Complex Scalar Dark Matter with a Vector-Like Quark and Lepton: Precision, Flavor, and HL-LHC
Abstract
We investigate a minimal extension of the SM consisting of a ℤ3-stabilized complex scalar dark matter (CSDM) candidate, a down-type vector-like quark (VLQ), and a charged vector-like lepton (VLL). The additional vector-like fermions not only enable the CSDM to reproduce the observed relic abundance beyond the Higgs-resonance region through semi-annihilation and co-annihilation processes, but also induce correlated signatures across flavor, electroweak precision, dark matter, and collider observables. We perform a comprehensive one-loop analysis of neutral meson mixing, rare meson decays, charged lepton flavor violation, anomalous magnetic moments of charged leptons, and Z-pole observables. We find that neutral meson mixing and rare meson decays provide the dominant constraints on the VLQ sector, while charged lepton flavor-violating processes strongly restrict the VLL Yukawa couplings. Current direct-detection limits require Higgs-DM coupling λΦH ≲5×10−3 and the VLQ Yukawa coupling yd ≲ 0.05 for TeV-scale VLQ masses, whereas present indirect-detection searches impose no additional constraints. Combining all flavor, electroweak precision, dark matter, and collider constraints, we identify viable parameter regions with CSDM masses above approximately 1.0 TeV and VLQ masses above about 1.5 TeV. We also find that the LHC can exclude VLQs (VLLs) with masses up to approximately $1.6~(0.38)$ TeV, depending on the CSDM mass, at the 2σ confidence level. The HL-LHC can further probe an extended region of the parameter space, with discovery prospects at the 3σ level. Finally, we demonstrate the complementarity of flavor, dark matter, and collider searches in probing this framework.
Related
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BibTeX
@misc{kolay2026complex,
title = {{Complex Scalar Dark Matter with a Vector-Like Quark and Lepton: Precision, Flavor, and HL-LHC}},
author = {Lipika Kolay and Rusa Mandal and Manimala Mitra and Dipankar Pradhan and Subham Saha},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09120},
eprint = {2609.09120},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09120},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Complex Scalar Dark Matter with a Vector-Like Quark and Lepton: Precision, Flavor, and HL-LHC
AU - Lipika Kolay
AU - Rusa Mandal
AU - Manimala Mitra
AU - Dipankar Pradhan
AU - Subham Saha
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.09120
UR - https://arxiv.org/abs/2609.09120
AB - We investigate a minimal extension of the SM consisting of a ℤ_3-stabilized complex scalar dark matter (CSDM) candidate, a down-type vector-like quark (VLQ), and a charged vector-like lepton (VLL). The additional vector-like fermions not only enable the CSDM to reproduce the observed relic abundance beyond the Higgs-resonance region through semi-annihilation and co-annihilation processes, but also induce correlated signatures across flavor, electroweak precision, dark matter, and collider observables. We perform a comprehensive one-loop analysis of neutral meson mixing, rare meson decays, charged lepton flavor violation, anomalous magnetic moments of charged leptons, and Z-pole observables. We find that neutral meson mixing and rare meson decays provide the dominant constraints on the VLQ sector, while charged lepton flavor-violating processes strongly restrict the VLL Yukawa couplings. Current direct-detection limits require Higgs-DM coupling λ_ΦH ≲5×10^−3 and the VLQ Yukawa coupling y_d ≲ 0.05 for TeV-scale VLQ masses, whereas present indirect-detection searches impose no additional constraints. Combining all flavor, electroweak precision, dark matter, and collider constraints, we identify viable parameter regions with CSDM masses above approximately 1.0 TeV and VLQ masses above about 1.5 TeV. We also find that the LHC can exclude VLQs (VLLs) with masses up to approximately $1.6~(0.38)$ TeV, depending on the CSDM mass, at the 2σ confidence level. The HL-LHC can further probe an extended region of the parameter space, with discovery prospects at the 3σ level. Finally, we demonstrate the complementarity of flavor, dark matter, and collider searches in probing this framework.
ER -