Periodic Variations of the Radon Concentration Measured by the Large Volume Detector at the Gran Sasso Underground Laboratory

Time series of gamma-ray photons from natural radioactivity measured with the Large Volume Detector (LVD) at the Gran Sasso underground laboratory (Laboratori Nazionali del Gran Sasso, Italy) have been analyzed. The instrument is used to detect neutrinos from gravitational collapses of stellar cores in the Galaxy. The background of the experiment is due to neutrons and gamma-ray photons from the decays of daughter nuclei of uranium and thorium. An analysis of periodic variations of the number of gamma-ray photons caused by the radon concentration in the underground laboratory has shown the presence of diurnal, weekly, monthly, and annual modulations. Data collected from 2004 to 2021, including a period of low activity in the hall of the Gran Sasso laboratory during the COVID-19 pandemic, have been reported.