Zeuthen Crossing Angle Meeting (Physics & Backgrounds only)

Meeting and Study Goals:
1.      Quantitative comparison of physics capabilities and background levels in TESLA with and without a 2*10
         mrad crossing angle,  order to make an assessment of how desirable each option is from the point of physics.
         The results should then serve as input to the overall evaluation of the crossing angle issue in TESLA, together
         with several related machine issues presently under discussion  (e.g. see 7th item in the
         ECFA BDIR project matrix).

2.      Initiate collaborative work with our American and Asian colleagues to evaluate/compare/improve the
         expected capabilities of the warm and cold technologies for physics channels requiring good high energy
         electron veto capabilities in the very forward region and for measuring the properties of the spent beam.


     Want to present conclusions for input to the ITRP by the Paris meeting in April, including considerations for
          both detector/physics issues and accelerator issues.

P. Bambade summary:
1.  "my preliminary conclusion is that both head-on and crossing-angle are acceptable, with some slight advantages
      for each depending on the physics topic. For me the overall (physics) balance seems slightly in favour of head-
      on, but even in the worst cases it is possible to deal with a crossing-angle."
2.  "...the driving issues are clearly on the technical side:
       - more constrained head-on extraction; it would be nasty if the head-on scheme would induce luminosity
          and/or energy limitations...
       - electrostatic separators
       - on the other hand for the crossing-angle the small SC quads must be demonstrated to work and the crab-
          crossing certainly makes things more complicated;
      The first two and last two items could be considered as risks for the head-on scheme and crossing-angle
      scheme, respectively.
      So in some sense the cold project offers some more flexibility here over the warm, since there is a fall-back
      solution if the preferred choice (which ever it is) were to later turn out to have some overwhelming problems. In
      this sense the fact that both are acceptable for physics is also an advantage."
      I am still drafting a summary report on this which I will distribute to the group before making it final."
3.  "Another positive outcome is that the work done has led to further questions on many aspects, which may turn
     out to be even more important than the crossing-angle study itself, e.g. the need to have fast read-out in the
     LumCAL at a warm LC, and revisiting some of the backgrounds. Also the SUSY study itself is important as it
     can help strengthen the LC physics case (considering also the discussion of complementarity with LHC and
     synergy with cosmology)."