Energy Consumption and Jet Multiplicity from the Leading Log BFKL Evolution

TL;DR

This work investigates energy consumption and jet multiplicity arising from leading-log BFKL evolution in forward dijet production at hadron colliders. By enforcing energy-momentum conservation via a BFKL Monte Carlo, it shows that PDF suppression nearly cancels the partonic exponential growth with rapidity difference, yet a substantial amount of BFKL radiation persists, especially in central rapidities. The paper provides detailed predictions for mini-jet, partonic, and hadronic jet multiplicities and demonstrates that BFKL dynamics remain experimentally observable through angular decorrelations and multi-jet activity, even at LHC energies. These results underscore the continued relevance of BFKL evolution for QCD observables and as a background in searches for new phenomena at hadron colliders.

Abstract

We study the associated jet multiplicity arising from t-channel BFKL gluon evolution in forward dijet production at hadron colliders. Previous results have shown that the effect of conserving overall energy and momentum is to introduce a pdf suppression that completely compensates the predicted exponential BFKL rise with rapidity difference between the leading dijets. However, we show that there is still expected to be a significant amount of BFKL radiation, especially in the central region, and we give predictions for the multiplicity of the resulting mini-jets at the LHC.

Figures (5)

• Figure 1: The average centre of mass energy in $gg\to gg$ scattering with (red/dashed) and without (green/dotted) BFKL evolution of the $t$ channel gluon, with $p_{\perp\mathrm{min}}=20$ GeV for the dijets and $\alpha_s=0.1635$. Also plotted is the hadronic centre of mass energy squared for the Tevatron ($(1.8\mathrm{TeV})^2$) and the LHC($(14\mathrm{TeV})^2$).
• Figure 2: The contribution to the partonic cross section for choices of the rapidity separation from different numbers of resolved gluons with (a) $k_{i\perp}>1$ GeV and (b) $k_{i\perp}>20$ GeV. The leading dijets have $p_{\perp\mathrm{min}}=20$ GeV in both cases.
• Figure 3: The $0$--, $1$, $2$--, $3$-- and $4$--jet parton--level cross sections as a function of $\mu_R$, for a rapidity span of $\Delta y = 5$ and $p_{\perp\mathrm{min}}=20$ GeV for the leading dijets. Also shown is the analytic $0$--jet prediction valid for small $\mu_R$.
• Figure 4: The average density of emitted gluons along the BFKL chain. Please see text for further details.
• Figure 5: The average density of emitted gluons along the BFKL chain for the constant coupling formalism in the case hadronic dijet production. Please see text for further details.