REPORT OF THE MUONS INTERNAL REVIEW 2003

T.CAMPORESI, S.SCHAEL, D.TREILLE

 For all systems: 
•	impressive progress, positive impression (but at different levels...). Understandably, in the review, the accent was put on planning and installation matters. It is however still imperative to focus also on quality tests (the ones already done and those still to be done). Even if feed­back may be already difficult in some cases, « un homme averti en vaut deux ». Furthermore it may be good to have some documentation (CMS Internal Notes) describing the findings at the production sites and detailing the quality assessment, quality control and the results obtained.
•	need to follow as long as possible one or few chambers, as final as possible, fed with gas in a way as close as possible to the final one, and irradiated, to see if something happens in the “long” term. It is also important to know under what conditions the installed chambers will be kept (gas, etc...) and what may happen to them.  A subset of these should regularly be checked for performance. 
•	since some problems are still found at intermediate stages in their travel to SX5, one should, besides identifying and correcting what is possible, be ready to have a sustantial program of testing (cooling, gas tightness, electronics, “flying DAQ”,...) at the final location. The required procedures should be well defined and one should get an idea of the windows of opportunity open for this sometimes parasitic activities.

DT:
last year we were still quoting potential mechanical unknowns (honeycomb non planarities corrected by applying weights, long term stability in particular of gluing). We had recommended submitting a chamber to the hardest conditions they may encounter (mechanical, cycling in tem­perature with gas leak tests,..). Clearly one should avoid that this be added to the workload at the ISR. Any comment on what has been done or could be done?
CSC:
apart from some worries concerning this last point (surprisingly high failure rate of some boards), very good situation overall. The late start of modules like LVDB/LVMB and ALCT has been recovered well. Two FAST sites have a 6-months delay due to the delay of electronics: they have good hope to catch­up.
For next year (or before): the problem of the staged ME4/2 station which, we guess, will be required at some level should be discussed, studied and scenarios put forward. Otherwise optimum benefit may not be taken from the current production.
DT:
besides the point raised above, the main concerns are:
•	delay in production startup in Torino. The reasons for the delayed start (tooling?) and the parameters governing the production should be clarified. All ways of recovering time (more manpower?) should be considered. It would be good in the near future that the Review Committee could have a more direct interaction with the physicists responsible of Torino center.
•	the first minicrate test in beam was successful. Several components may have changed. Is there a complete record of irradiation tests? Clearly a test of a final chamber with its minicrate under irradiation in GIF would be extremely valuable: the best way to do it and the infor­ mation to be extracted should be discussed soon.
•	concerning the minicrate production schedule it is clear that it appears tight. All should be done to speed up and especially to avoid lowering chambers without minicrates.
•	the beam tests have been successful. The “emulator” is a nice check. Could it reproduce the 10% inefficiency observed when two SL are supposed to see a muon?

Hard work has been necessary to start ‘dressing’ chambers in the ISR. It appears to be going well now. All concerned are to be commended.
RPC:
One should first acknowledge the progress which has been accomplished.
•	the objective to be reached for the start of CMS (oiling, the full barrel and a forward system reduced by half) is now clearly defined and sounds reasonable. Because oiling is made for all chambers, questions concerning the reduction of the noise rate are, at least at present, of secondary importance.
•	the progress of the production and assembly is good. The gap (single and double) production, the chamber production and the testing procedures seem satisfactory, although some more documentation would still be welcome: which fraction of the chambers go through the “hospital”, which diagnostics, etc..?
Among other successful activities, one can in particular acknowledge the excellent work done in Korea. Also the “thin” version of the RPC is in good shape.
But again one would like to know a bit more on the conditions under which the production and oiling are done, for instance the control of humidity,...
•	although much work and progress happened in GIF, one has not yet used the closed gas circuit with purifiers, and one does not yet know how the chambers behave in realistic conditions. The presentation of the results obtained in GIF was hard to follow, the goals pursued and the question marks left should be underlined.  It is satisfactory that the important and maybe crucial roles of the water content and rate of gas flow have been recognized. However this has now to be implemented in a correct and controllable way both in test and for the final gas system of CMS.
•	There was a clear attitude of the RPC community to ask to be relieved of a too strong involvement in the test program in order to focus on the production of chambers. The manpower problem seems acute. However the next 6 months or so of GIF will be crucial to get the answers needed. The optimal way to proceed (more focused program, help from the gas group, common activities with Atlas, help from outside...) has to be rapidly defined, in close liaison with F.Hahn. Equally important is to define the CMS gas system, within the freedom which is still left.
•	One could still be worried, if one recalls the Babar experience, that the inefficiency problems, for instance due to drying under gas flow, may be local (near inlet and outlet?) rather than uniform. In this respect, for a chamber large enough, the cosmic test (concerning a large area) and the beam test (centered) may contain different information. The former can reveal local pockets of inefficiency.
•	a few questions, maybe too far away from realism, raised last year (segmentation of RPC to avoid loosing a full plane,...) have not been considered. Any comment?

Use of Cosmic ray muons:
•	among many others, the question of the use of cosmic muons is an important one. This cannot be improvised and it is urgent to define at least a strategy and check that one does not introduce features which will jeopardize this possibility. A workshop is fine.  But the definition of a TASK FORCE on this matter (of “interet general” for the experiment) with a few (young) people well put in charge could  be an excellent initiative as well.

Alignment
•	clearly the first question would be to know what CMS needs.
Tracks will give the final word on alignment. Each time something is done in CMS (opening, changing the field, ..) We suppose one will redo such an alignment. The problem is to know what happens in between and to get warnings if an “earthquake” of any origin occurs (within the “rigid” muon system, within the “rigid” tracker, or between the two), which is rather a monitoring problem. It is difficult to improvise on these matters, especially if there is no choice left anymore... What about the same as above: an “alignment” TASK, concerning all the experiment, thinking hard on what is needed, using the experience of LEP (what kind of problems happened during LEP time?), etc...
In particular the potential use of parallel halo muons crossing both RE1/1 and the forward part of the tracker should be considered.