Neutrinos are tiny subatomic particles that interact very little with any other particles. Many neutrinos on Earth are produced in nuclear fusion reactions in the sun. Even though neutrinos are one of the most abundant particles in the universe, they are very hard to detect. As a result, large detectors have to be built. These detectors contain two main components -- photomultiplier tubes (PMTs) and a large volume containing water, scintillator, or water based liquid scintillator. The PMTs surround the large volume. When a neutrino moves through this volume, it may cause a reaction that emits other particles. If the emitted particle is charged and in scintillator, it produces scintillation light. If the emitted particle is in water, it produces Cherenkov radiation. In water based liquid scintillator, both scintillation light and Cherenkov radiation are possible. The PMTs are responsible for detecting the light.
This summer I had the opportunity to help research one such neutrino detector in Professor Klein’s lab. My project was to run simulations of electrons moving through a detector in order to find out more about the energy resolution of the detector. Specifically, I looked at the number of PMTs hit each time light was emitted (NHits) and the number of electrons emitted in each PMT each time it detected light (NumPE) in a detector called THEIA. The THEIA detector is a large cylindrical detector containing water based liquid scintillator with about 90% of the surface area covered in PMTs. I simulated electrons moving through the detector; the electrons ranged in energy and position of origination. I ran simulations of the detector using a reaction analysis tool, RAT-PAC. Using ROOT and Python, I created plots of the simulations; histograms for NumPE and NHits and plots that showed the mean NumPE and mean Nhits as a function of energy or as a function of position. We also had to consider the error associated with each mean as a function of energy or position. Throughout this project, I gained skills in programming specifically in python and C++ which is a language used in ROOT. Finally, I developed my knowledge and understanding of neutrinos as wells as the physics of their detection.