Electroweak phase transition triggered by a long-lived scalar and LHC searches
Abstract
We investigate a long-lived scalar S that triggers a strongly first-order electroweak phase transition (SFOEWPT) in the singlet scalar extension of standard model (SM). A sufficient small mixing angle between S and the SM-like Higgs boson h naturally leads to a long lifetime for S. We focus on the mass range mS>mh/2, where the dominant production channel at the LHC is the Higgs-mediated process gg→ h*→ SS with an off-shell h. By analyzing the finite-temperature effective potential, we identify the parameter space realizing an SFOEWPT and calculate the associated gravitational-wave spectra, finding that part of the parameter space can be probed by LISA. We further study the LHC sensitivity to the long-lived S using the ATLAS detector and proposed far detectors, including ANUBIS, CODEX-b, FACET, FASER2, MoEDAL-MAPP1 and MAPP2, and MATHUSLA. The combined sensitivity of the main detector and far detectors, particularly ANUBIS and MATHUSLA, allows a large fraction of the SFOEWPT parameter space to be probed for 10−10≤ sinθ≤ 10−5, with mS up to 250 GeV. For sinθ≤ 10−11, however, the SFOEWPT parameter space becomes inaccessible to both the main detector and the far-detector searches.
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BibTeX
@misc{wang2026electroweak,
title = {{Electroweak phase transition triggered by a long-lived scalar and LHC searches}},
author = {Lei Wang and Xiaoting Zhao and Xiao-Fang Han and Hongxin Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.25601},
eprint = {2609.25601},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25601},
}
RIS
TY - UNPB
TI - Electroweak phase transition triggered by a long-lived scalar and LHC searches
AU - Lei Wang
AU - Xiaoting Zhao
AU - Xiao-Fang Han
AU - Hongxin Wang
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2609.25601
UR - https://arxiv.org/abs/2609.25601
AB - We investigate a long-lived scalar S that triggers a strongly first-order electroweak phase transition (SFOEWPT) in the singlet scalar extension of standard model (SM). A sufficient small mixing angle between S and the SM-like Higgs boson h naturally leads to a long lifetime for S. We focus on the mass range m_S>m_h/2, where the dominant production channel at the LHC is the Higgs-mediated process gg→ h^*→ SS with an off-shell h. By analyzing the finite-temperature effective potential, we identify the parameter space realizing an SFOEWPT and calculate the associated gravitational-wave spectra, finding that part of the parameter space can be probed by LISA. We further study the LHC sensitivity to the long-lived S using the ATLAS detector and proposed far detectors, including ANUBIS, CODEX-b, FACET, FASER2, MoEDAL-MAPP1 and MAPP2, and MATHUSLA. The combined sensitivity of the main detector and far detectors, particularly ANUBIS and MATHUSLA, allows a large fraction of the SFOEWPT parameter space to be probed for 10^−10≤ sinθ≤ 10^−5, with m_S up to 250 GeV. For sinθ≤ 10^−11, however, the SFOEWPT parameter space becomes inaccessible to both the main detector and the far-detector searches.
ER -