Improved measurement of CP violation parameters in Bs0→J/ψK+K− decays in the vicinity of the ϕ(1020) resonance

The decay-time-dependent C P asymmetry in B 0 s → J / ψ ( → μ + μ − ) K + K − decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6     fb − 1 , collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B 0 s signal decays with an invariant K + K − mass in the vicinity of the ϕ ( 1020 ) resonance, the C P -violating phase ϕ s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B 0 s − ¯ B 0 s system, Δ Γ s , and the difference of the average B 0 s and B 0 meson decay widths, Γ s − Γ d . The values obtained are ϕ s = − 0.039 ± 0.022 ± 0.006     rad , Δ Γ s = 0.0845 ± 0.0044 ± 0.0024     ps − 1 , and Γ s − Γ d = − 0.005 6 + 0.0013 − 0.0015 ± 0.0014     ps − 1 , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕ s is also measured independently for each polarization state of the K + K − system and shows no evidence for polarization dependence

Search for D∗(2007)0→μ+μ−D^{*}(2007)^{0} \rightarrow \mu ^{+} \mu ^{-} in B−→π−μ+μ−B^{-}\rightarrow \pi ^{-} \mu ^{+} \mu ^{-} decays

AbstractThe very rare $${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-}$$ D ∗ ( 2007 ) 0 → μ + μ - decay is searched for by analysing $${{{B} ^-}} \!\rightarrow {{\pi } ^-} {\mu ^+\mu ^-}$$ B - → π - μ + μ - decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9$$\text {\,fb} ^{-1}$$ \,fb - 1 . The signal signature corresponds to simultaneous peaks in the $${\mu ^+\mu ^-}$$ μ + μ - and $${{\pi } ^-} {\mu ^+\mu ^-}$$ π - μ + μ - invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at \mathcal{B}({{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} ) < 2.6\times 10^{-8} B ( D ∗ ( 2007 ) 0 → μ + μ - ) &lt; 2.6 × 10 - 8 at $$90\%$$ 90 % confidence level. This is the first limit on the branching fraction of $${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-}$$ D ∗ ( 2007 ) 0 → μ + μ - decays and the most stringent limit on $${{D} ^*} (2007)^0$$ D ∗ ( 2007 ) 0 decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.</jats:p