Dispersive evaluation of the second-class amplitude $\tau\to\eta\pi\nu_\tau$ in the standard model

S. Descotes-Genon; E. Kou; B. Moussallam

doi:10.1016/j.nuclphysbps.2014.09.016

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arXiv · 1303.2879

Dispersive evaluation of the second-class amplitude $\tau\to\eta\pi\nu_\tau$ in the standard model

S. Descotes-Genon·E. Kou·B. Moussallam

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Abstract

We reevaluate the two form factors relevant for the $\eta\pi$ second-class $\tau$ decay mode, making systematic use of analyticity, unitarity, combined with updated inputs to the NLO chiral constraints. We focus, in particular, on the shape of the $\rho$ resonance peak which is a background-free signature of a second-class current. Its dispersive construction requires the $\eta\pi\to\pi\pi$ scattering amplitude which we derive from a family of Khuri-Treiman equations solutions constrained with accurate recent results on the $\eta\to3\pi$ Dalitz plot.

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S. Descotes-Genon, E. Kou, B. Moussallam. 2013-03-12. Dispersive evaluation of the second-class amplitude $\tau\to\eta\pi\nu_\tau$ in the standard model. https://doi.org/10.1016/j.nuclphysbps.2014.09.016

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