Faculty of Mathematics, Physics
and Informatics
Comenius University Bratislava

The CRESST Symposium in Bratislava

FMPH CU is organizing during 12-15 June 2023 the CRESST Symposium to discuss present status and future plans in the development of the CRESST.

10. 06. 2023 22.45 hod.
By: Pavel Povinec

The Faculty of Mathematics, Physics, and Informatics of the Comenius University is organizing during 12-15 June 2023 the CRESST Symposium to discuss present status and future plans in the development of the CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) experiment. The main role of the CRESST experiment is to search for hypothetical dark matter (DM) particles, specifically for WIMPs (Weakly Interacting Massive Particles), which directly interact with normal known matter via some form of weak interaction, and therefore it is very difficult to observe them.

The DM particles have very small probability to scatter on atomic nuclei (directly on neutrons and protons), which is represented by a potentially measurable cross section for a given particle mass. The CRESST experiment has been specifically designed for searching for DM particles with masses below 2 GeV/c2, and in this mass range it is a world leader in DM experiments.

The CRESST uses highly sensitive cryogenic particle detectors to detect the small amount of energy deposited in a detection crystal by a single-particle interaction.  The detectors are cooled down to 15 mK, which enables to register even small temperature increases (of a millionth of a degree) using very sensitive devices to detect temperature changes. The CRESST collaboration developed very sensitive coincidence detection systems, combining temperature signals with scintillation signals, as a few percent of the deposited energy is emitted in the form of scintillation light. Various crystals were used in the experiments, including, e.g., CaWO4, LiAlO2, Si, diamond, etc. The CRESST experiment obtained the world’s lowest limit for the scattering of light-dark matter particles on protons (5・10-35 cm2 at mass of 1 GeV/c2).

The CRESST experiment is located in the LNGS (Laboratori Nazionali del Gran Sasso),  a deep underground laboratory operating under the Gran Sasso mountain in Italy. The LNGS is the world's largest underground laboratory (shielded by 1400 m of rocks) which is hosting several experiments. The CRESST collaboration combines about 60 physicists from eight institutes representing Germany, Italy, Austria, Slovakia, and the UK. Our contribution (R. Breier, M. Ješkovský, J. Kaizer, I. Kontuľ, P. Povinec, J. Zeman) to the experiment has been in the development of methods for radiopurity investigations of construction parts of the detectors (as the main contribution to their background has been from natural radionuclides), as well as in Monte Carlo simulations of the detector background due to interactions of cosmic-ray particles and radiation emitted from decays of natural radionuclides).

As the known matter represents only 5% of all matter (25% is estimated to be DM and 70% is dark energy), this fundamental research represents greatest challenge for a better understanding of physics and in general the Universe.