Ratios of dijet production cross sections as a function of the absolute difference in rapidity between jets in proton-proton collisions at sqrt(s) = 7 TeV

TL;DR

This paper measures the ratio of dijet production cross sections as a function of rapidity difference in proton-proton collisions at 7 TeV, comparing results with various Monte Carlo predictions to test QCD models.

Contribution

First measurement of the ratio of inclusive to exclusive dijet cross sections as a function of rapidity difference at 7 TeV, providing data to test QCD Monte Carlo models.

Findings

PYTHIA6 and PYTHIA8 agree with data

HERWIG++ shows a more pronounced rise than observed

BFKL-motivated generators predict a stronger rise than measured

Abstract

A study of dijet production in proton-proton collisions was performed at sqrt(s) = 7 TeV for jets with pt > 35 GeV and abs(y) < 4.7 using data collected with the CMS detector at the LHC in 2010. Events with at least one pair of jets are denoted as "inclusive". Events with exactly one pair of jets are called "exclusive". The ratio of the cross section of all pairwise combinations of jets to the exclusive dijet cross section as a function of the rapidity difference between jets abs(Delta(y)) is measured for the first time up to abs(Delta(y)) = 9.2. The ratio of the cross section for the pair consisting of the most forward and the most backward jet from the inclusive sample to the exclusive dijet cross section is also presented. The predictions of the Monte Carlo event generators PYTHIA6 and PYTHIA8 agree with the measurements. In both ratios the HERWIG++ generator exhibits a more pronounced rise versus abs(Delta(y)) than observed in the data. The BFKL-motivated generators CASCADE and HEJ+ARIADNE predict for these ratios a significantly stronger rise than observed.