NLO QCD corrections to multi-jet production at the LHC with a centre-of-mass energy of sqrt(s)=8 TeV

TL;DR

The paper delivers NLO QCD predictions for 3- and 4-jet production at the LHC with sqrt(s)=8 TeV, using an on-shell unitarity approach (NGluon/NJet) for virtual corrections and Catani-Seymour subtraction for real emission, interfaced with Sherpa. It confirms prior 7 TeV results and reveals large negative NLO corrections (~40-50%) alongside substantially reduced scale uncertainties, with a dynamical HT/2 scale producing nearly constant K-factors across observables. The analysis includes detailed differential distributions and parton-channel decompositions, and discusses normalization strategies and implications for matching to parton showers. Overall, the results underscore the importance of NLO corrections for accurate multi-jet predictions and provide a publicly available toolkit (NJet) for broader high-multiplicity QCD calculations.

Abstract

We study three and four jet production in hadronic collisions at next-to-leading order accuracy in massless QCD. We cross check results previously obtained by the BlackHat collaboration for the LHC with a centre-of-mass energy of sqrt(s)=7 TeV and present new results for the LHC operating at 8 TeV. We find large negative NLO corrections reducing the leading-order cross sections by about 40-50%. Furthermore we observe an important reduction of the scale uncertainty. In addition to the cross sections we also present results for differential distributions. The dynamical renormalization/factorization scale used in the calculation leads to a remarkably stable K-factor. The results presented here were obtained with the NJet package, a publicly available library for the evaluation of one-loop amplitudes in massless QCD.

Figures (20)

• Figure 1: $p_T$ distribution for the leading jet at the LHC with a centre-of-mass energy of 8 TeV. The upper plots show leading order (blue) and next-to-leading order (red) results for the central scale $\mu=\hat{H}_T/2$. The bands show the LO and NLO scale variations respectively. In the lower plot we show the ratio of LO and NLO together with the LO scale variations (blue band) and NLO scale variations (red band).
• Figure 2: Rapidity distribution in $pp\to3$ jets for the leading jet at the LHC with a centre-of-mass energy of 8 TeV.
• Figure 3: $p_T$ distribution in $pp\to4$ jets for the leading jet at the LHC with a centre-of-mass energy of 8 TeV.
• Figure 4: Rapidity distribution in $pp\to4$ jets for the leading jet at the LHC with a centre-of-mass energy of 8 TeV.
• Figure 5: Ratio $R_2$ of the rapidity distribution for the second jet with respect to the leading jet.