DeepInelastic

Deep inelastic scattering (DIS) refers to high-energy scattering processes in which leptons (such as electrons or muons) or neutrinos collide with hadrons and exchange a highly virtual gauge boson (photon or W/Z). The interaction transfers large momentum and typically breaks the hadron apart, producing a hadronic final state with many particles. DIS contrasts with elastic scattering, where the target remains intact.

DIS provided crucial insight into the internal structure of nucleons. In the parton model, the lepton scatters off quasi-free point-like constituents (partons) whose momentum distributions depend on resolution scale. Quantum chromodynamics (QCD) explains deviations from simple scaling as the scale Q^2 changes, revealing gluons and the evolution of parton densities with energy.

Kinematic variables include the squared four-momentum transfer Q^2, the Bjorken scaling variable x, and the invariant mass of the hadronic system W. Observables are structure functions, notably F1(x,Q^2) and F2(x,Q^2) (and FL, the longitudinal structure function). In the quark-parton model, F2 is related to the sum of quark charges squared times their distributions; measurements constrain parton distribution functions.

Experiments at SLAC, CERN, DESY and other facilities over several decades established the DIS framework and led to precise parton distribution functions used in high-energy physics, including LHC predictions. DIS continues to be extended to nuclear targets to study parton behavior in nuclei and to neutrino scattering for flavor separation and weak interaction studies.

Discussions of DIS include neutral-current and charged-current processes, with different probes (electromagnetic vs weak) providing complementary information about quark flavor and gluon content. Deep inelastic scattering remains a foundational tool in the study of quantum chromodynamics and hadronic structure.