Combined analysis of Belle and Belle II data to determine the CKM angle ϕ3 using B+→D(K0Sh−h+)h+ decays

Abstract

We present a measurement of the Cabibbo-Kobayashi-Maskawa unitarity triangle angle ϕ3 (also known as~γ) using a model-independent Dalitz plot analysis of \linebreak B+→D(K0Sh+h−)h+, where D is either a D0 or D¯0 meson and h is either a π or K. This is the first measurement that simultaneously uses Belle and Belle~II data, combining samples corresponding to integrated luminosities of \SI{711}{fb^{-1}} and \SI{128}{fb^{-1}}, respectively. All data were accumulated from energy-asymmetric e+e− collisions at a centre-of-mass energy corresponding to the mass of the Υ(4S) resonance. We measure ϕ3=(78.4±11.4±0.5±1.0)∘, where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is from the uncertainties on external measurements of the D-decay strong-phase parameters.