Dedicated Searches for Millicharged Particles at Intensity-Frontier Facilities: SpinQuest and SHiP

Leo Bailloeul; Matthew Citron; Yanou Cui; Saeid Foroughi-Abari; Insung Hwang; Fengyi Li; Yu-Dai Tsai; Ming Xiong Liu; Kranti Gunthoti; Jae Hyeok Yoo

arXiv · 2512.11027

Dedicated Searches for Millicharged Particles at Intensity-Frontier Facilities: SpinQuest and SHiP

Leo Bailloeul·Matthew Citron·Yanou Cui·Saeid Foroughi-Abari·Insung Hwang·Fengyi Li·Yu-Dai Tsai·Ming Xiong Liu·Kranti Gunthoti·Jae Hyeok Yoo

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Abstract

We conduct a dedicated study of searches for millicharged particles (mCPs) utilizing scintillator-based detectors at high-intensity fixed-target experiments, with particular focus on the SpinQuest and forthcoming Search for Hidden Particles experiment (SHiP) facilities. The analysis incorporates the three primary production mechanisms: meson decays, Drell-Yan processes, and proton bremsstrahlung. In particular, our updated analysis reveals that proton bremsstrahlung dominates the production rate in the sub-GeV mass regime. Detailed detector simulations and background evaluations are performed to obtain realistic sensitivity estimates. Our results demonstrate that future experiments located in the SpinQuest and SHiP facilities can achieve substantial improvements in discovery potential, enhancing sensitivity to the mCP charge parameter $\epsilon=q_{\chi}/e$ (with $q_\chi$ denoting the mCP electric charge) by up to two orders of magnitude relative to existing limits.

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Leo Bailloeul, Matthew Citron, Yanou Cui, Saeid Foroughi-Abari, Insung Hwang, Fengyi Li, Yu-Dai Tsai, Ming Xiong Liu, Kranti Gunthoti, Jae Hyeok Yoo. 2025-12-11. Dedicated Searches for Millicharged Particles at Intensity-Frontier Facilities: SpinQuest and SHiP. https://arxiv.org/abs/2512.11027

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