First observation of B̄s0→Ds2*+Xμ−ν̄ decays
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چکیده
a r t i c l e i n f o a b s t r a c t Using data collected with the LHCb detector in proton–proton collisions at a centre-of-mass energy of 7 TeV, the semileptonic decays B 0 s → D + s Xμ − ν and B 0 s → D 0 K + Xμ − ν are detected. Two structures are observed in the D 0 K + mass spectrum at masses consistent with the known D s1 (2536) + and D * s2 (2573) + mesons. The measured branching fractions relative to the total B 0 s semileptonic rate are B(B 0 s → D * + s2 Xμ − ν)/B(B 0 s → Xμ − ν) = (3.3 ± 1.0 ± 0.4)%, and B(B 0 s → D + s1 Xμ − ν)/B(B 0 s → Xμ − ν) = (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 B 0 s decays; we also measure its mass and width.
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