Abstract This paper presents an analysis of the Λ b 0 $$ {\Lambda}_b^0 $$ → J/ψΛ angular distribution and the transverse production polarisation of Λ b 0 $$ {\Lambda}_b^0 $$ baryons in proton-proton ...collisions at centre-of-mass energies of 7, 8 and 13 TeV. The measurements are performed using data corresponding to an integrated luminosity of 4.9 fb −1, collected with the LHCb experiment. The polarisation is determined in a fiducial region of Λ b 0 $$ {\Lambda}_b^0 $$ transverse momentum and pseudorapidity of 1 < p T < 20 GeV/c and 2 < η < 5, respectively. The data are consistent with Λ b 0 $$ {\Lambda}_b^0 $$ baryons being produced unpolarised in this region. The parity-violating asymmetry parameter of the Λ → pπ − decay is also determined from the data and its value is found to be consistent with a recent measurement by the BES III collaboration.
Abstract A precision measurement of the B c + $$ {B}_c^{+} $$ meson mass is performed using proton- proton collision data collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 ...TeV, corresponding to a total integrated luminosity of 9.0 fb −1. The B c + $$ {B}_c^{+} $$ mesons are reconstructed via the decays B c + $$ {B}_c^{+} $$ → J/ψπ +, B c + $$ {B}_c^{+} $$ → J/ψπ + π − π +, B c + → J / ψp p ¯ π + $$ {B}_c^{+}\to J/\psi p\overline{p}{\pi}^{+} $$ , B c + → J / ψ D s + $$ {B}_c^{+}\to J/\psi {D}_s^{+} $$ , B c + $$ {B}_c^{+} $$ → J/ψ D 0 K + and B c + → B s 0 π + $$ {B}_c^{+}\to {B}_s^0{\pi}^{+} $$ . Combining the results of the individual decay channels, the B c + $$ {B}_c^{+} $$ mass is measured to be 6274.47 ± 0.27 (stat) ± 0.17 (syst) MeV/c 2. This is the most precise measurement of the B c + $$ {B}_c^{+} $$ mass to date. The difference between the B c + $$ {B}_c^{+} $$ and B s 0 $$ {B}_s^0 $$ meson masses is measured to be 907.75 ± 0.37 (stat) ± 0.27 (syst) MeV/c.
Abstract Measurements of CP observables in B ± → DK ± and B ± → Dπ ± decays are presented, where D represents a superposition of D 0 and D ¯ 0 $$ {\overline{D}}^0 $$ states. The D meson is ...reconstructed in the three-body final states K S 0 K ± π ∓ $$ {K}_{\mathrm{S}}^0{K}^{\pm }{\pi}^{\mp } $$ and K S 0 K ∓ π ± $$ {K}_{\mathrm{S}}^0{K}^{\mp }{\pi}^{\pm } $$ . The analysis uses samples of B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb −1 collected with the LHCb detector at centre-of-mass energies of s $$ \sqrt{s} $$ = 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle γ.
Abstract A new baryon state is observed in the Λ b 0 π + π − $$ {\Lambda}_{\mathrm{b}}^0{\pi}^{+}{\pi}^{-} $$ mass spectrum with high significance using a data sample of pp collisions, collected with ...the LHCb detector at centre-of-mass energies s $$ \sqrt{s} $$ = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb −1. The mass and natural width of the new state are measured to be m = 6072.3 ± 2.9 ± 0.6 ± 0.2 MeV , Γ = 72 ± 11 ± 2 MeV , $$ {\displaystyle \begin{array}{l}m=6072.3\pm 2.9\pm 0.6\pm 0.2\ \mathrm{MeV},\\ {}\Gamma =72\pm 11\pm 2\ \mathrm{MeV},\end{array}} $$ where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the Λ b 0 $$ {\Lambda}_{\mathrm{b}}^0 $$ baryon mass. The new state is consistent with the first radial excitation of the Λ b 0 $$ {\Lambda}_{\mathrm{b}}^0 $$ baryon, the Λb(2S)0 resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed Λb(5912)0 and Λb(5920)0 states are also reported.
Abstract A search is presented for the lepton flavour violating decay B + → K + μ − τ + using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the ...LHCb detector and corresponding to a total integrated luminosity of 9 fb −1. The τ leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the τ lepton is determined by using B + mesons from B s 2 ∗ 0 → B + K − $$ {B}_{s2}^{\ast 0}\to {B}^{+}{K}^{-} $$ decays. No significant excess is observed, and an upper limit is set on the branching fraction ℬ(B + → K + μ − τ +) < 3.9 × 10−5 at 90 % confidence level. The obtained limit is comparable to the world-best limit.
Abstract The ratio of branching fractions of the decays Λ b 0 $$ {\Lambda}_b^0 $$ → pK − e + e − and Λ b 0 $$ {\Lambda}_b^0 $$ → pK − μ + μ − , R pK − 1 $$ {R}_{pK}^{-1} $$ , is measured for the ...first time using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb −1 recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range 0.1 < q 2 < 6.0 GeV2 /c 4 and the pK − mass range m(pK − ) < 2600 MeV/c 2, the ratio of branching fractions is measured to be R pK − 1 = 1.17 − 0.16 + 0.18 ± 0.07 $$ {R}_{pK}^{-1}={1.17}_{-0.16}^{+0.18}\pm 0.07 $$ , where the first uncertainty is statistical and the second systematic. This is the first test of lepton universality with b baryons and the first observation of the decay Λ b 0 $$ {\Lambda}_b^0 $$ → pK − e + e − .
Abstract The Cabibbo-suppressed semileptonic decay B + → p p ¯ μ + ν μ $$ {B}^{+}\to p\overline{p}{\mu}^{+}{\nu}_{\mu } $$ is observed for the first time using a sample of pp collisions corresponding ...to an integrated luminosity of 1.0, 2.0 and 1.7 fb −1 at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The differential branching fraction is measured as a function of the p p ¯ $$ p\overline{p} $$ invariant mass using the decay mode B + → J/ψK + for normalisation. The total branching fraction is measured to be ℬ B + → p p ¯ μ + ν μ = 5.27 − 0.24 + 0.23 ± 0.21 ± 0.15 × 10 − 6 , $$ \mathrm{\mathcal{B}}\left({B}^{+}\to p\overline{p}{\mu}^{+}{\nu}_{\mu}\right)=\left({5.27}_{-0.24}^{+0.23}\pm 0.21\pm 0.15\right)\times {10}^{-6}, $$ where the first uncertainty is statistical, the second systematic and the third is from the uncertainty on the branching fraction of the normalisation channel.
Abstract The decay-time-dependent CP asymmetry in B 0 → D ∗± D ∓ decays is mea- sured using a data set corresponding to an integrated luminosity of 9 fb −1 recorded by the LHCb detector in ...proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The CP parameters are measured as S D ∗ D = − 0.861 ± 0.077 stat ± 0.019 syst , Δ S D ∗ D = 0.019 ± 0.075 stat ± 0.012 syst , C D ∗ D = − 0.059 ± 0.092 stat ± 0.020 syst , ΔC D ∗ D = − 0.031 ± 0.092 stat ± 0.016 syst , A D ∗ D = 0.008 ± 0.014 stat ± 0.006 syst . $$ {\displaystyle \begin{array}{c}{S}_{D\ast D}=-0.861\pm 0.077\left(\mathrm{stat}\right)\pm 0.019\left(\mathrm{syst}\right),\\ {}\varDelta {S}_{D\ast D}=0.019\pm 0.075\left(\mathrm{stat}\right)\pm 0.012\left(\mathrm{syst}\right),\\ {}{C}_{D\ast D}=-0.059\pm 0.092\left(\mathrm{stat}\right)\pm 0.020\left(\mathrm{syst}\right),\\ {}{\varDelta C}_{D\ast D}=-0.031\pm 0.092\left(\mathrm{stat}\right)\pm 0.016\left(\mathrm{syst}\right),\\ {}{\mathcal{A}}_{D\ast D}=\kern0.75em 0.008\pm 0.014\left(\mathrm{stat}\right)\pm 0.006\left(\mathrm{syst}\right).\end{array}} $$ The analysis provides the most precise single measurement of CP violation in this decay channel to date. All parameters are consistent with their current world average values.
The Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected by the LHCb detector, corresponding to an ...integrated luminosity of 3fb−1. The ratio of branching fractions between the Λb0→Λc+K+K−π− and the Λb0→Λc+Ds− decays is measured to beB(Λb0→Λc+K+K−π−)B(Λb0→Λc+Ds−)=(9.26±0.29±0.46±0.26)×10−2, where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the Ds−→K+K−π− branching fraction. No structure on the invariant mass distribution of the Λc+K+ system is found, consistent with no open-charm pentaquark signature.
Abstract Using proton-proton collision data, collected with the LHCb detector and corresponding to 1.0, 2.0 and 1.9 fb−1 of integrated luminosity at the centre-of-mass energies of 7, 8, and 13 TeV, ...respectively, the decay Λ b 0 → χ c 1 $$ {\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1} $$ (3872)pK− with χc1(3872) → J/ψ π+π− is observed for the first time. The significance of the observed signal is in excess of seven standard deviations. It is found that (58 ± 15)% of the decays proceed via the two-body intermediate state χc1(3872)Λ(1520). The branching fraction with respect to that of the Λ b 0 $$ {\Lambda}_{\mathrm{b}}^0 $$ → ψ(2S)pK− decay mode, where the ψ(2S) meson is reconstructed in the J/ψ π+π− final state, is measured to be: β Λ b 0 → χ c 1 3872 pK − β Λ b 0 → ψ 2 S pK − × β χ c 1 3872 → J / ψ π + π − β ψ 2 S → J / ψ π + π − = 5.4 ± 1.1 ± 0.2 × 10 − 2 , $$ \frac{\beta \left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}(3872){\mathrm{pK}}^{-}\right)}{\beta \left({\Lambda}_{\mathrm{b}}^0\to \uppsi \left(2\mathrm{S}\right){\mathrm{pK}}^{-}\right)}\times \frac{\beta \left({\upchi}_{\mathrm{c}1}(3872)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}{\beta \left(\uppsi \left(2\mathrm{S}\right)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}=\left(5.4\pm 1.1\pm 0.2\right)\times {10}^{-2}, $$ where the first uncertainty is statistical and the second is systematic.
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