We report measurements of the decays B -→Ds(*)+K -ℓ -ν ̄ℓ in a data sample containing 657×106BB̄ pairs collected with the Belle detector at the KEKB asymmetric-energy e +e - collider. We observe a signal with a significance of 6σ for the combined D s and Ds* modes and find the first evidence of the B -→Ds+K -ℓ -ν ̄ℓ decay with a significance of 3.4σ. We measure the following branching fractions: B(B -→Ds+K -ℓ -ν ̄ℓ)=(0.30±0.09(stat)-0.08+0.11(syst)) ×10 -3 and B(B -→Ds(*)+K -ℓ -ν ̄ℓ)=(0.59±0.12(stat) ±0.15(syst))×10 -3 and set an upper limit B(B -→Ds*+K -ℓ -ν ̄ℓ)<0.56×10 -3 at the 90% confidence level. We also present the first measurement of the Ds+K - invariant mass distribution in these decays, which is dominated by a prominent peak around 2.6GeV/c2.
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|State||Published - 2012 Oct 23|