23 October, 1992
CLOSED SESSION :
Present: 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, H.J.Hilke (replacing J.V.Allaby), W.Hoogland, E.Iarocci, P.G.Innocenti, K.Kajantie, V.Khovansky, G.W.London, L.Maiani, G.Mikenberg, K.Potter, K.Pretzl, C.Rubbia*, K.Schubert, D.M.Sendall (Secretary), D.O.Williams
*) Part time
Apologies: J.V.Allaby, S.Yamada
1. INTRODUCTORY REMARKS
The Chairman welcomed the members of this new committee and thanked them for agreeing to take part.
C.Rubbia also thanked the members for taking on this important task. The committee would need to work in a flexible way, cooperating with the experiments and the machine designers. Council had formally voted the LHC as "the right machine for the advance of the subject and of the future of CERN". The approval of LHC experiments could not follow traditional procedures. The costs of the experiments would not be negligible compared with the machine, and very large numbers of physicists would be involved. Detectors and triggers posed problems far exceeding those of LEP, and new technologies would be needed. Interaction with the machine would also be more important than with electron machines.
A coherent picture must be presented to Council at the end of 1993, including the machine, the detectors, and the relation to the rest of the physics programme. Council will then be in the position to start the final approval procedure for the whole project. Examination of experiments would go in stages. Following the first reactions to the letters of intent, full technical proposals would be prepared, with construction plans and credible figures for costs. The general orientation should be clear for the DG to present to Council in a preliminary report in mid 1993.
A figure of 300 MSF had been mentioned as a guideline for the material cost of a large detector at turn-on. The detectors should be able to do interesting physics at this point, and also have the potential to evolve. A cost significantly higher than this at startup would mean delays in the programme. There should be more than one large pp detector, but more than two would be difficult to justify.
Detectors designed to operate with high luminosity pp collisions would already have solved many of the problems of running with heavy ions. They could thus also be used for heavy ion physics. A general-purpose heavy ion detector should probably be built, to tackle aspects that the pp detectors could not handle.
Similarly, pp detectors might do some beauty physics, with a specialised B experiment going further. Physics with ep would be for later, since Hera was only now starting up, and it would also need a substantial extra investment and interference with the LEP and LHC programmes.
The LHCC should get expert advice from the DRDC on technical issues. It would also be natural to have small specialised bodies advising on magnets, costs and other problems as needed.
The LHCC would need to consider the effect of increasing luminosity on physics potential. For the machine, a startup of 10**33cm-2s-1 seems already within the scope of present performances, and this should go to 10**34 with foreseen improvements. The startup figure is relatively conservative, but allows good physics to be done. Experiments should therefore plan to start up with around 1 event per bunch crossing, and evolve to cope with higher rates.
The timescales for machine and detector construction should be in phase. It would be best to go as fast as possible to the startup configuration and leave room for later improvements. If detector construction times were likely to be significantly longer than machine construction times, the LHCC should draw attention to this.
2. STATUS OF LHC PROJECT AND CONSTRAINTS FOR EXPERIMENTS
G.Brianti presented an update to the situation described at Evian. He summarised the LHC main parameters. Work is continuing on the injection scheme and tests are already under way. A new cell layout with 3 long dipoles per half-cell is being considered; this gives better machine energy per field, and lower costs. Work on magnets continues to make good progress.
Bunch spacing is under review: there are two options for pp, giving 15 or 25 nsec per crossing. (The corresponding figure for ions is 135 nsec). Going to 25 nsec gives some improvement in luminosity, and it is important for the LHCC to comment on this. The costs of the two options are similar, but they need two different RF systems, which (apart from the question of cost) cannot be installed simultaneously. This means that a choice has to be made. A decision on the initial configuration is needed soon so that the full injection chain could be tested. The Experimental Requirements Committee has had some preliminary discussions on this.
Interface to experiments: interaction regions 3 and 5 would be reserved for beam cleaning and dump. Possible ways of using the other intersections for physics were presented. Experimental areas would be substantially more expensive than for LEP.
3. TIMESCALE AND ORGANISATION OF LHCC WORK
The Chairman summarised the terms of reference and guidelines for submitting letters of intent, and the timescales for the LHCC work. Timescales for heavy ion and B physics letters of intent were discussed. A decision will be taken later this year. The LHCC should also have an idea of other kinds of physics which might be of interest.
Since the LHCC lacks the necessary technical knowledge, a magnet advisory group has been set up. This will assess the feasibility, risks, milestones, timescales and cost estimates of the different designs. The members are D.E.Baynham (Rutherford Appleton Lab.), H.Desportes (CE-Saclay), E.Klimenko (Kurchatov Inst. Moscow), P.Komarek (Kernforschungszentrum Karlsruhe), P.Lazeyras (CERN, Chairman), T.Taylor (CERN). D.M.Sendall (CERN) will act as secretary. The group met on 21 September, and has requested technical information from the collaborations. Magnet designs will be presented to the group on 2-4 November, and a first report will be made to the LHCC meeting of 8-9 December
The following referees were nominated:
Atlas: P.J.Dornan, P.Duinker, F.Eisele (Coordinator), P.Sharp (DRDC), S.Yamada.
CMS: K.Einsweiler, L.Foa (Coordinator), V.Khovansky, G.Mikenberg, D.H.Saxon (DRDC)
L3P: R.J.Cashmore (Coordinator), E.Fernandez, R.Klanner (DRDC), G.W.London, K.Pretzl
In addition the following group will make a comparison of physics performance:
L.Di Lella (Coordinator), J.Ellis, K.Kajantie, G.W.London, L.Maiani, K.Schubert
W.Hoogland drew attention to the following committees: the Experimental Requirements Committee, the Magnet Study Group (now superseded by the LHCC magnet advisory group), the Microelectronics User Group, and the LHC computing committee.
P.G.Innocenti presented ideas for a cost review procedure. Names of people with suitable experience were considered, and the Chairman will set up a working group. One referee for each experiment (to be nominated by the coordinators) will join the group.
Questions of safety are the responsibility of CERN. H.Hoffmann and TIS will be informed of the LHCC work.
At the open session of the LHCC meeting on 5 November 1992 the collaborations will be asked to present their letters of intent. Each presentation should take 11/2 hours, and consist of one or two talks. At the closed session on 6 November each of the referees will make a short report.
A combined "Cogne-style" meeting with the DRDC is tentatively proposed for 2-5 March near Frascati.
The Committee agreed to treat its internal working documents as confidential.
4. REPORTS FROM DRDC
The Committee heard reports on the status and prospects of DRDC projects and proposals from R.Klanner (Calorimetry), J.Harvey (Trigger and Data Acquisition Architecture) and E.Iarocci (Tracking and General R&D).
5. DATES FOR 1992 MEETINGS
Thursday and Friday, 5-6 November
Tuesday and Wednesday, 8-9 December
6. DATES FOR 1993 MEETINGS
2-5 March with DRDC (to be confirmed)
31 August - 1 September
The LHCC received the following documents:
o The CMS Collaboration: The Compact Muon Solenoid: Letter of Intent for a General Purpose Detector at the LHC (LHCC 92-1 / I 1)
o The ATLAS Collaboration: Letter of Intent for a General-Purpose pp Experiment at the Large Hadron Collider at CERN (LHCC 92-4 / I 2)
o The L3P Collaboration: Lepton and Photon Precision Physics (LHCC 92-5 / I 3)
__________________________________________________________________MS, 21 July 1993