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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2019). First Measurement of Charm Production in its Fixed-Target Configuration at the LHC. Phys. Rev. Lett., 122(13), 132002–12pp.
Abstract: The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/psi and D-0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of root s(NN) = 86.6 and 110.4 GeV, respectively. The J/psi and D-0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be sigma(J/psi) = 652 +/- 33(stat) +/- 42(syst) nb/nucleon and sigma(D0) = 80.8 +/- 2.4(syst) +/- 6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). First measurement of the CP-violating phase in B-s(0) -> J/Psi (-> e(+) e(-))phi decays. Eur. Phys. J. C, 81(11), 1026–18pp.
Abstract: A flavour-tagged time-dependent angular analysis of B-s(0) -> J/Psi phi decays is presented where the J/Psi meson is reconstructed through its decay to an e(+)e(-) pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8TeV, corresponding to an integrated luminosity of 3 fb(-1). The CP-violating phase and lifetime parameters of the B-s(0) s system are measured to be phi(s) = 0.00 +/- 0.28 +/- 0.07 rad, Delta Gamma(s) = 0.115 +/- 0.045 +/- 0.011 ps(-1) and Delta Gamma(s) = 0.608 +/- 0.018 +/- 0.012 ps(-1) where the first uncertainty is statistical and the second systematic. This is the first time that CP-violating parameters are measured in the B-s(0) -> J/Psi phi decay with an e+e- pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). First measurement of the CP-violating phase phi(dd)(s) in B-s(0) -> (K+pi(-))(K-pi(+)) decays. J. High Energy Phys., 03(3), 140–32pp.
Abstract: A flavour-tagged decay-time-dependent amplitude analysis of B-s(0) -> (K+pi(-))(K-pi(+)) decays is presented in the K-+/-pi(-/+) mass range from 750 to 1600 MeV/c(2). The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb(-1). Several quasi-two-body decay modes are considered, corresponding to K-+/-pi(-/+) combinations with spin 0, 1 and 2, which are dominated by the K-0(*)(800)(0) and K-0(*)(1430)(0), the K*(892)(0) and the K-2(*)(1430)(0) resonances, respectively. The longitudinal polarisation fraction for the B-s(0) -> K-*(892)(0) (K*) over bar (892)(0) decay is measured as f(L) = 0.208 +/- 0.032 +/- 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP-violating phase in phi(d (d) over bar)(s), in b -> d (s) over bars transitions is performed, yielding a value of phi(d (d) over bar)(s)= -0.10 +/- 0.13 (stat) +/- 0.14 (syst) rad.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). First Observation of a Baryonic B-s(0) Decay. Phys. Rev. Lett., 119(4), 041802–10pp.
Abstract: We report the first observation of a baryonic B-s(0) decay, B-s(0). p (Lambda) over barK(-), using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb(-1). The branching fraction is measured to be B(B-s(0) -> p (Lambda) over bar K-)+ B(B-s(0) -> p (Lambda) over bar K+) [5.46 +/- 0.61 +/- 0.57 +/- 0.50(B) +/- 0.32(f(s)/(d))] x 10(-6), where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the B-0 -> p (Lambda) over bar pi(-) decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of b-quark hadronization probabilities f(s)/f(d).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). First observation of B+ -> D-s(+) K+ K- decays and a search for B+ -> D-s(+) phi decays. J. High Energy Phys., 01(1), 131–22pp.
Abstract: A search for B+ -> D-s(+) K+ K- decays is performed using pp collision data corresponding to an integrated luminosity of 4.8 fb(-1), collected at centre-of-mass energies of 7, 8 and 13 TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to be B(B+ -> D-s(+) K+ K-) = (7.1 +/- 0.5 +/- 0.6 +/- 0.7) x 10(-6), where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode B+ -> D-s(+)(D) over bar (0). A search is also performed for the pure annihilation decay B+ -> D-s(+)(D) over bar (0). No significant signal is observed and a limit of B(B+ -> D-s(+) phi) < 4.9 x 10(-7) (4.2 x 10(-7)) is set on the branching fraction at 95% (90%) confidence level.
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