Anomaly detection search for new resonances decaying into a Higgs boson and a generic new particle $$X$$ in hadronic final states using $$\sqrt{s}$$ = 13 TeV $pp$ collisions with the ATLAS detector
- Centre National de la Recherche Scientifique (CNRS) (France); Aix-Marseille Univ., Marseille (France); ATLAS Collaboration. et al.
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 $$\sqrt{s}$$ = 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 smallradius jets. The analysis selects Higgs boson decays into $$b$$$\overline{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$$ → $XH$ → $$q$$$\overline{q}$$$$b$$$$\overline{b}$$) for signals with $$m_Y$$ between 1.5 and 6 TeV and $$m_X$$ between 65 and 3000 GeV
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF)
- Contributing Organization:
- ATLAS Collaboration
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 2280930
- Journal Information:
- Physical Review. D., Vol. 108, Issue 5; ISSN 2470-0010
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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