Dear Colleagues,

First let me say that I really appreciated this document and think that
it is an excellent summary of current ideas and a great launching point for
contributors to get informed and start asking and hopefully answering some questions.
I missed the first general meeting. Are there minutes of that available ?

Not sure how best to deal with comments. Will probably forward detailed ones
in the near future to the contact persons.

Less detailed but more important ones for now :

o page 5/6 performance tables are messed up. These numbers are important to convey,
although I can guess what they are likely to be !

o I notice that the document studiously ignores the C word (ie. cost). It is
important to place the focus on detector/physics performance at this time
which is done, but I think that the cost issues should at least not be ignored.

Without introducing this aspect, alternative choices especially in the
(B, R) plane and consequences of such are downplayed.
Eg. putting the calorimetry inside the coil is portrayed as a "no-brainer".
This is true, IF such a large coil is both technically feasible, a tolerable risk,
and financially affordable.

o When we get further with the discussions re 1/2 IRs, we need a better appreciation of
whether the primary goal is to nurture a design concept which seeks an
overall optimized detector, or one which is purposefully complementary in eg. both
performance and technical risk to other concepts.

One example of an area where this plays a role is the vertex detector.
For the sake of argument, one could imagine a scenario where one detector concept
has a higher B-field than in the LDC case, and a design optimized for vertexing,
somewhat to the exclusion of other goals.
I think there is then a lot of potential for a detector design like LDC/GLD
in that case to put reduced emphasis on high B field, give up a little on vertex
performance,and do a superb job of tracking and particle flow, while highlighting a
bit more probably unique capabilities like particle ID.

So while I appreciate that the sketch document was aimed at being inclusive, we may end
up being prodded to explore options which are at some level different for the sake of
getting two complementary detectors. I agree that it is a good starting point to aim at
a detector which is optimized in all facets, although I think in practice there has to
be some tension between the different facets.

o The sketch document does not address at all how the detector concept interfaces with the
needs of initial-state condition measurements ( lumi, energy, polarization both
absolute and differential).


regards,

Graham Wilson