Direct leptons in hadron collisions

A systematic review of the results of experiments on the study of processes of direct production of leptons in hadron collisions is presented. The experimental facilities are described. Dependences of spectra of single direct leptons and dileptons on different kinematic variables and other parameters are analyzed. Different possibilities of theoretical interpretation of direct leptons are discussed. It is noted that contribution of lepton and half-lepton modes of charmed D- and F-meson decays is essential for the leptons with 2 GeV/c<=P1<=4 GeV/c. Perspectives of investigating direct leptons in further experiments are considered