Measurement of the Three-jet Mass Cross Section in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV

This thesis describes the measurement of the inclusive three-jet cross section in proton-antiproton collisions at √s = 1.96 TeV measured at the D0 experiment at the Fermilab Tevatron Collider in the Fermi National Accelerator Laboratory, Batavia, Illinois, USA. The cross section as a function of three-jet invariant mass is provided in three regions of the third jet transverse momentum and three regions of jet rapidities. It utilizes a data sample collected in the so called Run IIa data taking period (2002-2006) corresponding to the integrated luminosity of about 0.7 fb-1. The results are used to test the next-to-leading order predictions of Quantum chromodynamics computed using the latest parton distribution functions.