LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). Amplitude analysis of the radiative decay Bs0 → K+K-γ. J. High Energy Phys., 08(8), 093–39pp.
Abstract: A search for radiative decay of B-s(0) mesons to orbitally excited K+K- states is performed using proton proton collisions recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The dikaon spectrum in the mass range m(KK) < 2400 MeV/c(2) is dominated by the phi(1020) resonance that accounts for almost 70% of the decay rate. Considering the possible contributions of f(2)(1270), f(2)'(1525) and f(2)(2010) meson states, the overall tensor contribution to the amplitude is measured to be F-{f2} = 16.8 +/- 0.5 (stat.) +/- 0.7 (syst.)%, mostly dominated by the f2 '(1525) state. Several statistically equivalent solutions are obtained for the detailed resonant structure depending on whether the smaller amplitudes interfere destructively or constructively with the dominant amplitude. The preferred solution that corresponds to the lowest values of the fit fractions along with constructive interference leads to the relative branching ratio measurement B(B-s(0) -> f(2)'gamma)/B(B-s(0) -> phi gamma) = 19.4(-0.8)(+0.9)(stat.)(-0.5)(+1.4) (syst.) +/- 0.5(B)%, where the last uncertainty is due to the ratio of measured branching fractions to the K+K- final state. This result represents the first observation of the radiative B-s(0) -> f(2)'(1525)gamma decay, which is the second radiative transition observed in the B-s(0) sector.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). First observation of the Λb0→ D+D-Λ decay. J. High Energy Phys., 07(7), 140–22pp.
Abstract: The Lambda(0)(b) -> D+D-Lambda decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.3 fb(-1). Using the B-0 -> (D+D-KS0) decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = sigma(Lambda b0)/sigma(B0) x B(Lambda(0)(b) -> D+D-Lambda)/B(B-0 -> (D+D-KS0))=0.179 +/- 0.022 +/- 0.014, where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B(B-0 -> (D+D-KS0)), and the cross-section ratio, sigma Lambda(b0)/sigma(B0), previously measured by LHCb are used to derive the branching fraction of the Lambda(0)(b)-> D+D-Lambda decay B(Lambda(0)(b) -> D+D-Lambda) = (1.24 +/- 0.15 +/- 0.10 +/- 0.28 +/- 0.11)x10(-4), where the third and fourth contributions are due to uncertainties of B(B-0 -> (D+D-KS0)) and sigma(Lambda b0)/sigma(B0), respectively. Inspection of the D+Lambda and D+D- invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Lambda(0)(b) -> D*+D-Lambda decay is also observed for the first time as a partially reconstructed component in the D+D-Lambda invariant mass spectrum.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). Search for the Bs0 → μ+ μ-γ decay. J. High Energy Phys., 07(7), 101–27pp.
Abstract: A search for the fully reconstructed B-s(0)-> mu(+)mu(-)gamma decay is performed at the LHCb experiment using proton-proton collisions at root s = 13 TeV corresponding to an integrated luminosity of 5.4 fb(-1). No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B-s(0)-> mu(+)mu(-)gamma) < 4.2 x 10(-8), m(mu(+)mu(-)) is an element of[2m(mu),1.70] GeV/c(2), B(B-s(0) -> mu(+)mu(-)gamma) < 7.7 x 10(-8), m(mu(+)mu(-)) is an element of [1.70, 2.88] GeV/c(2), B(B-s(0) -> mu(+)mu(-)gamma) < 4.2 x 10(-8), m(mu(+)mu(-) ) is an element of[3.92, m(Bs0)]GeV/c(2), at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2m(mu), 1.70] GeV/c(2) dimuon mass region excluding the contribution from the intermediate phi(1020) meson, and in the region combining all dimuon-mass intervals.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). Comprehensive analysis of local and nonlocal amplitudes in the B0 → K*0μ+μ- decay. J. High Energy Phys., 09(9), 026–60pp.
Abstract: A comprehensive study of the local and nonlocal amplitudes contributing to the decay B-0 -> K-*0(-> K+pi(-))mu(+)mu(-) is performed by analysing the phase-space distribution of the decay products. The analysis is based on pp collision data corresponding to an integrated luminosity of 8.4 fb(-1) collected by the LHCb experiment. This measurement employs for the first time a model of both one-particle and two-particle nonlocal amplitudes, and utilises the complete dimuon mass spectrum without any veto regions around the narrow charmonium resonances. In this way it is possible to explicitly isolate the local and nonlocal contributions and capture the interference between them. The results show that interference with nonlocal contributions, although larger than predicted, only has a minor impact on the Wilson Coefficients determined from the fit to the data. For the local contributions, the Wilson Coefficient C9, responsible for vector dimuon currents, exhibits a 2.1 sigma deviation from the Standard Model expectation. The Wilson Coefficients C-10, C-9 ' and C-10 ' are all in better agreement than <mml:msub>C9 with the Standard Model and the global significance is at the level of 1.5 sigma. The model used also accounts for nonlocal contributions from B-0 -> K-*0[tau(+)tau(-)-> mu(+)mu(-)] rescattering, resulting in the first direct measurement of the bs tau tau vector effective-coupling C-9 tau.
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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), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). First observation and branching fraction measurement of the Λb0 → Ds- p decay. J. High Energy Phys., 07(7), 075–23pp.
Abstract: The first observation of the Lambda(0)(b) -> D-s(-) p decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of root s = 13TeV, corresponding to a total integrated luminosity of 6 fb(-1). Using the Lambda(0)(b) -> Lambda(+pi-)(c) decay as the normalisation mode, the branching fraction of the Lambda(0)(b) -> D-s(-) p decay is measured to be B (Lambda(0)(b) -> D-s(-) p) = (12.6 +/- 0.5 +/- 0.3 +/- 1.2) x 10(-6), where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the Lambda(0)(b) -> Lambda(+pi-)(c), D-s(-) -> K-K+pi(-) and Lambda(+)(c) -> pK(-)pi(+) decays.
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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). Measurement of the ratio of branching fractions B(B+c → B0sπ+)/B(B+c → J/ψπ+). J. High Energy Phys., 07(7), 066–19pp.
Abstract: The ratio of branching fractions of B-c(+) -> B-s(0)pi(+) and B-c(+) -> J/psi pi(+) decays is measured with proton-proton collision data of a centre-of-mass energy of 13TeV. The data were collected with the LHCb experiment during 2016-2018, corresponding to an integrated luminosity of 5.4 fb(-1). The B-s(0) mesons are reconstructed via the decays B-s(0) -> J/psi phi and B-s(0) -> D-s(-)pi(+). The ratio of branching fractions is measured to be B(B-c(+) -> B-s(0)pi(+))/B(B-c(+) -> J/psi pi(+)) = 91 +/- 10 +/- 8 +/- 3 where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.
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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). Search for CP violation in D(s)+ → K- K+ K+ decays. J. High Energy Phys., 07(7), 067–25pp.
Abstract: A search for direct CP violation in the Cabibbo-suppressed decay D-s(+) -> K-K+ K+ and in the doubly Cabibbo-suppressed decay D+ -> K- K+ K+ is reported. The analysis is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13TeV corresponding to an integrated luminosity of 5.6 fb(-1). The search is conducted by comparing the D-(s)(+) and D-(s)(-) Dalitz-plot distributions through a model-independent binned technique, based on fits to the K-K+K+ invariantmass distributions, with a total of 0.97 (1.27) million D-s(+) (D+) signal candidates. The results are given as p-values for the hypothesis of CP conservation and are found to be 13.3% for the D+ -> K-K+ K+ decay and 31.6% for the D+ -> K-K+ K+ decay. No evidence for CP violation is observed in these decays.
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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). Search for the lepton-flavour violating decays B-0 -> K-*0 mu(+/-)e(-/+) and B-s(0)-> phi mu(+/-)e(-/+). J. High Energy Phys., 06(6), 073–25pp.
Abstract: A search for the lepton-flavour violating decays B-0 -> K-*0 μe(-/+) and B-s(0)-> mu(+/-)e(-/+) is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb(-1). No significant signals are observed and upper limits of are set at 90% (95%) confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay B-s(0) -> phi mu(+/-) e(-/+) the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.
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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). Λc+ polarimetry using the dominant hadronic mode. J. High Energy Phys., 07(7), 228–26pp.
Abstract: The polarimeter vector field for multibody decays of a spin-half baryon is introduced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the Lambda(+)(c) -> pK(-)pi(+) decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the Lambda(+)(c) baryon and eases inclusion of the Lambda(+)(c)-> pK(-)pi(+) decay mode in hadronic amplitude analyses.
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