semiexclusive

Semiexclusive is a term used in high-energy and nuclear physics to describe a class of scattering events in which only part of the final-state particles are observed or specified, while the rest of the final state remains unobserved or is integrated over in the analysis. This places semiexclusive measurements between inclusive processes, where no final-state restrictions exist, and exclusive processes, where every final-state particle is detected and identified.

Typical semiexclusive scenarios include semi-exclusive deep inelastic scattering, where the scattered lepton is detected and a particular hadron or system is identified, but the remaining hadronic final state is not fully reconstructed. Another common case is semi-exclusive meson production in photon- or lepton-induced reactions, described by processes such as a virtual photon interacting with a target and producing a clearly identified meson alongside an unmeasured hadronic system X. In some experimental setups, features like a leading particle or a rapidity gap may be used to tag semiexclusive events, without requiring full reconstruction of X.

The semiexclusive approach is useful for probing dynamics of hadronization, parton correlations, and fragmentation, while offering higher event yields than fully exclusive analyses. It also poses challenges for cross-section extraction, since results depend on models or simulations to account for the unobserved final state and detector acceptance. Consequently, semiexclusive measurements often rely on unfolding, background subtraction, and careful systematic studies to relate observed yields to underlying physical quantities. See also inclusive and exclusive scattering, diffractive processes, and factorization concepts.