Detector performance at SHiP for cascade-produced long-lived particles
Abstract
Previous studies have shown that cascade production in the thick target of the SHiP experiment may substantially enhance the number of light long-lived particles (LLPs) decaying in the fiducial volume. However, cascade-produced LLPs are typically soft, so daughter-level acceptance and reconstruction effects can strongly suppress the observable event rate. We quantify this suppression for two representative cases: photophilic axion-like particles produced in electromagnetic cascades, and heavy neutral leptons produced in decays of secondary kaons. We combine a semi-analytic event-rate calculation with a detector-level study of ALP reconstruction in the electromagnetic calorimeter. For the nominal SHiP detector design, cascade ALPs give at most a moderate enhancement over primary production, and only at the lightest masses; at higher masses, the cascade contribution becomes subdominant or negligible. For HNLs from secondary kaons, the cascade contribution is already subdominant after imposing daughter-level geometric acceptance. We also identify possible ways to recover part of the cascade event rate, including relaxed event-selection criteria and an active-target subdetector.
Versions
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BibTeX
@misc{climescu2026detector,
title = {{Detector performance at SHiP for cascade-produced long-lived particles}},
author = {Matei Climescu and Yehor Kyselov and Maksym Ovchynnikov},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2606.07743},
eprint = {2606.07743},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.07743},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Detector performance at SHiP for cascade-produced long-lived particles
AU - Matei Climescu
AU - Yehor Kyselov
AU - Maksym Ovchynnikov
PY - 2026
DA - 2026/08/26
PB - arXiv
DO - 10.48550/arxiv.2606.07743
UR - https://arxiv.org/abs/2606.07743
AB - Previous studies have shown that cascade production in the thick target of the SHiP experiment may substantially enhance the number of light long-lived particles (LLPs) decaying in the fiducial volume. However, cascade-produced LLPs are typically soft, so daughter-level acceptance and reconstruction effects can strongly suppress the observable event rate. We quantify this suppression for two representative cases: photophilic axion-like particles produced in electromagnetic cascades, and heavy neutral leptons produced in decays of secondary kaons. We combine a semi-analytic event-rate calculation with a detector-level study of ALP reconstruction in the electromagnetic calorimeter. For the nominal SHiP detector design, cascade ALPs give at most a moderate enhancement over primary production, and only at the lightest masses; at higher masses, the cascade contribution becomes subdominant or negligible. For HNLs from secondary kaons, the cascade contribution is already subdominant after imposing daughter-level geometric acceptance. We also identify possible ways to recover part of the cascade event rate, including relaxed event-selection criteria and an active-target subdetector.
ER -