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[en] Following a description of the PLUTO detector and its operation at PETRA, four major topics are addressed: (1) QED violations in Bhabha scattering and e⁺e^- → μ⁺μ^-; (2) e⁺e^- hadron production and the search for the top quark; (3) evidence for gluon bremstrahlung; and finally (4) first results on hadron production in two-photon interactions

[en] JADE and the other PETRA experiments have recently completed a scan to the highest available e⁺e^- center-of-mass energies (46.8 GeV) as part of the search for toponium. There was no evidence for production of a standard charged 2/3 top quark, and an upper limit was derived for the leptonic width times hadronic branching ratio of such a resonance (GAMMA/sub ee/B/sub h/ < 1.9 keV at the 95% C.L.). Mass limits were also derived for the production of composite scalar bosons. Other important results from the JADE collaboration include a new (preliminary) measurement of the B lifetime (tau/sub B/ = 1.8 +/- 0.5 +/- 0.3 psec), and measurements of the b and c quark electroweak charge asymmetry. Finally, a measurement has been made of the two photon radiative width of the eta meson using the JADE detector operating at PETRA. The reaction studied was e⁺e^- → e⁺e^- eta (eta → γγ). For an e⁺e^- luminosity of 14.65 pb^-1, the event sample of eta's after background subtraction was 220.8 +/- 14.8 +/- 16.8 events

[en] Preliminary experimental results of collective ion acceleration using a linear beam from the University of Maryland Electron Ring Accelerator injector are presented. Neutron yield of 10⁹ neutrons/pulse from Cu(p,n)Zn reactions are observed. From the Q value of the reaction, the energy of the proton must be above 4 MeV. The number of protons per pulse is estimated to exceed 10¹³. (auth)

[en] Acceleration of ions by intense relativistic electron beams in an vacuum was studied using the injector of the Maryland ERA. Effects of floating electrodes and an impressed axial magnetic field were investigated. Maximum proton energies above 16 MeV and proton beam currents of 12 kA were obtained. An impressed axial magnetic field of 1.8 kilogauss resulted in focused proton beams less than 1 cm in diameter

[en] First, the PLUTO detector, which has recently been improved for the γγ detection, is presented. The central magnetic field is 16.5 kG, and the momentum is measured with sigma (p)/p = 8 % . p(GeV/c). The central detector region has a good shower counter coverage down to theta = 15 deg. Tracking and muon coverage are down to theta = about 30 deg. The forward spectrometer has the theta angle coverage of 4.9 - 14.9 deg, and it can analyze 40 -- 50 % of particles from γγ - multihadrons. It can also identify electrons, hadrons below 1 - 2 GeV/c and muons having momentum over about 1 GeV/c. The shower counter placed before the quadrupoles, which are at distance of 4.4 m form the interaction point, detects electrons with theta = 1.6 - 4.3 deg. This PLUTO detector will be further improved to complete its transformation into a modern state-of-the-art detector, and will be installed in PLUTO after the 1982 run in preparation for the next PETRA run. Second, a new γγ detector is proposed, based on the following criteria: good solid angle coverage, compactness and optimization for the detection of single photon annihilation events. The angular coverage of this detector is theta = 6 - 90 deg. A central detector of jet chamber type has a 15 kG magnetic field, and enables a momentum precision of sigma (p)/p = 3% . p(GeV/c) and a dE/dx precision of about 18 % (FWHM). This detector would carry out electron identification with a liquid argon counter and dE/dx measurement. The practicality of this new detector remains to be demonstrated. (Ito, K.)

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[en] Two collective ion acceleration schemes are being studied at the University of Maryland: (a) the electron ring method (ERA) and (b) collective acceleration with linear beams. In the ERA, a hollow, axially moving (β /sub z/ approximately 0.2) electron beam is formed by the cusp method. This beam is to be stopped for ion loading by resistive wall interaction and a fast magnetic mirror system. The rings are then accelerated by the magnetic expansion method over a distance of 1.4 m. During stopping experiments with resistive walls, a rapid growth of the radial beam width was observed which led to severe particle loss. This effect is attributed to radial off-centering in the cusp, mismatch in the equilibrium radius due to self fields, and the negative mass instability. It can be suppressed by the use of cusp correction coils, proper boundaries and Landau damping with scattering foils. In the linear-beam experiment, proton beams of 16 MeV energy, peak currents of 10 kA, pulse length of 3 ns, focused to 1 cm diameter were obtained. Slow-wave structures to increase the ion energy are studied

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