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). Study of CP violation in B0 → DK*(892)0 decays with D → Kπ(ππ), ππ(ππ), and KK final states. J. High Energy Phys., 05(5), 025–30pp.
Abstract: A measurement of CP-violating observables associated with the interference of B-0 -> (DK)-K-0*(892)(0) and B-0 -> (D) over bar K-0*(892)(0) decay amplitudes is performed in the D-0 -> K-+/- pi(+/-)(pi(+)pi(-)), D-0 -> pi(+) pi(-)(pi(+)pi(-)), and D-0 -> K+ K- final states using data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb(-1). CP-violating observables related to the interference of B-s(0) -> D-0 (K) over bar*(892)(0) and B-s(0) -> (D) over bar (0) (K) over bar*(892)(0) are also measured, but no evidence for interference is found. The B-0 observables are used to constrain the parameter space of the CKM angle. and the hadronic parameters gamma(DK*) (0)(B) and delta(DK*) (0)(B) with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average.
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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). Modification of χc1(3872) and ψ(2S) Production in pPb Collisions at √sNN=8.16 TeV. Phys. Rev. Lett., 132(24), 242301–12pp.
Abstract: The LHCb Collaboration measures production of the exotic hadron chi(c1)(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state psi(2S) suggests that the exotic chi(c1)(3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify chi(c1)(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron.
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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 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). 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). 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., 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., 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), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Search for B+c → π+μ+μ- decays and measurement of the branching fraction ratio B(B+c → ψ(2S)π+)/B(B+c< /i> → J/ψπ+). Eur. Phys. J. C, 84(5), 468–17pp.
Abstract: The first search for nonresonant B-c(+) -> pi(+)mu(+)mu(-) decays is reported. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb(-1). No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio B(B-c(+) -> pi(+)mu(+)mu(-))/B(B-c(+) -> J/psi pi(+)) < 2.1x10(-4) at 90% confidence level. Additionally, an updated measurement of the ratio of the B-c(+) -> psi(2S)pi(+) and B-c(+) -> J/psi pi(+) branching fractions is reported. The ratio B(B-c(+) -> psi(2S)pi+)/B(B-c(+) -> J/psi pi(+)) is measured to be 0.254 +/- 0.018 +/- 0.003 +/- 0.005, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic J/psi and psi(2S) decays. This measurement is the most precise to date and is consistent with previous LHCb results.
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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). Study of the Bose-Einstein correlations of same-sign pions in proton-lead collisions. J. High Energy Phys., 09(9), 172–29pp.
Abstract: Correlations of same-sign charged pions are analysed using proton-lead collision data collected by the LHCb experiment at a nucleon-nucleon centre-of-mass energy of 5.02TeV, corresponding to an integrated luminosity of 1.06 nb(-1). Bose-Einstein correlations are observed in the form of an enhancement of pair production for same-sign charged pions with a small four-momentum difference. The dependence of the correlation radius and the intercept parameter on the reconstructed charged-particle multiplicity is investigated. The measured correlation radii scale linearly with the cube root of the reconstructed charged-particle multiplicity, being compatible with predictions of hydrodynamic models on the collision system evolution.
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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). Observation and branching fraction measurement of the decay Ξb- → Λ0 bπ-. Phys. Rev. D, 108(7), 072002–16pp.
Abstract: The decay E-b -> A0bx-- is observed using a proton-proton collision data sample collected at center-of-ffiffimass energy p s 1/4 13 TeV with the LHCb detector, corresponding to an integrated luminosity of 5.5 fb-1. This process is mediated by the s -> uu over bar d quark-level transition, where the b quark in the E-b baryon is a spectator in the decay. Averaging the results obtained using the two A0b decay modes, A0b -> A thorn c x-- and A0b -> A thorn c x--x- thorn x--, the relative production ratio is measured to be ofE-b =fA0b thorn BoE-b -> A0bx-- thorn 1/4 o7.3 ⠂ 0.8 ⠂ 0.6 thorn x 10-4. Here the uncertainties are statistical and systematic, respectively, and fE-bofA0b thorn is the fragmentation fraction for a b quark into a E-b (A0b) baryon. Using an independent measurement of fE-b =fA0b, the branching fraction BoE-b -> A0bx-- thorn 1/4 o0.89 ⠂ 0.10 ⠂ 0.07 ⠂ 0.29 thorn % is obtained, where the last uncertainty is due to the assumed SU(3) flavor symmetry in the determination of fE-b =fA0b.
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