Boosted top tagging via lepton-in-jet topology for vector-like quark searches in FCC-hh
Abstract
In this paper, we present a machine-learning-based framework for identifying leptonically decaying, highly boosted top quarks, t→ bℓν, at the Future Circular Collider: hadron-hadron mode (FCC-hh) operating at a center-of-mass energy of √s=100~TeV. At these energies, the large Lorentz boost causes the top-quark decay products to become highly collimated, with the lepton embedded within the resulting top-quark jet. In this regime, it is not a priori clear whether constituent-based jet taggers, which rely on information from individual jet constituents, retain the high discrimination power achieved at LHC energies. To answer this question, we employ two complementary approaches: a variable-based tagger trained with a deep neural network (DNN) using physics-motivated observables and a constituent-based Particle Transformer (ParT) acting on the jet constituents. Both approaches are optimised for the characteristic non-isolated lepton signature of boosted leptonic top decays and achieve comparable performance in discriminating leptonic top jets from hadronic top jets and heavy-flavor b- and c-jet backgrounds. We then incorporate the tagging framework into an event-level search for single production of a vector-like B′ quark decaying through B′→ tW, and use it to evaluate sensitivity to B′ in the range of $3$ to $10$~TeV. For the reference B′ benchmark, the proposed search strategy achieves a 5σ discovery reach of approximately $7$~TeV under the width requirement ΓB′/mB′<25%, in both the statistics-only and 10% background systematic uncertainty scenarios. Relaxing the width requirement to ΓB′/mB′≲ 50% extends the discovery reach to approximately $10$~TeV.
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BibTeX
@misc{bhattacharyya2026boosted,
title = {{Boosted top tagging via lepton-in-jet topology for vector-like quark searches in FCC-hh}},
author = {Sanchari Bhattacharyya and Biplob Bhattacherjee and Kirana K. K. and Swagata Mukherjee},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05104},
eprint = {2610.05104},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.05104},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Boosted top tagging via lepton-in-jet topology for vector-like quark searches in FCC-hh
AU - Sanchari Bhattacharyya
AU - Biplob Bhattacherjee
AU - Kirana K. K.
AU - Swagata Mukherjee
PY - 2026
DA - 2026/10/04
PB - arXiv
DO - 10.48550/arxiv.2610.05104
UR - https://arxiv.org/abs/2610.05104
AB - In this paper, we present a machine-learning-based framework for identifying leptonically decaying, highly boosted top quarks, t→ bℓν, at the Future Circular Collider: hadron-hadron mode (FCC-hh) operating at a center-of-mass energy of √s=100~TeV. At these energies, the large Lorentz boost causes the top-quark decay products to become highly collimated, with the lepton embedded within the resulting top-quark jet. In this regime, it is not a priori clear whether constituent-based jet taggers, which rely on information from individual jet constituents, retain the high discrimination power achieved at LHC energies. To answer this question, we employ two complementary approaches: a variable-based tagger trained with a deep neural network (DNN) using physics-motivated observables and a constituent-based Particle Transformer (ParT) acting on the jet constituents. Both approaches are optimised for the characteristic non-isolated lepton signature of boosted leptonic top decays and achieve comparable performance in discriminating leptonic top jets from hadronic top jets and heavy-flavor b- and c-jet backgrounds. We then incorporate the tagging framework into an event-level search for single production of a vector-like B^′ quark decaying through B^′→ tW, and use it to evaluate sensitivity to B^′ in the range of $3$ to $10$~TeV. For the reference B^′ benchmark, the proposed search strategy achieves a 5σ discovery reach of approximately $7$~TeV under the width requirement Γ_B^′/m_B^′<25%, in both the statistics-only and 10% background systematic uncertainty scenarios. Relaxing the width requirement to Γ_B^′/m_B^′≲ 50% extends the discovery reach to approximately $10$~TeV.
ER -