LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Analysis of Neutral B-Meson Decays into Two Muons. Phys. Rev. Lett., 128(4), 041801–13pp.
Abstract: The branching fraction B(B-s(0)->mu(+)mu(-)) = (3.09(-0.43-0.11)(+0.46+0.15)) x 10(-9) and the effective lifetime to tau(B-s(0) -> mu(+)mu(-)) = 2.07 +/- 0.29 +/- 0.03 ps are measured, where the first uncertainty is statistical and the second systematic. No significant signal for B-0 ->mu(+)mu(-)gamma) and B-s(0)->mu(+)mu(-)gamma decays is found and upper limits B(B(B-0 ->mu(+)mu(-)) < 2.6 x 10(-10) and B(B-s(0) -> mu(+)mu(-)gamma) < 2.0 x 10(-9) at the 95% C.L. are determined, where the latter is limited to the range m(mu mu) > 4.9 GeV/c(2). The results are in agreement with the standard model expectations.Branching fraction and effective lifetime measurements of the rare decay B-s(0) -> mu(+)mu(-) and searches for the decays B-0 -> mu(+)mu(-) and B-s(0) -> mu(+)mu(-)gamma are reported using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a luminosity of 9 fb(-1).
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2024). Analysis of Λ0b →pK- μ+ μ- decays. J. High Energy Phys., 12(12), 147–33pp.
Abstract: The differential branching fraction and angular coefficients of Lambda(0)(b) -> pK(-) mu(+) mu(-)decays are measured in bins of the dimuon mass squared and dihadron mass. The analysis is performed using a data set corresponding to 9 fb(-1) of integrated luminosity collected with the LHCb detector between 2011 and 2018. The data are consistent with receiving contributions from a mixture of. resonances with different spin-parity quantum numbers. The angular coefficients show a pattern of vector-axial vector interference that is a characteristic of the type of flavour-changing neutral-current transition relevant for these decays.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Angular analysis of B0 -> D*- D*s+ with D*s+ -> Ds + gamma decays. J. High Energy Phys., 06(6), 177–30pp.
Abstract: The first full angular analysis of the B0 -> D-Ds+ 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 Ds+-> Ds+gamma and D*- -> D<overbar></mml:mover>0- vector meson decays are used with the subsequent Ds+ -> K+K-pi (+) and D<overbar></mml:mover>0 -> K+pi (-) decays. All helicity amplitudes 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 amplitude magnitudes is found to align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [B(B0 -> D-Ds+) x B(Ds+-> Ds+gamma)]/B(B-0 -> D(*-)Ds+) 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(*-)Ds+ decay is made with a significance of seven standard deviations. The branching fraction ratio B(B-s -> D(*-)Ds<mml:mo>+)/B(B-0 -> D(*-)Ds<mml:mo>+) 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.<fig id=“Figa” position=“anchor”><graphic position=“anchor” specific-use=“HTML” mime-subtype=“JPEG” xmlns:xlink=“http://www.w3.org/1999/xlink” xlink:href=“MediaObjects/13130202116089FigaHTML.jpg” id=“MO1”></graphic
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Angular Analysis of D0 -> x plus x-mu plus mu- and D0 -> K plus K-mu plus mu- Decays and Search for CP Violation. Phys. Rev. Lett., 128(22), 221801–11pp.
Abstract: The first full angular analysis and an updated measurement of the decay-rate CP asymmetry of the D0→π+π−μ+μ− and D0→K+K−μ+μ− decays are reported. The analysis uses proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data set corresponds to an integrated luminosity of 9 fb−1. The full set of CP-averaged angular observables and their CP asymmetries are measured as a function of the dimuon invariant mass. The results are consistent with expectations from the standard model and with CP symmetry.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Angular Analysis of the B+ -> K*(+)mu(+) mu(-) Decay. Phys. Rev. Lett., 126(16), 161802–11pp.
Abstract: We present an angular analysis of the B+ -> K*(+)(-> K-S(0)pi(+))mu(+) mu(-) decay using 9 fb(-1) of pp collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B-0 -> K*(0)mu(+)mu(-) decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Angular analysis of the rare decay B-s(0) -> phi mu(+)mu(-). J. High Energy Phys., 11(11), 043–45pp.
Abstract: An angular analysis of the rare decay B-s(0) -> phi mu(+)mu(-) is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 8.4 fb(-1). The observables describing the angular distributions of the decay B-s(0) -> phi mu(+)mu(-) are determined in regions of q(2), the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Associated production of prompt J/ψ and Υ mesons in pp collisions at √s=13 TeV. J. High Energy Phys., 08(8), 093–24pp.
Abstract: The associated production of prompt J/psi and Υ mesons in pp collisions at a centre-of-mass energy of root s = 13T eV is studied using LHCb data, corresponding to an integrated luminosity of 4 fb(-1). The measurement is performed for J/psi (Υ) mesons with a transverse momentum pT < 10 (30) GeV/ c in the rapidity range 2.0 < y < 4.5. In this kinematic range, the cross-section of the associated production of prompt J/psi and Υ(1S) mesons is measured to be 133 +/- 22 +/- 7 +/- 3 pb, with a significance of 7.9 s, and that of prompt J/psi and Υ(2S) mesons to be 76 +/- 21 +/- 4 +/- 7 pb, with a significance of 4.9 sigma. The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of J/psi and Υ(1S) in proton-proton collisions. Differential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the J/psi and Υ(1S) mesons. The effective cross-sections of the associated production of prompt J/psi and Υ mesons are obtained and found to be compatible with measurements using other particle productions.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Branching Fraction Measurements of the Rare B-s(0) -> phi mu(+)mu(-) and B-s(0)-> f(2)' (1525)mu(+)mu(-) Decays. Phys. Rev. Lett., 127(15), 151801–11pp.
Abstract: The branching fraction of the rare B-s(0) -> phi mu(+)mu(-) decay is measured using data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6 fb(-1), respectively. The branching fraction is reported in intervals of q(2), the square of the dimuon invariant mass. In the q(2) region between 1.1 and 6.0 GeV2/c(4) , the measurement is found to lie 3.6 standard deviations below a standard model prediction based on a combination of light cone sum rule and lattice QCD calculations. In addition, the first observation of the rare B-s(0)-> f(2)' (1525)mu(+)mu(-) decay is reported with a statistical significance of 9 standard deviations and its branching fraction is determined.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Centrality determination in heavy-ion collisions with the LHCb detector. J. Instrum., 17(5), P05009–31pp.
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 root s(NN) = 5 TeV and lead-neon fixed-target collisions at root 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.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Charmonium production in pNe collisions at √sNN=68.5 GeV. Eur. Phys. J. C, 83(7), 625–11pp.
Abstract: The measurement of charmonium states produced in proton-neon (pNe) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of J/Psi and Psi(2S) mesons is studied with a beam of 2.5 TeV protons colliding on gaseous neon targets at rest, cvorresponding to a nucleon-nucleon centre-of-mass energy root(NN)-N-s = 68.5GeV. The data sample corresponds to an integrated luminosity of 21.7 +/- 1.4 nb(-1). The J/Psi and Psi(2S) hadrons are reconstructed in mu(+) mu(-) final states. The J/Psi production cross-section per target nucleon in the centre-of-mass rapidity range y* is an element of [-2.29, 0] is found to be 506 +/- 8 +/- 46 nb/nucleon. The ratio of J/Psi and D-0 cross-sections is evaluated to (1.06 +/- 0.02 +/- 0.09)%. The Psi(2S) to J/Psi relative production rate is found to be (1.67 +/- 0.27 +/- 0.10)% in good agreement with other measurements involving beam and target nuclei of similar sizes.
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