Towards LHC experiments

From 5-8 March, Evian-les-Bains on the shores of Lake Geneva was the scene of a major meeting on the experiments for CERN's planned LHC proton collider in the 27-kilome­ tre LEP tunnel.

As plans for the LHC proton collider to be built in CERN's 27-kilometre LEP tunnel take shape, interest wid­ ens to bring in the experiments ex­ ploiting the big machine. The first public presentations of 'expressions of interest' for LHC experiments fea­ tured from 5-8 March at Evian-les-Bains on the shore of Lake Geneva, some 50 kilometres from CERN, at the special Towards the LHC Experimental Programme' meeting. (A report from the meeting will be included in our next issue.) This event followed soon after CERN Council's unanimous Decem­ ber 1991 vote that the LHC machine, to be installed in the existing 27-kilo­ metre LEP tunnel, is 'the right ma­ chine for the advance of the subject and for the future of CERN'. With de­ tailed information on costs, feasibility and prospective delivery schedules cial Detector Research and Develop­ Another will be reserved for the beam to be drawn up before the end of next ment Committee was set up along dump where the LHC protons will be year, and now with plans for experi­ the lines of traditional Experiments absorbed once the circulating beams ments under discussion, the prepara­ Committees, but this time with the are no longer required. This leaves tions for LHC move into higher gear. objective of stimulating and fostering room for two big new LHC collider The Evian meeting was a public forum the new technology needed to reap detectors, plus the potential of the for a full range of expressions of inter­ the LHC physics rewards (November existing LEP experimental areas, us­ est in LHC experiments, setting the 1991, page 2). This scheme was de­ ing either adapted LEP experiments stage for the submission of Letters of liberately set up before global detec­ or new apparatus mounted in push- Intent later this year and cementing tor designs emerged, so that the final pull to alternate with LEP running. the proto-collaboration arrangements. configurations would benefit from this At Evian, four major detectors for So that all interested physicists can new technology. studying proton-proton collisions eventually access LHC, another im­ As well as its main objective of pro­ were being tabled, three of which are portant aim of the Evian meeting was ton-proton collisions, LHC also opens new, and one a development from an to acquaint the potential physics up possibilities for ion-ion collisions, existing LEP experiment. community with the full range of pro­ for fixed target studies and eventually The ASCOT (Apparatus with posals and ideas. As well as plans for electron-proton collisions as well. Superconducting Toroids) general for experiments, participants at the Most of these areas were covered at purpose detector is proposed by a meeting also heard the latest news on Evian. team from CERN, the UK (Edinburgh LHC machine studies, and the think­ LHC beams can in principle collide and Rutherford Appleton Laboratory), ing on preparations for experimental at eight points. Four of these coincide Germany (Wuppertal and Munich areas and LHC physics potential. with the four big experiments at the MPI and University), France (Saclay) CERN is very aware of the chal­ LEP electron-positron collider. Of the and Russia (Moscow, Dubna and lenges of the LHC for its detectors - remaining four points, one, deep un­ Protvino). It is based on a 24 metre- handling collision rates more than a der the Jura mountains, will have to long superconducting toroid thousand times those of existing be used for an LHC 'beam cleaning' instrumented with drift tubes for pre­ colliders and having to withstand in­ system to ensure high performance cision muon detection. tense radiation levels. In 1990, a spe­ by reducing troublesome beam halo. Inside the magnet, the emphasis is

CERN Courier, April 1992 1 FINLAND AT CERN

Industrial exhibition at the main building 31 March - 3 April 1992

ORGANISER

THE FINNISH FOREIGN TRADE ASSOCIATION P.O.Box 908 SF-00101 HELSINKI Tel +358 0 695 91 Fax +358 0 694 0028 LIST OF PARTICIPANTS

ORNTECH \VO INTERNATIONAL LTD kIoInIe TECHNOLOGY DEVELOPMENT CENTRE FINLAND O outokumpu copper mm SUPERCONDUCTORS Helsinki University of Technology TUMO The Institute of Particle Physics O outokumpu copper CJEFT RAUMA-REPOLA PORI RESEARCH INSTITUTE OFFSHORE DRAWN PRODUCTS DIVISION FOR HIGH ENERGY PHYSICS M VALMET 78 Circle advertisement number on reader service form CERN Courier, April 1992 Around the

Prince K. Malhotra of Bombay's Tata Laboratories Institute of Fundamental Research died while attending the Evian meet­ ing. A tribute will appear in the May issue.

on electrons, with a lead/liquid argon arsenide) strip detectors and electromagnetic calorimeter, and microstrip gas chambers, to ensure CERN tracking through interleaved layers of good pattern recognition under the scintillators and transition radiation stringent LHC conditions. Also inside LEP in the Alps detectors, with semiconductor pads the coil is a high resolution electro­ close to the beam pipe. A 1.5T su­ magnetic calorimeter and a hadron perconducting solenoid in front of the calorimeter. With CERN's 27-kilometre LEP elec­ electromagnetic calorimeter distin­ CMS involves a team from 12 tron-positron collider shut down for guishes electrons and positrons. CERN Member States, plus the winter, LEP specialists met in Hadron calorimetry uses iron and liq­ Byelorussia, Bulgaria, Estonia, Geor­ Chamonix in the French Alps from uid argon. gia, Hungary, Russia and the US. A 19-25 January to review the ma­ The EAGLE (Experiment for Accu­ wide range of ongoing R and D work chine's 1991 performance (January/ rate Gamma, Lepton and Energy examines the possible detector tech­ February, page 6) and to look at measurements) collaboration pro­ nologies before deciding on final so­ ways of improving it. poses a comprehensive detector to lutions. Nine specialist areas were covered cover a wide range of physics, and The L3 experiment at LEP was - operations, instrumentation, ma­ already involves physicists from 14 originally designed for use at both chine optics, the 'pretzl' scheme to CERN Member States, plus Canada, LEP and LHC, with a large experi­ increase the number of colliding Russia, Australia, Brazil and Israel. mental hall and magnet. Upgrade for bunches, energy calibration and po­ EAGLE foresees a powerful inner LHC would involve improving the larization, beam-beam interactions, electron detector inside a 2T central muon resolution, adding a fine-grain optics for the LEP2 energy upgrade, superconducting solenoid. The de­ hadron calorimeter, increasing the and radiofrequency to power LEP2. sign features high quality electromag­ magnetic field, and being able to lift Operational experience had shown netic sampling calorimetry combined the detector 120 centimetres from the the machine's limitations. While the with fine-grained electron and photon LEP position to the LHC beams total number of collisions in 1991 was preshower detection, a high precision above. For the work, 39 institutes twice that of the previous year, actual vertex detector for lower collision from the L3 LEP line-up have been beam intensity had not changed sig­ rates, hadron calorimetry, and a con­ joined by 20 more, mainly from China nificantly. Experience had also ventional toroid muon spectrometer. and the former Soviet bloc. shown the need for better measure­ Many different detector technolo­ Supplementing the main proton-pro­ ments of machine optics parameters. gies are under study, and a final ton LHC programme are a range of A long list of problems await further choice of the specification for the other experiments, including fixed investigation, and the machine physi­ various EAGLE components will be target studies. Expressions of inter­ cists warn that experiments may made when R and D work is com­ est received so far include ideas for have to learn to live with higher back­ plete. two neutrino experiments and three grounds if beam intensities are to be The Compact Muon Solenoid studies concentrating on CP-violation improved. (CMS) LHC detector is designed to in B-particle decays, one using a In the instrumentation sector, the be compatible with the highest LHC gas-jet target, one using extracted specially developed streak camera collision rates, and is built around a beams and one a colliding-beam had shown its worth in investigating 15 m-long superconducting solenoid setup. little understood beam behaviour, providing a 4T field. The strong field Although not the spearhead of LHC and will be better exploited with a di­ gives relatively compact muon meas­ physics, ion-ion collisions will still rect link to the control room. urement. R and D work for the muon play a major role, continuing a CERN From the start, LEP has continually detectors is looking at resistive plate tradition in this field (page 8). For ion tried different tuning schemes to find chambers and parallel plate cham­ collisions, three teams are interested an optimal working point, with 'split' bers for timing information and hon­ - one using CMS, another using the horizontal and vertical tunes being eycomb strip chambers and wall-less (suitably modified) Delphi experiment popular. Additional options are to drift chambers for spatial information. at LEP, and a third using a new dedi­ change the phase of the transverse The central tracker will use small cated detector. (betatron) oscillations. Each choice cells, based on silicon (or gallium has advantages and disadvantages,

CERN Courier, April 1992 3