We show that an endpoint overlap model can explain the scaling laws observed
in exclusive hadronic reactions at large momentum transfer. The model assumes
one of the valence quarks carries most of the hadron momentum. Hadron form
factors and fixed angle scattering are related directly to the quark wave
function, which can be directly extracted from experimental data. A universal
linear endpoint behavior explains the proton electromagnetic form factor,
proton-proton fixed angle scattering, and the t-dependence of proton-proton
scattering at large s>>t. Endpoint constituent counting rules relate the number
of quarks in a hadron to the power-law behavior. All proton reactions surveyed
are consistent with three quarks participating. The model is applicable at
laboratory energies and does not need assumptions of asymptotically-high energy
regime. A rich phenomenology of lepton-hadron scattering and hadron-hadron
scattering processes is found in remarkably simple relationships between
diverse processes.Comment: 23 pages, 7 figure
