Jumping into buckets, or How to decontaminate overlapping fat jets

TL;DR

This paper introduces a novel jet tagging method using the mass-jump algorithm and bucket collection to improve identification of boosted resonances in complex LHC events, enabling better reconstruction of top quarks, Higgs bosons, and vectorlike top partners.

Contribution

It proposes a new jet tagging and reconstruction approach based on the mass-jump algorithm and bucket method, enhancing performance in high-multiplicity environments.

Findings

Better tagging of boosted resonances than generalized $k_T$ algorithm.

Effective reconstruction of top quarks, Higgs bosons, and vectorlike top partners.

Accurate mass measurement of vectorlike top partners.

Abstract

At the LHC, tagging boosted heavy particle resonances which decay hadronically, such as top quarks and Higgs bosons, can play an essential role in new physics searches. In events with high multiplicity, however, the standard approach to tag boosted resonances by a large-radius fat jet becomes difficult because the resonances are not well-separated from other hard radiation. In this paper, we propose a different approach to tag and reconstruct boosted resonances by using the recently proposed mass-jump jet algorithm. A key feature of the algorithm is the flexible radius of the jets, which results from a terminating veto that prevents the recombination of two hard prongs if their combined jet mass is substantially larger than the masses of the separate prongs. The idea of collecting jets in "buckets" is also used. As an example, we consider the fully hadronic final state of pair-produced vectorlike top partners at the LHC, $pp\to T\bar{T}\to t\bar{t}HH$, and show that the new approach works better than the corresponding generalized $k_T$ jet clustering algorithm. We also show that tagging and kinematic reconstruction of boosted top quarks and Higgs bosons are possible with good quality even in these very busy final states. The vectorlike top partners are kinematically reconstructed, which allows their direct mass measurement.