Neutrino Induced Cascade Reconstruction in the Baikal-GVD Neutrino Telescope

AbstraktAbstract

The sources of the high-energy cosmic rays and the cosmic accelerator mechanisms still remain long-standing research questions. However, neutrinos are ideal cosmic messengers, which can reveal information about these sources. Since neutrinos have no electric charge, they can be registered only indirectly through the weak interactions with matter. In the neutrino interactions, secondary charged particles with ultra relativistic energies are created. During the propagation through the transparent medium (i.e. water), they produce Cherenkov radiation, which can be registered by photo-sensors of the neutrino telescope. The Baikal-GVD detector is designed to detect high-energy neutrinos. It is a threedimensional grid of optical modules, which is placed 1366 meters deep in Lake Baikal. For easier maintenance and operation, the whole detector is divided to 7 independent units, called clusters. Each cluster comprises 288 optical modules. One of the topologies created by emitted Cherenkov light is called a cascade. In this thesis the software for the reconstruction of the cascade position, generation time and also the energy and direction is presented. For the extraction of the very rare high-energy cascade events from the pile of background, different kinds of event filters have been developed, tested and optimized. This reconstruction algorithm was tuned on the Monte Carlo cascade simulations and finally it was successfully applied to real experimental data for season 2016 and three cascade-like candidates above 100 TeV were found.

The sources of the high-energy cosmic rays and the cosmic accelerator mechanisms still remain long-standing research questions. However, neutrinos are ideal cosmic messengers, which can reveal information about these sources. Since neutrinos have no electric charge, they can be registered only indirectly through the weak interactions with matter. In the neutrino interactions, secondary charged particles with ultra relativistic energies are created. During the propagation through the transparent medium (i.e. water), they produce Cherenkov radiation, which can be registered by photo-sensors of the neutrino telescope. The Baikal-GVD detector is designed to detect high-energy neutrinos. It is a threedimensional grid of optical modules, which is placed 1366 meters deep in Lake Baikal. For easier maintenance and operation, the whole detector is divided to 7 independent units, called clusters. Each cluster comprises 288 optical modules. One of the topologies created by emitted Cherenkov light is called a cascade. In this thesis the software for the reconstruction of the cascade position, generation time and also the energy and direction is presented. For the extraction of the very rare high-energy cascade events from the pile of background, different kinds of event filters have been developed, tested and optimized. This reconstruction algorithm was tuned on the Monte Carlo cascade simulations and finally it was successfully applied to real experimental data for season 2016 and three cascade-like candidates above 100 TeV were found.