Seminar - Prof. Seodong Shin (Jeonbuk Natl. U.)

Monday Sep 21, 2026, 5:00 PM → 6:00 PM Asia/Seoul

Yonsei University (S327)

Title :  High-Energy Nuclear Recoils from Boosted Dark Matter for the LZ 248-keV Event: Beyond the Halo-Dependent High-Velocity Tail

Abstract:

The LUX-ZEPLIN (LZ) Collaboration has reported a nuclear-recoil candidate at ER = 248 ± 23stat ± 23sys keV, with a maximum local significance of 3.4σ and a global significance of 2.6σ. A prominent interpretation invokes heavy halo dark matter near an inelastic threshold and therefore depends sensitively on the poorly constrained high-speed tail of the Galactic velocity distribution. In this Letter, we propose a qualitatively different possibility based on light boosted dark matter (BDM), whose incident energy is determined primarily by the dark-sector mass spectrum. We con- sider multi-component scenarios in which the boosted state scatters elastically or inelastically off xenon nuclei. For elastic scattering, pseudoscalar-mediated momentum dependence suppresses low- energy recoils. Near-threshold endothermic scattering of a nearly monochromatic BDM flux can instead confine the signal between kinematically determined recoil endpoints, suppressing events in both the low- and high-energy sidebands. The upscattered state may furthermore decay in- visibly within the dark sector, preserving a single-nuclear-recoil signature without requiring it to be detector-stable. We present representative benchmark spectra and discuss complementary tests using other target nuclei and large-volume liquid-scintillator experiments.

 

Paper : https://arxiv.org/pdf/2609.06890v1