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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of the ratio of branching fractions B(B-c(+) -> J/psi K+)/B(B-c(+) -> J/psi pi(+)). J. High Energy Phys., 09(9), 153–15pp.
Abstract: The ratio of branching fractions R-K/pi = B (B-c(+) -> J/psi K+)/B(B-c(+) -> J/psi pi(+)) is measured with pp collision data collected by the LHCb experiment at centre-of-mass energies of 7TeV and 8TeV, corresponding to an integrated luminosity of 3 fb(-1). It is found to be R-K/pi = 0.079 +/- 0.007 +/- 0.003, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Measurement of the forward Z boson production cross-section in pp collisions at root s=13 TeV. J. High Energy Phys., 09(9), 136–33pp.
Abstract: A measurement of the production cross-section of Z bosons in pp collisions at root s=13 TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range 2.0 < eta < 4.5, transverse momenta pT > 20 GeV and dilepton invariant mass in the range 60 < m(ll) < 120 GeV. The integrated cross-section from averaging the two final states is sigma(ll)(Z) = 194.3+/-0.9+/-3.3+/-7.6 pb, where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable phi(eta)*.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Measurement of the CKM angle gamma from a combination of LHCb results. J. High Energy Phys., 12(12), 087–59pp.
Abstract: A combination of measurements sensitive to the CKM angle gamma from LHCb is performed. The inputs are from analyses of time-integrated B+ -> DK+, B-0 -> DK*(0), B-0 -> DK+ pi(-) and B+ -> DK+ pi(+) pi(-) tree-level decays. In addition, results from a time-dependent analysis of B-s(0) -> (DsK +/-)-K--/+ decays are included. The combination yields = (72: 2(-7.3)(+6:8) 7 : 3)degrees, where the uncertainty includes systematic effects. The 95.5% confidence level interval is determined to be gamma is an element of [55.9, 85.2]degrees. A second combination is investigated, also including measurements from B+ -> DK+, B-0 -> DK*(0), B-0 -> DK+ pi(-) and B+ -> DK+ pi(+) pi decays, which yields compatible results.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Measurement of CP Violation in B-0 -> D+D- Decays. Phys. Rev. Lett., 117(26), 261801–10pp.
Abstract: The CP violation observables S and C in the decay channel B-0 -> D+D- are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb(-1). The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S = -0.54(-0.16)(+0.17) (stat) +/- 0.05(syst) ,C=0.26(-0.17)(+0.18) (stat) +/- 0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of Delta phi = -0.16(-0.21)(+0.19) rad.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Search for the CP-violating strong decays eta -> pi(+)pi(-) and eta ' (958) -> pi(+)pi(-). Phys. Lett. B, 764, 233–240.
Abstract: A search for the CP-violating strong decays eta -> pi(+)pi(-) and eta ' (958) -> pi(+)pi(-) has been performed using approximately 2.5 x 10(7) events of each of the decays D+ -> pi(+)pi(+)pi(-) and D-s(+) -> pi(+)pi(+)pi(-), recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb(-1) of pp collision data recorded during LHC Run 1 and 0.3fb(-1) recorded in Run 2. No evidence is seen for D-(s)(+) -> pi(+)eta((')) with eta((')) -> pi(+)pi(-), and upper limits at 90% confidence level are set on the branching fractions, B(eta -> pi(+)pi(-)) < 1.6 x 10(-5) and B(eta' -> pi(+)pi(-)) < 1.8 x 10(-5). The limit for the eta decay is comparable with the existing one, while that for the eta' is a factor of three smaller than the previous limit.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Search for Higgs-like bosons decaying into long-lived exotic particles. Eur. Phys. J. C, 76(12), 664–15pp.
Abstract: A search is presented for massive long-lived particles, in the 20-60 GeV/c(2) mass range with lifetimes between 5 and 100 ps. The dataset used corresponds to 0.62 fb(-1) of proton-proton collision data collected by the LHCb detector at root s = 7 TeV. The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140 GeV/c(2). No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Study of B-c(+) decays to the K+K-pi(+) final state and evidence for the decay B-c(+) -> chi(c0)pi(+). Phys. Rev. D, 94(9), 091102–10pp.
Abstract: A study of B-c(+) -> K+K-pi(+) decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 TeV. Evidence for the decay B-c(+) -> chi(c0)(K+K-)pi(+) is reported with a significance of 4.0 standard deviations, giving sigma(B-c(+))/sigma(B+) x B(B-c(+) -> chi(c0)pi+) = (9.8(-3.0)(+3.4)(stat) +/- 0.8(stat)) x 10(-6). Here B denotes a branching fraction while sigma(B-c(+)) and sigma(B+) are the production cross sections for B-c(+) and B+ mesons. An indication of (b) over barc weak annihilation is found for the region m(K-pi(+)) < 1.834 GeV/c(2), with a significance of 2.4 standard deviations.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of the B-s(0) -> J/Psi eta lifetime. Phys. Lett. B, 762, 484–492.
Abstract: Using a data set corresponding to an integrated luminosity of 3fb(-1), collected by the LHCb experiment in ppcollisions at centre-of-mass energies of 7 and 8TeV, the effective lifetime in the B-s(0) -> J/Psi eta decay mode, teff, is measured to be tau(eff) = 1.479 +/- 0.034 (stat)+/- 0.011 (syst) ps. Assuming CP conservation, tau(eff) corresponds to the lifetime of the light B-s(0) mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurements of long-range near-side angular correlations in root sNN=5TeV proton-lead collisions in the forward region. Phys. Lett. B, 762, 473–483.
Abstract: Two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-ofmass energy of root sNN= 5 TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, Delta eta, and relative azimuthal angle, Delta phi, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, Delta phi approximate to 0, is observed in the pseudorapidity range 2.0 < eta < 4.9. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to eta= 4.9. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). First study of the CP-violating phase and decay-width difference in B-s(0) -> psi(2S)phi decays. Phys. Lett. B, 762, 253–262.
Abstract: A time-dependent angular analysis of B-s(0) -> psi(2S)phi decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb(-1) collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the B-s(0) system are measured to be phi(s)=0.23(-0.28)(+0.29)+/- 0.02rad and Delta Gamma(s)=0.066(-0.044)(+0.041)+/- 0.007ps(-1), respectively, where the first uncertainty is statistical and the second systematic. This is the first time that phi s and Delta Gamma s have been measured in a decay containing the psi(2S) resonance.
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