Observation of Exclusive Dijet Production at the Fermilab Tevatron p-pbar Collider

TL;DR

This work reports the first observation of exclusive dijet production in proton–antiproton collisions at the Tevatron, identifying events where both hadrons survive and only a central dijet system is produced via double Pomeron exchange. The authors develop a data-driven strategy based on the dijet mass fraction $R_{jj}=M_{jj}/M_X$, supplemented by large rapidity gaps and forward proton tagging, to separate exclusive from inclusive DPE events. By combining inclusive-DPE simulations (POMWIG) with exclusive-dijet MC models (ExHuME and ExclDPE) and performing data–MC fits, they extract an exclusive fraction of about 15–24% in the analyzed samples, with a significance exceeding 6σ for ET thresholds of 10 GeV. The measured exclusive cross sections are broadly consistent with perturbative QCD predictions (KMR/ExHuME) and provide a crucial benchmark for calibrating exclusive Higgs production predictions at the LHC, while also supporting a suppressed heavy-flavor component in exclusive dijets due to the $J_z=0$ selection rule. The results strengthen the case for using exclusive dijets as a standard candle to constrain models of exclusive Higgs production and related processes at higher energies.

Abstract

We present the first observation and cross section measurement of exclusive dijet production in pbar-p interactions, pbar + p --> pbar + dijet + p. Using a data sample of 310 pb-1 collected by the Run II Collider Detector at Fermilab at sqrt{s}=1.96 TeV, exclusive cross sections for events with two jets of transverse energy ET >= 10 GeV have been measured as a function of minimum ET(jet). The exclusive signal is extracted from fits to data distributions based on Monte Carlo simulations of expected dijet signal and background shapes. The simulated background distribution shapes are checked in a study of a largely independent data sample of 200 pb-1 of b-tagged jet events, where exclusive dijet production is expected to be suppressed by the Jz=0 total angular momentum selection rule. Results obtained are compared with theoretical expectations, and implications for exclusive Higgs boson production at the pp Large Hadron Collider at sqrt{s}=14 TeV are discussed.

Figures (23)

• Figure 1: Illustration of event topologies in pseudorapidity, $\eta$, and associated Pomeron exchange diagrams for dijet production in (a) single diffraction and (b) double Pomeron exchange. The shaded areas on the left side represent "underlying event" particles not associated with the jets [from Ref. RunI_DPE].
• Figure 2: Leading order diagrams for (a) exclusive dijet and (b) exclusive Higgs boson production in $\bar{p}p$ collisions.
• Figure 3: Schematic drawing (not to scale) of the CDF II detector.
• Figure 4: Schematic cross sectional view of one of the two forward MiniPlug Calorimeters installed in CDF II.
• Figure 5: (a) $\xi_{\bar{p}}^X$ distribution of DPE events passing the ${\rm LRG}_p$ requirement (solid histogram), with the shaded area representing events in the region $0.01<\xi_{\bar{p}}^X<0.12$; the dashed histogram shows the $\xi_{\bar{p}}^X$ distribution for ND events passing the same ${\rm LRG}_p$ requirement and normalized to the solid histogram in the plateau region of $0.22<\xi_{\bar{p}}^X<0.50$; (b) MPCAL hit multiplicity, ${\rm N}_{MP}^{p}$, vs. ${\rm BSC1}_p$ hit counter multiplicity, ${\rm N}_{BSC1}^p$, in SD events with $0.01<\xi_{\bar{p}}^X<0.12$.