Searching for low-mass dark matter via Migdal effect in COSINE-100

Abstract

We report on the search for weakly interacting massive particle (WIMP) dark matter candidates in the galactic halo that interact with sodium and iodine nuclei in the COSINE-100 experiment and produce energetic electrons that accompany recoil nuclei via the the Migdal effect. The WIMP mass sensitivity of previous COSINE-100 searches that relied on the detection of ionization signals produced by target nuclei recoiling from elastic WIMP-nucleus scattering was restricted to WIMP masses above $\sim$5 GeV/$c^2$ by the detectors' 1 keVee energy-electron-equivalent threshold. The search reported here looks for recoil signals enhanced by the Migdal electrons that are ejected during the scattering process. This is particularly effective for the detection of low-mass WIMP scattering from the crystals' sodium nuclei in which a relatively larger fraction of the WIMP's energy is transferred to the nucleus recoil energy and the excitation of its orbital electrons. In this analysis, the low-mass WIMP search window of the COSINE-100 experiment is extended to WIMP mass down to 200 MeV/$c^2$. The low-mass WIMP sensitivity will be further improved by lowering the analysis threshold based on a multivariable analysis technique. We consider the influence of these improvements and recent developments in detector performance to re-evaluate sensitivities for the future COSINE-200 experiment. With a 0.2 keVee analysis threshold and high light-yield NaI(Tl) detectors (22 photoelectrons/keVee), the COSINE-200 experiment can explore low-mass WIMPs down to 20 MeV/$c^2$ and probe previously unexplored regions of parameter space.

10 pages, 8 figures

References in corpus (17)

• A direct empirical proof of the existence of dark matter
• Results from a search for dark matter in the complete LUX exposure
• Observation of Coherent Elastic Neutrino-Nucleus Scattering
• Dark Matter Search Results from the Complete Exposure of the PICO-60 C${}_3$F${}_8$ Bubble Chamber
• Searching for low-mass dark matter particles with a massive Ge bolometer operated above-ground
• Low-Mass Dark Matter Search with CDMSlite
• New Limits on Interactions between Weakly Interacting Massive Particles and Nucleons Obtained with CsI(Tl) Crystal Detectors
• Probing sub-GeV Dark Matter with conventional detectors
• Final Results of the PICASSO Dark Matter Search Experiment
• An experiment to search for dark matter interactions using sodium iodide detectors
• Nuclear spin structure in dark matter search: The finite momentum transfer limit
• Strong constraints from COSINE-100 on the DAMA dark matter results using the same sodium iodide target
• Performance of a prototype active veto system using liquid scintillator for a dark matter search experiment
• COSINE-100 and DAMA/LIBRA-phase2 in WIMP effective models
• A facility for mass production of ultra-pure NaI powder for the COSINE-200 experiment
• The environmental monitoring system at the COSINE-100 experiment
• Measurement of the quenching and channeling effects in a CsI crystal used for a WIMP search