Probing Ultra-Compressed Scotogenic Dark Matter at the HL-LHC via 4D Spacetime Tracking
Abstract
The ultra-compressed scotogenic regime, in which a 2\,GeV mass splitting between the charged inert scalar and the dark-matter fermion is motivated by and compatible with co-annihilation to the observed relic density for suitable choices of the remaining model parameters, produces decay leptons for which existing LHC displaced-lepton and disappearing-track searches retain only partial, unoptimised acceptance, leaving room for a dedicated timing-assisted strategy. We propose exploiting the 30\,ps timing resolution of the HL-LHC precision timing detectors as a fourth observable, converting the macroscopic scalar decay length of 100--1000\,mm into an arrival-time delay of 70--700\,ps---more than three orders of magnitude above the sub-picosecond delays of all prompt Standard Model backgrounds. Operating at the level of a low-pT disappearing-track stub matched to a delayed timing hit, without requiring full lepton reconstruction, our 4D timing strategy achieves signal efficiencies of 12--36\% across the probed mass range (14\% at the 200\,GeV benchmark) and zero background across 4.20×106 simulated prompt SM events, projecting 95\%\,C.L.\ exclusion up to scalar masses of ≃ 670\,GeV at 3000\,fb−1 under conservative background assumptions. The scalar lifetime is set by the Yukawa coupling y through cτ∝ y−2, while sub-eV neutrino masses constrain only the product y2λ5; the small couplings that place the charged scalar in the optimal timing window are therefore compatible with, though not uniquely fixed by, the radiative neutrino-mass mechanism, making the co-annihilation corridor---conventionally the most elusive regime---an accessible target for 4D spacetime tracking at the HL-LHC.
Versions
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BibTeX
@misc{wang2026probing,
title = {{Probing Ultra-Compressed Scotogenic Dark Matter at the HL-LHC via 4D Spacetime Tracking}},
author = {Renjie Wang},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.29275},
eprint = {2608.29275},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29275},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Probing Ultra-Compressed Scotogenic Dark Matter at the HL-LHC via 4D Spacetime Tracking
AU - Renjie Wang
PY - 2026
DA - 2026/08/29
PB - arXiv
DO - 10.48550/arxiv.2608.29275
UR - https://arxiv.org/abs/2608.29275
AB - The ultra-compressed scotogenic regime, in which a 2\,GeV mass splitting between the charged inert scalar and the dark-matter fermion is motivated by and compatible with co-annihilation to the observed relic density for suitable choices of the remaining model parameters, produces decay leptons for which existing LHC displaced-lepton and disappearing-track searches retain only partial, unoptimised acceptance, leaving room for a dedicated timing-assisted strategy. We propose exploiting the 30\,ps timing resolution of the HL-LHC precision timing detectors as a fourth observable, converting the macroscopic scalar decay length of 100--1000\,mm into an arrival-time delay of 70--700\,ps---more than three orders of magnitude above the sub-picosecond delays of all prompt Standard Model backgrounds. Operating at the level of a low-p_T disappearing-track stub matched to a delayed timing hit, without requiring full lepton reconstruction, our 4D timing strategy achieves signal efficiencies of 12--36\% across the probed mass range (14\% at the 200\,GeV benchmark) and zero background across 4.20×10^6 simulated prompt SM events, projecting 95\%\,C.L.\ exclusion up to scalar masses of ≃ 670\,GeV at 3000\,fb^−1 under conservative background assumptions. The scalar lifetime is set by the Yukawa coupling y through cτ∝ y^−2, while sub-eV neutrino masses constrain only the product y^2λ_5; the small couplings that place the charged scalar in the optimal timing window are therefore compatible with, though not uniquely fixed by, the radiative neutrino-mass mechanism, making the co-annihilation corridor---conventionally the most elusive regime---an accessible target for 4D spacetime tracking at the HL-LHC.
ER -