfectly consistent with the W-S predictions. A recent measurement of parity violation in ato­ mic transitions which has been per­ formed at Novosibirsk (and at Berke­ ley, with larger experimental uncer­ tainties) seems to agree with the ex­ pectations from W-S, contrary to some previous experiments. Altogether, the large variety of data which are now available allows a model-independent analysis to be made of the weak neutral current. The results of such an analysis are well described by W-S and tend to exclude many proposed alternatives. As for the neutrino charged current deep inelastic interactions, the high statistics experiments (essentially tho­ se performed at CERN) have been analyzed in terms of the quark and gluon distributions inside the nu­ cleons. Quantitative comparisons of the scaling violation observed in these structure functions, with the predic­ tions of quantum chromodynamics ha­ ve been attempted but the situation does not look conclusive yet. However, interesting information has been ex­ tracted from the data on the momen­ tum distribution of the gluons inside the nucleon. A striking discovery has been re­ ported from a CERN experiment, with a beam, where the  /J particle is

EPS International Conference on High Energy Physics, 27 June - 4 July