Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the semileptonic decays B0s→D+s+Xμν̄ and B0s→D0K+Xμν̄ are detected. Two structures are observed in the D0K+ mass spectrum at masses consistent with the known Ds1(2536)+ and Ds2*(2573)+ mesons. The measured branching fractions relative to the total B-s0 semileptonic rate are B(B0s→Ds2*+Xμν̄)/B(B0s→Xμν̄)=(3.3±1.0±0.4)%, and B(B0s→D+s1Xμν̄)/B(B0s→Xμν̄)=(5.4±1.2±0.5)%, where the first uncertainty is statistical and the second is systematic. This is the first observation of the D*+s2 state in B0s decays; we also measure its mass and width. © 2011 CERN.
- Nuclear and High Energy Physics