Nested disappearing-track plus displaced-vertex topology at the HL-LHC: a dual long-lived-particle signature of the scotogenic model
- 1Institute of High Energy Physics
Abstract
The scotogenic model generates sub-eV neutrino masses radiatively through small Yukawa couplings ∼ 𝒪(10−3) ∼ O ( 10 - 3 ) that also set the decay length of the heavy neutral fermion N2 N 2 ; in the compressed regime a separate, much smaller Yukawa entry ∼ 𝒪(10−6) ∼ O ( 10 - 6 ) additionally renders the charged scalar η ̃± η ~ ± long-lived. We study the compressed-spectrum regime of its two-inert-doublet variant ( varDelta Mcomp= mη ̃± − mN2≃ 200 MeV Δ M comp = m η ~ ± - m N 2 ≃ 200 MeV ), in which small Yukawa entries render both the charged scalar η ̃± η ~ ± and the heavy neutral fermion N2 N 2 long-lived and produce a nested cascade at the High-Luminosity LHC (HL-LHC): η ̃± η ~ ± leaves a disappearing track (DT), decays to an invisible N2 N 2 , which travels macroscopically before forming a displaced dilepton vertex (DV). The two slow flights combine into a 4D time-of-flight delay varDelta t∼ 200 Δ t ∼ 200 – 800 ps 800 ps resolvable by the CMS MIP Timing Detector, while the DT-to-DV displacement vector inherits the parent track direction, yielding a spatial back-pointing correlation with no SM analogue. These two handles are expected to suppress the background to B∼ 10−5 B ∼ 10 - 5 – 10−3 10 - 3 events, and the discovery remains 5σ 5 σ -significant for any background up to B∼ 10 B ∼ 10 events. At the benchmark ( mN2=150 GeV m N 2 = 150 GeV and proper decay lengths cτ η ̃± =300 mm c τ η ~ ± = 300 mm , cτ N2=189 mm c τ N 2 = 189 mm ) the strategy yields Ns≈ 1212 N s ≈ 1212 signal events at 3000 fb−1 3000 fb - 1 and establishes sensitivity across 15 mm≲ cτ η ̃± ≲ 300 mm 15 mm ≲ c τ η ~ ± ≲ 300 mm , 10 mm≲ cτ N2≲ 1000 mm 10 mm ≲ c τ N 2 ≲ 1000 mm , a correlated region left uncovered by any standalone DT or DV search. Because the N2 N 2 decay length is controlled by the same Yukawa couplings that generate sub-eV neutrino masses, mapping this nested cascade turns the HL-LHC into a direct collider probe of the interaction responsible for neutrino mass.
Versions
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BibTeX
@article{wang2026nested,
title = {{Nested disappearing-track plus displaced-vertex topology at the HL-LHC: a dual long-lived-particle signature of the scotogenic model}},
author = {Renjie Wang},
journal = {The European Physical Journal C},
year = {2026},
month = oct,
doi = {10.1140/epjc/s10052-026-16416-2},
url = {https://link.springer.com/article/10.1140/epjc/s10052-026-16416-2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Nested disappearing-track plus displaced-vertex topology at the HL-LHC: a dual long-lived-particle signature of the scotogenic model
AU - Renjie Wang
PY - 2026
DA - 2026/10/19
JO - The European Physical Journal C
DO - 10.1140/epjc/s10052-026-16416-2
UR - https://link.springer.com/article/10.1140/epjc/s10052-026-16416-2
AB - The scotogenic model generates sub-eV neutrino masses radiatively through small Yukawa couplings ∼ 𝒪(10^−3) ∼ O ( 10 - 3 ) that also set the decay length of the heavy neutral fermion N_2 N 2 ; in the compressed regime a separate, much smaller Yukawa entry ∼ 𝒪(10^−6) ∼ O ( 10 - 6 ) additionally renders the charged scalar η ̃^± η ~ ± long-lived. We study the compressed-spectrum regime of its two-inert-doublet variant ( varDelta M_comp= m_η ̃^± − m_N_2≃ 200 MeV Δ M comp = m η ~ ± - m N 2 ≃ 200 MeV ), in which small Yukawa entries render both the charged scalar η ̃^± η ~ ± and the heavy neutral fermion N_2 N 2 long-lived and produce a nested cascade at the High-Luminosity LHC (HL-LHC): η ̃^± η ~ ± leaves a disappearing track (DT), decays to an invisible N_2 N 2 , which travels macroscopically before forming a displaced dilepton vertex (DV). The two slow flights combine into a 4D time-of-flight delay varDelta t∼ 200 Δ t ∼ 200 – 800 ps 800 ps resolvable by the CMS MIP Timing Detector, while the DT-to-DV displacement vector inherits the parent track direction, yielding a spatial back-pointing correlation with no SM analogue. These two handles are expected to suppress the background to B∼ 10^−5 B ∼ 10 - 5 – 10^−3 10 - 3 events, and the discovery remains 5σ 5 σ -significant for any background up to B∼ 10 B ∼ 10 events. At the benchmark ( m_N_2=150 GeV m N 2 = 150 GeV and proper decay lengths cτ _η ̃^± =300 mm c τ η ~ ± = 300 mm , cτ _N_2=189 mm c τ N 2 = 189 mm ) the strategy yields N_s≈ 1212 N s ≈ 1212 signal events at 3000 fb^−1 3000 fb - 1 and establishes sensitivity across 15 mm≲ cτ _η ̃^± ≲ 300 mm 15 mm ≲ c τ η ~ ± ≲ 300 mm , 10 mm≲ cτ _N_2≲ 1000 mm 10 mm ≲ c τ N 2 ≲ 1000 mm , a correlated region left uncovered by any standalone DT or DV search. Because the N_2 N 2 decay length is controlled by the same Yukawa couplings that generate sub-eV neutrino masses, mapping this nested cascade turns the HL-LHC into a direct collider probe of the interaction responsible for neutrino mass.
SN - 1434-6044
SN - 1434-6052
ER -