Search for the $B0 \to K^{∗0} \tau^{+} \tau^{-}$ decay with an hadronic tagged approach

Sumitted to PubDB: 2025-08-25

Category: Physics / performance paper, Visibility: Latest Version Public

Authors	Claudia Cecchi, Elisa Manoni, Stefano Moneta
Date	2025-10-07
Working group	Radiative and Electroweak Penguin
Belle II Number	BELLE2-PUB-PH-2025-038
Abstract	We present a search for the rare flavor-changing neutral-current decay $B^{0} \to K^{∗0} \tau^{+} \tau^{−}$ with data collected by the Belle II experiment at the SuperKEKB electron-positron collider. The analysis uses a 365 fb$^{−1}$ data sample recorded at the center-of-mass energy of the $\Upsilon(4S)$ resonance. One of the $B$ mesons produced in the $\Upsilon(4S)\to B^{0}\bar{B^{0}}$ process is fully reconstructed in a hadronic decay mode, while its companion $B$ meson is required to decay into a $K^{∗0}$ and two $\tau$ leptons of opposite charge. The $\tau$ leptons are reconstructed in final states with a single electron, muon, charged pion or charged $\rho$ meson, and additional neutrinos. We set an upper limit on the branching fraction of $\mathcal{B}(B^{0}\to K^{*0}\tau^{+}\tau^{-}) < 1.8 \times 10^{−3}$ at the 90% confidence level, which is the most stringent constraint reported to date.
ArXiv	https://arxiv.org/abs/2504.10042
Journal	Phys.Rev.Lett.
Authorship confirmation page	https://authors.belle2.org/#62
Analysis	Search for the $B^{0} \to K^{*0} \tau^+ \tau^-$ decay with an hadronic tagged approach