Jet energy flow at the LHC

TL;DR

The paper tackles interjet energy flow at the LHC by numerically solving the Banfi–Marchesini–Smye (BMS) equation for single-logarithmic accuracy in the large-$N_c$ limit. It uncovers a hidden SU(1,1) symmetry that collapses the solution to a function of a geodesic distance on the Poincaré disk and validates this through numerical results. It then applies the formalism to two LHC-relevant problems: discriminating jets from boosted heavy electroweak bosons versus QCD jets by out-of-cone energy flow, and computing perturbative gap survival in BFKL dijet production, showing sizable cross-section suppression and enhanced discriminatory power. Overall, the work demonstrates energy-flow observables as a quantitative, perturbatively calculable diagnostic tool for jet physics at the LHC.

Abstract

We present a quantitative study of energy flow away from jets by numerically solving the evolution equation derived by Banfi, Marchesini and Smye (BMS), and apply the result to two processes at the LHC: Discriminating high-p_t jets originating from decays of heavy electroweak bosons from the QCD background, and the survival probability of BFKL-initiated dijet rapidity gaps. As a byproduct, we find a hidden symmetry of the BMS equation which is a remnant of conformal symmetry.

Figures (14)

• Figure 1: Back--to--back jets in $e^+e^-$ annihilation.
• Figure 2: (a) Two jets in two opposite cones. (b) Two jets in the same cone. (c) The single--cone case. In all the configurations the two jets are triggered by a color--singlet $q\bar{q}$ dipole.
• Figure 3: Stereographic map between a sphere with unit diameter and a plane. The angles $(\theta,\phi)$ are measured with respect to the cone axis.
• Figure 4: Solid curves: the numerical solution of Eq. (\ref{['p']}) in the two--cone case. Dotted curves: the Sudakov contribution. Four curves correspond different values of $\tau$: From top to bottom, $\tau=0.6,0.8.1.0,1.2$.
• Figure 5: Numerical solution of Eq. (\ref{['p']}) in the single--cone case.