LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Observation of Λb0 → Λc+ (D)over-bar(*)0 K- and Λb0 → Λc+ Ds*- decays. Eur. Phys. J. C, 84(6), 575–18pp.
Abstract: The decays Lambda(0)(b) -> Lambda(+)(c) (D) over bar (()*()0) K- and Lambda(0)(b) -> Lambda(+)(c) D-s*(-) are observed for the first time, in proton-proton collision data at root s = 13TeV, corresponding to an integrated luminosity of 5.4fb(-1) collected with the LHCb detector. Their ratios of branching fractions with respect to the Lambda(0)(b) -> Lambda(+)(c) D-s(-) mode are measured to be B(Lambda(0)(b) -> Lambda(+)(c) (D) over bar (0) K-)/B(Lambda(0)(b) -> Lambda(+)(c) D-s(-)) = 0.1908(-0.0034-0.0018)(+0.0036+0.0016) +/- 0.0038, B(Lambda(0)(b) -> Lambda(+)(c) (D) over bar*(0) K-)/B(Lambda(0)(b) -> Lambda(+)(c) D-s(-)) = 0.589(-0.017-0.018)(+0.018+0.017) +/- 0.012, B(Lambda(0)(b) -> Lambda(+)(c) D-s*(-))/B(Lambda(0)(b) -> Lambda(+)(c) D-s(-)) = 1.668 +/- 0.022(-0.055)(+0.061), where the first uncertainties are statistical, the second systematic, and the third, for the Lambda(0)(b) -> Lambda(+)(c) (D) over bar (()*()0) K- decays, are due to the uncertainties on the branching fractions of the D-s(-) -> K- K+ pi(-) and (D) over bar0 -> K+ pi(-) decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in Lambda(0)(b) -> Lambda(+)(c) (D) over bar (()*()0) K- decay channels.
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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. (2024). Fraction of χc Decays in Prompt J/ψ Production Measured in pPb Collisions at root s(NN)=8.16 TeV. Phys. Rev. Lett., 132(10), 102302–12pp.
Abstract: The fraction of chi(c1) and chi(c2) decays in the prompt J=psi yield, F-chi c -> J=psi = sigma(chi c) -> J=psi/ sigma(J/ psi) , is measured by the LHCb detector in pPb collisions at root s(NN) = 8.16 TeV. The study covers the forward (1.5 < y* < 4.0) and sNN backward (-5.0 < y* < -2.5) rapidity regions, where y* is the J=psi rapidity in the nucleon -nucleon centerof -mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 +/- 0.3 and 20.8 +/- 0.5 nb(-1) , respectively. The result is presented as a function of the J=psi transverse momentum pT;J/ psi in the range 1 < pT -> J/ psi < 20 GeV=c. The F-chi c -> J=psi fraction at forward rapidity is compatible with the LHCb measurement performed in pp collisions at root s= 7 TeV, whereas the result at s backward rapidity is 2.4 sigma larger than in the forward region for 1 < pT,(J/ psi) < 3 GeV/ c. The increase of F-chi c -> J/ psi at low pT;J/ psi at backward rapidity is compatible with the suppression of the psi(2S) contribution to the prompt J/ psi yield. The lack of in -medium dissociation of chi(c) states observed in this study sets an upper limit of 180 MeV on the free energy available in these pPb collisions to dissociate or inhibit charmonium state formation.
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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. (2024). Observation of Ξb0→ Ξc + Ds- and Ξb0 c D- s decays. Eur. Phys. J. C, 84(3), 237–17pp.
Abstract: The Ξ0b→Ξ+cD−s and Ξ−b→Ξ0cD−s decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of s√=13TeV, corresponding to an integrated luminosity of 5.1fb−1. The relative branching fractions times the beauty-baryon production cross-sections are measured to be (formula), where the first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the branching fractions of relevant charm-baryon decays. The masses of Ξ0b and Ξ−b baryons are measured to be mΞ0b=5791.12±0.60±0.45±0.24MeV/c2 and mΞ−b=5797.02±0.63±0.49±0.29MeV/c2, where the uncertainties are statistical, systematic, and those due to charm-hadron masses, respectively.
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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. (2024). Measurement of CP Violation in B0 → ψ(→ l+ l-)KS0(→ π+ π-) Decays. Phys. Rev. Lett., 132(2), 021801–12pp.
Abstract: A measurement of time-dependent CP violation in the decays of B-0 and (B) over bar (0) mesons to the final states J/psi(-> mu(+) mu(-))K-S(0), psi(2S)(-> mu(+) mu(-))K-S(0) and J/psi(-> e(+)e(-))K-S(0) with K-S(0) -> pi(+)pi(-) is presented. The data correspond to an integrated luminosity of 6 fb(-1) collected at a center-of-mass energy of root s = 13 TeV with the LHCb detector. The CP-violation parameters are measured to be S-psi KS0 = 0.717 +/- 0.013(stat) +/- 0.008(syst) and C-psi KS0 = 0.008 +/- 0.012(stat) +/- 0.003(syst). This measurement of S-psi KS0 represents the most precise single measurement of the CKM angle beta to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed.
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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. (2024). Determination of short- and long-distance contributions in B0 → K*0 μ+ μ- decays. Phys. Rev. D, 109(5), 052009–28pp.
Abstract: An amplitude analysis of the B-0 -> K-*0 mu(+)mu(-) decay is presented. The analysis is based on data collected by the LHCb experiment from proton-proton collisions at root s = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 4.7 fb(-1). For the first time, Wilson coefficients and nonlocal hadronic contributions are accessed directly from the unbinned data, where the latter are parametrized as a function of q(2) with a polynomial expansion. Wilson coefficients and nonlocal hadronic parameters are determined under two alternative hypotheses: the first relies on experimental information alone, while the second one includes information from theoretical predictions for the nonlocal contributions. Both models obtain similar results for the parameters of interest. The overall level of compatibility with the Standard Model is evaluated to be between 1.8 and 1.9 standard deviations when looking at the C-9 Wilson coefficient alone, and between 1.3 and 1.4 standard deviations when considering the full set of C-9; C(1)0; C-9(') and C-10(') Wilson coefficients. The ranges reflect the theoretical assumptions made in the analysis.
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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 Λb0 → Σc(*)+ + D(*) – K- decays. Phys. Rev. D, 110(3), L031104–13pp.
Abstract: The four decays, Λ0b→Σ(∗)++cD(∗)−K−, are observed for the first time using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 6fb−1. By considering the Λ0b→Λ+cD⎯⎯⎯⎯0K− decay as reference channel, the following branching fraction ratios are measured to be
(Λ0b→Σ++cD−K−)(Λ0b→Λ+cD⎯⎯⎯⎯0K−)=0.282±0.016±0.016±0.005,(Λ0b→Σ∗++cD−K−)(Λ0b→Σ++cD−K−)=0.460±0.052±0.028,(Λ0b→Σ++cD∗−K−)(Λ0b→Σ++cD−K−)=2.261±0.202±0.129±0.046,(Λ0b→Σ∗++cD∗−K−)(Λ0b→Σ++cD−K−)=0.896±0.137±0.066±0.018,
where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more data set to become available following the LHCb upgrade.
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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. (2024). Observation of strangeness enhancement with charmed mesons in high-multiplicity pPb collisions at √sNN=8.16 TeV. Phys. Rev. D, 110(3), L031105–14pp.
Abstract: The production of prompt D-s(+) and D+ mesons is measured by the LHCb experiment in proton-lead (pPb) collisions in both the forward (1.5 < y* < 4.0) and backward (-5.0 < y* < -2.5) rapidity regions at a nucleon-nucleon center-of-mass energy of root s(NN) = 8.16 TeV. The nuclear modification factors of both D-s(+) and D+ mesons are determined as a function of transverse momentum, p(T), and rapidity. In addition, the D-s(+) to D+ cross section ratio is measured as a function of the primary charged particle multiplicity in the event. An enhanced D-s(+) to D+ production in high-multiplicity events is observed for the whole measured pT range, in particular at low p(T) and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity pPb collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions.
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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). 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., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Enhanced Production of Λb0 Baryons in High-Multiplicity pp Collisions at √s=13 TeV. Phys. Rev. Lett., 132(8), 081901–12pp.
Abstract: The production rate of Lambda(0)(b) baryons relative to B-0 mesons in pp collisions at a center-of-mass energy root s = 13 TeV is measured by the LHCb experiment. The ratio of Lambda(0)(b) to B-0 production cross sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity. At low multiplicity, the ratio measured at LHCb is consistent with the value measured in ethorne- collisions, and increases by a factor of similar to 2 with increasing multiplicity. At relatively low transverse momentum, the ratio of Lambda(0)(b) to B-0 cross sections is higher than what is measured in e(+)e(-) collisions, but converges with the ethorne- ratio as the momentum increases. These results imply that the evolution of heavy b quarks into finalstate hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed.
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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). Observation of muonic Dalitz decays of chib mesons and precise spectroscopy of hidden-beauty states. J. High Energy Phys., 10(10), 122–28pp.
Abstract: The decays of the chi(b1)(1P), chi(b2)(1P), chi(b1)(2P) and chi(b2)(2P) mesons into the Upsilon(1S)mu(+)mu(-) final state are observed with a high significance using proton-proton collision data collected with the LHCb detector and corresponding to an integrated luminosity of 9 fb(-1). The newly observed decays together with the Upsilon(2S) -> Upsilon(1S)pi(+)pi(-) and Upsilon(3S) -> Upsilon(2S)pi(+)pi(-) decay modes are used for precision measurements of the mass and mass splittings for the hidden-beauty states.
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