BSM searches in the MeV-GeV mass range

par Aleksandr PUSTYNTSEV (Univ. Mainz)

jeudi 15 oct. 2026, 11:00 → 12:00 Europe/Paris

Auditorium Vivargent (LAPTh)

The search for light dark-sector particles in the MeV-GeV mass range has intensified over the past decade. In this talk, I will present projected sensitivities for light Beyond the Standard Model (BSM) mediators with masses below 100 MeV at two state-of-the-art low-energy precision facilities. First, I will discuss the MAGIX experiment at MESA (Mainz), which uses high-intensity electron beams incident on a heavy $^{181}$Ta target. In this setup, the BSM mediator is produced via the Bethe-Heitler process, and the asymmetric double-spectrometer geometry of MAGIX is optimized to maximize the signal-to-background ratio. Second, I will consider the polarized positron program at Jefferson Lab (USA), with emphasis on the beam-normal single-spin asymmetry in Bhabha scattering. The Standard Model contribution to this observable exhibits a zero crossing at a fixed scattering angle, creating a particularly clean kinematic point for BSM searches. Finally, I will briefly discuss ongoing efforts to search for GeV-mass mediators at intensity-frontier $e^+e^-$ collider experiments, in the context of current Belle II and BESIII data taking.