Development of Tau Polarimetry for measuring beam polarization in e+e- colliders
Date
2023-04-26
Authors
Miller, Caleb
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Abstract
The Belle II experiment is considering the addition of longitudinal polarization to the e- beam of SuperKEKB. The addition of beam polarization would allow for a number of world leading electroweak precision measurements, and the dominant uncertainty in these future measurements is expected to be how well the average beam polarization is known. The development of the Tau Polarimetry technique provides a highly precise way for detectors at e+e- colliders, at a centre-of-mass energy of 10.58 GeV, to determine the average beam polarization in data collected. As Belle II is in the process of collecting a significant data-set and maximizing the detector performance, the Tau Polarimetry technique has been developed and demonstrated on the resemblant BaBar detector. To enable Belle II to take high luminosity data, which is required for the additional physics enabled by the beam polarization, the beam backgrounds must be well modelled and understood. Thermal neutron detectors have been deployed to monitor neutron backgrounds arising from the high energy beams. The calibration, operation, and analysis of the data collected from these detectors is presented in this dissertation. In addition to the background studies, the Belle II detector sensitivity to electroweak asymmetries with polarized beams has been carried out with state-of-the-art Monte Carlo generators and the results compared with leading theoretical calculations. The development of Tau Polarimetry at BaBar is the primary focus of the dissertation and the expected statistical and systematic limitations are established. This work provides a road map for the application of Tau Polarimetry at Belle II and the sensitivity expected.
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Keywords
tau, polarimetry, BABAR, Belle II, Chiral Belle