Jet Charge at the LHC

TL;DR

This paper introduces a method to determine the electric charge of jets at the LHC using a weighted sum of constituent charges, aiding in Standard Model tests and new physics searches despite hadronization complexities.

Contribution

It develops a systematic, calculable approach combining fragmentation functions and perturbative techniques to predict jet charge distributions at the LHC.

Findings

Jet charge can distinguish jets with different charges.

The method predicts energy and size dependence of jet charge.

Calculations are robust against fragmentation function uncertainties.

Abstract

Knowing the charge of the parton initiating a light-quark jet could be extremely useful both for testing aspects of the Standard Model and for characterizing potential beyond-the-Standard-Model signals. We show that despite the complications of hadronization and out-of-jet radiation such as pile-up, a weighted sum of the charges of a jet's constituents can be used at the LHC to distinguish among jets with different charges. Potential applications include measuring electroweak quantum numbers of hadronically decaying resonances or supersymmetric particles, as well as Standard Model tests, such as jet charge in dijet events or in hadronically-decaying W bosons in t-tbar events. We develop a systematically improvable method to calculate moments of these charge distributions by combining multi-hadron fragmentation functions with perturbative jet functions and pertubative evolution equations. We show that the dependence on energy and jet size for the average and width of the jet charge can be calculated despite the large experimental uncertainty on fragmentation functions. These calculations can provide a validation tool for data independent of Monte-Carlo fragmentation models.