Determination of

Abstract

We present a determination of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| from the decay B → Dℓνℓ using a 365 fb-1 e+e- → ϒ(4S) → BB¯ data sample recorded by the Belle II experiment at the SuperKEKB collider. The semileptonic decay of one B meson is reconstructed in the modes B0 → D−(→ K+π−π−)ℓ+νℓ and B+ → D¯0( → K+π−)ℓ+νℓ, where ℓ denotes either an electron or a muon. Charge conjugation is implied. The second B meson in the ϒ(4S) event is not reconstructed explicitly. Using an inclusive reconstruction of the unobserved neutrino momentum, we determine the recoil variable w = vB·vD, where vB and vD are the four-velocities of the B and D mesons. We measure the total decay branching frac..