22 December, 1992
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, E.Iarocci, P.G.Innocenti, K.Kajantie, V.Khovansky, C.Llewellyn Smith, G.W.London, G.Mikenberg, K.Potter*, K.Pretzl, C.Rubbia*, K.Schubert, D.M.Sendall (Secretary), D.O.Williams.
*) Part time
Apologies: L.Maiani, S.Yamada
1. The minutes of the second LHCC meeting (LHCC 92-15/LHCC 2) were approved without amendment.
2. REFEREES' REPORTS
L. Di Lella gave a comparative report on the potential of ATLAS, CMS and L3P for the study of Higgs -> 4 leptons, Higgs -> gamma gamma, and resonant states of the WZ system for high Higgs masses. For H -> 4l, it had been found that the decay top -> W+ b was not correctly described by the PYTHIA event generator. Estimates of the background from t-tbar production therefore need to be redone. Preliminary results from ATLAS indicate that this effect may not be too important: corrected results from all the experiments are expected by end January 1993. The possibility of distinguishing between Standard Model and Supersymmetric Higgs via rates and widths in the 4 lepton channel was discussed. Sensitivities for the H -> gamma gamma channel were also compared under various assumptions for the detector options.
J. Ellis summarised the situation for SUSY searches: the three experiments have now provided figures which are more readily comparable. For missing ET some studies have been made, but more effort is needed for a realistic simulation. For like-sign dilepton pairs, estimates for sign misidentification have now been made. The potential of the three experiments for discovery / exclusion in the mA / tanbeta plane was summarised.
K. Kajantie summarised the potential for Upsilon spectroscopy in dilepton systems. This is an area where the pp experiments may cover phenomena not accessible to dedicated heavy ion experiments.
F.Eisele, L.Foa and R.Cashmore gave progress reports on the work of the ATLAS, CMS and L3P referees, and summarised the responses of the collaborations to a number of questions put by them on behalf of the LHCC.
In the general discussion a number of concerns were expressed about aspects of each of the three experiments. The Chairman was asked to bring these orally to the attention of the Spokesmen.
3. SAFETY ISSUES
H.Schoenbacher presented preliminary reactions to safety aspects of the Letters of Intent. The following topics were dealt with: radiation, superconducting magnets, liquid Argon, engineering and mechanics, gases, flammable materials, fire prevention and fighting, general industrial safety, and a safety audit.
Positive aspects included the absence of Uranium and warm liquids (TMS, TMP): serious efforts had also been made to minimise the use of flammable gases. Collaborations have been aware of radiation safety since an early stage, and predictions of dose levels have been well addressed in the Letters of Intent. This awareness will need to be translated into an engineering design for the technical proposals. For liquid Argon, superconducting magnets, and engineering and mechanics, design parameters and choice of structures will need to be quantitatively justified in the technical proposals, with explicitly defined safety factors.
In the discussion, it was proposed to identify one or more people per experiment to serve as GLIMOS at an early stage, rather than waiting until approval as is the usual practice.
Attention was drawn to the Radiation Workshop on the Design of LHC Forward Detectors, held by the LHC Experimental Requirements Committee on 9-10 November. Some common problems were identified. The ERC has decided to set up a Working Group on Radiation Questions in the LHC Experiments, with representatives from the collaborations, TIS and the accelerator sector.
It was noted that liquid argon safety may have implications for civil engineering, and costs must be understood as early as possible.
4. COSTS REVIEW GROUP
F. Brasse reported on the work of the group, which has held two meetings. A plan of work and timetable was given. Boundaries between the experiments and the machine infrastructure would need to be defined. A summary of cost estimates was presented for general infrastructure and for calorimetry, and an overall comparison by detector was made for the three experiments. The group is preparing a detailed report to be available by the end of February 1993.
5. MAGNET ADVISORY GROUP
P. Lazeyras presented a preliminary status report. The group has held discussions with the magnet experts of the collaborations concerning the ATLAS air-core superconducting toroids, the ATLAS warm iron toroid, and the CMS and L3P superconducting solenoids.
All the projects present technical difficulties by reason of their advanced nature, and new features compared to existing magnets. However, the consensus is that their feasibility has been established at a conceptual level, without uncovering really critical problems or serious risks. (In the case of L3P it may be too early to judge the design presented).
Questionnaires have been sent to the collaborations on costs and technical issues: this will allow a more detailed comparison to be made. The requirements from CERN in terms of infrastructure at the various stages of construction, testing and assembly will be addressed. The group is preparing a detailed report to be available by the end of February 1993.
6. TIMETABLE AND FUTURE MEETINGS
Joint DRDC-LHCC meeting 2-5 March 1993: it was decided not to hold such a meeting. However, the dates of 3-4 March 1993 will be kept in reserve for a possible LHCC meeting.
B Physics workshop: a preliminary meeting had been held with those interested. It was decided to hold a small closed workshop on 11-12 May 1993 where perspectives for B physics at the LHC will be presented and discussed. K. Schubert has agreed to organise this. Participation in addition to LHCC members will be about 5 people from each of the pp collaborations, and from each of the groups that presented Expressions of Interest at Evian. LHC machine experts will also participate.
Meeting of 4-5 February 1993: several topics were proposed for the Agenda. The question of 15 or 25 nsec bunch crossing will be discussed. The collaborations have given their preliminary reactions to the ERC, and a request for further information will be sent to them. A report will also be requested on radiation and forward detectors.
7. DATES FOR 1993 MEETINGS
3-4 March (provisional)
11-12 May (B physics workshop)
31 August - 1 September
__________________________________________________________________MS, 21 July 1993