Dark Matter again

I went to the talk "Measuring Dark Matter at Colliders:" how could I not go? Dark matter and dark energy are all the rage at the moment--a quite embarrasing rage, since nobody knows what or why yet. (And some of us still wonder if the cosmologists got their models quite right.) And I'm a collider guy.

Dr. Birkedal started with a nice model-independent calculation, which looked interesting if a bit out of range.

Then he started in on the bulk of his talk, which used supersymmetry. Strike one: that's been a super-cemetery of career time, with nothing to show but limits. The annihilation cross-section (or creation cross-section) is largely independent of the mass. Very good! He went on to demonstrate that the dark matter particle candidates were most easily generated in e+ e- machines, such as the linear collider being bruited about. OK. But the best signature is a colinear photon plus missing energy, and the background rate of bogus colinear photons is incredible in electron machines. Strike two. Further, measurements of the creation rate depend on quite a few supersymmetric particle masses. Strike three--we've never seen even one. Measuring these masses can be made using angular distributions by looking close to the endpoint. Strike four--detector response smears these things out.

I think I can contain my enthusiasm.