Effects of order α3 on the determination of the Pauli form factor F2 of the τ -lepton

F. Krinner, N. Kaiser

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Abstract

We introduce optimal observables to measure the Pauli form factor F2 of the τ-lepton in the pair-production process e -e +→ τ-τ+ from the intensity distribution of the decay products. The spin-density matrix for the production process is calculated in QED up to order α3 including virtual photon-loops and soft bremsstrahlung, as well the γZ interference. We find that the decay channel (ρ-ντ) × (ρ+ν¯ τ) yields the best resolution for ReF2(s) and ImF2(s) due to its high branching fraction. We also study the bias that is introduced in the determination of F2, if the production spin-density matrix is taken in tree-level (one-photon exchange) approximation.

Original languageEnglish
Article number410
JournalEuropean Physical Journal C
Volume82
Issue number5
DOIs
StatePublished - May 2022

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