Speaker
Description
Low-energy precision experiments provide unique sensitivity to feebly coupled light states that are inaccessible at high-energy colliders. In this talk, we present projected sensitivities for light Beyond the Standard Model (BSM) mediators with masses below 100 MeV at two such facilities. First, we explore the MAGIX experiment at MESA, utilizing high-intensity electron beams on a heavy $^{181}\text{Ta}$ target. The BSM mediator is produced via the Bethe-Heitler process, and the asymmetric double-spectrometer kinematic setup of MAGIX is optimized to achieve the highest signal-to-background ratio. Second, we examine the JLab polarized positron program, focusing on the beam normal spin asymmetry in Bhabha scattering. The Standard Model contribution to this observable features a zero crossing at a fixed scattering angle, providing a clean, effectively background-free kinematic point for BSM searches. We consider scalar, pseudoscalar, vector, and axial vector mediators and find that the combination of kinematic optimization, high beam rates, and state-of-the-art precision extends current search sensitivities, probing parameter space well beyond existing constraints.
| Primary Abstract Topic | Theory: Other Dark Matter |
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