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A measurement of the phase difference between the short- and long-distance contributions to the [Formula: see text] decay is performed by analysing the dimuon mass distribution. The analysis is based on collision data corresponding to an integrated luminosity of 3[Formula: see text] collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the [Formula: see text] decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the [Formula: see text] and [Formula: see text] resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, [Formula: see text] and [Formula: see text], and the branching fraction of the short-distance component is measured.

Tau lepton decays with up to two π 0 s in the final state – τ + → π + ν ¯ τ , ρ + ( π + π 0 ) ν ¯ τ , and a 1 + ( π + π 0 π 0 ) ν ¯ τ – are used to study the performance of the barrel region of the silicon-tungsten electromagnetic calorimeter (Si-W ECAL) of the International Large Detector (ILD) at the future e + e - International Linear Collider. Correct reconstruction of the tau decay mode is crucial for constraining the spin state of tau lepton and measuring the Higgs boson CP state in H → τ + τ - decays. We find that about 95 % of π + ν ¯ τ , and 90 % of ρ + ν ¯ τ and a 1 + ν ¯ τ decays produced by the e + e - → Z 0 ∗ → τ + τ - process at an e ± beam energy of 125 GeV are correctly reconstructed. In a smaller ILD detector, with the inner Si-W ECAL radius reduced by about 20 %, these efficiencies are reduced by at most 2 %. The π 0 mass resolution remains below 10 %. Since failures in tau lepton reconstruction are mainly due to photons, an increase of the ILD magnetic field from 3.5 to 4 T does not bring any significant improvement.

The first study of$$C\\!P$$C P violation in the decay mode$${{B} ^\\pm } \\rightarrow [{{K} ^+} {{K} ^-} {{\\uppi } ^+} {{\\uppi } ^-} ]_{D} h^\\pm $$B ± → [ K + K - π + π - ] D h ± , with$$h=K,\\pi $$h = K , π , is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of$$9\\text {\\,fb} ^{-1} $$9 \\,fb - 1 . The analysis is performed in bins of phase space, which are optimised for sensitivity to local$$C\\!P$$C P asymmetries.$$C\\!P$$C P -violating observables that are sensitive to the angle$$\\gamma $$γ of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for$${{B} ^\\pm } \\rightarrow [{{K} ^+} {{K} ^-} {{\\uppi } ^+} {{\\uppi } ^-} ]_{D} h^\\pm $$B ± → [ K + K - π + π - ] D h ± and$${{B} ^\\pm } \\rightarrow [{{\\uppi } ^+} {{\\uppi } ^-} {{\\uppi } ^+} {{\\uppi } ^-} ]_{D} h^\\pm $$B ± → [ π + π - π + π - ] D h ± decays.

The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5$$\\,\\text {Te\\hspace{-1.00006pt}V}$$Te V incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and$$110\\,\\text {Ge\\hspace{-1.00006pt}V\\!/}c $$110 Ge V\\!/ c . The dominant antihyperon contribution, namely$${\\overline{\\varLambda }} \\rightarrow {\\overline{{p}}} {{\\pi } ^+} $$Λ ¯ → p ¯ π + decays from promptly produced$$\\overline{\\varLambda }$$Λ ¯ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.

After the Higgs discovery, precise measurements of the Higgs properties and the electroweak observables become vital for the experimental particle physics. A powerful Higgs/Z factory, the Circular Electron Positron Collider (CEPC) is proposed. The Particle Flow oriented detector design is proposed to the CEPC and a Particle Flow algorithm, Arbor is optimized accordingly. We summarize the physics object reconstruction performance of the Particle Flow oriented detector design with Arbor algorithm and conclude that this combination fulfills the physics requirement of CEPC.

Abstract The decays B+ → J/ψπ+π − K+ are studied using a data set corresponding to an integrated luminosity of 9 fb −1 collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ2(3823), χc1(3872) and ψ(2S) states are reported. The values are B B + → ψ 2 3823 K + × B ψ 2 3823 → J / ψπ + π − B B + → χ c 1 3872 K + × B χ c 1 3872 → J / ψπ + π − = 3.56 ± 0.67 ± 0.11 × 10 − 2 , B B + → ψ 2 3823 K + × B ψ 2 3823 → J / ψπ + π − B B + → ψ 2 S K + × B ψ 2 S → J / ψπ + π − = 1.31 ± 0.25 ± 0.04 × 10 − 3 , B B + → χ c 1 3872 K + × B χ c 1 3872 → J / ψπ + π − B B + → ψ 2 S K + × B ψ 2 S → J / ψπ + π − = 3.69 ± 0.07 ± 0.06 × 10 − 2 , $$ {\\displaystyle \\begin{array}{c}\\frac{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\uppsi}_2(3823){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi_2(3823)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\upchi}_{\\mathrm{c}1}(3872){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\upchi_{\\mathrm{c}1}(3872)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(3.56\\pm 0.67\\pm 0.11\\right)\\times {10}^{-2},\\\ {}\\frac{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\uppsi}_2(3823){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi_2(3823)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to \\uppsi \\left(2\\mathrm{S}\\right){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi \\left(2\\mathrm{S}\\right)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(1.31\\pm 0.25\\pm 0.04\\right)\\times {10}^{-3},\\\ {}\\frac{{\\mathcal{B}}_{\\mathrm{B}+\\to {\\upchi}_{\\mathrm{c}1}(3872){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\upchi_{\\mathrm{c}1}(3872)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to \\uppsi \\left(2\\mathrm{S}\\right){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi \\left(2\\mathrm{S}\\right)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(3.69\\pm 0.07\\pm 0.06\\right)\\times {10}^{-2},\\end{array}} $$ where the first uncertainty is statistical and the second is systematic. The decay of B+ → ψ2(3823)K+ with ψ2(3823) → J/ψπ+π − is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ2(3823), χc1(3872) and ψ(2S) states are measured to be m χ c 1 3872 − m ψ 2 3823 = 47.50 ± 0.53 ± 0.13 MeV / c 2 , m ψ 2 3823 − m ψ 2 2 S = 137.98 ± 0.53 ± 0.14 MeV / c 2 , m χ c 1 3872 − m ψ 2 2 S = 185.49 ± 0.06 ± 0.03 MeV / c 2 , $$ {\\displaystyle \\begin{array}{c}{m}_{\\upchi_{\\mathrm{c}1}(3872)}-{m}_{\\uppsi_2(3823)}=47.50\\pm 0.53\\pm 0.13\\;\\mathrm{MeV}/{c}^2,\\\ {}{m}_{\\uppsi_2(3823)}-{m}_{\\uppsi_2\\left(2\\mathrm{S}\\right)}=137.98\\pm 0.53\\pm 0.14\\;\\mathrm{MeV}/{c}^2,\\\ {}{m}_{\\upchi_{\\mathrm{c}1}(3872)}-{m}_{\\uppsi_2\\left(2\\mathrm{S}\\right)}=185.49\\pm 0.06\\pm 0.03\\;\\mathrm{MeV}/{c}^2,\\end{array}} $$ resulting in the most precise determination of the χc1(3872) mass. The width of the ψ2(3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χc1(3872) state is measured to be Γ χ c 1 3872 BW = 0.96 − 0.18 + 0.19 ± 0.21 MeV $$ {\\Gamma}_{\\upchi_{\\mathrm{c}1}(3872)}^{\\mathrm{BW}}={0.96}_{-0.18}^{+0.19}\\pm 0.21\\;\\mathrm{MeV} $$ which is inconsistent with zero by 5.5 standard deviations.

A search for the lepton-flavour violating decays B$_{s}^{0}$  → e$^{±}$μ$^{∓}$ and B$^{0}$ → e$^{±}$μ$^{∓}$ is performed based on a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb$^{−1}$, collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the B$_{s}^{0}$  → e$^{±}$μ$^{∓}$ decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate. The results are $ \\frac{@}{@}\\mathrm{\\mathcal{B}}\\left({B}_s^0\\to {e}^{\\pm }{\\mu}^{\\mp}\\right)<6.3(5.4)\\times 1{0}^{-9} $ and $ \\frac{@}{@}\\mathrm{\\mathcal{B}}\\left({B}_s^0\\to {e}^{\\pm }{\\mu}^{\\mp}\\right)<7.2(6.0)\\times 1{0}^{-9} $ at 95% (90%) confidence level, respectively. The upper limit on the branching fraction of the B$^{0}$ → e$^{±}$μ$^{∓}$ decay is also evaluated, obtaining $ \\frac{@}{@}\\mathrm{\\mathcal{B}}\\left({B}^0\\to {e}^{\\pm }{\\mu}^{\\mp}\\right)<1.3(1.0)\\times 1{0}^{-9} $ at 95% (90%) confidence level. These are the strongest limits on these decays to date.

The angular distribution and differential branching fraction of the decay $B^{0} \\to K^{*0} \\mu^{+}\\mu^{-}$ are studied using a data sample, collected by the LHCb experiment in $pp$ collisions at $\\sqrt{s}=7\\,{\\rm TeV}$, corresponding to an integrated luminosity of $1.0\\,{\\rm fb}^{-1}$. Several angular observables are measured in bins of the dimuon invariant mass squared, $q^{2}$. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be $q_{0}^{2} = 4.9 \\pm 0.9 \\,{\\rm GeV}^{2}/c^{4}$, where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.

A measurement of the CP-violating observables from B -> (DK +/-)-K-* and B-+/- -> D-*pi(+/-) decays is presented, where D-*(D) is an admixture of D-*0 and D-0 (D-0 and (0)) states and is reconstructed through the decay chains D-*-> D pi(0)/gamma and D -> KS0 pi+pi-/KS0K+K-. The measurement is performed by analysing the signal yield variation across the D decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb(-1) at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle gamma is determined to be (69(-14)(+13))degrees using the measured CP-violating observables. The hadronic parameters r(B)(D)*(K +/-),r(B)(D)*(pi +/-),delta(D)(B)*(K +/-),delta(D)(B)*(pi +/-), which are the ratios and strong phase differences between favoured and suppressed B-+/- decays, are also reported.

The Υ (2 S ) and Υ (3 S ) production cross-sections are measured relative to that of the Υ (1 S ) meson, as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of 13 TeV. The measurement uses data collected by the LHCb experiment in 2018 corresponding to an integrated luminosity of 2 fb − 1 . Both the Υ (2 S )-to- Υ (1 S ) and Υ (3 S )-to- Υ (1 S ) cross-section ratios are found to decrease significantly as a function of event multiplicity, with the Υ (3 S )-to- Υ (1 S ) ratio showing a steeper decline towards high multiplicity. This hierarchy is qualitatively consistent with the comover model predictions, indicating that final-state interactions play an important role in bottomonia production in high-multiplicity events.