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Precision $e^-$ Beam Polarimetry at an $e^+e^-$ B Factory using Tau-Pair Events

by Caleb Miller

Submission summary

Abstract

A novel technique for measuring the average beam polarization in $e^+e^-$ collisions, known as Tau Polarimetry, has been developed by the \babar~collaboration. This technique makes use of the relationship between the polarization of the beams, the resulting polarization of the $\tau^+\tau^-$ produced, and the kinematics of the decay products. Using this technique \babar~has measured the average $e^-$ beam polarization of PEP-II to be 0.0034 $\pm$ 0.0024$_{\textrm{stat}} \pm $0.0029$_{\textrm{sys}}$. This technique is expected to be used at Belle~II after a proposed polarization upgrade as the most precise method with which beam polarization can be determined.