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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. (2025). Search for charge-parity violation in semileptonically tagged D0 → K+ π- decays. J. High Energy Phys., 03(3), 149–30pp.
Abstract: An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of D-0 -> K+ pi(-) and D-0 -> K- pi(+) decay rates is measured as a function of the decay time of the D-0 meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding (B) over bar -> D*(2010)(+) mu(-) X and D*(2010)(+) -> D-0 pi(+) decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV and corresponding to an integrated luminosity of 5.4 fb(-1). The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be y' = (5.8 +/- 1.6) x10(-3) and (x')(2) = (0.0 +/- 1.2) x10(-4). No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be A(D) = (2.3 +/- 1.7)%.
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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. (2025). Measurement of CP asymmetry in Bs0 → Ds∓ K± decays. J. High Energy Phys., 03(3), 139–33pp.
Abstract: A measurement of the CP-violating parameters in B-s(0) -> D-s(-/+) K-+/- decays is reported, based on the analysis of proton-proton collision data collected by the LHCb experiment corresponding to an integrated luminosity of 6 fb(-1) at a centre-of-mass energy of 13TeV. The measured parameters are obtained with a decay-time dependent analysis yielding C-f = 0.791 +/- 0.061 +/- 0.022, A(f)(Delta Gamma) = -0.051 +/- 0.134 +/- 0.058, A((f) over bar)(Delta Gamma) = -0.303 +/- 0.125 +/- 0.055, S-f = -0.571 +/- 0.084 +/- 0.023 and S-(f) over bar = -0.503 +/- 0.084 +/- 0.025, where the first uncertainty is statistical and the second systematic. This corresponds to CP violation in the interference between mixing and decay of about 8.6 sigma. Together with the value of the B-s(0) mixing phase -2 beta s, these parameters are used to obtain a measurement of the CKM angle gamma equal to (74 +/- 12)degrees modulo 180 degrees, where the uncertainty contains both statistical and systematic contributions. This result is combined with the previous LHCb measurement in this channel using 3 fb(-1) resulting in a determination of gamma = (81(-11)(+12))degrees.
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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. (2025). Measurement of φ(1020) meson production in fixed-target pNe collisions at √sNN=68.5 GeV. J. High Energy Phys., 03(3), 151–21pp.
Abstract: The first measurement of phi(1020) meson production in fixed-target pNe collisions at root s(NN) = 68.5 GeV is presented. The phi(1020) mesons are reconstructed in their K+K- decay in a data sample consisting of proton collisions on neon nuclei at rest, corresponding to an integrated luminosity of 21.7 +/- 1.4 nb(-1), collected by the LHCb detector at CERN. The phi(1020) production cross-section in the centre-of-mass rapidity range of -1.8 < y* < 0 and transverse momentum range of 800 < p(T) < 6500MeV/ c is found to be sigma = 182.7 +/- 2.7 (stat.) +/- 14.1 (syst) μb/nucleon. A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the phi(1020) meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.
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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. (2025). Measurement of CP violation in B0 → D+D- and B0s→ D+ s D- s decays. J. High Energy Phys., 01(1), 061–26pp.
Abstract: A time-dependent, flavour-tagged measurement of CP violation is performed with B-0 -> D+D- and B-s(0)-> D+ (s) D- (s)decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13TeV corresponding to an integrated luminosity of 6 fb(-1). In B-0 -> D+D- decays the CP-violation parameters are measured to be S-D(+) (-)(D) = -0.552 +/- 0.100 (stat) +/- 0.010 (syst), C-D(+) (-)(D) = 0.128 +/- 0.103 (stat) +/- 0.010 (syst). In B-s(0)-> D+ (s) D- (s) decays the CP-violating parameter formulation in terms of phi(s) and |lambda| results in phi s = -0.086 +/- 0.106 (stat) +/- 0.028 (syst) rad, |lambda (+)(D) (-)(s D) (s) | = 1.145 +/- 0.126 (stat) +/- 0.031 (syst). These results represent the most precise single measurement of the CP-violation parameters in their respective channels. For the first time in a single measurement, CP symmetry is observed to be violated in B-0 -> D+D- decays with a significance exceeding six standard deviations.
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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. (2025). Measurement of the CKM angle γ in B± → DK*(892)± decays. J. High Energy Phys., 02(2), 113–37pp.
Abstract: Measurements of CP observables and the CKM angle gamma are performed in B-+/- -> DK*(892)(+/-) decays, where D represents a superposition of D-0 and (D) over bar (0) states, using the LHCb dataset collected during Run 1 (2011-2012) and Run 2 (2015-2018). A study of this channel is presented with the D meson reconstructed in two-body final states K-+/- pi(+/-), K+ K- and pi(+)pi(-); four-body final states K-+/-pi(-/+) pi(+/-) pi(-/+) and pi(+) pi(-) pi(+)pi(-); and threebody final states K-S(0)pi(+) pi(-) and K-S(0) K+ K-. This analysis includes the first observation of the suppressed B +/-. [pi(+/-) K-+/-](D)K*(+/-) and B +/-. [pi(+/-) K--/+ pi(+/-)pi(-/+)](D)K*(+/-) decays. The combined result gives gamma = (63 +/- 13)degrees.
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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. (2025). Measurement of the multiplicity dependence of Γ production ratios in pp collisions at √s=13 Tev. J. High Energy Phys., 05(5), 011–24pp.
Abstract: The Gamma(2S) and Gamma(3S) production cross-sections are measured relative to that of the Gamma(1S) meson, as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of 13TeV. The measurement uses data collected by the LHCb experiment in 2018 corresponding to an integrated luminosity of 2 fb(-1). Both the Gamma(2S)to-Gamma(1S) and Gamma(3S)-to-Gamma(1S) cross-section ratios are found to decrease significantly as a function of event multiplicity, with the Gamma(3S)-to-Gamma(1S) 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.
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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. (2025). Angular analysis of B0 → K*0 e+ e- decays. J. High Energy Phys., 06(6), 140–53pp.
Abstract: An angular analysis of B0 -> K*0e+e- decays 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 9 fb-1. The analysis is performed in the region of the dilepton invariant mass squared of 1.1-6.0 GeV2/c4. In addition, a test of lepton flavour universality is performed by comparing the obtained angular observables with those measured in B0 -> K*0 mu+mu- decays. In general, the angular observables are found to be consistent with the Standard Model expectations as well as with global analyses of other b -> s & ell;+& ell;- processes, where & ell; is either a muon or an electron. No sign of lepton-flavour-violating effects is observed.
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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. (2025). Search for the Bc+→ χc1(3872)π+ decay. J. High Energy Phys., 06(6), 013–28pp.
Abstract: A search for the decay B-c(+)-> chi(c1)(3872)pi(+) is reported 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, corresponding to an integrated luminosity of 9 fb(-1). No significant signal is observed. Using the decay B-c(+)-> psi(2S)pi(+) as a normalisation channel, an upper limit for the ratio of branching fractions R psi(chi c1(3872))((2s)) = BBc+-> chi c1(3872)pi+/BBc+-> psi(2S)pi+ x B chi c1(3872)-> J/psi pi(+)pi(-)/BB psi(2S)-> J/psi pi+pi- <0.05(0.06), is set at the 90 (95)% confidence level.
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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. (2025). Measurement of the ψ(2S) to J/ψ cross-section ratio as a function of centrality in PbPb collisions at √sNN=5.02 TeV. J. High Energy Phys., 07(7), 235–20pp.
Abstract: The ratio of prompt production cross-sections of psi(2S) and J/psi mesons in their dimuon final state is measured as a function of centrality, using data collected by the LHCb detector in PbPb collisions at root s(NN) = 5.02 TeV, for the first time in the forward rapidity region. The measured ratio shows no dependence on the collision centrality, and is compared to the latest theory predictions and to the recent measurements in literature.
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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. (2025). Measurement of the branching fraction ratio RK at large dilepton invariant mass. J. High Energy Phys., 07(7), 198–36pp.
Abstract: A test of lepton universality between muons and electrons is performed using B+ -> K+ l(+)l(-) decays (where l = e, mu), in the dilepton invariant-mass-squared region above 14.3 GeV2/c(4). The data used for the measurement consists of beauty meson decays produced in proton-proton collisions, corresponding to an integrated luminosity of 9 fb(-1), collected by the LHCb experiment between 2011 and 2018. The ratio of branching fractions for B+ -> K+ mu(+)mu(-) and B+ -> K+ e(+)e(-) decays is measured to be R-K = 1.08(-0.09)(+0.11) (stat) (+0.04)(-0.04) (syst), which is consistent with the Standard Model prediction of unity. This constitutes the most precise test of lepton flavour universality using B+ -> K+ l(+)l(-) decays with dilepton invariant-mass-squared above the psi(2S) mass, whilst being the first of its kind at a hadron collider.
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