Jets with electrons from boosted top quarks

TL;DR

This paper introduces a novel method for identifying jets originating from boosted top quarks decaying semileptonically to electrons, effectively distinguishing them from background jets using energy distribution, jet substructure, and decay kinematics.

Contribution

The proposed technique combines energy distribution analysis, jet substructure, and a new kinematic variable construction to improve top jet identification in electron decay channels.

Findings

Reduces background from light flavor and QCD b jets.

Successfully distinguishes top decay jets from electron-rich non-top jets.

Demonstrates effectiveness with simulated data.

Abstract

We propose a method to identify jets consisting of all the visible remnants of boosted top particles when these decay semileptonically to electrons. Within these jets, the electron shower overlaps with the shower initiated by the $b$ quark, which makes the identification of the electron hard. Even if an electron inside a jet is identified, it is difficult to pinpoint whether the electron rich jet is indeed due to top quark decay or not, since the invisible neutrino carries away a nontrivial part of the energy-momentum of the original top quark. Broadly speaking, the method proposed here has three key components. It uses the distribution of energy in various parts of the detector to identify whether the observed jet is consistent with a jet containing an energetic electron. It uses the substructure of the jet to determine the momentum associated with the electron. Finally, it constructs new variables that carry tell-tale features of top quark decay kinematics using an extra ansatz that, there exists a massless invisible four-momentum \emph{roughly} collimated to the electron, which reconstructs a $W$ and a top when it is combined with the electron and the full jet respectively. We demonstrate the efficacy of this proposal using simulated data and show that our method not only reduces the backgrounds from light flavor jets, $b$ jets from QCD, and hadronic top jets, it can also tell apart jets rich in electrons but not due to top quark decays.