Deriving experimental constraints on the scalar form factor in the second-class τ→ηπν mode

2021/12/08 by Moussallam, B.
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)

paper · doi:10.48550/arxiv.2112.04429

Abstract

The rare second-class decay mode of the τ into ηπν could be observed for the first time at Belle II. It is important to try to derive a reliable evaluation of the branching fraction and of the energy distribution of this mode within the standard-model. Many predictions exist already in the literature which can differ by one to two orders of magnitude. Here, an approach based on a systematic use of the property of analyticity of form factors and scattering amplitudes in QCD is discussed. In particular, we will show that the scalar form factor in the τ decay can be related to photon-photon scattering and radiative ϕ decay amplitudes for which precise experimental measurements have been performed by the Belle and KLOE collaborations.

Related

• Analyticity of ηπ isospin-violating form factors and the τ→ηπν second-class decay
• The strong coupling from hadronic τ-decay data including τ→π^-π⁰ν_τ from Belle
• What can be learned from the transition form factor γ^*γ^*→η': feasibility study
• Recent Results on τ Decays
• Predictions for the eta_c-gamma transition form factor