Researchers from various institutions, including the University of Chinese Academy of Sciences, the University of Science and Technology of China, and the University of California, Berkeley, have recently delved into the intriguing high-energy nuclear-recoil excess observed in liquid xenon experiments, XENONnT and LZ. These experiments, designed to detect weakly interacting massive particles (WIMPs), a leading candidate for dark matter, have reported data that cannot be explained by standard elastic spin-independent WIMP scattering. The researchers, led by Haipeng An and including Fei Gao, Jia Liu, Minghao Liu, Haoming Nie, and Changlong Xu, have published their findings in a recent study.
The team utilized a unified framework called DIAMX, which is built on openly available data and likelihood models, to perform the first combined profile-likelihood fits to multiple WIMP-search datasets. The total exposure of these datasets amounts to an impressive 7.3 tonne × year. The researchers investigated two broad classes of dark matter nucleon interactions: those with velocity-dependent cross-sections and those involving inelastic (both endothermic and exothermic) scattering. Their analysis revealed that these interactions could potentially reproduce the observed high-energy recoil spectrum, achieving local significances of up to 4σ.
One of the critical aspects of their study was the quantification of the impact of 124Xe double electron capture (DEC) backgrounds. The researchers found that variations in the poorly understood DEC charge yields could significantly shift the inferred significances, ranging from below 1σ to as high as 4σ. This highlights the importance of understanding and accurately modeling background processes in dark matter experiments.
The researchers also pointed out that extending the analysis to include data from XENONnT and LZ with recoil energies up to 300 keV, once available, would provide a robust test of the dark matter interpretation. This is because the 124Xe DEC background is expected to be negligible in this high-energy range, potentially offering a clearer signal of dark matter interactions.
The practical implications for the energy sector, particularly in nuclear energy, could be significant. Understanding dark matter and its interactions with ordinary matter could lead to advancements in nuclear technologies, including improved nuclear reactors and better safety measures. Additionally, the development of more sensitive detection methods for dark matter could have applications in other areas of energy research, such as monitoring and controlling nuclear reactions.
In summary, the study by An et al. provides a comprehensive analysis of the high-energy nuclear-recoil excess observed in XENONnT and LZ experiments. Their findings suggest that certain types of dark matter interactions could explain the observed data, although background processes like 124Xe DEC need to be better understood. The research was published in the journal Physical Review D.
This article is based on research available at arXiv.