# A no-go theorem for non-standard explanations of the $\tau\to K_S\pi\nu_\tau$ CP asymmetry

### Submission summary

 As Contributors: Martin Hoferichter Preprint link: scipost_201811_00001v1 Date accepted: 2019-01-15 Date submitted: 2018-11-02 01:00 Submitted by: Hoferichter, Martin Submitted to: SciPost Physics Proceedings Proceedings issue: The 15th International Workshop on Tau Lepton Physics (Amsterdam, 2018-09) Academic field: Physics Specialties: High-Energy Physics - Experiment High-Energy Physics - Phenomenology Nuclear Physics - Theory Approach: Theoretical

### Abstract

A new tensor interaction is the only possibility to explain the $2.8\sigma$ tension observed by the BaBar collaboration in the CP asymmetry in $\tau\to K_S\pi\nu_\tau$ with physics beyond the Standard Model (BSM) realized above the electroweak scale. However, the strong phase generated by the interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watson's final-state-interaction theorem, and the strength of the CP-violating tensor interaction is strongly constrained by bounds from the neutron electric dipole moment and $D$-$\bar{D}$ mixing. As a result, a confirmation of the tension at Belle II would point to light BSM physics.

Published as SciPost Phys. Proc. 1, 007 (2019)

### Submission & Refereeing History

Submission scipost_201811_00001v1 on 2 November 2018

## Reports on this Submission

### Anonymous Report 1 on 2018-12-12 (Invited Report)

• Cite as: Anonymous, Report on arXiv:scipost_201811_00001v1, delivered 2018-12-12, doi: 10.21468/SciPost.Report.735

### Report

The conference contribution under consideration is entirely based on the reviewed journal publication Phys. Rev. Lett. 120 (2018) 141803. It is well written and clear. Hence, in my opinion there is no need for a more detailed report.

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