CERN/LHCC 2001-008 LHCC 51
26 March 2001
LARGE HADRON COLLIDER COMMITTEE

Minutes of the fifty-first meeting held on

Wednesday and Thursday, 21-22 March 2001





OPEN SESSION:

1. ALICE Addendum to Dimuon Forward Spectrometer TDR: F. Staley

2. Report from the Steering Group of the LHC Computing Review: S. Bethke

3. ATLAS Status Report: P. Jenni
 

CLOSED SESSION:

Present: S. Bethke*, G. Carboni*, R. Cashmore, D. Cassel, J. Dainton, M. Delfino*, M. Della Negra*, J. Engelen (Chairman), A. Ereditato,
M. Hauschild, G. Iaselli*, P. Jenni*, Y. Karyotakis, J. Lee-Franzini, L. Maiani*, M. Mangano, J. May*, J. Nash, A. Norton*
(replacing G. Goggi), J. Panman, K. Potter, D. Ressing, P. Roudeau, R. Santonico*, H. Schellman, D. Schlatter*
(replacing G. Goggi), K. Tokushuku, E. Tsesmelis (Secretary), E. Vercellin*, G. Zech.   *) Part timeApologies: G. Goggi, J.-J. Gomez-Cadenas, P. Lebrun, B. Löhr.  

1.  INTRODUCTION

The minutes of the fiftieth LHCC meeting (LHCC 2001-003/LHCC 50) were approved without modification.

The Director-General presented the LHC schedule as drawn up by a working group consisting of representatives from the LHC machine and the experiments. The main dates have the LHC machine closed and cooled down at the end of December 2005, with commissioning of the machine to be performed in January 2006. Single proton beam will be provided in February-March 2006, followed immediately by first proton collisions during a 4-week pilot run in April 2006. After a 3-month shutdown period, a 7-month proton physics run will commence in August 2006 with the aim of collecting at least 10 fb-1. A 6-week lead ion is scheduled commencing in March 2007.

2.  REPORT ON THE ATLAS GENERAL SCHEDULE

P. Jenni reported on the ATLAS plan for detector completion, installation and commissioning. A new scenario with eight phases is being worked out that will leave a detector for first collisions after the first seven phases and which can be completed in a shutdown period of a few months afterwards. The physics priorities - SUSY, Standard Model Higgs and MSSM Higgs - have been re-visited recently in the context of the priorities and flexibility for the sequence of installation. The LHCC takes note that the schedule is known to be in cases limited by resources, both in terms of money for installation contracts and in terms of expert manpower available from collaborating institutes for parallel installations. The LHCC commends the Collaboration for their impressive progress towards the realization of an experimental set-up ready to record data at the beginning of the LHC operation in 2006. This plan will be presented to the upcoming ATLAS Resource Review Board in April.

3.  REPORT ON THE CMS GENERAL SCHEDULE

M. Della Negra reported on the CMS plan for detector completion, installation and commissioning. The CMS schedule foresees a complete detector for the physics run starting in August 2006. The LHCC takes note that the delay in the underground caverns has serious implications for the detector installation and commissioning and may lead to more resources being required to carry out additional tasks on the surface. The Collaboration is trying to ensure that the funding shortfalls and cash flow do not cause critical delays to the overall project. A contingency plan is being developed in case of difficulties. The LHCC commends the Collaboration for their impressive progress towards the realization of an experimental set-up ready to record data at the beginning of the LHC operation in 2006. This overall schedule will be presented to the upcoming CMS Resource Review Board in April.

4.  REPORT ON RPCs FOR THE LHC EXPERIMENTS

4.1  REPORT FROM THE PISA WORKSHOP ON RPC
R. Santonico reported on the workshop held in Pisa on 18-20 January 2001 to discuss the BaBar RPC project status and plans for future RPC production. The presentation concentrated primarily on tests of the current generation of RPCs, which are planned for the new BaBar production, and for which the chambers are of the same type as those intended for the LHC. The main conclusions from the workshop are (a) the observed noise in RPCs depends strongly on the temperature, and (b) the noise is due to spontaneous discharges which are not uniformly distributed but are rather concentrated in particular positions inside the chamber. The degradation of the surface could be triggered by the mechanism whereby the noise produces an increase of the local temperature and therefore a decrease in the local resistivity. This in turn increases the noise rate thus creating a positive feedback loop, which in the extreme case produces a permanent damage to the chamber. Operating the chambers in streamer mode is more critical because the energy delivered per single discharge is much higher than in the avalanche mode. In order to overcome this positive feedback loop, the Bakelite plates have been coated in linseed oil in order to obtain a higher control of the surface properties before closing the chamber.
    4.2  REPORT ON THE ALICE RPCs
    E. Vercellin presented the status of the ALICE RPCs intended to be used in the Dimuon Forward Spectrometer. Prototype RPCs with diluted oil coating exhibit excellent behaviour when tested with beam. The ageing of these chambers has shown not to be dramatic. Similar prototypes but without linseed oil coating seem not to be as robust when operated in streamer mode and with low resistivity Bakelite. These results are still preliminary and ALICE intends to clarify the matter in the coming months.

    4.3  REPORT ON THE ATLAS RPCs
    R. Santonico reported on the status of the ATLAS RPCs. Ageing tests in the Gamma Irradiation Facility (GIF) on chambers coated with a few microns of polymerised linseed oil show encouraging results. After the equivalent of operating 12 years in ATLAS, the module tested still exhibits a rate capability that is within the ATLAS requirements.

    4.4  REPORT ON THE CMS RPCs
    G. Iaselli presented the status of the CMS RPCs. He noted that the CMS RPC trigger was designed under the assumption that the single hit rate is dominated by neutrons. However, results from beam tests indicate that the noise from the chambers themselves is much higher than the neutron rate in the barrel, leading to an unacceptably high trigger rate. Current results from beam tests on chambers without the linseed oil coating show that the trigger rate can be kept to within the requirements but with little or no safety margin. Ways to improve the RPC working parameters are being considered ó coating the electrode surface with linseed oil, performing additional extensive R&D, and reviewing the construction procedure. CMS will evaluate these options in the coming months and will also inject in the discussion the improvements in the triggering.

    4.5  REPORT ON THE LHCb RPCs
    G. Carboni reported on the status of the LHCb RPC detector. Although tests indicate that coating the Bakelite with linseed oil reduces the noise and the dark current, thereby presenting less of a load on the trigger and minimizing the ageing, it does nonetheless complicate the chamber construction by making the manufacture more critical and introducing additional quality control factors. Therefore, LHCb has a preference for favouring a solution without requiring the use of linseed oil. Tests on prototype LHCb chambers will continue until the end of the year, at which point a decision on the construction method will be made.
    Following an additional report, the LHCC will discuss the matter at its May 2001 session and present its conclusions and recommendations.

5.  REPORT FROM THE CMS REFEREES The Committee heard a report from the CMS referees, concentrating on the review of the Technical Design Report for the Level-1 Trigger, performed with D. Ressing as consultant. The trigger is the start of the physics event selection process. The input rate to the Level-1 Trigger is the full LHC rate of 40 MHz, and the output rate aimed for is 75 KHz. The CMS Level-1 Trigger is based on the identification of muons, electrons, photons, jets and missing transverse energy and will operate in both proton and heavy-ion running.

The referees also reviewed the status of the various CMS detectors and reported on the overall schedule and milestones. The LHCC considers that it is realistic to expect CMS to install a detector for the beginning of LHC operation in 2006, although detector installation is foreseen beyond the initial running. The presented lay-out of the initial detector will allow CMS to address satisfactorily the physics issues for Higgs and SUSY at the 10 fb-1 luminosity level.

Progress was reported on the performance of the tracking and these studies will continue. It was also shown that a concerted effort is being made by CMS to control the material budget of the Tracker.

Concerning the ECAL, preliminary results show improved robustness of the APDs to photon irradiation. Moreover, ingots can now be grown in Russia with a diameter large enough to cut two crystals per ingot, thus considerably improving the production rate.

6.  DISCUSSION ON THE LHC COMPUTING REVIEW The LHCC deliberated on the Report of the Steering Group of the LHC Computing Review. The LHC Computing Review evaluated the current situation, plans and prospects of data management and computing at the LHC. Fulfillment of these requirements will, on the same basis as the successful construction of the LHC accelerator and particle detectors, be crucial for the success of the LHC physics programme. Based on the detailed work of three independent panels - the Software Project Panel, the Worldwide Analysis and Computer Model Panel and the Management and Resources Panel, the Steering Group reached a number of conclusions as given in the report of the group (reference LHCC 2001-004 and RRB-D 2001-3). Following an additional review, the LHCC will discuss the matter at its May 2001 session and provide its conclusions and recommendations.7.   CMS LEVEL-1 TRIGGER TECHNICAL DESIGN REPORT The LHCC has completed its scientific, and technical evaluation of the CMS Level-1 Trigger (L1) TDR submitted in January 2001. The Committee was impressed by the quality of the work presented in the TDR and congratulates the Collaboration. The concept of the L1 trigger built around the topological association of predefined elements associated with leptons, photons, jets and missing energy is well suited to the challenge of triggering in a flexible and responsive manner. The TDR demonstrates that technological issues do not pose potentially prohibitive problems.

The Committee has no major concerns. An ancillary document (LHCC 2001-009) records the overall assessment by the LHCC of the project at this time, thereby emphasizing some points which should be monitored in the future as the project progresses. This document also contains a list of agreed milestones for monitoring the progress of the project. The LHCC review of the TDR was not a detailed review of engineering or procurement readiness. These are anticipated in the planned progress of the project (Electronic Procurement Readiness Review PRR and the Electronics Systems Review ESR). Written reports of each PRR and ESR should be made available to the LHCC through its referees.

Recommendation:

The LHCC recommends general approval of the CMS Level-1 Trigger Technical Design Report, pending a final cost evaluation. The LHCC considers the schedule given in the TDR and the list of milestones in the ancillary document to be appropriate. They will be used by the Committee to measure and regulate the future progress of the project.

8.  REPORT FROM THE ALICE REFEREES The LHCC heard a report from the ALICE referees, concentrating on the overall status of the experiment, a more detailed presentation by H. Dijkstra, who is acting as a consultant, on the Inner Tracking System and the preliminary reactions to the Addendum to the Dimuon Forward Spectrometer TDR.

Good overall progress was reported since the recent ALICE Comprehensive Review. The list of milestones presented at the Comprehensive Review has become the ALICE reference baseline, but some minor adjustments may arise after the new Technical Coordinator has completed his review. Some delays in the Muon Spectrometer, in the Trigger and ZDC were reported. Although not currently critical, the Collaboration is making efforts to recover the time. Moreover, in order to gauge better the progress of the TPC project, the referees have asked for a more detailed and complete report from the TPC group prior to the May session of the LHCC. Finally, it is expected that the milestones for the PHOS will be met as scheduled.

H. Dijkstra reported on the status of the Inner Tracking System. The reduction in the length of the two outer SSD layers and the two inner Pixel layers was reported. This reduces the overall cost of the ITS without affecting the physics performance and results in an overall matching of the ITS geometry to the acceptance of the TPC. Finally, good progress was reported on minimizing the thickness of the Pixel detectors and on the technology and yield of the bump-bonding process.

The referees also reported on their preliminary reactions to the Addendum to the Dimuon Forward Spectrometer Technical Design Report. The Addendum details the design modifications to the tracking chambers, and the resulting integration and overall performance issues. It also provides a status report of the associated detector sub-systems and introduces the conceptual design of the newly-proposed V0 detector, whose aim is to reject background events produced in the LHC machine during pp data-taking. Following further questions and discussions, the referees will make a full report at the next meeting of the LHCC.

Finally, plans are underway to organize a dedicated workshop on heavy-ion physics at the LHC, which will bring together theorists and experimentalists from the international heavy-ion community. The first session of the workshop will be held in the week 8-12 October 2001 and the entire multi-session forum is expected to last until mid-2002.

9.  REPORT FROM THE ATLAS REFEREES The Committee heard a report from the ATLAS referees, concentrating on the experimentís plan for detector completion, installation and commissioning, the status of the Muon Spectrometer, Pixel detector, and the Trigger/DAQ.

The referees reviewed the ATLAS general schedule. The LHCC considers that it is realistic to expect ATLAS to install a detector for the beginning of LHC operation in 2006, although detector installation is foreseen beyond the initial running. The presented lay-out of the initial detector will allow ATLAS to address satisfactorily the physics issues for Higgs and SUSY at the 10 fb-1 luminosity level.

Good progress was reported on the construction of the Muon Spectrometer - MDTs, CSCs, RPCs and TGCs. In addition, the referees reported on the Pixel detector. The failure of the DMILL process has resulted in a switch to DSM technology, resulting in a 15-month delay of the Pixel project. Such a delay does not allow installation of the Pixel detector inside the Inner Detector in 2004, and a new lay-out is required so that the Pixel detector installation can be performed independently of the Inner Detector in 2005. The LHCC noted that the design of the innermost B-layer is not changed. The LHCC takes note of the proposed modifications and asks to be informed of progress in the future.

The referees also reported on the status of the ATLAS Trigger/DAQ. Results from the studies of the trigger performance for various physics channels was presented, illustrating that the proposed system is robust. Further comparisons between the ATLAS and CMS trigger rates will be pursued. The new Trigger/DAQ organization has been put in place with the aim of preparing the TDR for submission in December 2002 rather than in December 2001. The LHC considers that the schedule for preparing the Trigger/DAQ TDR is tight but reasonable and remains appropriate for the timely completion of ATLAS. Finally, the LHCC asks for the detailed milestones on the hardware development and production.

10.  REPORT FROM THE LHCb REFEREES The Committee heard a report from the LHCb referees, covering progress towards the submission of the TDRs for the Vertex Locator (VELO) and Muon detectors, the organization of the collaboration and the developments in the various sub-systems. Currently, no known delay appears to be critical, and the LHCC will continue monitoring carefully the LHCb schedule and milestones. The Collaboration remains committed to be ready for installation in mid-2004.

The TDRs for the VELO and Muon detectors are on track for presentation to the LHCC at its session in July. For the former, the referees reported good overall progress for the mechanics and vacuum, the silicon technology, the material budget and the position of the off-detector electronics. Furthermore, good progress was reported on the design of the Muon detector.

The referees also reported on updates to the organization of the collaboration. A number of major countries have now signed the LHCb Memorandum of Understanding, representing a substantial part of the total cost.

11.  TEST BEAMS M. Hauschild presented a status report on the SPS and PS Fixed Target Programmes. The Lepton Pre-injector (LPI) at the PS Complex has been running since 26 February for COLDEX and for the CMS HF group. It is scheduled to run until 12 April. First injection tests in the PS were scheduled for 22 March with physics in the East Hall scheduled to commence on 2 April. However, a magnet serving the East Hall has developed a leak and the time needed for the replacement could lead to some short delay of physics start-up in the East Hall. Finally, some beam-time is still available in the East Hall.

Concerning the SPS, agreement was found between the NA57 heavy-ion experiment and CMS, so that the former could collect additional proton reference data at H4. The revised schedule includes also some further minor modifications.

12. DATES FOR 2001 LHCC MEETINGS 16-17 May
4-5 July
3-4 October
21-22 November

The LHCC received the following documents:
 

  • Report of the steering Group of the LHC Computing Review (LHCC 2001-004).*
  • ALICE Comprehensive Review (LHCC 2001-005).*
  • *Restricted circulation
     
     
      Emmanuel Tsesmelis
    Eómail: LHCC.Secretary@CERN.CH
    Tel. 78949, 164057
    LHCC Secretariat: Janet Grant (Bldg. 14/4-022) Tel. 73424, Janet.Grant@CERN.CH