LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). First Evidence for Direct CP Violation in Beauty to Charmonium Decays. Phys. Rev. Lett., 134(10), 101801–13pp.
Abstract: The CP asymmetry and branching fraction of the Cabibbo-Kobayashi-Maskawa-suppressed decay B+ -> J/psi pi(+) are precisely measured relative to the favored decay B+ -> J/psi K+ using a sample of protonproton collision data corresponding to an integrated luminosity of 5.4 fb(-1) recorded at a center-of-mass energy of 13 TeV during 2016-2018. The results of the CP asymmetry difference and branching fraction ratio are Delta A(CP)= A(CP)(B+ -> J/psi pi(+))-A(CP)(B+ -> J/psi K+)=(1.29 +/- 0.49 +/- 0.08)x10(-2), R-pi/K [B(B+ -> J/psi pi(+))/ B(B+-> J/psi K+)] = (3.852 +/- 0.022 +/- 0.018)x10(-2), where the first uncertainties are statistical and the second are systematic. A combination with previous LHCb results based on data collected at 7 and 8 TeVin 2011 and 2012 yields Delta A(CP) = (1.42 +/- 0.43 +/- 0.08) x 10(-2) and R pi/K = (3.846 +/- 0.018 +/- 0.018) x 10(-2). The combined Delta A(CP) value deviates from zero by 3.2 standard deviations, providing the first evidence for direct CP violation in the amplitudes of beauty decays to charmonium final states.
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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). Study of Λb0 and Ξb0 Decays to Λh+ h'- – and Evidence for CP Violation in Λb0 → ΛK+ K- Decays. Phys. Rev. Lett., 134(10), 101802–16pp.
Abstract: A study of Lambda(0)(b) and Xi(0)(b) decays to Lambda h(+) h'(-) (h((')) = pi, K) is performed using pp collision data collected by the LHCb experiment during LHC Runs 1-2, corresponding to an integrated luminosity of 9 fb(-1). The branching fractions for these decays are measured using the Lambda(0)(b) -> Lambda pi(+)pi(-) decay as a control channel. The decays Lambda(0)(b) -> Lambda pi(+)pi(-) and and Xi(o)(b) -> pi Lambda K-pi(+)- are observed for the first time. For decay modes with sufficient signal yields, CP asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for CP violation in the Lambda(0)(b) -> Lambda K+K- decay, interpreted as originating primarily from an asymmetric Lambda(0)(b) -> N*K-+(-) decay amplitude. The measured CP asymmetries for other decays are compatible with zero.
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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). Test of Lepton Flavor Universality with Bs0 → φl+ l- Decays. Phys. Rev. Lett., 134(12), 121803–15pp.
Abstract: Lepton flavor universality in rare b -> s transitions is tested for the first time using B-s(0) meson decays. The measurements are performed using pp collision data collected by the LHCb experiment between 2011 and 2018, corresponding to a total integrated luminosity of 9 fb(-1). Branching fraction ratios between the B-s(0) -> phi e(+) e(-) and B-s(0) -> phi mu(+) mu(-) decays are measured in three regions of dilepton mass squared, q(2), with 0.1 < q(2) < 1.1, 1.1 < q(2) < 6.0, and 15 < q(2) < 19 GeV2/c(4). The results agree with the standard model expectation of lepton flavor universality.
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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). Test of Lepton Flavor Universality with B+ → K+ π+ π- l+ l- Decays. Phys. Rev. Lett., 134(18), 181803–13pp.
Abstract: The first test of lepton flavor universality between muons and electrons using B+ -> K+ pi(+) pi(-) l(+) l(-) (l = e, mu) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb(-1). The ratio of branching fractions between B+ -> K+ pi(+) pi(-) mu(+) mu(-) decays is measured in the dilepton invariant-mass-squared range 1.1 < q(2) < 7.0 GeV2/c(4) and is found to be R-K pi pi(-1) = 1.31(-0.17)(+0.18) (stat)(-0.09)(+0.12) (syst), in agreement with the standard model prediction. The first observation of the B+ -> K+ pi(+) pi(-) e(+) e(-) decay is also reported.
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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). Observation of New Charmonium or Charmoniumlike States in B+ → D*±D∓K+ Decays. Phys. Rev. Lett., 133(13), 131902–14pp.
Abstract: A study of resonant structures in B+ -> D*(DK+)-D-+/--K--/+ and B+ -> D*(DK+)-D-+/--K--/+ decays is performed, using proton-proton collision data at center-of-mass energies of root s = 7, 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to D*D-+/-(+) and D*D-+/-(-) states linked by C parity. This procedure allows the C parities of resonances in the D*D-+/-(-/+) mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into D*D-+/-(-/+): eta(c)(3945), h(c)(4000), chi(c1)(4010), and h(c)(4300), with quantum numbers J(PC) equal to 0(-+), 1(+-), 1(+-), and 1(+-), respectively. At least three of these states have not been observed previously. In addition, the existence of the T-(c) over bar(s) over bar0*(2870)(0) and T-(c) over bar(s) over bar1*(2900)(0) resonances in the D-K+ mass spectrum, already observed in the B+ -> D+D-K+ decay, is confirmed in a different production channel.
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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 Time-Dependent CP Violation in D0 → π+ π- π0 Decays. Phys. Rev. Lett., 133(10), 101803–12pp.
Abstract: A measurement of time-dependent CP violation in D-0 -> pi(+) pi(-) pi(0) decays using a pp collision data sample collected by the LHCb experiment in 2012 and from 2015 to 2018, corresponding to an integrated luminosity of 7.7 fb(-1), is presented. The initial flavor of each D-0 candidate is determined from the charge of the pion produced in the D*(2010)(+) -> D-0 pi(+) decay. The decay D-0 -> K- pi(+) pi(0) is used as a control channel to validate the measurement procedure. The gradient of the time-dependent CP asymmetry Delta Y in D-0 -> pi(+) pi(-) pi(0) decays is measured to be Delta Y = (-1.3 +/- 6.3 +/- 2.4) x 10(-4), where the first uncertainty is statistical and the second is systematic, which is compatible with CP conservation.
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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). Measurement of CP Violation Observables in D+ → K- K+ π+ Decays. Phys. Rev. Lett., 133(25), 251801–13pp.
Abstract: A search for violation of the charge-parity (CP) symmetry in the D+ -> K- K+ pi(+) decay is presented, with proton-proton collision data corresponding to an integrated luminosity of 5.4 fb(-1), collected at a center-of-mass energy of 13 TeV with the LHCb detector. A novel model-independent technique is used to compare the D+ and D- phase-space distributions, with instrumental asymmetries subtracted using the D-s(+) -> K- K+ pi(+) decay as a control channel. The p value for the hypothesis of CP conservation is 8.1%. The CP asymmetry observables A(CP vertical bar S)(phi pi+) = (0.95 +/- 0.43(stat) +/- 0.26(syst)) x 10(-3) and A(CP vertical bar S)((K) over bar *0 K+) = (-0.26 +/- 0.56(stat) +/- 0.18(syst)) x 10(-3) are also measured. These results show no evidence of CP violation and represent the most sensitive search performed through the phase space of a multibody decay.
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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). Measurement of Λ0b, Λ+c, and Λ Decay Parameters Using Λ0b →Λ+c h- Decays. Phys. Rev. Lett., 133(26), 261804–15pp.
Abstract: A comprehensive study of the angular distributions in the bottom-baryon decays Lambda(0)(b) ->Lambda(+)(c)h(-) (h = pi,K) , followed by Lambda(0)(c) ->Lambda h(+) with Lambda -> p pi(-) or Lambda(+)(c)-> pK(S)(0) decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 9 fb(-1) collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The decay parameters and the associated charge-parity (CP) asymmetries are measured, with no significant CP violation observed. For the first time, Lambda(0)(b) ->Lambda(+)(c)h(-) decay parameters are measured. The most precise measurements of the decay parameters alpha, ss, and are obtained for Lambda(+)(c) decays and an independent measurement of the decay parameters for the strange-baryon Lambda decay is provided. The results deepen our understanding of weak decay dynamics in baryon
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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 Cabibbo-Suppressed Two-Body Hadronic Decays and Precision Mass Measurement of the Ω0c Baryon. Phys. Rev. Lett., 132(8), 081802–11pp.
Abstract: The first observation of the singly Cabibbo-suppressed 0c -> -K thorn and 0c -> -z thorn decays is reported, using proton -proton collision data at a center -of -mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be Bo0c ->-K thorn thorn Bo0c ->-z thorn thorn 1/4 1/26.08 ⠂ 0.51ostat thorn ⠂ 0.40osyst thorn ⠃%; Bo0c ->-z thorn thorn Bo0c ->-z thorn thorn 1/4 1/215.81 ⠂ 0.87ostat thorn ⠂ 0.44osyst thorn ⠂ 0.16oext thorn ⠃%. In addition, using the 0c -> -z thorn decay channel, the 0c baryon mass is measured to be Mo0c thorn 1/4 2695.28 ⠂ 0.07ostat thorn ⠂ 0.27osyst thorn ⠂ 0.30oext thorn MeV; improving the precision of the previous world average by a factor of 4.
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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). Improved Measurement of CP Violation Parameters in B0s → J/ψ K+ K- Decays in the Vicinity of the φ(1020) Resonance. Phys. Rev. Lett., 132(5), 051802–12pp.
Abstract: The decay-time-dependent CP asymmetry in B0s -> J=psi(-> mu+mu-)K+K- decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb-1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B0s signal decays with an invariant K+K- mass in the vicinity of the phi(1020) resonance, the CP-violating phase phi s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B0s-B over bar 0s system, Delta Gamma s, and the difference of the average B0s and B0 meson decay widths, Gamma s – Gamma d. The values obtained are phi s = -0.039 +/- 0.022 +/- 0.006 rad, Delta Gamma s = 0.0845 +/- 0.0044 +/- 0.0024 ps-1, and -0.0015 +/- 0.0014 ps-1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase phi s is also measured independently for each polarization state of the K+K- system and shows no evidence for polarization dependence.
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