TY  - JOUR
PB  - SciPost Foundation
DO  - 10.21468/SciPostPhysProc.16.009
TI  - Deriving experimental constraints on the scalar form factor in the second-class $\tau \to\eta \pi \nu$ mode
PY  - 2025/07/14
UR  - https://scipost.org/SciPostPhysProc.16.009
JF  - SciPost Physics Proceedings
JA  - SciPost Phys. Proc.
VL  - 
IS  - 16
SP  - 009
A1  - Moussallam, Bachir
AB  - The rare second-class decay mode of the $\tau$ into $\eta\pi\nu$ 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 $\tau$ decay can be related to photon-photon scattering and radiative $\phi$ decay amplitudes for which precise experimental measurements have been performed by the Belle and KLOE collaborations.
ER  -

@Article{10.21468/SciPostPhysProc.16.009,
	title={{Deriving experimental constraints on the scalar form factor in the second-class $\tau \to\eta \pi \nu$ mode}},
	author={Bachir Moussallam},
	journal={SciPost Phys. Proc.},
	pages={009},
	year={2025},
	publisher={SciPost},
	doi={10.21468/SciPostPhysProc.16.009},
	url={https://scipost.org/10.21468/SciPostPhysProc.16.009},
}