73 research outputs found

    Test of lepton universality in b→sℓ+ℓ−b \rightarrow s \ell^+ \ell^- decays

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    The first simultaneous test of muon-electron universality using B+→K+ℓ+ℓ−B^{+}\rightarrow K^{+}\ell^{+}\ell^{-} and B0→K∗0ℓ+ℓ−B^{0}\rightarrow K^{*0}\ell^{+}\ell^{-} decays is performed, in two ranges of the dilepton invariant-mass squared, q2q^{2}. The analysis uses beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb−1\mathrm{fb}^{-1}. Each of the four lepton universality measurements reported is either the first in the given q2q^{2} interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb public pages

    Precision measurement of CP\it{CP} violation in the penguin-mediated decay Bs0→ϕϕB_s^{0}\rightarrow\phi\phi

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    A flavor-tagged time-dependent angular analysis of the decay Bs0→ϕϕB_s^{0}\rightarrow\phi\phi is performed using pppp collision data collected by the LHCb experiment at % at s=13\sqrt{s}=13 TeV, the center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The CP\it{CP}-violating phase and direct CP\it{CP}-violation parameter are measured to be ϕssˉs=−0.042±0.075±0.009\phi_{s\bar{s}s} = -0.042 \pm 0.075 \pm 0.009 rad and ∣λ∣=1.004±0.030±0.009|\lambda|=1.004\pm 0.030 \pm 0.009 , respectively, assuming the same values for all polarization states of the ϕϕ\phi\phi system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using pppp collisions at center-of-mass energies of 7 and 8 TeV, yielding ϕssˉs=−0.074±0.069\phi_{s\bar{s}s} = -0.074 \pm 0.069 rad and ∣lambda∣=1.009±0.030|lambda|=1.009 \pm 0.030. This is the most precise study of time-dependent CP\it{CP} violation in a penguin-dominated BB meson decay. The results are consistent with CP\it{CP} symmetry and with the Standard Model predictions.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-001.html (LHCb public pages

    Observation of a resonant structure near the Ds+Ds−D_s^+ D_s^- threshold in the B+→Ds+Ds−K+B^+\to D_s^+ D_s^- K^+ decay

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    An amplitude analysis of the B+→Ds+Ds−K+B^+\to D_s^+ D_s^- K^+ decay is carried out to study for the first time its intermediate resonant contributions, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. A near-threshold peaking structure, referred to as X(3960)X(3960), is observed in the Ds+Ds−D_s^+ D_s^- invariant-mass spectrum with significance greater than 12 standard deviations. The mass, width and the quantum numbers of the structure are measured to be 3956±5±103956\pm5\pm10 MeV, 43±13±843\pm13\pm8 MeV and JPC=0++J^{PC}=0^{++}, respectively, where the first uncertainties are statistical and the second systematic. The properties of the new structure are consistent with recent theoretical predictions for a state composed of ccˉssˉc\bar{c}s\bar{s} quarks. Evidence for an additional structure is found around 4140 MeV in the Ds+Ds−D_s^+ D_s^- invariant mass, which might be caused either by a new resonance with the 0++0^{++} assignment or by a J/ψϕ↔Ds+Ds−J/\psi \phi\leftrightarrow D_s^+ D_s^- coupled-channel effect.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-018.html (LHCb public pages

    Measurement of the Λb0→Λ(1520)ÎŒ+Ό−\Lambda_{b}^{0}\to \Lambda(1520) \mu^{+}\mu^{-} differential branching fraction

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    The branching fraction of the rare decay Λb0→Λ(1520)ÎŒ+Ό−\Lambda_{b}^{0}\to \Lambda(1520) \mu^{+}\mu^{-} is measured for the first time, in the squared dimuon mass intervals, q2q^2, excluding the J/ψJ/\psi and ψ(2S)\psi(2S) regions. The data sample analyzed was collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of $9\ \mathrm{fb}^{-1}.Theresultinthehighest. The result in the highest q^{2}interval, interval, q^{2} >15.0\ \mathrm{GeV}^2/c^4$, where theoretical predictions have the smallest model dependence, agrees with the predictions.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-050.html (LHCb public pages

    Precision measurement of CP violation in the penguin-mediated decay Bs0→ϕϕ

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    A flavor-tagged time-dependent angular analysis of the decay B 0 s → ϕ ϕ is performed using p p collision data collected by the LHCb experiment at the center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6     fb − 1 . The C P -violating phase and direct C P -violation parameter are measured to be ϕ s ÂŻ s s s = − 0.042 ± 0.075 ± 0.009     rad and | λ | = 1.004 ± 0.030 ± 0.009 , respectively, assuming the same values for all polarization states of the ϕ ϕ system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using p p collisions at center-of-mass energies of 7 and 8 TeV, yielding ϕ s ÂŻ s s s = − 0.074 ± 0.069     rad and | λ | = 1.009 ± 0.030 . This is the most precise study of time-dependent C P violation in a penguin-dominated B meson decay. The results are consistent with C P symmetry and with the standard model predictions

    Search for rare decays of D0 mesons into two muons

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    A search for the very rare D 0 → ÎŒ + ÎŒ − decay is performed using data collected by the LHCb experiment in proton-proton collisions at √ s = 7 , 8, and 13 TeV, corresponding to an integrated luminosity of 9     fb − 1 . The search is optimized for D 0 mesons from D * + → D 0 π + decays but is also sensitive to D 0 mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at B ( D 0 → ÎŒ + ÎŒ − ) < 3.1 × 10 − 9 at a 90% C.L. This represents the world’s most stringent limit, constraining models of physics beyond the standard model

    Direct CP violation in charmless three-body decays of B± mesons

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    Measurements of C P asymmetries in charmless three-body decays of B ± mesons are reported using proton-proton collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.9     fb − 1 . The previously observed C P asymmetry in B ± → π ± K + K − decays is confirmed, and C P asymmetries are observed with a significance of more than five standard deviations in the B ± → π ± π + π − and B ± → K ± K + K − decays, while the C P asymmetry of B ± → K ± π + π − decays is confirmed to be compatible with zero. The distributions of these asymmetries are also studied as a function of the three-body phase space and suggest contributions from rescattering and resonance interference processes. An indication of the presence of the decays B ± → π ± χ c 0 ( 1 P ) in both B ± → π ± π + π − and B ± → π ± K + K − decays is observed, as is C P violation involving these amplitudes

    Measurement of the ratios of branching fractions R(D*) and R(D0)

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    The ratios of branching fractions R ( D ∗ ) ≡ B ( ÂŻ B → D ∗ τ − ÂŻ Îœ τ ) / B ( ÂŻ B → D ∗ ÎŒ − ÂŻ Îœ ÎŒ ) and R ( D 0 ) ≡ B ( B − → D 0 τ − ÂŻ Îœ τ ) / B ( B − → D 0 ÎŒ − ÂŻ Îœ ÎŒ ) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0     fb − 1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ − → ÎŒ − Îœ τ ÂŻ Îœ ÎŒ . The measured values are R ( D ∗ ) = 0.281 ± 0.018 ± 0.024 and R ( D 0 ) = 0.441 ± 0.060 ± 0.066 , where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ = − 0.43 . The results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model

    Measurement of antiproton production from antihyperon decays in p He collisions at √sNN = 110 GeV

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    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 6.5TeV 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 110GeV. The dominant antihyperon contribution, namely Λ¯→pÂŻÏ€+ decays from promptly produced 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

    Test of lepton universality in b→sℓ+ℓ− decays

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    The first simultaneous test of muon-electron universality using B + → K + ℓ + ℓ − and B 0 → K * 0 ℓ + ℓ − decays is performed, in two ranges of the dilepton invariant-mass squared, q 2 . The analysis uses beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9     fb − 1 . Each of the four lepton universality measurements reported is either the first in the given q 2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model
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