Identifying the b quark inside a boosted hadronically decaying top quark using jet substructure in its center-of-mass frame

TL;DR

This paper presents a novel jet substructure method in the jet's center-of-mass frame to identify b quarks within boosted hadronic top decays, significantly reducing QCD background and fake rates, especially in high pileup conditions.

Contribution

The paper introduces a new b quark identification technique in the jet's center-of-mass frame that improves background rejection while maintaining efficiency.

Findings

Reduces QCD jet background in high pileup environments.

Achieves nearly tenfold improvement in background rejection when combined with jet substructure.

Maintains high top quark identification efficiency.

Abstract

In this paper we study the identification of the b quark inside a boosted hadronically decaying top quark in the center-of-mass frame of the jet. We demonstrate that the method can be used to greatly reduce the QCD jet background even in a very high pileup condition. The method has a much smaller fake rate for QCD jets compared to typical b quark identification algorithms in jets at the same signal efficiency. When combining the b quark identification in the center-of-mass frame of the jet with jet substructure information, we can improve the rejection rate of QCD jet background by almost an order of magnitude while maintaining the same identification efficiency for the boosted top quark.