Improving tau decay simulations for detecting tau neutrinos at IceCube

• Main Author: Thor, Simon
• Format: Bachelor Thesis
• Language: English
• Published: KTH, Fysik 2024
• Subjects: particle physics; Tauola; Geant4; partikelfysik; Physical Sciences; Fysik; South Pole; South pole
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-347222

Tau neutrinos are one of the least understood elementary particles, as they are difficult to detect. One of the few detectors that can detect them is the IceCube neutrino observatory, located on the south pole. When tau neutrinos interact with a nucleus in the ice at IceCube, a tau lepton can form, which decays almost instantaneously. The decay products of the tau lepton will then emit light, which can be detected at IceCube. To gain a better understanding of tau neutrinos, it is therefore crucial to accurately simulate tau lepton decays. In this thesis, the tau lepton decays within the IceCube simulation framework are evaluated by comparing the simulations to TAUOLA, a high-precision tau decay simulation library, Through this work, several issues with the current simulations were discovered. Specifically, the polarization of the tau lepton is neglected, hadronic resonances are not implemented for tau decays, and several decay modes are missing. These issues result in an overestimate of the energy of the visible decay products, which means that the light emitted from the tau decay is dimmer in reality than what is predicted by the current IceCube simulations. To address this, TAUOLA was integrated into the IceCube simulations, thereby enabling high-precision tau decay simulations for future studies. Tauneutriner är en av de allra minst studerade partiklarna på grund av att de är svåra att detektera. En av få detektorer som han observera tau neutriner är neutrinoteleskopet IceCube vid sydpolen. När tauneutriner interagerar med isen kan en taulepton skapas, som snabbt sönderfaller. De partiklar som bildas vid sönderfallet avger ljus som kan mätas i IceCube. För att kunna studera tauneutriner är det därför fundamentalt att simulera korrekta och noggranna tausönderfall. Under detta examensarbete jämfördes IceCubes simuleringar av tausönderfall mot mjukvarubiblioteket TAUOLA, som är ämnat för högprecisionssimuleringar av tausönderfall. Genom detta upptäcktes ett flertal problem med IceCubes ...