This thesis focuses on the task of separating detector events caused by atmospheric neutrinos from those caused by atmospheric muons. Performance on this task is analysed using simulated data of...Show moreThis thesis focuses on the task of separating detector events caused by atmospheric neutrinos from those caused by atmospheric muons. Performance on this task is analysed using simulated data of these events as they are detected in the KM3NeT/ORCA10 detector setup. We present a new procedure for training the Machine Learning (ML) classifiers that handle this separation task. This most notably includes separating the data into track- and shower- like events, and training separate classifiers on these subsets of data. We show a significant improvement in the resulting neutrino signal when compared to the current classification procedure.Show less
Cosmic rays produce muons that cast Cherenkov light cones in the water. With the Cherenkov light cones, KM3NeT can reconstruct the track of the muon across the sky, this result is named an event....Show moreCosmic rays produce muons that cast Cherenkov light cones in the water. With the Cherenkov light cones, KM3NeT can reconstruct the track of the muon across the sky, this result is named an event. Between September 22 2022 GMT and June 09 2023 GMT, the ARCA site was measuring, and detecting Cherenkov light from any bypassing muon. From this measurement simulations were created, containing 6 times more events as the measurement. In this thesis, we analyse the events from the simulation. We bin the events on one- \& two-dimensional maps of the sky, where we bin all reconstructed events relative to the location of the Moon. Two models are fitted to the maps. One model assumes the absence of the Moon; another model respects a valley in events at the Moon's location. These fits are tested with the use of $\chi^2$-tests. The one-dimensional analysis indicates a relative amplitude of $0.65 \pm 0.10$ and angular resolution of $0.81\degree \pm 0.12\degree$. The rotational calibration of the telescope is tested. Although the $\chi^2$ values differ most for no rotational calibration an angle of -0.2 and -0.4 are larger than expected. Quality cuts of the data set are based on the variables' likelihood and track reconstruction uncertainty. It is the superposition of a likelihood of 100 or higher and a track reconstruction uncertainty of 0.1 or smaller that causes an increase in the difference in $\chi^2$ values.Show less
KM3NeT is a collaboration that is currently constructing a research infras- tructure in the Mediterranean Sea, consisting of deep-sea neutrino tele- scopes. Its main scientific goals are to probe...Show moreKM3NeT is a collaboration that is currently constructing a research infras- tructure in the Mediterranean Sea, consisting of deep-sea neutrino tele- scopes. Its main scientific goals are to probe into the cosmos for high- energy neutrino sources, and to determine fundamental properties of these particles. These goals are pursued by dividing the detector volume over two sites, ORCA and ARCA, each housing a detector that is opti- mised for a distinct energy range. To achieve the final science, KM3NeT re- quires a time and position calibration accuracy of roughly 1 ns and 20 cm, respectively. This study presents an examination of two independent cali- bration methods, which utilise the detection of muons produced by cosmic ray showers. The time calibration provides consistent results for different cuts of data. When the movement of detection units due to varying sea currents is low, the systematic error is entirely explained via an asymme- try in the detector geometry. Ultimately, an accuracy of 2.5 ns is achievable. The position calibration is a novel technique that is developed during this project. We demonstrate its feasibility by applying it to the detector data, and estimate the currently obtainable accuracy to be within 2 m. Although both methods currently cannot meet the standards set by KM3NeT, their techniques are far from perfected. Overall, a fast cross check of the exist- ing calibration techniques can be provided, while requiring no additional setups or measurements.Show less
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 an international collaboration currently engaged in the development of a neutrino detector situated in the Mediterranean Sea. By investigating atmospheric neutrinos, its objective is to...Show moreKM3NeT is an international collaboration currently engaged in the development of a neutrino detector situated in the Mediterranean Sea. By investigating atmospheric neutrinos, its objective is to explore the fundamental characteristics of neutrinos, while also striving to study astro-particle physics by detecting high-energy neutrinos originating from celestial objects. Neutrinos interacting with seawater surrounding the detector create muons that emit Cherenkov radiation that can be detected. The reconstruction software employed aims to determine the energy and direction of these muons. This thesis briefly studies the underlying model, referred to as the PDF, shedding qualitative light on some of its internal mechanisms. The reconstruction software comprises a prefit stage and a fit of the PDF. In the second part of this thesis, the watershed algorithm is shown to be a promising alternative in the determination of the best distinct solutions of the prefit by effectively discerning symmetries among other considerations.Show less
In hopes of understanding the universe we inhabit, scientists search for signals from the universe that could give as clues about its nature. When these signals are composed of particles, they are...Show moreIn hopes of understanding the universe we inhabit, scientists search for signals from the universe that could give as clues about its nature. When these signals are composed of particles, they are given the name of ”cosmic rays”. Once cosmic rays have reached our atmosphere, they interact with molecules there, creating pions and kaons that decay into muons and neutrinos. Studying these, we can deepen our knowledge and understanding of the universe. It is in the interest of this that this thesis explores the effect of seasonal changes in temperature on the rate of atmospheric muons that reaches the ARCA site of KM3NeT, a neutrino telescope being built in the Mediterranean sea. Exploiting their depth dependence we were able to establish a new method to quantify a muon rate, allowing the investigation of different energy ranges through the filtering of certain coincidences. After fitting these curves to an exponential decay, the fit parameters were extracted and compared to the temperatures in different pressure levels of the atmosphere. This showed a weak negative correlation for the normalization factor and a moderate positive correlation for the slope. For lower energies, the relationship between the slope and temperature was proportional by a factor αT = 0.0029 ± 0.00012. For higher energies, this proportionality was given by αT = 0.0051 ± 0.00034. Due to the weak correlation exhibited, no constant of proportionality was found for the normalization factor.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
This project is part of the research of the KM3NeT neutrino detector located in the Mediterranean Sea and which is currently under construction. Calibration of the detector is of utmost importance...Show moreThis project is part of the research of the KM3NeT neutrino detector located in the Mediterranean Sea and which is currently under construction. Calibration of the detector is of utmost importance as it has to reconstruct particle tracks as accurately as possible. It is shown that mispointing, i.e. the detector not having a perfectly aligned coordinate system, leads to artifacts in the data. The pointing accuracy can be cross-checked by the Moon and the Sun. Evaluation of event densities around the regions of the Moon and the Sun with the current ORCA-6 data concludes that deficits of events could not yet be significantly detected. Investigations of the background event densities showed that the background has statistical fluctuations that are consistent within the 2 sigma range. Further investigation of the background event density slope leads to the result of a linear line being a better fit to the background than a flat line.Show less
KM3NeT is an international collaboration currently working on the construction of a neutrino detector in the Mediterranean Sea. During the period evaluated in this research, two detection strings...Show moreKM3NeT is an international collaboration currently working on the construction of a neutrino detector in the Mediterranean Sea. During the period evaluated in this research, two detection strings were deployed and active. With this new detector, the KM3NeT collaboration aims to discover the neutrino mass ordering and scan for cosmic neutrino sources. In order to accurately reconstruct neutrino interactions, the detector elements must be synchronized within nanoseconds. The goal of this research is to evaluate whether the signal of passing atmospheric muons can contribute in the time calibration. The data was scrutinized for detector malfunctions and cleaned. The detector performance was then checked by using signal coincidences between detector elements to evaluate correlated signals, stemming from atmospheric muons. This allowed also to determine the dependence of the muon rate on the depth and assess potential time o sets. A time offset of 30 ns between the two operating detector strings was found, which will require further investigations.Show less
The KM3NeT Neutrino telescope is a telescope in the Mediterranean sea researching neutrino events to study both neutrino properties and neutrino sources in the universe. While searching for...Show moreThe KM3NeT Neutrino telescope is a telescope in the Mediterranean sea researching neutrino events to study both neutrino properties and neutrino sources in the universe. While searching for neutrinos, the detector observes noise from bioluminescence and 40K decay as well. The 40K noise is constant and homogeneous, and the bioluminescence consists of high peaks in the signal (bursts) and is periodic in nature. In this research the periodicity of the bioluminescence was researched for the different detectors, together with the general noise characteristics of the detectors and their effect on the muon track reconstruction. The periodicity was found to be consistent with the current around the detectors and the inertial waves caused by the Coriolis force, though there is slight variation in the frequency. The bioluminescence can cause slightly less muon events to be reconstructed, though track distributions are similar to those with less bioluminescent noise.Show less
KM3NeT is a research collaboration currently building a neutrino telescope in the Mediterranean Sea. The aim of KM3NeT is to discover the source of astrophysical neutrinos and to uncover the true...Show moreKM3NeT is a research collaboration currently building a neutrino telescope in the Mediterranean Sea. The aim of KM3NeT is to discover the source of astrophysical neutrinos and to uncover the true neutrino mass hierarchy. In order to achieve its scientific goals, KM3NeT requires 1-2 ns time calibration accuracy. Preliminary time calibration is currently executed using a laser setup. This research explores the use of background signals from air showers instead. The air shower method is shown to be robust and consistent within 0.5 ns. Furthermore, this time calibration corresponds to laser calibrations within 1 ns. Thus, the air shower time calibration provides a cross check for current methods and it could be used as a cheaper and easier method for future time calibration facilities. Secondly, the decay of atmospheric muon signals in the sea is investigated as a detector performance cross check. The muon depth dependence is very stable after all corrections and considerations discussed in this research. Any large deviations from the expected muon signal may be used as an indicator for lower efficiency in the detector. Furthermore, comparisons between detectors can show consistency in the time calibrations. Overall, background signals of atmospheric origin, though not being the objective for KM3NeT, are shown to provide valuable detector cross checks.Show less
KM3NeT is a international collaboration focused on neutrino telescopy. Its main goals are to detect high energy cosmological objects through neutrino detection and reveal the neutrino mass...Show moreKM3NeT is a international collaboration focused on neutrino telescopy. Its main goals are to detect high energy cosmological objects through neutrino detection and reveal the neutrino mass hierarchy. For this it uses two detectors, the ARCA detector which is constructed on the coast of Italy and the ORCA detector which had its first two detection strings deployed in the fall of 2017. In this thesis we focus on measuring the background produced by muons generated in atmospheric events. This will allow us to gain an estimation of the expected background from which we obtain an indication of the performance of the detector. We have used two methods of filtering uncorrelated backgrounds such as the signals produced by decay of 40K in the ocean to extract atmospheric signals. Through the two methods we have found two halving lengths of muons flux in the water of the Mediterranean. A halving length of 239 meters for the method filtering low energy hits and a halving length of 267 meters for signals extracted by correlations between DOMs. The results give a good estimation of the order of magnitude of muon decay through increasing depths, however we have found systematic artifacts in the DOMs, which are expected to be caused by differences in the DOM efficiencies. For this reason further research is required to obtain a definitive result.Show less
This research paper presents the investigations on the impact of Earth’s magnetic field on the efficiency of 3-inch photomultiplier tubes used in the KM3NeT neutrino telescope. The research...Show moreThis research paper presents the investigations on the impact of Earth’s magnetic field on the efficiency of 3-inch photomultiplier tubes used in the KM3NeT neutrino telescope. The research includes measurements of three Hamamatsu PMTs. The measurements show that the efficiency of the PMTs are directional-dependent. However, this significance is most probably not caused by Earth’s magnetic field only. Further investigation is needed to determine where these external effects come from.Show less
Currently still under construction, the KM3NeT neutrino telescope in the Mediterranean Sea will be used to detect atmospheric and cosmic neutrinos. KM3NeT will consist of large cubic arrays of...Show moreCurrently still under construction, the KM3NeT neutrino telescope in the Mediterranean Sea will be used to detect atmospheric and cosmic neutrinos. KM3NeT will consist of large cubic arrays of large amounts of optical sensors. The detector will exploit Cherenkov radiation emitted by energetic secondary particles. To have an understanding of the performance of the detector, knowing about the performance of the different digital optical modules (DOMs) is vital. Using various methods (mainly potassium decay, 40K -> 40Ca), relative sensitivities of the different DOMs have been measured. However, only rough estimates for absolute efficiencies are known. A novel method will be developed to cross check the results previously found. This research will exploit atmospheric muons and probe the sensitivity of the KM3NeT neutrino telescope. Events in which multiple DOMs in a row detect a muon are used. Both threefold and fourfold combinations are used. Ratios are introduced to describe the fraction of times all DOMs are hit over the outer DOMs. This scales with efficiency. Simulations are used to describe extinction and propagation of Cherenkov photons and muons in water.Show less
This thesis studies the origin of large signals detected in the KM3NeT optical modules. The origin of the signals is directly studied with the single PMT and indirectly with the DOM. The results of...Show moreThis thesis studies the origin of large signals detected in the KM3NeT optical modules. The origin of the signals is directly studied with the single PMT and indirectly with the DOM. The results of both the single PMT and the DOM point toward a high energetic particle origin. Further measurements are required to conclude this with certainty.Show less
The KM3NeT-neutrino telescope is a large detector under construction in the Mediterranean Sea. Its main objectives are the observation of cosmic high-energy neutrinos and the determination of the...Show moreThe KM3NeT-neutrino telescope is a large detector under construction in the Mediterranean Sea. Its main objectives are the observation of cosmic high-energy neutrinos and the determination of the neutrino mass hierarchy. However, the deep sea is an extraordinary location and environment and entails uncontrolled phenomena like bioluminescence. Bioluminescence is the emission of light by organisms. This light is detected by the KM3NeT-detector when bioluminescent organisms collide with the structure of KM3NeT. It is interesting to study the signal of the bioluminescence, because it tells a lot about life in deep-sea and it can be a nuisance in the quest to observe and research neutrinos. Characteristics of bioluminescence like the amount of detected bioluminescence over a long period of time, the location of the increased bioluminescence in the detector, the number of bioluminescent bursts that happen at the same time, the duration of these bursts and the periodicity of the detected bioluminescence are investigated. Finally in the analysis of the data it has been found that some parts of the detector are showing unexpected behaviour, examples of this behaviour are shown.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
The KM3NeT detector is a neutrino telescope under construction in the Mediterranean Sea. High-energy particles travelling at great velocities can emit underwater light, which is measured by the...Show moreThe KM3NeT detector is a neutrino telescope under construction in the Mediterranean Sea. High-energy particles travelling at great velocities can emit underwater light, which is measured by the detector. Data coming from the parts that are already deployed can be interpreted and analysed to determine characteristics of these incident particles. Muons are of particular interest in this research, because they can be easily identified as such. Nearly all muons approach the detector from above and, as it spans well over 600 m in length, muons are measured at different depths. Because of the large volume of sea water between the highest and the lowest part of the detector, it is expected that more muons are measured at the top than at the bottom. In a few separate ways it has been shown that this is indeed the case. Fewer hits are measured deeper down the detector, which means that the muon hit rate is dependent of the depth. It has been demonstrated that the distance over which the muon intensity halves is equal to 530 m. Comparing the data with Monte Carlo simulations has shown good agreement.Show less
The KM3NeT/ORCA experiment will use part of the detector which is currently being built in the Mediterranean Sea to determine the neutrino mass hierarchy by measuring the pattern of atmospheric...Show moreThe KM3NeT/ORCA experiment will use part of the detector which is currently being built in the Mediterranean Sea to determine the neutrino mass hierarchy by measuring the pattern of atmospheric neutrino oscillations. In this thesis, in addition to the neutrino oscillations in the Earth, the oscillations in the atmosphere have been included in the simulations and the impact of the atmosphere on the measurements has been evaluatedShow less
