Probing third-generation New Physics with $K\to \pi \nu\bar\nu$ and $B\to K^{(*)} \nu\bar\nu$

Lukas Allwicher; Marzia Bordone; Gino Isidori; Gioacchino Piazza; Alfredo Stanzione

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arXiv · 2410.21444

Probing third-generation New Physics with $K\to \pi \nu\bar\nu$ and $B\to K^{(*)} \nu\bar\nu$

Lukas Allwicher·Marzia Bordone·Gino Isidori·Gioacchino Piazza·Alfredo Stanzione

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Abstract

The recent observation of the $K^+ \to \pi^+ \nu\bar\nu$ decay by NA62 is an important milestone in precision flavor physics. Together with evidence of $B^+ \to K^+\nu\bar\nu$ reported by Belle-II, they are the only FCNC decays involving third-family leptons where a precision close to the SM expectation has been reached. We study the implications of these recent results in the context of a new physics scenario aligned to the third generation, with an approximate $U(2)^5$ flavor symmetry acting on the light families. We find that the slight excess observed in both channels supports the hypothesis of non-standard TeV dynamics of this type, as also hinted at by other $B$-meson decays, consistently with bounds from colliders and electroweak observables. We further discuss how future improvements in precision could affect this picture, highlighting the discovery potential in these di-neutrino modes.

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Lukas Allwicher, Marzia Bordone, Gino Isidori, Gioacchino Piazza, Alfredo Stanzione. 2024-10-28. Probing third-generation New Physics with $K\to \pi \nu\bar\nu$ and $B\to K^{(*)} \nu\bar\nu$. https://arxiv.org/abs/2410.21444

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