Science magazine has an article this week entitled High Energy Physics: Exit America?. It describes the US HEP budget situation, and gives details of the probable cancellation of the BTeV experiment. Evidently neither Michael Witherell, the Fermilab director, nor any of the physicists working on BTeV, had any idea this was going to happen until the day the FY 2006 budget was released.
The Science article is a lot more pessimistic about the future of high energy physics in the U.S. than any of the public reports you will read produced by the US high energy physics community, but it is also a lot more realistic. The underlying reality is that after the Tevatron stops operations in 2010 (because it can’t compete with the LHC), for the first time in the history of modern physics there will be no machine operatiing at the high energy frontier in the US. Fermilab is planning an active neutrino physics program, but this will be much more limited in scope than what the lab is doing today and has been doing since its founding.
The only plan on the table for the US to get back into the high energy accelerator business is the International Linear Collider (ILC), but the question of how such a machine would be financed, and whether it would even be constructed in the US at all, remains up in the air. In a very real sense, the future of experimental high energy physics in the US after 2010 is a very large question mark.