Jet-jet and hadron-jet correlations in hadro- and electro-production

TL;DR

The paper examines jet-jet and hadron-jet correlations in hadro- and electro-production within next-to-leading order perturbative QCD to test BFKL dynamics against DGLAP-like evolution. It analyzes Tevatron jet-jet azimuthal decorrelations and forward hadron-jet correlations in DIS using NLO calculations, highlighting how energy-momentum conservation and kinematic constraints shape decorrelation patterns. The findings show that NLO pQCD, with direct and resolved photon contributions in DIS, can describe hadroproduction data reasonably well, while decorrelations in electroproduction are stronger and guided by phase-space constraints, suggesting careful interpretation of BFKL signals. The work underscores the utility of forward hadron-jet observables as probes of small-$x$ dynamics, while acknowledging data limitations for some observables and the potential need for NNLO or shower-based refinements.

Abstract

We discuss, in the framework of perturbative QCD at next to leading order, two related observables which are usually considered to provide tests of the BFKL dynamics : jet-jet correlations at Tevatron energies and forward particle-jet correlations at HERA. In the first case we study the rapidity gap dependence of the azimuthal correlations and find slightly too strong correlations at large gap. In the second case we discuss the cross section as well as the azimuthal correlations over a rapidity gap range of 5 units. We find that the requirement of a forward particle imposes strong kinematical constraints which distort the distributions, notably at small rapidity gaps. We also show that the decorrelation is stronger in electroproduction than in hadron-hadron collisions. Unfortunately no data are yet available for comparison.

Figures (7)

• Figure 1: Theoretical predictions, at NLO in perturbative QCD, of the two-jet correlations (squares: scale $P_{\bot}/2$; diamonds: scale $P_{\bot}/4$) compared with DØ data Abachi:1996et (solid dots). The solid line indicates the systematic errors.
• Figure 2: The cross section $d\sigma/dx_{Bj}$ corresponding to the range 4.5 GeV$^2 \leq Q^2 \leq 15$ GeV$^2$ compared to H1 data Adloff:1998fa. The various theoretical components of the cross section are shown. The symbol HO$_s$ denotes the HO correction from which the lowest order resolved contribution has been subtracted.
• Figure 3: Examples of higher order corrections to (a) the direct contribution, (b) the resolved contribution. The forward hadron is emitted from the bottom parton line.
• Figure 4: Variation of the cross section as a function of the rapidity gap between the forward pion and the largest $p_\perp$ jet.
• Figure 5: Variation of the cross section as a function of the rapidity gap between the forward pion and the jet with the largest rapidity gap with the pion.