ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2010, vol. 105, p. -
Observation of Bs0→Ds(*)+Ds(*)- using e⊃+e⊃- collisions and a determination of the Bs-B̄s width difference ΔΓs
We have made the first observation of Bs0→Ds(*)+Ds(*)- decays using 23.6fb⊃-1 of data recorded by the Belle experiment running on the Υ(5S) resonance. The branching fractions are measured to be B(Bs0→Ds+Ds-)=(1.03-0.32-0.25+0.39+0.26)%, B(Bs0→Ds*±Ds)= (2.75-0.71+0.83±0.69)%, and B(Bs0→Ds*+Ds*-)=(3.08-1.04- 0.86+1.22+0.85)%; the sum is B[Bs0→Ds(*)+Ds(*)-]=(6.85-1.30-1. 80+1.53+1.79)%. Assuming Bs0→Ds(*)+Ds(*)- saturates decays to CP-even final states, the branching fraction determines the ratio ΔΓs/cosφ, where ΔΓs is the difference in widths between the two Bs-B̄s mass eigenstates, and φ is a CP-violating weak phase. Taking CP violation to be negligibly small, we obtain ΔΓs/Γs=0. 147-0.030+0.036(stat)-0.041+0.042(syst), where Γs is the mean decay width. © 2010 The American Physical Society.