Jet vetoing at the LHC

TL;DR

This work analyzes gaps-between-jets in LHC dijet events with a central jet veto, developing a soft-gluon resummation framework for global emissions and assessing the impact of Coulomb gluons and super-leading logarithms. It compares the all-orders resummation to the HERWIG++ parton shower, finding substantial Coulomb-gluon corrections at high jet $Q$ and large rapidity separations that are not captured by conventional showers, while one-gluon-out-of-gap SLL effects are moderate but non-negligible. The study highlights the need to match resummed results to NLO and to include non-global and high-energy logarithms for precise predictions, with important implications for Higgs plus two jets central-jet veto strategies at the LHC.

Abstract

We study the effect of a veto on additional jets in the rapidity region between a pair of high transverse momentum jets at the LHC. We aim to sum the most important logarithms in the ratio of the jet transverse momentum to the veto scale and to that end we attempt to assess the significance of the super-leading logarithms that appear at high orders in the perturbative expansion. We also compare our results to those of HERWIG++, in an attempt to ascertain the accuracy of the angular ordered parton shower. We find that there are large corrections that arise for large enough jet transverse momenta as a consequence of Coulomb gluon exchanges.

Figures (8)

• Figure 1: A map of the $(L,Y)$ plane.
• Figure 2: The double differential Born cross-section (nb) computed using Eq. (\ref{['explgapsxsec']}) without any resummation (solid lines), compared to the one obtained using Herwig++ at the parton level (histograms) and without any parton showering. On the left the cross-section is plotted as a function of $Q$, for $Y=3$ (upper lines) and $Y=5$ (lower lines). On the right it is plotted as a function of $Y$, for $Q=100$ GeV (upper lines) and $Q=500$ GeV (lower lines).
• Figure 3: The gap cross-section as a function of $Q$, for $Y=3$, and as a function of $Y$, for $Q=500$ GeV, at both parton shower level (solid) and after hadronisation (dotted).
• Figure 4: Plot of the gap fraction as a function of $Q$, for $Y=3$ (left) and for $Y=5$ (right). The dashed lines are obtained by dropping the imaginary part of the evolution matrices.
• Figure 5: Plot of the gap fraction as a function of $Y$, for $Q=100$ GeV (left) and for $Q=500$ GeV (right). The dashed lines are obtained by dropping the imaginary part of the evolution matrices.