Deep Inelastic Scattering

Electron-proton scattering reveals the quark substructure of matter

Beam energy E (GeV) 50 GeV
Scattering angle θ 60°
y inelasticity y = 0.40
250
Q² (GeV²)
0.25
Bjorken x
750
W² (GeV²)
0.38
F₂(x,Q²)

About

Deep inelastic scattering (DIS) — the electron-proton equivalent of Rutherford scattering — was performed at SLAC in 1968-69 (Nobel 1990 to Friedman, Kendall, Taylor). The scaling of the structure function F₂(x) approximately independent of Q² at fixed x (Bjorken scaling) was direct evidence for pointlike partons. The kinematic variables Q² = −q² (virtuality), x = Q²/2p·q (Bjorken x = parton momentum fraction), and W² = (p+q)² (hadronic invariant mass) completely characterize each event.