Search for new physics in $B\to K\pi \pi \gamma$ with Belle II data

Abstract

The measurement of the time-dependent CP-asymmetry of $B^0\to K_S^0{\pi }^{+}{\pi }^{-}\gamma$ decays is sensitive to contributions from physics beyond the Standard Model. To translate this measurement into a constraint on new physics, it is necessary to distinguish between decay modes that contribute to the final state via a kaonic resonance that is a CP eigenstate, and those that proceed through non-CP eigenstates. This requires an amplitude analysis of the $B\to K_{res}\gamma \to K{\pi }^{+}{\pi }^{-}\gamma$ decay, that is discussed in this article.

Contribution to the 2026 Electroweak session of the 60th Rencontres de Moriond