Charged Kaons at the Main Injector (CKM)
  The CKM collaboration is proposing to measure the branching ratio of the rare K decay (K+ --> pi+ nu nubar) at the Main Injector at Fermilab. Our goal is to be able to observe about 100 events, for a Standard Model branching ratio of about 1.0E-10. This implies that we must be able to reduce the background to a few events. 
C. Milstene, et al, CKM collaboration