A
bstract
The decay mode
$ B_s^0 \to D_s^{ \mp }{K^{\pm }} $
allows for one of the theoretically cleanest measurements of the CKM angle γ through the study of time-dependent
CP
violation. This paper ...reports a measurement of its branching fraction relative to the Cabibbo-favoured mode
$ B_s^0 \to D_s^{ - }{\pi^{ + }} $
based on a data sample corresponding to 0.37 fb
−1
of proton-proton collisions at
$ \sqrt {s} = 7\;{\text{TeV}} $
collected in 2011 with the LHCb detector. In addition, the ratio of B meson production fractions
f
s
/f
d
, determined from semileptonic decays, together with the known branching fraction of the control channel
B
0
→
D
−
π
+
, is used to perform an absolute measurement of the branching fractions:
$ \begin{gathered} \mathcal{B}\left( {B_s^0 \to D_s^{ - }{\pi^{ + }}} \right) = \left( {2.95\pm 0.05\pm 0.17_{{ - 0.22}}^{{ + 0.18}}} \right) \times {10^{{ - 3}}}, \hfill \\ \mathcal{B}\left( {B_s^0 \to D_s^{ \mp }{K^{\pm }}} \right) = \left( {1.90\pm 0.12\pm 0.13_{{ - 0.14}}^{{ + 0.12}}} \right) \times {10^{{ - 4}}}, \hfill \\ \end{gathered} $
where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to
f
s
/f
d
.
The first observation of the decay Bs0→K⁎0K¯⁎0 is reported using 35 pb−1 of data collected by LHCb in proton–proton collisions at a centre-of-mass energy of 7 TeV. A total of 49.8±7.5Bs0→(K+π−)(K−π+) ...events are observed within ±50 MeV/c2 of the Bs0 mass and 746 MeV/c2<mKπ<1046 MeV/c2, mostly coming from a resonant Bs0→K⁎0K¯⁎0 signal. The branching fraction and the CP-averaged K⁎0 longitudinal polarization fraction are measured to be B(Bs0→K⁎0K¯⁎0)=(2.81±0.46(stat.)±0.45(syst.)±0.34(fs/fd))×10−5 and fL=0.31±0.12(stat.)±0.04(syst.).
A search for the decays Bs0→μ+μ− and B0→μ+μ− is performed with 0.37 fb−1 of pp collisions at s=7 TeV collected by the LHCb experiment in 2011. The upper limits on the branching fractions are ...B(Bs0→μ+μ−)<1.6×10−8 and B(B0→μ+μ−)<3.6×10−9 at 95% confidence level. A combination of these results with the LHCb limits obtained with the 2010 dataset leads to B(Bs0→μ+μ−)<1.4×10−8 and B(B0→μ+μ−)<3.2×10−9 at 95% confidence level.
The first observation of the decay B¯s0→D0K⁎0 using pp data collected by the LHCb detector at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 36 pb−1, is reported. A ...signal of 34.4±6.8 events is obtained and the absence of signal is rejected with a statistical significance of more than nine standard deviations. The B¯s0→D0K⁎0 branching fraction is measured relative to that of B¯0→D0ρ0: B(B¯s0→D0K⁎0)B(B¯0→D0ρ0)=1.48±0.34±0.15±0.12, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the B0 and Bs0 hadronisation fractions.
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