Designing Observables for Quantum Interference in Jets at Subleading Color

TL;DR

This paper introduces new kinematic observables sensitive to subleading color interference effects in jets, revealing sinusoidal oscillations and highlighting limitations of current Monte Carlo simulations.

Contribution

It proposes specific angular observables based on energy correlators to detect quantum interference effects at subleading color in jet events.

Findings

Color interference causes sinusoidal oscillations in three-particle jets.

Standard Monte Carlo simulations have limitations in predicting these interference effects.

The observables are sensitive to quantum effects beyond the leading-color approximation.

Abstract

The large-$N_c$ or topologically planar limit of gauge theories can be considered as a classical limit because all gauge bosons are distinguishable particles and therefore cannot exhibit interference. Quantum effects due to the flow of color therefore arise starting at subleading in $1/N_c$. We introduce kinematic observables explicitly sensitive to effects at subleading color formed from the ratio of interfering to squared color-ordered amplitudes. Such observables are in general not infrared and collinear safe, so we introduce angular observables defined from appropriate multi-point energy correlators motivated by the form of color-ordered amplitudes. We demonstrate that color interference effects are manifest as sinusoidal oscillation in the simplest system, a collinear jet with three particles, and show the limitations of predicting this observable in all-purpose, leading-color parton shower Monte Carlos.