ORCID Profile
0000-0002-3500-7398
Current Organisations
École Polytechnique Fédérale de Lausanne
,
University of Oxford
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Publisher: American Physical Society (APS)
Date: 20-04-2022
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb − 1 collected with the LHCb detector, seven decay modes of the $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + meson into a J / ψ or ψ(2S) meson and three charged hadrons, kaons or pions, are studied. The decays $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + → (ψ(2S) → J / ψπ + π − )π + , $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + → ψ(2S)π + π − π + , $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + → J / ψK + π − π + and $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + → J / ψK + K − K + are observed for the first time, and evidence for the $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + → ψ(2S)K + K − π + , decay is found, where J / ψ and ψ(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different $$ {\\mathrm{B}}_{\\mathrm{c}}^{+} $$ B c + decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.
Publisher: American Physical Society (APS)
Date: 25-05-2022
Publisher: Springer Science and Business Media LLC
Date: 06-05-2022
Abstract: The $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{\\prime +}{\\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 . 4 fb − 1. The $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{\\prime +}{\\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is reconstructed partially, where the photon from the $$ {\\varXi}_c^{\\prime +}\\to {\\varXi}_c^{+}\\gamma $$ Ξ c ′ + → Ξ c + γ decay is not reconstructed and the pK − π + final state of the $$ {\\varXi}_c^{+} $$ Ξ c + baryon is employed. The $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{\\prime +}{\\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + branching fraction relative to that of the $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{+}{\\pi}^{+} $$ Ξ cc + + → Ξ c + π + decay is measured to be 1 . 41 ± 0 . 17 ± 0 . 10, where the first uncertainty is statistical and the second systematic.
Publisher: Springer Science and Business Media LLC
Date: 07-2022
Abstract: A precision measurement of the Z boson production cross-section at $$ \\sqrt{\\mathrm{s}} $$ s = 13 TeV in the forward region is presented, using pp collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb − 1 . The production cross-section is measured using Z → μ + μ − events within the fiducial region defined as pseudorapidity 2 . 0 η 4 . 5 and transverse momentum p T 20 GeV /c for both muons and dimuon invariant mass 60 M μμ 120 GeV /c 2 . The integrated cross-section is determined to be $$ \\sigma \\left(Z\\to {\\mu}^{+}{\\mu}^{-}\\right)=196.4\\pm 0.2\\pm 1.6\\pm 3.9\\ \\mathrm{pb}, $$ σ Z → μ + μ − = 196.4 ± 0.2 ± 1.6 ± 3.9 pb , where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions within uncertainties.
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: The first search for the rare radiative decay $$ {\\Xi}_b^{-} $$ Ξ b − → Ξ − γ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb − 1 . The $$ {\\Xi}_b^{-} $$ Ξ b − → Ξ − J/ψ channel is used as normalization. No $$ {\\Xi}_b^{-} $$ Ξ b − → Ξ − γ signal is found and an upper limit of $$ \\mathcal{B} $$ B ( $$ {\\Xi}_b^{-} $$ Ξ b − → Ξ − γ ) 1 . 3 × 10 − 4 at 95% confidence level is obtained.
Publisher: American Physical Society (APS)
Date: 08-03-2017
Publisher: Springer Science and Business Media LLC
Date: 30-01-2017
DOI: 10.1038/NPHYS4021
Publisher: American Physical Society (APS)
Date: 24-02-2022
Publisher: American Physical Society (APS)
Date: 25-01-2022
Publisher: American Physical Society (APS)
Date: 09-06-2021
Publisher: IOP Publishing
Date: 05-2022
DOI: 10.1088/1748-0221/17/05/P05009
Abstract: The centrality of heavy-ion collisions is directly related to the created medium in these interactions. A procedure to determine the centrality of collisions with the LHCb detector is implemented for lead-lead collisions at √ s NN = 5 TeV and lead-neon fixed-target collisions at √ s NN = 69 GeV. The energy deposits in the electromagnetic calorimeter are used to determine and define the centrality classes. The correspondence between the number of participants and the centrality for the lead-lead collisions is in good agreement with the correspondence found in other experiments, and the centrality measurements for the lead-neon collisions presented here are performed for the first time in fixed-target collisions at the LHC.
Publisher: American Physical Society (APS)
Date: 21-04-2022
Publisher: Springer Science and Business Media LLC
Date: 06-2021
Abstract: Searches for CP violation in the two-body decays $$ {D}_{(s)}^{+}\\to {h}^{+}{\\pi}^0 $$ D s + → h + π 0 and $$ {D}_{(s)}^{+}\\to {h}^{+}\\eta $$ D s + → h + η (where h + denotes a π + or K + meson) are performed using pp collision data collected by the LHCb experiment corresponding to either 9 fb − 1 or 6 fb − 1 of integrated luminosity. The π 0 and η mesons are reconstructed using the e + e − γ final state, which can proceed as three-body decays π 0 → e + e − γ and η → e + e − γ , or via the two-body decays π 0 → γγ and η → γγ followed by a photon conversion. The measurements are made relative to the control modes $$ {D}_{(s)}^{+}\\to {K}_{\\mathrm{S}}^0{h}^{+} $$ D s + → K S 0 h + to cancel the production and detection asymmetries. The CP asymmetries are measured to be $$ {\\displaystyle \\begin{array}{c}{\\mathcal{A}}_{CP}\\left({D}^{+}\\to {\\pi}^{+}{\\pi}^0\\right)=\\left(-1.3\\pm 0.9\\pm 0.6\\right)\\%,\\\\ {}{\\mathcal{A}}_{CP}\\left({D}^{+}\\to {K}^{+}{\\pi}^0\\right)=\\left(-3.2\\pm 4.7\\pm 2.1\\right)\\%,\\\\ {}\\begin{array}{c}{\\mathcal{A}}_{CP}\\left({D}^{+}\\to {\\pi}^{+}\\eta \\right)=\\left(-0.2\\pm 0.8\\pm 0.4\\right)\\%,\\\\ {}{\\mathcal{A}}_{CP}\\left({D}^{+}\\to {K}^{+}\\eta \\right)=\\left(-6\\pm 10\\pm 4\\right)\\%,\\\\ {}\\begin{array}{c}{\\mathcal{A}}_{CP}\\left({D}_s^{+}\\to {K}^{+}{\\pi}^0\\right)=\\left(-0.8\\pm 3.9\\pm 1.2\\right)\\%,\\\\ {}\\begin{array}{c}{\\mathcal{A}}_{CP}\\left({D}_s^{+}\\to {\\pi}^{+}\\eta \\right)=\\left(0.8\\pm 0.7\\pm 0.5\\right)\\%,\\\\ {}{\\mathcal{A}}_{CP}\\left({D}_s^{+}\\to {K}^{+}\\eta \\right)=\\left(0.9\\pm 3.7\\pm 1.1\\right)\\%,\\end{array}\\end{array}\\end{array}\\end{array}} $$ A CP D + → π + π 0 = − 1.3 ± 0.9 ± 0.6 % , A CP D + → K + π 0 = − 3.2 ± 4.7 ± 2.1 % , A CP D + → π + η = − 0.2 ± 0.8 ± 0.4 % , A CP D + → K + η = − 6 ± 10 ± 4 % , A CP D s + → K + π 0 = − 0.8 ± 3.9 ± 1.2 % , A CP D s + → π + η = 0.8 ± 0.7 ± 0.5 % , A CP D s + → K + η = 0.9 ± 3.7 ± 1.1 % , where the first uncertainties are statistical and the second systematic. These results are consistent with no CP violation and mostly constitute the most precise measurements of $$ {\\mathcal{A}}_{CP} $$ A CP in these decay modes to date.
Publisher: Springer Science and Business Media LLC
Date: 07-2022
Abstract: A data s le collected with the LHCb detector corresponding to an integrated luminosity of 9 fb − 1 is used to measure eleven CP violation observables in B ± → Dh ± decays, where h is either a kaon or a pion. The neutral D meson decay is reconstructed in the three-body final states: K ± π ∓ π 0 π + π − π 0 K + K − π 0 and the suppressed π ± K ∓ π 0 combination. The mode where a large CP asymmetry is expected, B ± → [ π ± K ∓ π 0 ] D K ± , is observed with a significance greater than seven standard deviations. The ratio of the partial width of this mode relative to that of the favoured mode, B ± → [ K ± π ∓ π 0 ] D K ± , is R ADS( K ) = (1 . 27 ± 0 . 16 ± 0 . 02) × 10 − 2 . Evidence for a large CP asymmetry is also seen: A ADS( K ) = −0 . 38 ± 0 . 12 ± 0 . 02. Constraints on the CKM angle γ are calculated from the eleven reported observables.
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: The production cross-section of the χ c 1 (3872) state relative to the ψ (2 S ) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $$ \\sqrt{s} $$ s = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb − 1 , respectively. The two mesons are reconstructed in the J/ψπ + π − final state. The ratios of the prompt and nonprompt χ c 1 (3872) to ψ (2 S ) production cross-sections are measured as a function of transverse momentum, p T , and rapidity, y , of the χ c 1 (3872) and ψ (2 S ) states, in the kinematic range 4 p T 20 GeV/ c and 2 . 0 y 4 . 5. The prompt ratio is found to increase with p T , independently of y . For the prompt component, the double ratio of the χ c 1 (3872) and ψ (2 S ) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of p T and centre-of-mass energy.
Publisher: Springer Science and Business Media LLC
Date: 16-06-2022
DOI: 10.1038/S41567-022-01614-Y
Abstract: Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively 1,2 . Here, we report the observation of a hadronic state containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a $$\\overline{{{{{u}}}}}$$ u ¯ and a $$\\overline{{{{{d}}}}}$$ d ¯ quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of D 0 D 0 π + mesons just below the D *+ D 0 mass threshold. The near-threshold mass together with the narrow width reveals the resonance nature of the state.
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Abstract: An angular analysis of the rare decay $$ {B}_s^0 $$ B s 0 → ϕμ + μ − is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 8.4 fb − 1 . The observables describing the angular distributions of the decay $$ {B}_s^0 $$ B s 0 → ϕμ + μ − are determined in regions of q 2 , the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.
Publisher: Springer Science and Business Media LLC
Date: 10-08-2023
Publisher: American Physical Society (APS)
Date: 17-08-2021
Publisher: Springer Science and Business Media LLC
Date: 06-2021
Abstract: The first full angular analysis of the $$ {B}^0\\to {D}^{\\ast -}{D}_s^{\\ast +} $$ B 0 → D ∗ − D s ∗ + decay is performed using 6 fb − 1 of pp collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The $$ {D}_s^{\\ast +}\\to {D}_s^{+}\\gamma $$ D s ∗ + → D s + γ and D * − → $$ {\\overline{D}}^0{\\pi}^{-} $$ D ¯ 0 π − vector meson decays are used with the subsequent $$ {D}_s^{+} $$ D s + → K + K − π + and $$ {\\overline{D}}^0 $$ D ¯ 0 → K + π − decays. All helicity litudes and phases are measured, and the longitudinal polarisation fraction is determined to be f L = 0 . 578 ± 0 . 010 ± 0 . 011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity litude magnitudes is found to align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [ℬ( $$ {B}^0\\to {D}^{\\ast -}{D}_s^{\\ast +} $$ B 0 → D ∗ − D s ∗ + ) × ℬ( $$ {D}_s^{\\ast +}\\to {D}_s^{+}\\gamma $$ D s ∗ + → D s + γ )] / ℬ( B 0 → D * − $$ {D}_s^{+} $$ D s + ) is measured to be 2 . 045 ± 0 . 022 ± 0 . 071 with world-best precision. In addition, the first observation of the Cabibbo-suppressed B s → D * − $$ {D}_s^{+} $$ D s + decay is made with a significance of seven standard deviations. The branching fraction ratio ℬ( B s → D * − $$ {D}_s^{+} $$ D s + ) / ℬ( B 0 → D * − $$ {D}_s^{+} $$ D s + ) is measured to be 0 . 049 ± 0 . 006 ± 0 . 003 ± 0 . 002, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions.
Publisher: American Physical Society (APS)
Date: 07-02-2022
Publisher: IOP Publishing
Date: 02-2022
DOI: 10.1088/1748-0221/17/02/P02028
Abstract: The identification of charm jets is achieved at LHCb for data collected in 2015–2018 using a method based on the properties of displaced vertices reconstructed and matched with jets. The performance of this method is determined using a dijet calibration dataset recorded by the LHCb detector and selected such that the jets are unbiased in quantities used in the tagging algorithm. The charm-tagging efficiency is reported as a function of the transverse momentum of the jet. The measured efficiencies are compared to those obtained from simulation and found to be in good agreement.
Publisher: American Physical Society (APS)
Date: 24-11-2021
Publisher: Springer Science and Business Media LLC
Date: 16-06-2022
DOI: 10.1038/S41467-022-30206-W
Abstract: Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D 0 D 0 π + mass spectrum just below the D *+ D 0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar $${{{{{{\\rm{T}}}}}}}_{{{{{{\\rm{c}}}}}}{{{{{\\rm{c}}}}}}}^{+}$$ T c c + tetraquark with a quark content of $${{{{{\\rm{c}}}}}}{{{{{\\rm{c}}}}}}\\overline{{{{{{\\rm{u}}}}}}}\\overline{{{{{{\\rm{d}}}}}}}$$ c c u ¯ d ¯ and spin-parity quantum numbers J P = 1 + . Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D *+ mesons is consistent with the observed D 0 π + mass distribution. To analyse the mass of the resonance and its coupling to the D * D system, a dedicated model is developed under the assumption of an isoscalar axial-vector $${{{{{{\\rm{T}}}}}}}_{{{{{{\\rm{c}}}}}}{{{{{\\rm{c}}}}}}}^{+}$$ T c c + state decaying to the D * D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the $${{{{{{\\rm{T}}}}}}}_{{{{{{\\rm{c}}}}}}{{{{{\\rm{c}}}}}}}^{+}$$ T c c + state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.
Publisher: American Physical Society (APS)
Date: 20-08-2021
Publisher: American Physical Society (APS)
Date: 23-03-2022
Publisher: Springer Science and Business Media LLC
Date: 03-2022
Abstract: The multihadron decays $$ {\\Lambda}_b^0 $$ Λ b 0 → D + pπ−π− and $$ {\\Lambda}_b^0 $$ Λ b 0 → D * + pπ−π− are observed in data corresponding to an integrated luminosity of 3 fb − 1 , collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay $$ {\\Lambda}_b^0 $$ Λ b 0 → $$ {\\Lambda}_c^{+} $$ Λ c + π + π − π − as a normalisation channel, the ratio of branching fractions is measured to be $$ \\frac{\\mathcal{B}\\left({\\Lambda}_b^0\\to {D}^{+}p{\\pi}^{-}{\\pi}^{-}\\right)}{\\mathcal{B}\\left({\\Lambda}_b^0\\to {\\Lambda}_c^0{\\pi}^{+}{\\pi}^{-}{\\pi}^{-}\\right)}\\times \\frac{\\mathcal{B}\\left({D}^{+}\\to {K}^{-}{\\pi}^{+}{\\pi}^{+}\\right)}{\\mathcal{B}\\left({\\Lambda}_c^0\\to {pK}^{-}{\\pi}^{-}\\right)}=\\left(5.35\\pm 0.21\\pm 0.16\\right)\\%, $$ B Λ b 0 → D + p π − π − B Λ b 0 → Λ c 0 π + π − π − × B D + → K − π + π + B Λ c 0 → pK − π − = 5.35 ± 0.21 ± 0.16 % , where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the $$ {\\Lambda}_b^0 $$ Λ b 0 → D *+ pπ − π − and $$ {\\Lambda}_b^0 $$ Λ b 0 → D + pπ − π − decays is found to be $$ \\frac{\\mathcal{B}\\left({\\Lambda}_b^0\\to {D}^{\\ast +}p{\\pi}^{-}{\\pi}^{-}\\right)}{\\mathcal{B}\\left({\\Lambda}_b^0\\to {D}^{+}p{\\pi}^{-}{\\pi}^{-}\\right)}\\times \\left(\\mathcal{B}\\left({D}^{\\ast +}\\to {D}^{+}{\\pi}^0\\right)+\\mathcal{B}\\left({D}^{\\ast +}\\to {D}^{+}\\gamma \\right)\\right)=\\left(61.3\\pm 4.3\\pm 4.0\\right)\\%. $$ B Λ b 0 → D ∗ + p π − π − B Λ b 0 → D + p π − π − × B D ∗ + → D + π 0 + B D ∗ + → D + γ = 61.3 ± 4.3 ± 4.0 % .
Publisher: Springer Science and Business Media LLC
Date: 13-05-2015
DOI: 10.1038/NATURE14474
Abstract: The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strange B meson (B(s)(0)) and the B0 meson decaying into two oppositely charged muons (μ+ and μ−) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B(s)(0) →µ+µ− and B(0) →µ+µ− decays are very rare, with about four of the former occurring for every billion mesons produced, and one of the latter occurring for every ten billion B0 mesons. A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (Compact Muon Solenoid) and LHCb (Large Hadron Collider beauty) collaborations have performed a joint analysis of the data from proton–proton collisions that they collected in 2011 at a centre-of-mass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B(s)(0) → µ+µ− decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B(0) → µ+µ− decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton–proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B(s)(0) and B0 mesons and lead to further improvements in the precision of these crucial tests of the standard model.
Publisher: American Physical Society (APS)
Date: 07-09-2021
Publisher: American Physical Society (APS)
Date: 03-03-2022
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data s le recorded by the LHCb experiment at a centre-of-mass energy of $$ \\sqrt{s} $$ s = 13 TeV. The data s le, collected with an unbiased trigger, corresponds to an integrated luminosity of 5 . 4 nb − 1 . The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges p T ∈ [80 , 10 000) MeV /c and η ∈ [2 . 0 , 4 . 8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
Publisher: Springer Science and Business Media LLC
Date: 05-2021
Abstract: The Cabibbo-suppressed decay $$ {\\Lambda}_{\\mathrm{b}}^0 $$ Λ b 0 → χ c1 pπ − is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6 fb − 1 , collected with the LHCb detector at a centre-of-mass energy of 13 TeV. Evidence for the $$ {\\Lambda}_{\\mathrm{b}}^0 $$ Λ b 0 → χ c2 pπ − decay is also found. Using the $$ {\\Lambda}_{\\mathrm{b}}^0 $$ Λ b 0 → χ c1 pK − decay as normalisation channel, the ratios of branching fractions are measured to be $$ {\\displaystyle \\begin{array}{c}\\frac{\\mathcal{B}\\left({\\Lambda}_{\\mathrm{b}}^0\\to {\\upchi}_{\\mathrm{c}1}{\\mathrm{p}\\uppi}^{-}\\right)}{\\mathcal{B}\\left({\\Lambda}_{\\mathrm{b}}^0\\to {\\upchi}_{\\mathrm{c}1}{\\mathrm{p}\\mathrm{K}}^{-}\\right)}=\\left(6.59\\pm 1.01\\pm 0.22\\right)\\times {10}^{-2},\\\\ {}\\frac{\\mathcal{B}\\left({\\Lambda}_{\\mathrm{b}}^0\\to {\\upchi}_{\\mathrm{c}2}{\\mathrm{p}\\uppi}^{-}\\right)}{\\mathcal{B}\\left({\\Lambda}_{\\mathrm{b}}^0\\to {\\upchi}_{\\mathrm{c}1}{\\mathrm{p}\\uppi}^{-}\\right)}=0.95\\pm 0.30\\pm 0.04\\pm 0.04,\\\\ {}\\frac{\\mathcal{B}\\left({\\Lambda}_{\\mathrm{b}}^0\\to {\\upchi}_{\\mathrm{c}2}{\\mathrm{p}\\mathrm{K}}^{-}\\right)}{\\mathcal{B}\\left({\\Lambda}_{\\mathrm{b}}^0\\to {\\upchi}_{\\mathrm{c}1}{\\mathrm{p}\\mathrm{K}}^{-}\\right)}=1.06\\pm 0.05\\pm 0.04\\pm 0.04,\\end{array}} $$ B Λ b 0 → χ c 1 pπ − B Λ b 0 → χ c 1 pK − = 6.59 ± 1.01 ± 0.22 × 10 − 2 , B Λ b 0 → χ c 2 pπ − B Λ b 0 → χ c 1 pπ − = 0.95 ± 0.30 ± 0.04 ± 0.04 , B Λ b 0 → χ c 2 pK − B Λ b 0 → χ c 1 pK − = 1.06 ± 0.05 ± 0.04 ± 0.04 , where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of χ c1 , 2 → J / ψγ decays.
Publisher: Springer Science and Business Media LLC
Date: 04-2022
DOI: 10.1140/EPJC/S10052-022-10186-3
Abstract: A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200 $$\\text {\\,GeV\\!/}c^2$$ \\,GeV\\!/ c 2 is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10 $$\\text {\\,GeV\\!/}c^2$$ \\,GeV\\!/ c 2 up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90 $$\\text {\\,GeV\\!/}c^2$$ \\,GeV\\!/ c 2 . The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at $$\\sqrt{s} = 13\\text {\\,TeV} $$ s = 13 \\,TeV , corresponding to an integrated luminosity of 5.4 $$\\text {\\,fb} ^{-1}$$ \\,fb - 1 . No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.
Publisher: Springer Science and Business Media LLC
Date: 03-2022
Abstract: Searches for rare $$ {B}_s^0 $$ B s 0 and B 0 decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . Direct decays and decays via light scalar and J/ψ resonances are considered. No evidence for the six decays searched for is found and upper limits at the 95% confidence level on their branching fractions ranging between 1 . 8 × 10 − 10 and 2 . 6 × 10 − 9 are set.
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D 0 and $$ \\overline{D} $$ D ¯ 0 mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $$ x=\\left({0.400}_{-0.053}^{+0.052}\\right)\\% $$ x = 0.400 − 0.053 + 0.052 % and y = $$ \\left({0.630}_{-0.030}^{+0.033}\\right)\\% $$ 0.630 − 0.030 + 0.033 % . The angle γ is found to be γ = $$ \\left({65.4}_{-4.2}^{+3.8}\\right){}^{\\circ} $$ 65.4 − 4.2 + 3.8 ° and is the most precise determination from a single experiment.
Publisher: American Physical Society (APS)
Date: 22-04-2021
Publisher: Springer Science and Business Media LLC
Date: 08-04-2022
Abstract: A study of B + → J / ψηK + decays, followed by J / ψ → μ + μ − and η → γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The J / ψη mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the B + → (ψ 2 (3823) → J / ψη)K + and B + → (ψ(4040) → J / ψη)K + decays with significance of 3.4 and 4.7 standard deviations, respectively. This constitutes the first evidence for the ψ 2 (3823) → J / ψη decay.
Publisher: IOP Publishing
Date: 09-2021
Abstract: The first search for the doubly heavy baryon and a search for the baryon are performed using collision data collected via the experiment from 2016 to 2018 at a centre-of-mass energy of , corresponding to an integrated luminosity of 5.2 . The baryons are reconstructed via their decays to and . No significant excess is found for invariant masses between 6700 and 7300 , in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 . Upper limits are set on the ratio of the and production cross-section times the branching fraction to ( ) relative to that of the ( ) baryon, for different lifetime hypotheses, at 95% confidence level. The upper limits range from to for the ( ) decay, and from to for the ( ) decay, depending on the considered mass and lifetime of the ( ) baryon.
Publisher: American Physical Society (APS)
Date: 24-08-2022
Publisher: American Physical Society (APS)
Date: 02-03-2021
Publisher: Elsevier BV
Date: 03-2022
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: A search for the doubly charmed baryon $$ {\\varXi}_{cc}^{+} $$ Ξ cc + is performed in the $$ {\\varXi}_c^{+}{\\pi}^{-}{\\pi}^{+} $$ Ξ c + π − π + invariant-mass spectrum, where the $$ {\\varXi}_c^{+} $$ Ξ c + baryon is reconstructed in the pK − π + final state. The study uses proton-proton collision data collected with the LHCb detector at a centre- of-mass energy of 13 TeV, corresponding to a total integrated luminosity of 5.4 fb − 1 . No significant signal is observed in the invariant-mass range of 3.4–3.8 GeV/ c 2 . Upper limits are set on the ratio of branching fractions multiplied by the production cross-section with respect to the $$ {\\varXi}_{cc}^{++} $$ Ξ cc + + → ( $$ {\\varXi}_c^{+} $$ Ξ c + → pK − π + ) π + decay for different $$ {\\varXi}_{cc}^{+} $$ Ξ cc + mass and lifetime hypotheses in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 2.5 to 25 GeV/ c . The results from this search are combined with a previously published search for the $$ {\\varXi}_{cc}^{+} $$ Ξ cc + → $$ {\\varLambda}_c^{+} $$ Λ c + K − π + decay mode, yielding a maximum local significance of 4.0 standard deviations around the mass of 3620 MeV/ c 2 , including systematic uncertainties. Taking into account the look-elsewhere effect in the 3.5–3.7 GeV/ c 2 mass window, the combined global significance is 2.9 standard deviations including systematic uncertainties.
Publisher: Springer Science and Business Media LLC
Date: 31-08-2021
DOI: 10.1007/S11433-021-1742-7
Abstract: A search for the doubly charmed baryon Ω cc + with the decay mode Ω cc + → Ξ c + K − π + is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb −1 . No significant signal is observed within the invariant mass range of 3.6 to 4.0GeV/ c 2 . Upper limits are set on the ratio R of the production cross-section times the total branching fraction of the Ω cc + → Ξ c + K − π + decay with respect to the $$\\Xi _{cc}^{ + + } \\to \\Lambda _c^ + {K^ - }{\\pi ^ + }{\\pi ^ + }$$ Ξ c c + + → Λ c + K − π + π + decay. Upper limits at 95% credibility level for R in the range 0.005 to 0.11 are obtained for different hypotheses on the Ω cc + mass and lifetime in the rapidity range from 2.0 to 4.5 and transverse momentum range from 4 to 15 GeV/ c .
Publisher: American Physical Society (APS)
Date: 27-08-2021
Publisher: Springer Science and Business Media LLC
Date: 2022
DOI: 10.1038/S41567-021-01394-X
Abstract: Mesons comprising a beauty quark and strange quark can oscillate between particle ( $${B}_{\\mathrm{s}}^{0}$$ B s 0 ) and antiparticle ( $${\\overline{B}}_{\\mathrm{s}}^{0}$$ B ¯ s 0 ) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δ m s . Here we present a measurement of Δ m s using $${B}_{\\mathrm{s}}^{0}\\to {D}_{\\mathrm{s}}^{-}$$ B s 0 → D s − π + decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δ m s = 17.7683 ± 0.0051 ± 0.0032 ps −1 , where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δ m s precision by a factor of two. We combine this result with previous LHCb measurements to determine Δ m s = 17.7656 ± 0.0057 ps −1 , which is the legacy measurement of the original LHCb detector.
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Abstract: The production cross-sections of J/ψ mesons in proton-proton collisions at a centre-of-mass energy of $$ \\sqrt{s} $$ s = 5 TeV are measured using a data s le corresponding to an integrated luminosity of 9 . 13 ± 0 . 18 pb − 1 , collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum, p T , and rapidity, y , and separately for J/ψ mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised J/ψ mesons, the production cross-sections integrated over the kinematic range 0 p T 20 GeV/ c and 2 . 0 y 4 . 5 are $$ {\\displaystyle \\begin{array}{c}{\\sigma}_{\\mathrm{prompt}}\\ J/\\psi =8.154\\pm 0.010\\pm 0.283\\ \\upmu \\mathrm{b},\\\\ {}{\\sigma}_{\\mathrm{nonprompt}}\\ J/\\psi =0.820\\pm 0.003\\pm 0.034\\ \\upmu \\mathrm{b},\\end{array}} $$ σ prompt J / ψ = 8.154 ± 0.010 ± 0.283 μb , σ nonprompt J / ψ = 0.820 ± 0.003 ± 0.034 μb , where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at $$ \\sqrt{s} $$ s = 8 TeV and 13 TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for J/ψ mesons at a centre-of-mass energy per nucleon pair of $$ \\sqrt{s_{\\mathrm{NN}}} $$ s NN = 5 TeV. The results are compared with theoretical predictions.
Publisher: American Physical Society (APS)
Date: 03-06-2022
Publisher: American Physical Society (APS)
Date: 26-10-2021
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: A data set corresponding to an integrated luminosity of 9 fb − 1 of proton-proton collisions collected by the LHCb experiment has been analysed to search for $$ {B}_c^{+}\\to {D}_{(s)}^{\\left(\\ast \\right)+}{\\genfrac{}{}{0pt}{}{\\left(\\hbox{---} \\right)}{D}}^{\\left(\\ast \\right)0} $$ B c + → D s ∗ + — D ∗ 0 decays. The decays are fully or partially reconstructed, where one or two missing neutral pions or photons from the decay of an excited charm meson are allowed. Upper limits for the branching fractions, normalised to B + decays to final states with similar topologies, are obtained for sixteen $$ {B}_c^{+} $$ B c + decay modes. For the decay $$ {B}_c^{+}\\to {D}_s^{+}{\\overline{D}}^0 $$ B c + → D s + D ¯ 0 , an excess with a significance of 3.4 standard deviations is found.
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: The W boson mass is measured using proton-proton collision data at $$ \\sqrt{s} $$ s = 13 TeV corresponding to an integrated luminosity of 1.7 fb − 1 recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon q T distribution of a s le of W → μν decays and the ϕ * distribution of a s le of Z → μμ decays the W boson mass is determined to be $$ {m}_w=80354\\pm {23}_{\\mathrm{stat}}\\pm {10}_{\\mathrm{exp}}\\pm {17}_{\\mathrm{theory}}\\pm {9}_{\\mathrm{PDF}}\\mathrm{MeV}, $$ m w = 80354 ± 23 stat ± 10 exp ± 17 theory ± 9 PDF MeV , where uncertainties correspond to contributions from statistical, experimental systematic, theoretical and parton distribution function sources. This is an average of results based on three recent global parton distribution function sets. The measurement agrees well with the prediction of the global electroweak fit and with previous measurements.
Publisher: Springer Science and Business Media LLC
Date: 07-2022
Abstract: Coherent production of J/ψ mesons is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data s le collected by the LHCb experiment corresponding to an integrated luminosity of about 10 μb −1 . The J/ψ mesons are reconstructed in the dimuon final state and are required to have transverse momentum below 1 GeV. The cross-section within the rapidity range of 2 . 0 y 4 . 5 is measured to be 4 . 45 ± 0 . 24 ± 0 . 18 ± 0 . 58 mb, where the first uncertainty is statistical, the second systematic and the third originates from the luminosity determination. The cross-section is also measured in J/ψ rapidity intervals. The results are compared to predictions from phenomenological models.
Publisher: Springer Science and Business Media LLC
Date: 11-05-2022
Abstract: A search for the decay B 0 → ϕμ + μ − is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9 fb − 1 . No evidence for the B 0 → ϕμ + μ − decay is found and an upper limit on the branching fraction, excluding the ϕ and charmonium regions in the dimuon spectrum, of 4 . 4 × 10 − 3 at a 90% credibility level, relative to that of the $$ {B}_s^0 $$ B s 0 → ϕμ + μ − decay, is established. Using the measured $$ {B}_s^0 $$ B s 0 → ϕμ + μ − branching fraction and assuming a phase-space model, the absolute branching fraction of the decay B 0 → ϕμ + μ − in the full q 2 range is determined to be less than 3 . 2 × 10 − 9 at a 90% credibility level.
Publisher: Springer Science and Business Media LLC
Date: 10-2021
Abstract: This article presents differential measurements of the asymmetry between $$ {\\varLambda}_b^0 $$ Λ b 0 and $$ {\\overline{\\varLambda}}_b^0 $$ Λ ¯ b 0 baryon production rates in proton-proton collisions at centre-of-mass energies of $$ \\sqrt{s} $$ s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb − 1 . The $$ {\\varLambda}_b^0 $$ Λ b 0 baryons are reconstructed through the inclusive semileptonic decay $$ {\\varLambda}_b^0 $$ Λ b 0 → $$ {\\varLambda}_c^{+} $$ Λ c + μ − $$ \\overline{\\nu} $$ ν ¯ μ X . The production asymmetry is measured both in intervals of rapidity in the range 2 . 15 y 4 . 10 and transverse momentum in 2 p T 27 GeV/ c . The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $$ \\sqrt{s} $$ s = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in P ythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b -hadron production at LHC energies.
Publisher: American Physical Society (APS)
Date: 07-04-2022
Publisher: American Physical Society (APS)
Date: 25-01-2022
Publisher: American Physical Society (APS)
Date: 11-05-2022
Publisher: American Physical Society (APS)
Date: 20-09-2021
Publisher: American Physical Society (APS)
Date: 13-05-2022
Publisher: American Physical Society (APS)
Date: 27-12-2021
Publisher: American Physical Society (APS)
Date: 05-10-2021
Publisher: Springer Science and Business Media LLC
Date: 27-07-2015
DOI: 10.1038/NPHYS3415
Publisher: Elsevier BV
Date: 07-2021
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Oliver Lupton.