semiinclusive

Semiinclusive is a term used in experimental physics to describe reaction channels in which some, but not all, of the final-state particles are detected and analyzed. In contrast to inclusive measurements, where all final states are summed over, and exclusive measurements, where every final-state particle is identified, semiinclusive analyses select events based on a subset of the final-state topology while integrating over the rest. The term is sometimes written as semi-inclusive, but semiinclusive is also common in literature.

In high-energy physics, semiinclusive processes are widely used. Examples include semi-inclusive deep inelastic scattering (SIDIS), where a scattered lepton and one or more hadrons are detected in the final state, and semi-inclusive hadron production in electron-positron annihilation. Measurements typically depend on variables such as momentum transfer Q^2, Bjorken x, the detected hadron’s fractional energy z, and transverse momentum pT. These analyses provide access to fragmentation functions and transverse-momentum-dependent parton distributions, offering insight into how quarks and gluons form observable hadrons.

Practical considerations include corrections for detector acceptance and efficiency and careful background subtraction. The unobserved final-state dynamics can introduce model dependence, since cross sections are obtained by integrating over those unmeasured components. Nevertheless, semiinclusive data offer a balance between statistical precision and sensitivity to underlying dynamics, enabling constraints on parton-level quantities without the full specificity required of exclusive measurements.

See also: inclusive process, exclusive process, SIDIS, fragmentation function, parton distribution function.