Karel Melis, promovendus aan het Nikhef, verdedigt zijn proefschrift woensdag 10 november 2021 om 11.00 aan de Universiteit van Amsterdam.
“Het heelal bestuderen vanaf -3000m N.A.P.”
Neutrinos are elementary particles with an extremely low probability to interact with any matter. Almost all neutrinos fly completely unhindered through humans, the Earth and even almost the entire universe. This makes them notoriously hard to detect, but also makes them ideal messengers to study the furthest objects in outer space, from which other particles such as photons cannot reach the Earth.
A detector capable of detecting neutrinos is called KM3NeT (‘cubic kilometre neutrino telescope’). This detector is currently under construction in the deep waters of the Mediterranean Sea. The detector instruments approximately one cubic kilometre of seawater, at a depth of about 3000 meters with a grid of thousands of very sensitive light sensors. These sensors detect the flash of light emitted by secondary particles produced in the interaction of a neutrino with one of the water molecules (an ‘event’). The properties of the interacting neutrino such as its direction and energy can be estimated from the pattern of detected light.
Results from data obtained during the first months of operation will be discussed in this thesis. A method to calibrate the detector using light emitted by backgrounds only will be discussed, leading to a measurement of the depth-dependence of the atmospheric muon flux. Potential neutrino-induced events have been identified.
A novel method to identify and study any (collection of) cosmic neutrino source(s) has been developed. Detailed functions describing the source properties, propagation and interaction of neutrinos, the detector and the observed events are used to maximise the amount of used information, thus maximising the potential to discover cosmic neutrino sources. Only a few concessions are made to limit the computing power required to evaluate these. One of the novelties is the use of ‘event likelihood landscapes’, describing the probability that an event is caused by a neutrino of certain energy and direction, interacting in the detector at a certain position and time. With the evaluation of these functions for a set of simulated events, the novel method is proven to be applicable to data.
“Studying the Universe from -3000m N.A.P.” (pdf)
De promotie vindt plaats op woensdag november, om 11.00 in de Aula van de Universiteit van Amsterdam, Singel 411, 1012 XM Amsterdam
De promotie zal online te volgen zijn op het youtubekanaal van de Universiteit van Amsterdam:
Meer informatie op de website van de UvA.
Promotor: prof. dr. P.M. Kooijman
Co-promotor: dr. R. Bruijn
contact: Karel Melis