Abstract

A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, varDelta phi _{12}, is presented. The measurement considers events where the two leading jets are nearly collinear (“back-to-back”) in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of 13,text {Te}text {V} and corresponding to an integrated luminosity of 35.9{,text {fb}^{-1}} are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region 177^circ< varDelta phi _{12} < 180^circ . The 2- and 3-jet measurements are not simultaneously described by any of models.

Highlights

  • Azimuthal correlations in inclusive 2-jet events have been ms[p3ipoe],nacssoaulanlrtdiesadiobcpnyersnettvbheiyero-outChfs-eMlmyASabTsysCLetoAhnlSelearbDCgoyo0rlaolCtafiboo√onllrsaaab=ttioor√1na.ts9iao6tn=√TiensV7=p,[p1 ̄8,7,c2oT]a,lenliVidn13 TeV [4,5,6], but none of the measurements considered in detail the region close to the back-to-back configuration

  • The effects of applying a transverse momentum dependent parton showering to the dijet azimuthal angular correlation were studied in [12]

  • The resulting jet energy scale calibration (JES) uncertainties in the normalized inclusive 2-jet distributions due to bin migrations are less than 2%, whereas for the normalized inclusive 3-jet distributions they are less than 3%

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Summary

Introduction

Azimuthal correlations in inclusive 2-jet events have been ms[p3ipoe],nacssoaulanlrtdiesadiobcpnyersnettvbheiyero-outChfs-eMlmyASabTsysCLetoAhnlSelearbDCgoyo0rlaolCtafiboo√onllrsaaab=ttioor√1na.ts9iao6tn=√TiensV7=p,[p1 ̄8,7,c2oT]a,lenliVidn TeV [4,5,6], but none of the measurements considered in detail the region close to the back-to-back configuration. A detailed study of azimuthal correlations close to the backto-back configuration allows a more precise test of different resummation strategies, and it is a first step towards an improved understanding of the effects of soft initial and final state gluons [7,8]. The inclusive 3-jet distributions, differential in Δφ12 and pTmax, with the pT of third highest pT jet typically being 1-2 orders of magnitude smaller than pTmax, are suitable to test resummation effects arising from the presence of multiple scales in the interaction.

The CMS detector
Theoretical predictions
Jet reconstruction and event selection
Measurements of the normalized inclusive 2- and 3-jet distributions
Comparison to theoretical predictions
Findings
Summary
Full Text
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