13 December 2006


Please find attached the statements from three detector concept
study groups on the push-pull option The WWS would like to
add a few general comments:

The WWS thinks it is fundamental for the scientific program of
the ILC to have two complementary detectors which create the support
of a large HEP community in the world.  Without such support the ILC
project would not be funded. We therefore believe that there is
a serious risk in eliminating the 2nd IR unless the viability of
the push-pull option can be convincingly proven.

The concept studies have not found any show stoppers for the
push-pull option, but the depth of the studies so far is not
sufficient to place a high level of confidence on this conclusion.
Since we cannot conclude with certainty that the push-pull option
can meet the requirements of engineering and physics,
if the push-pull approach is implemented in the reference design
we think a two IR option must be maintained as a back-up in the RDR
until the details have been studied more, and a higher level
of confidence has been achieved.

The ideal scheme for the HEP community which was intended in the
2 IR scheme was a fast and frequent switching between two experiments
where there is little need for re-tuning of the beamlines so that
there is no significant loss of luminosity. We wonder if sufficient
resources have been used toward realizing such a scenario.

We acknowledge that the push-pull scheme for two detectors
would reduce the cost considerably. A large amount of efforts from
the concept studies went into this direction with however
insufficient time to fully prove the feasibility.
They are willing to actively continue their effort.

Finally, even though we understand the tight schedule of GDE,
we are concerned that the push-pull option is already included in
the IWA (Interim Working Assumption) upon which future design
efforts will be based. The normal change control process
seems to be bypassed for this issue, and we worry that it might
disturb the change control process in future. 

will be posted here