Sent to CCB on Dec 13, 06


The MDI panel had a meeting on Dec. 8 and discussed the push-pull option.
There were reports from the three concept studies and the WWS about their
respective statements.

In general there was grave concern about the risk of losing the 2-detector
scenario in its entirety. There was also concern that the push-pull option for
2 detectors at a single IR has not been investigated sufficiently thoroughly to
allow a sound technical basis for its acceptance as the baseline.

The fact that the primary motivation for the push-pull model is to save on the
cost of the accelerator has caused considerable misunderstanding within the
detector community, which does not enjoy the same level of cost-consciousness
as the GDE. We thus suggest that there be efforts both by GDE and WWS/Concepts
to share and communicate the overall cost reduction strategy, possible trade-offs,
and its implementation.

Regarding CCR#23, we recommend that, if the push-pull option be included
as the baseline, then the 2 IR option be also explicitly included in RDR as
an 'alternative configuration', with a cost estimate. We understand that such a
cost estimate may, by necessity, be less complete than the baseline cost.
In addition, provisions should be included in the baseline design to facilitate
a change to the 2 IR design in the event of either:

a) the push-pull model proving unfeasible, or
b) additional funding being secured for a second BDS and IR.

Finally, we urge the GDE and the WWS to give a new charge to the
push-pull task force to continue the study of the technical implementation
of the push-pull option.