The decay Bs -> J/\psi K+ K- is investigated using 0.16/fb of data collected with the LHCb detector using 7 TeV pp collisions. Although the J/\psi \phi\ channel is well known, final states at higher ...K+K- masses have not previously been studied. In the K+K- mass spectrum we observe a significant signal in the f'2(1525) region as well as a non-resonant component. After subtracting the non-resonant component, we find B(Bs->J/\psi f'_2(1525))/B(Bs->J/\psi \phi)=(26.4 +/- 2.7 +/- 2.4)%.
Measurement of the mixing-induced CP-violating phase \phi s in Bs decays is of prime importance in probing new physics. Here 7421 +/- 105 signal events from the dominantly CP-odd final state ...J/\psi\pi+\pi- are selected in 1/fb of pp collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A time-dependent fit to the data yields a value of \phi s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard Model expectation. No evidence of direct CP violation is found.
Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the semileptonic decays Bs -> Ds+ X mu nu and Bs -> D0 K+ X mu nu are detected. Two ...structures are observed in the D0 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 Bs semileptonic rate are B(Bs -> D_{s2}^{*+} X mu nu)/B(Bs -> X mu nu)= (3.3\pm 1.0\pm 0.4)%, and B(Bs -> D_{s1}^+ X munu)/B(Bs -> X mu nu)= (5.4\pm 1.2\pm 0.5)%, where the first uncertainty is statistical and the second is systematic. This is the first observation of the D_{s2}^{*+} state in Bs decays; we also measure its mass and width.
The decay mode $\B^{0}_{s} \to D^{\mp}_{s} K^{\pm} $ allows for one of the theoretically cleanest measurements of the CKM angle $\gamma$ through the study of time-dependent $\ensuremath{CP}\xspace$ ...violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode $\B^{0}_{s} \to D^{-}_{s} \pi^{+}$ based on a data sample of 0.37 fb$^{-1}$ proton-proton collisions at $\sqrt{s} = 7$ TeV collected in 2011 with the LHCb detector. In addition, the ratio of $\ensuremath{\mathrm{B}}\xspace$ meson production fractions $\ensuremath{f_s/f_d}$, determined from semileptonic decays, together with the known branching fraction of the control channel $B^{0} \to D^{-} \pi^{+}$, is used to perform an absolute measurement of the branching fractions: $B (\B^0_s \to D^-_s \pi^+) \;= (2.95 \pm 0.05 \pm 0.17^{\,+\,0.18}_{\,-\,0.22}) \times 10^{-3}$, $B (\B^0_s \to D^\mp_s K^\pm) = (1.90 \pm 0.12 \pm 0.13^{\,+\,0.12}_{\,-\,0.14}) \times 10^{-4}\,$, where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to $f_s/f_d$.
The production of $J/\psi$ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of ...$355pb^{-1}$ collected with the LHCb detector. Model independent measurements of absolute cross-sections are given together with ratios to the measured $J/\psi$ and open charm cross-sections. The properties of these events are studied and compared to theoretical predictions.
The effective lifetime of the Bs meson in the decay mode Bs->J/\psi fo(980) is measured using 1.0/fb of data collected in pp collisions at sqrt(s) = 7 TeV with the LHCb detector. The result is 1.700 ...+/- 0.040 +/- 0.026 ps where the first uncertainty is statistical and the second systematic. As the final state is CP-odd, and CP violation in this mode is measured to be small, the lifetime measurement can be translated into a measurement of the decay width of the heavy Bs mass eigenstate, \Gamma_H = (0.588 +/- 0.014 +/- 0.009)/ps.
Measurement of mixing-induced CP violation in Bs decays is of prime importance in probing new physics. So far only the channel Bs->J/\psi \phi\ has been used. Here we report on a measurement using an ...LHCb data sample of 0.41/fb in the CP odd eigenstate J\psi f0(980), where f0(980)->\pi+ \pi-. A time dependent fit of the data with the Bs lifetime and the difference in widths of the heavy and light eigenstates constrained to the values obtained from Bs-> J/\psi\phi\ yields a value of the CP violating phase of -0.44 +/- 0.44 +/- 0.02 rad, consistent with the Standard Model expectation.
A precise determination of the effective $B_s^0 \rightarrow K^+ K^-$ lifetime can be used to constrain contributions from physics beyond the Standard Model in the $B_s^0$ meson system. Conventional ...approaches select $B$ meson decay products that are significantly displaced from the $B$ meson production vertex. As a consequence, $B$ mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb$^{-1}$ of data recorded by the LHCb experiment, the effective $B_s^0 \rightarrow K^+ K^-$ lifetime is measured as $1.455 \pm 0.046 \; \mathrm{(stat.)} \pm 0.006 \; \mathrm{(syst.)} \, \mathrm{ps}.$
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