Article révisé par les pairs
Résumé : Three-jet production is studied for the first time in deep-inelastic positron-proton scattering. The measurement carried out with the H1 detector at HERA covers a large range of four-momentum transfer squared 5 < Q2 < 5000 GeV2 and invariant three-jet masses 25 < M3jet ≲ 140 GeV. Jets are defined by the inclusive k⊥ algorithm in the Breit frame. The size of the three-jet cross section and the ratio of the three-jet to the dijet cross section R3/2 are described over the whole phase space by the predictions of perturbative QCD in next-to-leading order. The shapes of angular jet distributions deviate significantly from a uniform population of the available phase space but are well described by the QCD calculation. © 2001 Elsevier Science B.V. All rights reserved.