A Neutrino Detector Design
A Simulation Study on the Design of the Cherenkov Near Detector of the Proposed ESSnuSB
Summary, in English
Today, the neutrino oscillation is very well established by experiment. It is described by a theoretical framework similar to that of quark mixing. Here is included a CP violating phase, delta_CP, which is the only known possible source of CP violation in the lepton sector. So far, delta_CP is completely unconstrained by experiment, and the determination of the value of delta_CP could further the search for an explanation of the matter-antimatter asymmetry observed in the Universe today.
Therefore, many next generation experiments are in development to measure delta_CP. One of the experiments under evaluation is the ESSnuSB; a proposed high intensity neutrino beam produced at the European Spallation Source (the ESS).
The ESS facility, now under construction in Lund, Sweden, would need to be upgraded in order to produce the high intensity neutrino beam. Neutrino oscillations in the nu_mu to nu_e channel could then be studied by the use of a megaton water Cherenkov detector separated from the beam source by some hundred kilometres. The phase delta_CP would thereby be determined by measuring the asymmetry between the oscillation probabilities of neutrinos and antineutrinos.
The precision of this experiment would be improved by characterising the beam close to the production point. This would be achieved by the use of a kiloton water Cherenkov detector, denoted as the Near Detector (ND), which is studied in this thesis. Firstly, concrete design recommendations for the near detector of the ESSnuSB should be found through simulations. Secondly, a set of algorithms should be developed that reconstructs the properties of a neutrino event vertex from the simulated detector response. It is essential that a muon neutrino event can be separated from an electron neutrino event, as the purpose of the ESSnuSB is to detect the transition from one flavour to the other.
The near detector is foreseen to be cylindrical in shape, with radius R_ND and length L_ND, and located at a distance z_ND from the neutrino beam production point. It will be filled with water and have photon detectors placed on the inner surface. In this project, several limits have been put on the design parameters of the ESSnuSB ND.
• The radius of the near detector: 2*R_ND > 2 m, R_ND < z_ND/50.
• The length of the near detector: L_ND > 3 m.
• The distance between the neutrino beam production and the near detector: zND > 200 m.
• The detector must have a spatial resolution smaller than 10 cm.
• The detector must have a time resolution shorter than 100 ps.
Additionally, a set of reconstruction algorithms was developed for a simplified detector environment, and the flavour identification algorithm was found to have a misidentification rate of 0.3%.
- Physics and Astronomy
- CP violation
- near detector
- Peter Christiansen
- Joakim Cederkäll (Professor)