LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Inclusive B-meson flavour-tagging algorithm at LHCb. J. High Energy Phys., 11(11), 041–32pp.
Abstract: A new algorithm is developed to identify the flavour of neutral B mesons at production in pp collisions by utilising all tracks from the hadronisation process. The algorithm is calibrated separately for B-0 and B-s(0) mesons using B-0 -> J/psi K+pi(-) and B-s(0) -> D-s(-)pi(+) decays from pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV. This new algorithm improves the tagging power by 35% for B-0 mesons and 20% for B-0 s mesons when compared to the combined performance of the existing LHCb flavour-tagging algorithms.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Study of charm mixing and CP violation with D0→ K±π∓π±π∓ decays. J. High Energy Phys., 12(12), 153–39pp.
Abstract: A study of charm mixing and CP violation in D0 -> K +/-pi -/+pi +/-pi -/+ decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6 fb-1. The ratio of promptly produced D0 -> K+pi-pi+pi- to D0 -> K-pi+pi-pi+ decay rates is measured as a function of D0 decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the D0-D<overline>0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {D}<^>0-{\overline{D}}<^>0 $$\end{document} mixing parameters x and y allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle gamma of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including triangle x and triangle y, which are nonzero in the presence of CP violation. It is found that x=0.85-0.24+0.15%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ x=\left(0.{85}{-0.24}<^>{+0.15}\right)\% $$\end{document}, y=0.21-0.27+0.29%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ y=\left(0.{21}{-0.27}<^>{+0.29}\right)\% $$\end{document}, triangle x = (-0.02 +/- 0.04) % and Delta y=0.02-0.03+0.04%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Delta y=\left(0.0{2}_{-0.03}<^>{+0.04}\right)\% $$\end{document}. These results are consistent with previous measurements and the hypothesis of CP conservation.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Branching fraction measurement of the Λ → pμ- (v)over-barμ decay. J. High Energy Phys., 04(4), 096–27pp.
Abstract: A measurement of the branching fraction for the decay Lambda -> p mu(-) (v) over bar (mu) is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb(-1). The result is obtained using Lambda -> p mu(-) decays as a normalisation channel. The measured branching fraction is B(Lambda -> p mu(-) (v) over bar (mu)) = (1.462 +/- 0.016 +/- 0.100 +/- 0.011) x 10(-4), where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s -> u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, R-mu e = Gamma(Lambda -> p mu(-)(v) over bar (mu))/Gamma(Lambda -> pe(-)(v) over bar (e)) = 0.175 +/- 0.012, agrees with the Standard Model prediction.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). First evidence of violation in beauty baryon to charmonium decays. Sci. Bull., 71(3), 547–557.
Abstract: A study of the difference in the CP asymmetries between Lambda(0)(b) -> J/psi p pi(-) and Lambda(0)(b) -> J/psi pK(-)decays, Delta A(CP), is performed using proton-proton collision data collected by the LHCb experiment in the years 2015-2018, corresponding to an integrated luminosity of 6fb(-1). This quantity is measured to be Delta A(CP) = (4.03 +/- 1.18 +/- 0.23)%, where the first uncertainty is statistical and the second is systematic. When combined with the previous LHCb result, a value of Delta A(CP) = (4.31 +/- 1.06 +/- 0.28)% is obtained, corresponding to a significance of 3.9 sigma against the CP symmetry hypothesis. Studies of triple-product asymmetries, which provide an additional probe of CP violation, show no significant deviation from CP symmetry.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Measurement of CP asymmetry in D0 → KS0KS0 decays with Run 3 data. J. High Energy Phys., 02(2), 253–25pp.
Abstract: A measurement of CP asymmetry in D-0 -> (KSKS0)-K-0 decays is reported, based on a data sample of proton-proton collisions collected with the LHCb detector in 2024 at a centre-of-mass energy of 13.6TeV, corresponding to an integrated luminosity of 6.2 fb(-1). The D-0 -> K-S(0)pi(+)pi(-) decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated CP asymmetry for the D-0 -> (KSKS0)-K-0 mode is measured to be A(CP) (D-0 -> (KSKS0)-K-0) = (1.86 +/- 1.04 +/- 0.41)%, where the first uncertainty is statistical, and the second is systematic. This measurement represents the most precise single-experiment determination of this quantity to date.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Measurement of the branching fraction of the Λb0 → J/ψΛ decay and isospin asymmetry of B → J/ψK decays. J. High Energy Phys., 01(1), 159–28pp.
Abstract: This paper describes a measurement of the Lambda(0)(b) -> J/psi Lambda branching fraction using data collected with the LHCb experiment in proton-proton collisions from 2016 to 2018. The dataset corresponds to an integrated luminosity of 5.4 fb(-1). The branching fraction is determined relative to that of B-0 -> J/psi K-S(0) decays, B(Lambda(0)(b) -> J/psi Lambda)/(B-0 -> J/psi K-S(0)) = 0.750 +/- 0.005 +/- 0.022 +/- 0.005 +/- 0.062, yielding B(Lambda(0)(b) -> J/psi Lambda) = (3.34 +/- 0.02 +/- 0.10 +/- 0.08 +/- 0.28) x 10(-4), where the first uncertainty is statistical, the second systematic, the third due to external inputs on branching fractions and the fourth due to the ratio of Lambda(0)(b) baryon and B-0 meson hadronisation fractions. In addition, the isospin asymmetry between the rates of B-0 -> J/psi K-S(0) and B+ -> J/psi K+ decays is measured to be A(I) = -0.0135 +/- 0.0004 +/- 0.0133, where the first uncertainty is statistical and the second systematic.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Angular analysis of the decay Bs0 → φ e+ e-. J. High Energy Phys., 07(7), 69–29pp.
Abstract: An angular analysis of the decay Bs0 -> phi e+e- is presented, using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8 and 13 TeV. The combined dataset corresponds to an integrated luminosity of 9 fb-1. Observables are determined by fitting time-integrated projections of the angular distribution in three bins of dielectron mass squared, q2, corresponding to [0.1, 1.1], [1.1, 6.0] and [15.0, 19.0] GeV2/c4. The results are compatible with predictions based on the Standard Model of particle physics.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Measurement of the B0→ ρ(770)0γ branching fraction. J. High Energy Phys., 12(12), 151–21pp.
Abstract: The ratio between the branching fractions of the B0 -> rho(770)0 gamma and B0 -> K*(892)0 gamma decays is measured with 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 9 fb-1. The measured value isBB0 ->rho 7700 gamma BB0 -> K & lowast;8920 gamma=0.0189 +/- 0.0007 +/- 0.0005, where the first uncertainty is statistical and the second systematic. The branching fraction for B0 -> rho(770)0 gamma decays is hence obtained asBB0 ->rho 7700 gamma=7.9 +/- 0.3 +/- 0.2 +/- 0.2x10-7, where the last uncertainty is due to the branching fraction of the normalisation mode. This result assumes that both the rho(770)0 and K*(892)0 decays saturate the dihadron mass spectra considered in the analysis. It is consistent with the current world-average value and by far the most precise measurement to date.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Measurement of the Ωc0 and Ξc0 baryon lifetimes using hadronic b-baryon decays. J. High Energy Phys., 09(9), 157–25pp.
Abstract: The lifetimes of the Omega(0)(c) and Xi(0)(c) baryons are measured using a pp collision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The charm baryons are produced in the fully reconstructed decay chains Omega(-)(b) -> Omega(0)(c)(-> pK(-)K(-)pi(+))pi(-) and Xi(-)(b) -> Xi(0)(c)(-> pK(-)K(-)pi(+))pi(-). The measurement uses topologically and kinematically similar B- -> D-0(-> K-K+pi(-)pi(+))pi(-) decays for normalisation. The measured lifetimes are tau(Omega c0) = 276.3 +/- 19.4 (stat) +/- 1.8 (syst) +/- 0.7(tau(D0))fs, tau(Xi c0) = 149.2 +/- 2.5 (stat) +/- 0.9 (syst) +/- 0.4(tau(D0))fs, where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the D-0 lifetime. These results are consistent with previous measurements performed by the LHCb experiment.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Observation of the decay B0s → K0p(p)over-bar and measurement of the B0(s) → K0p(p)over-bar branching fractions. J. High Energy Phys., 07(7), 121–25pp.
Abstract: A study of the charmless baryonic decays B-(s)(0) -> K(0)p (p) over bar is presented, where B-(s)(0) denotes either a B-0 or a B-s(0) meson. The analysis is based on 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 9 fb(-1). The decay B-s(0) -> K(0)p (p) over bar is observed for the first time, with a measured branching fraction of (9.14 +/- 1.69 +/- 0.90 +/- 0.33 +/- 0.20) x 10(-7) and a significance of 5.6 sigma. The uncertainties respectively account for statistical and systematic contributions, the precision of the branching fraction of the normalisation channel B-0 -> K-0 pi(+)pi(-) and the fragmentation fraction ratio f(s)/f(d). The branching fraction determined for B-0 -> K(0)p (p) over bar is (2.82 +/- 0.08 +/- 0.12 +/- 0.10) x 10(-6), which is the most precise measurement to date.
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