Anomaly detection search for new resonances decaying into a Higgs boson and a generic new particle X in hadronic final states using √𝑠=13 TeV 𝑝𝑝 collisions with the ATLAS detector
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(Published version)
Date
2023
Authors
Aad, G.
Abbott, B.
Abbott, D.C.
Abeling, K.
Abidi, S.H.
Aboulhorma, A.
Abramowicz, H.
Abreu, H.
Abulaiti, Y.
Abusleme Hoffman, A.C.
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Journal Title
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Journal article
Citation
Physical Review D, 2023; 108(5):052009-1-052009-33
Statement of Responsibility
ATLAS Collaboration
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Abstract
A search is presented for a heavy resonance 𝑌 decaying into a Standard Model Higgs boson 𝐻 and a new particle 𝑋 in a fully hadronic final state. The full Large Hadron Collider run 2 dataset of proton-proton collisions at √𝑠=13 TeV collected by the ATLAS detector from 2015 to 2018 is used and corresponds to an integrated luminosity of 139 fb−1. The search targets the high 𝑌-mass region, where the 𝐻 and 𝑋 have a significant Lorentz boost in the laboratory frame. A novel application of anomaly detection is used to define a general signal region, where events are selected solely because of their incompatibility with a learned background-only model. It is constructed using a jet-level tagger for signal-model-independent selection of the boosted 𝑋 particle, representing the first application of fully unsupervised machine learning to an ATLAS analysis. Two additional signal regions are implemented to target a benchmark 𝑋 decay into two quarks, covering topologies where the 𝑋 is reconstructed as either a single large-radius jet or two small-radius jets. The analysis selects Higgs boson decays into 𝑏¯𝑏, and a dedicated neural-network-based tagger provides sensitivity to the boosted heavy-flavor topology. No significant excess of data over the expected background is observed, and the results are presented as upper limits on the production cross section 𝜎(𝑝𝑝→𝑌→𝑋𝐻→𝑞𝑞𝑏𝑏) for signals with 𝑚𝑌 between 1.5 and 6 TeV and 𝑚𝑋 between 65 and 3000 GeV.
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Published 18 September 2023
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© 2023 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.