Carbon $^{14}$C and Tritium as possible background sources in XENON1T

Abstract

In this work, carbon $^{14}$C and Tritium were considered as possible background source in the XENON1T experiment. The simulation results show that if $^{14}$C is located in dust particles with a characteristic size of tens of micrometers, then its beta spectrum is softened and can contribute to the low-background part of the spectrum (up to 20 keV) of the XENON1T experiment. In addition, it has been shown that the tritium spectrum is also significantly distorted due to the threshold effect and the form in which tritium is living in xenon. Comparison of the simulation results with experimental data allowed us to estimate the activity level of $^{14}$C at about 1500 decays / t / year, which gives the level of organic impurities containing $^{14}$C at the level of 2x10$^{-13}$ g/g. In the case of tritium background, spectrum distortions are already caused by nanoparticles. Wherein the shape of the spectrum from tritium sitting on the surface of the dust fits better into the experimental data than the spectrum from pure tritium. In addition, since the dust absorbs part of the decays, the total amount of tritium in xenon can be several times greater than assuming a background from pure tritium in xenon (the factor strongly depends on the size of the dust particles).