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Llie SPS EXPERIMENTAL PROGRAM MARIA FIDECARO CERN lliE SPS EXPERIMENTAL PROGRAM MARIA FIDECARO CERN, Geneva (Switzerland) Abs tract : The experimental program at the SPS is reviewed as it takes shape from the proposals put forward up to this Spring . Resume : Le programme d'experiences aupres du SPS est passe en revue , tel qu 'il se profile d'apres les propositions presentees jusqu'a maintenant . 191 1. INTRODUCTION The Super (and Subterranean) Proton Synchrotron (SPS) is expected to start operating in the middle of 1976 when protons will be extracted in the West Hall at 200 GeV. experimental progrannne to be carried out in the first year of oper­ ation is at present being set-up . Thorough discussions took place at the Tirrenia Meeting in September, 1972 and in January, 1973 P. Falk-Vairant presentedAn the final report of the Executive Corrnnittee of the ECFA . In April Letters of Intent were called in; some of which were later transformed into proposals by the Spring of 1974 . I will try to give an outline of this progrannne as seen by an inter­ ested layman i I apologize for the distorsions and the omissions . Working within some boundary conditions , the physicists wanted to make use of: a) The West Hall (Fig . 1 and Appendix) b) A large bubble chamber BEBC , 3 m long , 3.70 m diameter to be filled with hydrogen or deuterium in a 5 Tesla magnetic field. Possibly a second heavy liquid bubble chamber 4.8 m long , 1.9 m diameter (Gargamelle) in a 2 Tesla magnetic field could be used. 3 c) A large magnet (2 x 3 x 1.5 m ) 1.8 Tesla, filled with a flexible system of detectors (Omega) . Also they had to bear in mind that particles are expected in the North Area at the beginning of 1978 . Here the Hall EHNl will include two hadron beams up to 350 GeV/c, an electron/hadron beam up to 270 GeV/c, a medium energy hadron beam up to 200 GeV/c. The Hall EHN2 will be reserved for muon and protons experiments only. A Working Group is looking at the feasibility and the opportunity of a general facility (Dynosaure) to perform experiments on hadron/electron phys ics in the Hall EHNl . A British, French , German Collaboration is preparing a wh ite book on possible ways of studying elastic and inelastic µ-p/d scattering (with polarized unpolarized targets) . 2. WANF (WEST NEUTRINO FAC ILI1Y) The importanceand ot neutrino and muon phys ics has already been recognized. In both cases the interest was shown mostly to utilize these particles as THE AREA 2 probes of internal structure of hadrons in an inclusive study of q , Vplot . The relative merits of using a narrow band (NB) beam (Ev at ± 7%, flux 192 at ±3%, 10 events on complex nuclei in 30 days) or a wide band beam 5 (108 events on complex nuclei, 103 in deuterium or hydrogen) were discussed. Eventually it was decided to build a beam capable of operating with protons to 400 GeV, and a NB beam in the West Area . (WB) About twenty Letters of Intent referred to neutrino experiments either WB with BEBC filled with or or Ne , or with Gargamelle filled with propane up or freon, with or without an external muon identifier EMI . The installation of Gargamelle behind an electronic experimental facility Hz Dz is now decided . The latter (SPSC-Pl) will consist of a (scintillator Fe) + calorimeter plus an iron core magnet sandwitched with scintillators drift chambers to form a modular system to momentum analyse the muons , Fig . The calorimeter could be eventually replaced by a more sophisticated liquid Argon counter , SPSC-P3 . There is also room for a somewhat smaller apparatusand z to perform other classes of experiments on neutrinos . 3. HADRONIC PHYSICS IN BEBC About forty groups who wrote Letters of Intent showed interest in per­ forming more conventional hadronic phys ics. Of these approximately thirteen wanted to use BEBC at a beam momenta 40-100 GeV/c (Mirabelle at Serpukhov works at 32 GeV/c) . Most of them called for an separated beam. Many concerned experiments with an external parti­ cle identifier (EPI) and for a track sensitive target (TST) . This chamber promises to be a competitive instrument up to - 100 GeV RF especially for the more complicated type of events , and one should remember that NAL does no t at present plan the installation of an separated beam, but that an important experimental bubble chamber progrannne with - and p TI beam is being requested there . RF It has now been decided that an separated (up to 75 GeV/c) beam will be constructed while for the external particle identifiers (based on relativ­ istic rise of ionisation and/or on forward gannna detection) progress status of the projects were reported . RF 4 . THE a.IEGA SPECTRa.IETER In four Letters of Intent and one proposal the groups wanted to use the Omega Spectrometer . Transformations of this spectrometer are planned to be carried out in steps in order to be able to start experiments as early as possible in the West Area . In addition to building a downstream lever arm consisting of drift chambers, three Cerenkov and a y-detector , it : .s planned 193 to gradually replace the optical system within the magnet by drift chamber modules or wire chamber planes . Special attention is being paid to the data acquisition problems in view of the expected high rate . The beams foreseen are an separated hadron beam (up to 40 GeV/c) and an electron-photon beam, including a photon tagging system. Various schools of thought flourish around Omega . Is Omega a bubble RF chamber with an electronic read out (Letters of Intent for a K+ interaction trigger, SPSC-I 73/37 and for inclusive studies from different particles and targets , SPSC-I 73/55) or should it be used for exclusive two body or quasi two body reactions with a rather selective trigger , where the geometry would be used to cover a large solid angle? In both cases the separated Kaan beam, which is for the first time available above 3 GeV/c to counter physicists , makes a new class of experiments possible. 4TI One of the groups at present working on Omega proposes to make use of high energy in order to produce heavier mesons , SPSC-I 73/38 . Another group proposes to explore a region where Regge poles might be important and which becomes accessible only at high energy , SPSC-I 73/54 . They want to be able to establish or to disprove the Reggeon-nucleon scattering model , -, ' ,�/·') s' p /� where a trigger with incident and outgoing of small momentum transfer ; - TI selects, in principle, events of Reggeized p-nucleon scattering - the choice = 2 of beam energy is given by s' << s (f.i.: s' � 1/10 s, s' 10 GeV , 0 s 100 GeV2) . The Omega seems ideal for this TIexperiment where moderate = multiplicities , small transverse momentum and restricted mass of the excited target particle are expected . Also new is the line of research of a British, French , German Collabor­ ation which want to make use of the tagged photon beam, SPSC-P 10, Fig . 3 and 4. The emphasis will be on multibody final states . They will expect 5 2 x 10 photons per pulse with energies above 20 GeV; the resolution on the proposed tagging system is ±150 MeV , while the uncertainty in transverse � momentum is 10 MeV/c. � The following experiments are of particular interest: i) photoprod� uction of vector mesons : p, w, ii) search for new vector mesons iii) diffraction dissociation processes iv) high multiplicity reactions : to compare with�. hadron-induced processes and 194 to obtain the energy dependence of the Illllltiplicity v) total hadronic cross-section, measured by summing all exclusive channels vi) elastic Compton scattering on protons vii) reactions with l'Psmall cross-sections : e.g., pseudoscalar meson production, deep inelastic Compton scattering and lepton pair production . The in­ variant masses W (W = 6.2 GeV at k 20 GeV, up to W = 13.7 GeV at k lCXJ GeV) are comparable to those which could be obtained in virtual photoproduction with higher energy electrons or IllllOns in the North Area . = The use of polarized photon beam and/or a polarized proton ·target is also = envisaged but at a later time . 5. HYPERON BEAM Strong interest has been expressed in the field of phys ics opened by the construction of a hyperon beam in the West Area. In Table 1 the particle 1HE fluxes expected when the attenuated primary beam is dump are shown . The inter­ est is roughly shared between weak and strong interaction experiments: a) elastic scattering and production of strange resonances by diffractive excitation in E-p and �-p interactions between 75 and 150 GeV/c . ± b) study of the decays �- + Ae-v, �- + E 0 e-v and E + Aev . Table 1 Particle fluxes at the end of the hyperon beam GeV/c GeV/c GeV/c Momentum Negative beam Negative beam Positive beam Incident protons 150x 100 x 100 x - - 11- ' 6 109 5 106 K 7 10 0 - - x E - - x ' 10x 6 10 - - 3 4 - 7 10 10 - 7 104 4 103 p - - x + 100 100 - - 11+ 0.6 x (lK 0.6- - x + 0.8 10 6 E - - 5 ± ± 2.4 10 Note that for p, 11 and K the figures represent the numbers of 2.4 104 these particles in the channel. For the hyperons they represent the numbers actually identified by the DISC. 150 195 A possible layout is shown in Fig . 5. The hadronic experiment would throw light on the mechanism for diffractive production, shrinkage of forward elas­ tic peak and various SU(3) and quark model predictions for baryon-baryon inter­ actions and for partial widths of and resonances .
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