Observation of the Bc+ → J/ψπ+π0 decay

The first observation of the Bc+→J/ψπ+π0 decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the Bc+→J/ψπ+ channel is measured to beBBc+→J/ψπ+π0BBc+→J/ψπ+=2.80±0.15±0.11±0.16, where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and Bc+→J/ψπ+ decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation

Search for the Bs0 → μ+μ−γ decay

A search for the fully reconstructed B0 s → µ +µ −γ decay is performed at the LHCb experiment using proton-proton collisions at √ s = 13 TeV corresponding to an integrated luminosity of 5.4 fb−1 . No signifcant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B 0 s → µ +µ −γ) < 4.2 × 10−8 , m(µ +µ −) ∈ [2mµ, 1.70] GeV/c2 , B(B 0 s → µ +µ −γ) < 7.7 × 10−8 , m(µ +µ −) ∈ [1.70, 2.88] GeV/c2 , B(B 0 s → µ +µ −γ) < 4.2 × 10−8 , m(µ +µ −) ∈ [3.92, mB0 s ] GeV/c2 , at 95% confdence level. Additionally, upper limits are set on the branching fraction in the [2mµ, 1.70] GeV/c2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals

First observation of the Λb0 → D+D−Λ decay

The Λ 0 b → D+D−Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.3 fb−1 . Using the B0 → D+D−K0 S decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σΛ0 b σB0 × B(Λ0 b → D+D−Λ) B(B0 → D+D−K0 S ) = 0.179 ± 0.022 ± 0.014 , where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B(B0 → D+D−K0 S ), and the cross-section ratio, σΛ0 b /σB0 , previously measured by LHCb are used to derive the branching fraction of the Λ 0 b → D+D−Λ decay B(Λ0 b → D+D−Λ) = (1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11) × 10−4 , where the third and fourth contributions are due to uncertainties of B(B0 → D+D−K0 S ) and σΛ0 b /σB0 , respectively. Inspection of the D+Λ and D+D− invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ 0 b → D∗+D−Λ decay is also observed for the first time as a partially reconstructed component in the D+D−Λ invariant mass spectrum

Study of Bc+ → χcπ+ decays

A study of Bc+→χcπ+ decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The decay Bc+→χc2π+ is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the Bc+→J/ψπ+ decay is measured to beBBc+→χc2π+BBc+→J/ψπ+=0.37±0.06±0.02±0.01, where the first uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the χc2→ J/ψγ branching fraction. No significant Bc+→χc1π+ signal is observed and an upper limit for the relative branching fraction for the Bc+→χc1π+ and Bc+→χc2π+ decays of BBc+→χc1π+BBc+→χc2π+=<0.49 is set at the 90% confidence level

Observation of the Bc+→J/ψπ+π0B_c^+ \to J/\psi \pi^+ \pi^0 decay

The first observation of the $B_c^+ \to J/\psi \pi^+ \pi^0$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the $B_c^+ \to J/\psi \pi^+$ channel is measured to be $$\frac{ {\cal{B}}_{( B_c^+ \to J/\psi \pi^+\pi^0 ) }} { {\cal{B}}_{( B_c^+ \to J/\psi \pi^+ ) }} = 2.80 \pm 0.15 \pm 0.11 \pm 0.16 \,,$$ where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for $B^+ \to J/\psi K^{*+}$ and $B^+ \to J/\psi K^+$ decays, which are used to determine the $\pi^0$ detection efficiency. The $\pi^+\pi^0$ mass spectrum is found to be consistent with the dominance of an intermediate $\rho^+$ contribution in accordance with a model based on QCD factorisation.The first observation of the ${B}_c^{+}\to J/\psi {\pi}^{+}{\pi}^0$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb$^{−1}$, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the ${B}_c^{+}\to J/\psi {\pi}^{+}$ channel is measured to be$\frac{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}{\pi}^0}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}}}=2.80\pm 0.15\pm 0.11\pm 0.16,$where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B$^{+}$ → J/ψK$^{*+}$ and ${B}_c^{+}\to J/\psi {\pi}^{+}$ decays, which are used to determine the π$^{0}$ detection efficiency. The π$^{+}$π$^{0}$ mass spectrum is found to be consistent with the dominance of an intermediate ρ$^{+}$ contribution in accordance with a model based on QCD factorisation.[graphic not available: see fulltext]The first observation of the $B_c^+ \to J/\psi \pi^+ \pi^0$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the $B_c^+ \to J/\psi \pi^+$ channel is measured to be $$\frac{ {\cal{B}}( B_c^+ \to J/\psi \pi^+\pi^0 ) } { {\cal{B}}( B_c^+ \to J/\psi \pi^+ ) } = 2.80 \pm 0.15 \pm 0.11 \pm 0.16 \,,$$ where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for $B^+ \to J/\psi K^{*+}$ and $B^+ \to J/\psi K^+$ decays, which are used to determine the $\pi^0$ detection efficiency. The $\pi^+\pi^0$ mass spectrum is found to be consistent with the dominance of an intermediate $\rho^+$ contribution in accordance with a model based on QCD factorisation