2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36871We present a preliminary measurement of the Standard Model CP violation parameter $\sin 2ϕ_1$ using the Belle detector. A $6.2~{\rm fb}^{-1}$ sample of events produced by the KEKB asymmetric $e^+e^-$ collider operating at the $Υ(4S)$ resonance is used. We report a preliminary result of $$\sin 2ϕ_1=0.45^{+0.43}_{-0.44}({\rm stat})^{+0.07}_{-0.09}({\rm syst}).$$13 pages, 12 figures, Talk given at the XXXth International Conference on High Energy Physics, july 27 - August 2, Osaka, JapanHigh Energy Physics - Experimenttext