Toy Parton Distribution Functions

What you are seeing: sketches of the longitudinal momentum fractions $x f_i(x)$ carried by each parton species. Valence quarks peak near $x \sim 0.2$ , sea quarks dominate at small $x$ , and the gluon carries the bulk of the proton momentum (about half at $Q^2 \sim 10$ GeV²).

Figure 1. Schematic

x f(x)

for valence, sea, and gluon partons.

x cursor0.200

x axis

WHAT TO TRY

Move the x cursor: valence quarks pile up near x ~ 0.2 while the sea and gluon blow up at small x. The proton momentum is shared, and most of it is not in the quarks you can name.
Switch the x axis to logarithmic: the small-x rise of the sea and gluon, hidden on a linear scale, dominates the picture. This is why colliders probing small x see a glue-rich proton.
Watch the sum-rule readout: the momentum fractions integrate to 1, with the gluon carrying roughly half. The valence quarks account for only a fraction of the proton momentum.