Representatives of the PETRA operations group and the JADE, Mark-J, PLUTO and TASSO collaborations at DESY celebrate in the control room at the end of a successful electron-positron run at 17.5 GeV per beam. In about six weeks during November and December, each of the four experimental groups collected a luminosity of 17 000 inverse nanobarns, despite a four-hour energy-saving shutdown every working day. (Photo DESY) Next speaker was Gustaf-Adolf physics with HERA. New structure physics. These devices also appear Voss of the DESY directorate who functions could be measured and to be important for a variety of other gave a comprehensive worldwide new particles found. Grand unifica­ applications to deal with high particle survey of current electron-proton tion, supersymmetry and Higgs par­ multiplicities and high energies. projects. Of these, only two, TRIS­ ticles could be explored. There ap­ Much progress has recently been TAN in Japan and HERA, have been pear to be many fields in which only a made, particularly in Europe, on the explicitly planned for electron-proton machine like HERA can provide new application of solid-state techniques collisions. Among the world's list of insights. to high energy instrumentation, and electron-proton projects, HERA a topical Workshop was organized scores well on both luminosity and FERMILAB at Fermilab on 15—16 October on the energy. use of silicon detectors. The meet­ After detailed technical discus­ Silicon detector ing, organized by Tom Ferbel from sions, further talks covered theoreti­ workshop... Rochester, had two major goals — cal ideas. Guido Altarelli and Don firstly to inform experimenters on re­ Perkins emphasized the importance The outstanding physics develop­ cent advances in the development of of testing quantum chromodynamics ments of recent years have included finely segmented silicon detectors, and electroweak theory at high the discovery of charm and beauty and secondly to bring together some momentum transfers which probe flavours and of the tau lepton. The of the world experts in the field to deeper inside matter and could show short lifetimes involved have di­ evaluate the feasibility of construct­ whether quarks and leptons are in­ rected interest towards techniques ing detector systems that could deed pointlike, or whether they in to measure the decays of these par­ complement present-day tracking fact have an internal structure. ticles. It is becoming increasingly devices for ultra high energies, large In his concluding remarks, John clear that silicon microstrip detec­ multiplicities and small inter-particle Ellis summarized the numerous theo­ tors and 'live' silicon targets may be distances. retical ideas and expectations for the particularly well suited to this new The Workshop opened with an ex- CERN Courier, January/February 1982 11 At a ceremony on 1 October, the Fermilab Auditorium was officially named the 'Norman F. Ramsey Auditorium' in honour of the first president of Universities Research Association (which operates Fermilab for the US Department of Energy). Ramsey (seen here) is Higgins Professor of Physics at Harvard. (Photo Fermilab) cellent state-of-the-art review by H.M. Heijne from CERN. Heijne also presented his group's impressive achievements in developing micro- strip hodoscopes in association with the Enertec division of Schlumber- ger. He emphasized repeatedly that the key to large-scale application of silicon strip devices was the devel­ opment of adequate electronic read­ outs. The electronic challenges were then tackled by V. Radeka from Brookhaven. He described the gen­ eral problem of signal formation, noise and position readout in these low signal detectors and discussed a particular system envisaged for fu­ ture collider operation, possibly at ISABELLE. C. Damerell of Rutherford gave a concise review of present and future possibilities for charged-cou- pled devices (CCDs) in the localiza­ tion of charged particle trajectories. The status of silicon dectector de­ velopment in the United States (es­ pecially efforts at Berkeley to meas­ ure decays of short-lived particles) was described by G. Kalbfleisch from Oklahoma. P. Shepard from Pitts­ burgh described a novel scheme based on the storage of ionization charge in shallow traps in doped sili­ con crystals operated at cryogenic temperatures. R. Carrigan of Fermi­ lab then reviewed the possibilities of using bent silicon crystals for chan­ nelling particle trajectories. A more intense presentation on the develop­ ment of solid-state detectors based on CCD concepts was given by A. were presented on how to deal with with samples of his silicon counters Bross from Berkeley. P. Manfredi readout of mega-channels of infor­ and electronics, discussed the devel­ from Pavia ended the first day with a mation. The evening session closed opment of ten-micron resolution de­ fine lecture on the design of electron­ with rather encouraging remarks vices in collaboration with EMI. His ics for silicon telescopes. from commercial representatives L. colleague, G. Lutz from MPI Munich, On the evening of 15 October, a Levit of LeCroy Systems and M. Mar­ presented a parallel approach for in­ special seminar was held in the Fer­ tini of ORTEC. strumenting a ten-micron resolution milab Users' Center. T. Ludlam from The second day of the Workshop system for spectrometers at CERN. Brookhaven and W. Vernon from covered the latest work in Europe. G. A. Menzione from Pisa described ex­ San Diego spoke on future prospects Bellini from Milan spoke on measure­ tensive efforts in manufacturing sili­ for semiconductor detectors in high ments of D meson lifetimes. B. con detectors while J. Poinsignon energy physics. In particular, ideas Hyams from CERN, fully equipped from Saclay presented details of an 12 CERN Courier, January/February 1982 ambitious programme for building a diction- by as much as a factor of two dependence of the elementary pion- multi-thousand channel detector for at an energy of 31 GeV. nucleon interaction can be exploited a CERN experiment. Finally, J. Killia- Reinholdt Ruckl discussed the con­ to unravel the neutron and proton ny of the US Naval Research Labora­ stituent interchange model contribu­ parts of the reaction mechanism as tory described studies of radiation tion to the direct photon cross-sec­ well as the spin structure of nuclear damage and hardening of silicon de­ tion. Geoffrey Fox's talk centred on excitations. It appears that no other vices. the hadronic final states in high trans­ nuclear probe is as effective as the The Workshop was attended by verse momentum collisions and en­ pion for suchjstudies. Such large dif­ about 150 physicists and, judging compassed the development of the ferences exist in the spectra of the from the remarks in the halls, it was possible away-side jets in direct pho­ inelastic scattering of positive and successful in meeting its goals. It ton measurements. Francis Halzen negative pions on carbon 14 that showed rather dramatically that sili­ reviewed the present world data in when comparing the two spectra, con devices have already found a earlier direct photon experiments measured under identical conditions, niche in high energy physics. There and the relation of the data to theo­ one physicist remarked, 'it hardly have been great strides forward, par­ ry- seems like the same nucleus.' ticularly in Europe, both in the Labo­ Peter Koehler summarized the cur­ The measurements were made ratories and in attracting commercial rent and planned experiments at the possible by the pion beams of high firms. The silicon age in high energy CERN SPS proton synchrotron. intensity, high resolution,*and varia­ physics looks as if it is here to stay There was also a presentation and ble energy provided by EPICS (Ener­ for a while. discussion of the past and current gy Pion Channel and Spectrome­ Because of the great interest, the data by experimentalists including ter). Workshop proceedings will be pub­ Brad Cox (covering Fermilab studies) The usefulness of pion beams is lished shortly. For more information, and Tom Ferbel, Steve Pordes and due to the 1232 MeV nucléon reso­ write to T. Ferbel, Department of David Leventhal (covering experi­ nance with spin and isospin quantum Physics, University of Rochester, Ro­ ments at the CERN ISR). numbers 3/2, 3/2. Between 100 chester, New York, 14627, USA. The experimental data indicated and 300 MeV the pion-nucleon inter­ that it is difficult to isolate a signal action is dominated by this reso­ ...and direct photon coming from a direct photon from nance. Consequently, the cross-sec­ workshop those arriving at a detector due to tion for elastic positive pion-nucleon neutral meson decays. Low trans­ scattering is about nine times larger A workshop held from 26—28 Sep­ verse momentum experiments also than that for negative pions. Con­ tember at Fermilab was devoted to suffer from the presence of a brems- versely, the elastic cross-section for the theory of and experiments on strahlung component. As a result it is negative pions on neutrons is nine direct photons. Attended by over 60 not clear that the ratio of photons to times larger than that for positive physicists, it was organized by Den­ neutral pions is the most revealing pions. If the free pion-nucleon inter­ nis Judd of Fermilab and Ed Berger of quantity to measure in the proposed action is not altered significantly by Argonne. experiments. The results of the the presence of the other nucléons in Direct single photon production at workshop suggest that one should a pion-nucleus collision (an assump­ high momentum transfer (a quark- look at jet correlations coupled with tion called 'the impulse approxima­ gluon interaction) provides a clear a direct gamma trigger. tion'), then these large ratios should test of quantum chromodynamics. also be observable in scattering off To illustrate this, Jeff Owens of Flo­ LOS ALAMOS nucléons in a nucleus.