The dijet cross section with a jet veto

TL;DR

This paper addresses dijet production with a central jet veto by developing a leading-log resummation of the gap fraction and matching it to LO QCD. It enhances the resummation with energy-momentum conservation and the first non-global logarithms, then performs LO matching to form a matched prediction. The approach yields good agreement with ATLAS data within sizable theoretical uncertainties, underscoring the crucial role of energy-momentum conservation and the need for higher-order (NLL/NLO) refinements. Comparisons with alternative methods (POWHEG, HEJ) highlight how different treatments of emissions and conservation affect predictions in gap-between-jets observables.

Abstract

We study dijet production in proton-proton collisions with a veto on the emission of a third jet in the rapidity region in between the two leading ones. We resum the leading logarithms in the ratio of the transverse momentum of the leading jets and the veto scale and we match this result to leading-order QCD matrix elements. We find that, in order to obtain sensible results, we have to modify the resummation and take into account energy-momentum conservation effects. We compare our theoretical predictions for the gap fraction to experimental data measured by the ATLAS collaboration and find good agreement, although our results are affected by large theoretical uncertainties. We then discuss differences and similarities of our calculation to other theoretical approaches.

Figures (5)

• Figure 1: The $K$-factor we use to estimated non-global effects, as a function of $Q$ for different values of $\Delta y$ (on the left) and as a function of $\Delta y$, for different values of $Q$ (on the right).
• Figure 2: The logarithmic derivative of the gap fraction $\frac{{\rm d} f^{\rm gap }}{{\rm d} \ln Q_0}$ as a function of $\ln Q_0/Q$ for fixed $Q=200$ GeV and $\Delta y =3$ ($\sqrt{S}=7$ TeV). The solid line is the coefficient obtained by expanding Eq. (\ref{['gapres']}) at ${\cal O} (\alpha_s)$.
• Figure 3: The gap fraction at ${\cal O}(\alpha_s)$ as a function of $Q$ in different $\Delta y$ bins. The points are the exact FO calculations, the dashed ones the expansions of the eikonal resummation (Eq. (\ref{['eikonalexp']})) and the solid curves correspond to the ${\cal O}(\alpha_s)$ expansion of the modified resummation.
• Figure 4: The matched gap fraction as a function of the transverse momentum $Q$ in different rapidity bins.
• Figure 5: The matched gap fraction as a function of rapidity separation $\Delta y$ in two different transverse momentum bins.