In this research the seasonal variation of the atmospheric muon rate at the KM3NeT/ARCA detector was studied in order to determine the temperature correlation coefficient αT. KM3NeT is a cubic...Show moreIn this research the seasonal variation of the atmospheric muon rate at the KM3NeT/ARCA detector was studied in order to determine the temperature correlation coefficient αT. KM3NeT is a cubic kilometer neutrino telescope consisting of two large volume water-Cherenkov detectors, ARCA and ORCA, located in the Mediterranean sea. The Cherenkov radiation emitted from high energy muons traveling through the seawater gets detected by an assembly of 31 Photo-multiplier tubes situated inside a sphere shaped Digital Optical Module (DOM). 18 of such DOMs are connected to form a Detection Unit (DU). For the ARCA detector, these DUs are located at the seafloor at around 3.5 km depth, extending vertically to about 2.7 km below sea level. Taking advantage of correlations between hits registered at different PMTs within a DOM, a measurement of the atmospheric muon rate at each DOM can be determined. Furthermore, the difference in height of the DOMs in each DU enables the utilization of the depth dependence of atmospheric muons to precisely determine the muon rate at the ARCA detector. This makes it possible to detect rate variations of a few percent. Additionally, the effective temperature is determined through a weighted integral of the available temperature data above the geographic location of the ARCA detector. Comparing the atmospheric muon rate and the effective temperature during the data taking period of 26.09.2021 until 1.06.2022 a temperature correlation of αT = 1.166 ± 0.128 was established. This is slightly above the theoretically predicted value of 0.86. To verify the robustness of the proposed method of determining the rate and temperature correlation, cross checks were done with Monte Carlo files, background signals and the examination of the depth relationship with time. All returned the expected results. However, when the same method was employed on a smaller data set covering the data taking period between 12.05.2021 and 2.09.2021, no significant correlation between the atmospheric muon rate and the effective temperature could be established. Furthermore, the performed cross checks on this data set did not confirm expectations. This is most likely due to the small data set which is not able to accurately capture the long term seasonal effect. However these results should not be neglected. Therefore, while the employed method did return promising results for a larger set of data, more investigation into the efficiency determination and the errors on the fitted slope are needed to confidently verify the reliability of the final result. It is further suggested to revisit this study once a consistent data set of minimally one year is available.Show less
The KM3NeT neutrino telescope, located presently at two different sites in the Mediterranean Sea, consists of two neutrino detecors As the telescope is still being built, the calibration is fully...Show moreThe KM3NeT neutrino telescope, located presently at two different sites in the Mediterranean Sea, consists of two neutrino detecors As the telescope is still being built, the calibration is fully underway. This research focuses on four potential biases present in the astrophysical focused part of the detector, ARCA. Muon light, both detected and reconstructed from simulations and $^{40}$K decay being used to determine the size of those biases. It is found that the PMTs shadowed by the titanium collar on the DOM show a different bias dependent on what hemisphere they are located. Furthermore it is found that the different gel transperacy in the DOMs causes different efficiencies, and that the new PMTs show lower efficiencies than the old PMTs.Show less
KM3NeT is a European research infrastructure hosting the new generation of neutrino telescopes. It is currently under construction and consists of two detectors. This report investigates data from...Show moreKM3NeT is a European research infrastructure hosting the new generation of neutrino telescopes. It is currently under construction and consists of two detectors. This report investigates data from six already deployed units of the ORCA detector to provide a characterisation of the detector efficiencies. The isotropic efficiencies used in the Monte Carlo simulation and estimated from 40K decays are compared to anisotropic efficiency measures based on light created by muons. Shadowing effects are shown to create a bias of approximately 5% in the detected number of photons. The simulation underestimates the amount of direct light and overestimates the amount of indirect light. The latter is likely the result of an overestimation of the muon bundle multiplicity. A comparison between the reference simulation and one that assumes 5% more absorption shows a preference for more absorption for larger distances and time residuals.Show less
KM3NeT neutrino detectors are currently under construction in the Mediterranean Sea. Their primary aim is to observe and study high energy cosmic neutrinos and the neutrino mass ordering. The...Show moreKM3NeT neutrino detectors are currently under construction in the Mediterranean Sea. Their primary aim is to observe and study high energy cosmic neutrinos and the neutrino mass ordering. The telescopes detect Cherenkov light from muons created in the Earth’s atmosphere and from products of neutrino interactions. Muons travelling in water stochastically loose energy by inducing electromagnetic showers. In this study a method for electromagnetic shower identification and fitting is developed. The two-tier identification method is based on (1) comparing the expected and detected photons emitted along the muon track, and (2) comparing the likelihood of a muon event having no shower to the likelihood of a muon event having a single shower along the track. The developed method is applied succesfully to Monte Carlo simulations of atmospheric muons in the ARCA detector, and to data from the ARCA detector with six detection lines in operation. Electromagnetic showers and hence muon energy losses are observed. For a large set of ARCA muon events with identified showers the fitted shower energies and distances are analysed and discussed. On average the shower energy increases with muon energy. Several challenges like multiple shower identification complicate good model fits to empirically verify an average shower energy decrease with distance.Show less
The KM3NeT neutrino telescope, currently under construction, aims to detect high energy neutrinos from distant astrophysical sources, as well as studying the properties of neutrinos by exploiting...Show moreThe KM3NeT neutrino telescope, currently under construction, aims to detect high energy neutrinos from distant astrophysical sources, as well as studying the properties of neutrinos by exploiting atmospheric neutrinos. 3-Dimensional arrays of thousands of optical sensors with a total volume of about five cubic kilometres will be distributed over three locations in the Mediterranean Sea. These optical sensor modules will detect the cherenkov light emitted by the charged particles (muons) produced in collisions of neutrinos and the Earth. To be able to reconstruct the path of the muons radiating the detected photons, an accurate time-calibration is vital. For efficient commissioning, already before deployment a pre-timecalibration of the modules is required. Currently, a laser-installation is used to perform this calibration procedure. In this thesis the possibility to use cosmic ray showers to perform this pre-calibration is investigated. Particles (muons, electrons) of secondary radiation reaching the earth in an air shower will hit the detectors at virtually the same moment, which makes the recorded coincident suitable for time-calibration. This study demonstrates that the optical modules can indeed detect these particles from cosmic showers, and that the subsequent data can be exploited for a robust time-calibration with an accuracy of within 0.3 ns.Show less
In this paper a new method of distinguishing shower-like from track-like neutrino interaction events using event reconstruction data is introduced. This method is then used to minimise the error...Show moreIn this paper a new method of distinguishing shower-like from track-like neutrino interaction events using event reconstruction data is introduced. This method is then used to minimise the error that a shower-like event is misidenti ed as a track-like event and vice versa, which is necessary for measuring the neutrino mass hierarchy in ORCA. In its current format, the method leads to errors of around 0.40 for noisy simulation data and approximately 0.15 for noiseless data. However, the method can still be extended to take into account more information of the reconstructions, thereby possibly improving the results.Show less
