Total energy E_sum (without rest-mass energy contribution) of the fluid elements within the jet head having βΓ larger than a certain value, as a function of such a value. The different lines and colours correspond to the result obtained by limiting the calculation within 10°, 20°, 30°, and 40° from the jet injection axis. The plot refers to ≈9 s after the jet launching time. The inset shows a selected zoomed-in portion of the same profiles.