  A measurement of the decorrelation of azimuthal angles between the two jets
with the largest transverse momenta is presented for seven regions of leading
jet transverse momentum up to 2.2 TeV. The analysis is based on the
proton-proton collision data collected with the CMS experiment at a
centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of
19.7 inverse femtobarns. The dijet azimuthal decorrelation is caused by the
radiation of additional jets and probes the dynamics of multijet production.
The results are compared to fixed-order predictions of perturbative quantum
chromodynamics (QCD), and to simulations using Monte Carlo event generators
that include parton showers, hadronization, and multiparton interactions. Event
generators with only two outgoing high transverse momentum partons fail to
describe the measurement, even when supplemented with next-to-leading-order QCD
corrections and parton showers. Much better agreement is achieved when at least
three outgoing partons are complemented through either next-to-leading-order
predictions or parton showers. This observation emphasizes the need to improve
predictions for multijet production.

High Energy Physics - Experiment