CERN/LHCC 93-2

LHCC 4

19 February, 1993

LARGE HADRON COLLIDER COMMITTEE

Minutes of the fourth meeting held on Thursday and Friday, 4-5 February 1993

CLOSED SESSION :

Present: J.V. Allaby, J.J.Aubert (Chairman), G.Brianti*, R.J.Cashmore, L.Di Lella, P.J.Dornan, P.Duinker, K.Einsweiler, F.Eisele, J.Ellis, E.Fernandez, L.Foa, W.Hoogland, P.G.Innocenti, K.Kajantie, V.Khovansky, C.Llewellyn Smith, G.W.London, L.Maiani, G.Mikenberg, K.Potter, K.Pretzl, C.Rubbia, D.M.Sendall (Secretary), D.O.Williams, S.Yamada

*) Part time

Apologies: E. Iarocci, K. Schubert

1. The minutes of the third LHCC meeting (LHCC 92-19/LHCC 3) were approved without amendment. The Chairman reported briefly on the conversations he had held with the spokesmen of the Letters of Intent following the LHCC meeting of 8-9 December 1992.

2. REFEREES' REPORTS

L. Di Lella gave a comparative report on the potential of ATLAS, CMS and L3P for heavy Higgs -> Z Z -> l+ l- nu nu-bar, and on hadronic calorimetry.

J. Ellis summarised the situation for SUSY Higgs searches, and for gluino / squark searches using missing ET and like sign dileptons.

R.Cashmore, L.Foa and F.Eisele gave progress reports on the work of the L3P, CMS and ATLAS referees, and summarised the responses of the collaborations to a number of questions put by them on behalf of the LHCC.

3. REPORT ON GEM AND SDC

K. Einsweiler gave a report on the physics performance of the SDC and GEM detectors at the SSC. This included a comparison of the LHC and SSC and their physics programmes, and an overview of the two detectors. The main physics topics covered included electroweak symmetry breaking, top physics, supersymmetry searches, heavy gauge boson searches, and compositeness searches.

4. MAGNET ADVISORY GROUP

P. Lazeyras summarised the current status of the work. A new report on the L3P magnet, and new information on costs of the ATLAS warm iron toroid, have been received and will be discussed by the advisory group. A draft report was circulated to the group on 27 January, and a meeting is planned for 12 February to discuss this. The report should be available for the LHCC by mid-March.

5. COSTS REVIEW GROUP

F. Brasse reported on the work of the group. A questionnaire has been circulated to the collaborations, and joint meetings held with each of them to discuss the replies. Areas where further study is needed include CeF3 crystals, frontend electronics, DAQ / trigger, and laboratory manpower. The next meeting will be on 24 February, and it is intended to produce the final report at a meeting on 17 March. Appreciation was expressed of the progress made by the group so far.

6. LHC MACHINE CONSIDERATIONS

G.Brianti summarised the implications for the LHC machine design of the choice between 15 and 25 nsec bunch interval. The collaborations have submitted papers giving their reactions to this option, and all three support the 25 nsec option. The LHCC therefore recognises the desirability of a 25 nsec bunch interval.

G.Brianti also summarised the progress made towards a final proposal for the machine. All parameters have been carefully reviewed. With respect to the Pink Book design two major changes have been made: an increase of magnet aperture from 50 to 56 mm, and an increase in magnet length from 9 to 13.5 m. In addition, two options are now under consideration: "high field" magnets or "reduced field" magnets using SSC-type superconducting cables with thinner strands. Designs are under way for both options, and a report will be made to the LHCC at a later stage. In the discussion it was pointed out that it would be unwise to go significantly below an energy of 7 TeV per beam, in view of the fall-off in the relevant cross-sections.

7. EXPERIMENTAL AREAS

K. Potter commented on possible use of experimental areas. Contrary to what had been presented earlier, it is not clear that the ATLAS air-core toroid with its present radius could be installed at Point 1, due to constraints on the cavern size imposed by essential LEP infrastructure.

8. DETECTORS IN THE FORWARD REGION

K. Potter summarised the work of the Radiation Workshop on the Design of LHC Forward Detectors, held by the LHC Experimental Requirements Committee on 9-10 November 1992. This workshop considered some of the problems of maintenance in this region due to induced radioactivity. Help and advice had been received from industry and the inspectorates of several member states. The ERC has set up a permanent Working Group on Radiation Questions in the LHC Experiments, under the Chairmanship of M. Price

9. INFORMAL PRESENTATIONS BY THE SPOKESMEN

The spokesmen of the Letters of Intent had been invited to attend, to present to the LHCC any recent developments or other points they wished to make in person. These presentations were made by M. Della Negra for CMS, by S.C.C. Ting and H. Hofer for L3P, and by F.Dydak and P. Jenni for ATLAS; they were followed by brief discussions.

10. TIMETABLE AND FUTURE MEETINGS

The collaborations had been asked to prepare a paper on staging their detectors by

26 February 1992. In view of the amount of work involved, the LHCC agreed to extend the deadline for this to 19 March 1993.

The response of the collaborations to the question on staging their detectors, and the reports of the Costs Review Group and the Magnet Advisory Group, will be available by the April meeting of the LHCC. It may therefore be possible for the committee to reach a decision on the Letters of Intent at this or a subsequent meeting.

The LHCC meeting provisionally proposed for 3-4 March 1993 was judged to be unnecessary, and will not be held. In view of the number of important topics to be considered at the April meeting, it was decided to extend this by one day: it will therefore be held on 6-8 April 1993. In addition, members are asked to reserve the date of

13 May after the B physics workshop, in case this is needed for a further meeting.

Letters of Intent for ion experiments had been requested for end February 1993: only one is expected. The following referees were appointed:

K. Kajantie, G. London, K. Pretzl

11. DATES FOR 1993 MEETINGS

6-8 April

11-12 May (B physics workshop) with possible extension to 13 May

8-9 June

31 August - 1 September

16-17 November

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MS, 21 July 1993