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

Abstract The $${\Lambda}_b^0$$ Λ b 0 → 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 → $${D}^{+}{D}^{-}{K}_S^0$$ D + D − K S 0 decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be$$\mathcal{R}=\frac{\sigma_{\Lambda_b^0}}{\sigma_{B^0}}=\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)}{\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)}=0.179\pm 0.022\pm 0.014,$$ R = σ Λ b 0 σ B 0 = B Λ b 0 → D + D − Λ B B 0 → D + D − K S 0 = 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, $$\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)$$ B B 0 → D + D − K S 0 , and the cross-section ratio, $${\sigma}_{\Lambda_b^0}/{\sigma}_{B^0}$$ σ Λ b 0 / σ B 0 , previously measured by LHCb are used to derive the branching fraction of the $${\Lambda}_b^0$$ Λ b 0 → D+D−Λ decay$$\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)=\left(1.24\pm 0.15\pm 0.10\pm 0.28\pm 0.11\right)\times {10}^{-4},$$ B Λ b 0 → 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 $$\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)$$ B B 0 → D + D − K S 0 and $${\sigma}_{\Lambda_b^0}/{\sigma}_{B^0}$$ σ Λ b 0 / σ B 0 , respectively. Inspection of the D+Λ and D+D− invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The $${\Lambda}_b^0$$ Λ b 0 → D*+D−Λ decay is also observed for the first time as a partially reconstructed component in the D+D−Λ invariant mass spectrum.</jats:p

Study of Bc+ → χc π+ decays

A study of B-c(+) -&gt; chi(c) pi(+) decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13TeV, corresponding to an integrated luminosity of 9 fb(-1). The decay B-c(+) -&gt; chi(c2)pi(+) is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the B-c(+) -&gt; J/psi pi(+) decay is measured to beBBc+ -&gt;chi c2 pi+/BBc+ -&gt; (J/psi pi+) = 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 chi(c2) -&gt; J/psi gamma branching fraction. No significant B-c(+) -&gt; chi(+)(c1 pi) signal is observed and an upper limit for the relative branching fraction for the B-c(+) -&gt; chi(c1)pi(+) and B-c(+) -&gt; chi(c2)pi(+) decays ofBBc+ -&gt;chi c1 pi+/BBc+ -&gt; chi(c2)pi(+) &lt; 0.49is set at the 90% confidence level

Observation of the Bc+→J/ψπ+π0 {B}_c^{+}\to J/\psi {\pi}^{+}{\pi}^0 decay

Abstract The first observation of the $${B}_c^{+}\to J/\psi {\pi}^{+}{\pi}^0$$ B c + → J / ψ π + π 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 $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + channel is measured to be$$\frac{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}{\pi}^0}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}}}=2.80\pm 0.15\pm 0.11\pm 0.16,$$ B B c + → J / ψ π + π 0 B B c + → J / ψ π + = 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 $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + 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.</jats:p

Measurement of the branching fraction of B0 → J/ψπ0 decays

Abstract The ratio of branching fractions between B0 → J/ψπ0 and B+ → J/ψK*+ decays is measured with proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The measured value is$$\frac{{\mathcal{B}}_{B^0\to J/\psi {\pi}^0}}{{\mathcal{B}}_{B^{+}\to J/\psi {K}^{\ast +}}}=\left(1.153\pm 0.053\pm 0.048\right)\times {10}^{-2},$$ B B 0 → J / ψ π 0 B B + → J / ψ K ∗ + = 1.153 ± 0.053 ± 0.048 × 10 − 2 , where the first uncertainty is statistical and the second is systematic. The branching fraction for B0 → J/ψπ0 decays is determined using the branching fraction of the normalisation channel, resulting in$${\mathcal{B}}_{B^0\to J/\psi {\pi}^0}=\left(1.670\pm 0.077\pm 0.069\pm 0.095\right)\times {10}^{-5},$$ B B 0 → J / ψ π 0 = 1.670 ± 0.077 ± 0.069 ± 0.095 × 10 − 5 , where the last uncertainty corresponds to that of the external input. This result is consistent with the current world average value and competitive with the most precise single measurement to date.</jats:p

Study of Bc+→χcπ+ {B}_c^{+}\to {\chi}_c{\pi}^{+} decays

Abstract A study of $${B}_c^{+}\to {\chi}_c{\pi}^{+}$$ B c + → χ c π + 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 $${B}_c^{+}\to {\chi}_{c2}{\pi}^{+}$$ B c + → χ c 2 π + is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + decay is measured to be$$\frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}}}=0.37\pm 0.06\pm 0.02\pm 0.01,$$ B B c + → χ c 2 π + B B c + → J / ψ π + = 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 $${B}_c^{+}\to {\chi}_{c1}{\pi}^{+}$$ B c + → χ c 1 π + signal is observed and an upper limit for the relative branching fraction for the $${B}_c^{+}\to {\chi}_{c1}{\pi}^{+}$$ B c + → χ c 1 π + and $${B}_c^{+}\to {\chi}_{c2}{\pi}^{+}$$ B c + → χ c 2 π + decays of \frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}=<0.49 B B c + → χ c 1 π + B B c + → χ c 2 π + = &lt; 0.49 is set at the 90% confidence level.</jats:p

Study of Bc+→χcπ+ {B}_c^{+}\to {\chi}_c{\pi}^{+} decays

Abstract A study of $${B}_c^{+}\to {\chi}_c{\pi}^{+}$$ B c + → χ c π + 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 $${B}_c^{+}\to {\chi}_{c2}{\pi}^{+}$$ B c + → χ c 2 π + is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + decay is measured to be$$\frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}}}=0.37\pm 0.06\pm 0.02\pm 0.01,$$ B B c + → χ c 2 π + B B c + → J / ψ π + = 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 $${B}_c^{+}\to {\chi}_{c1}{\pi}^{+}$$ B c + → χ c 1 π + signal is observed and an upper limit for the relative branching fraction for the $${B}_c^{+}\to {\chi}_{c1}{\pi}^{+}$$ B c + → χ c 1 π + and $${B}_c^{+}\to {\chi}_{c2}{\pi}^{+}$$ B c + → χ c 2 π + decays of \frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}=<0.49 B B c + → χ c 1 π + B B c + → χ c 2 π + = &lt; 0.49 is set at the 90% confidence level.</jats:p