Surfaces of (best-fit models) in the plane K₀ − δ. First row: fit performed on p data (free parameters α and q_p). Second row fit performed on He data (free parameters α and q_He). Third row: fit performed simultaneously on p and He data (free parameters α, q_p and q_He). The columns from left to right correspond respectively to AMS-01, BESS88 and BESS-TeV data. The colour code for the contour plots (iso-) superimposed on each graph is (from white to darker shades)  = {0.5, 1, 2, 5, 10}.