Measurement and QCD analysis of double-differential inclusive jet cross-sections in pp collisions at sqrt(s) = 8 TeV and ratios to 2.76 and 7 TeV

TL;DR

This paper reports a detailed measurement of inclusive jet cross sections at 8 TeV, compares them with QCD predictions, and uses the data to refine the understanding of parton distribution functions and the strong coupling constant.

Contribution

It provides the first comprehensive double-differential jet cross section measurement at 8 TeV and uses it to improve constraints on PDFs and determine alpha_S(MZ).

Findings

Jet cross sections agree with NLO QCD predictions within uncertainties.

Measured alpha_S(MZ) consistent with world averages.

Enhanced constraints on parton distribution functions from data.

Abstract

A measurement of the double-differential inclusive jet cross section as a function of the jet transverse momentum pT and the absolute jet rapidity abs(y) is presented. Data from LHC proton-proton collisions at sqrt(s) = 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns, have been collected with the CMS detector. Jets are reconstructed using the anti-kT clustering algorithm with a size parameter of 0.7 in a phase space region covering jet pT from 74 GeV up to 2.5 TeV and jet absolute rapidity up to abs(y) = 3.0. The low-pT jet range between 21 and 74 GeV is also studied up to abs(y) = 4.7, using a dedicated data sample corresponding to an integrated luminosity of 5.6 inverse picobarns. The measured jet cross section is corrected for detector effects and compared with the predictions from perturbative QCD at next-to-leading order (NLO) using various sets of parton distribution functions (PDF). Cross section ratios to the corresponding measurements performed at 2.76 and 7 TeV are presented. From the measured double-differential jet cross section, the value of the strong coupling constant evaluated at the Z mass is alpha[S(M[Z]) = 0.1164 +0.0060 -0.0043, where the errors include the PDF, scale, nonperturbative effects and experimental uncertainties, using the CT10 NLO PDFs. Improved constraints on PDFs based on the inclusive jet cross section measurement are presented.