Measurement of dijet azimuthal decorrelation in pp collisions at $$\sqrt{s}=8\,\mathrm{TeV} $$ s = 8 TeV

Abstract

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. The analysis is based on the proton-proton collision data collected with the CMS experiment at a centre-of-mass energy of 8 corresponding to an integrated luminosity of 19.7. 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.

Transverse-Momentum-Dependent Distributions with Jets

“…(2). This is closely related to the azimuthal decorrelation measured at the Tevatron [16], RHIC [17] and LHC [18,19], and calculated to next-to-leading logarithmic accuracy in Refs. [20][21][22].…”

Azimuthal correlations for inclusive 2-jet, 3-jet, and 4-jet events in pp collisions at $$\sqrt{s}= 13~\hbox {TeV}$$ s = 13 TeV

“…Finally, predictions from the dijet NLO HERWIG 7 event generator matched to parton shower contributions with the MC@NLO method provide a very good description of the ∆φ 1,2 measurements, showing improvement in comparison to HERWIG++. All these observations emphasize the need to improve predictions for multijet production. Similar observations, for the inclusive 2-jet cross sections differential in ∆φ 1,2 , were reported previously by CMS [5] at a different centre-of-mass energy of 8 TeV. The extension of ∆φ 1,2 correlations, and the measurement of the ∆φ min 2j distributions in inclusive 3-and 4-jet topologies are novel measurements of the present analysis.…”

“…The measurement of azimuthal angular correlations (or decorrelation from π) in inclusive 2-jet topologies is a useful tool to test theoretical predictions of multijet production processes. Previous measurements of azimuthal correlation in inclusive 2-jet events were reported by the D0 Collaboration in pp collisions at √ s = 1.96 TeV at the Fermilab Tevatron [1,2], and by the ATLAS Collaboration in pp collisions at √ s = 7 TeV [3] and the CMS Collaboration in pp collisions at √ s = 7 and 8 TeV [4,5] at the LHC. Multijet correlations have been measured by the ATLAS Collaboration at √ s = 8 TeV [6,7].…”

The complete NLO corrections to dijet hadroproduction

“…refs. [34][35][36][37][38][39][40][41][42][43][44][45][46] for a list of recent ATLAS and CMS papers approved as publications in the context of jet physics). Having said that, fixed-order perturbation theory is somehow pathological, precisely because a jet can coincide with a photon.…”