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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). Observation of the decay B-s(0) -> (D)over-bar(0)K (+) K-. Phys. Rev. D, 98(7), 072006–19pp.
Abstract: The first observation of the B-s(0) -> (D) over bar K-0 (+) K- decay is reported, together with the most precise branching fraction measurement of the mode B-0 -> (D) over bar K-0 (+) K- The results are obtained from an analysis of pp collision data corresponding to an integrated luminosity of 3.0 fb(-1). The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, The branching fraction of the B-0 -> (D) over bar K-0 (+) K- decay is measured relative to that of the decay B-0 -> (D) over bar (0)pi (+) pi(-) to be B(B-0 -> (D) over bar K-0 (+) K-)/B(B-0 -> (D) over bar (0)pi (+) pi(-)) =(69 +/- 0.4 +/- 0.3)%, where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the B-s(0) -> (D) over bar K-0 (+) K- decay mode relative to that of the corresponding B-0 decay is B(B-0 -> (D) over bar K-0 (+) K-)/B(B-0 -> (D) over bar K-0 (+) K-) = (93.0 +/- 809 +/- 6.9)%. Using the known branching fraction of B-0 -> (D) over bar (0)pi (+) pi(-), the values of B-0 -> (D) over bar K-0 (+) K- = (6.1 +/- 0.4 +/- 0.3 +/- 0.3) x 10(-5) and B(B-s(0) -> (D) over bar K-0 (+) K- = (5.7 +/- 0.5 +/- 0.4 +/- 0.5) x 10(-5) are obtained, where the third uncertainties arise from the branching fraction of the decay modes B-0 -> (D) over bar (0)pi (+) pi(-) and B-0 -> (D) over bar K-0 (+) K-, respectively.
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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). Measurement of Angular and CP Asymmetries in D-0 -> pi(+) pi(-) mu(+) mu(-) and D-0 -> K+ K- mu(+) mu(-) Decays. Phys. Rev. Lett., 121(9), 091801–10pp.
Abstract: The first measurements of the forward-backward asymmetry of the dimuon pair (A(FB)), the triple-product asymmetry (A(2 phi)), and the charge-parity-conjugation asymmetry (A(CP)), in D-0 -> pi(+) pi(-) mu(+) mu(-) and -> D-0 -> K+ K- mu(+) mu(-) decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb(-1). The asymmetries are measured to be A(FB) (D-0 -> pi(+) pi(-) mu(+) mu(-)) = (3.3 +/- 3.7 +/- 0.6)%, A(2 phi) (D-0 -> pi(+) pi(-) mu(+) mu(-)) = (-0.6 +/- 3.7 +/- 0.6)%, A(CP) (D-0 -> pi(+) pi(-) mu(+) mu(-)) = (4.9 +/- 3.8 +/- 0.7)%, A(FB) (D-0 -> K+ K- mu(+) mu(-)) = (0 +/- 11 +/- 2 +/-)%, A(2 phi) (D-0 -> K+ K- mu(+) mu(-)) = (9 +/- 11 +/- 1)%, A(CP) (D-0 -> K+ K- mu(+) mu(-)) = (0 +/- 11 +/- 2)% where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent 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). Observation of the decay (B)over-bar(s)(0) -> chi(c2) K+K- in the phi mass region. J. High Energy Phys., 08(8), 191–20pp.
Abstract: The (B) over bar (0)(s) -> chi(c2) K+ K- decay mode is observed and its branching fraction relative to the corresponding chi(c1) decay mode, in a +/- 15MeV/c(2) window around the phi mass, is found to be B ((B) over bar (0)(s) -> chi(c2) K+ K-)/B((B) over bar (0)(s) -> chi(c1) K+ K-) = (17.1 +/- 3.1 +/- 0.4 +/- 0.9)% where the fi rst uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative chi(c) decays. The decay mode (B) over bar (0)(s) -> chi(c1) K+ K- allows the B-s(0) mass to be measured as m(B-s(0)) = 5366.83 +/- 0.25 +/- 0.27MeV/c(2), where the fi rst uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the B-s(0) mass is made.
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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). Search for beautiful tetraquarks in the Î¥(1S)(+-) invariant-mass spectrum. J. High Energy Phys., 10(10), 086–22pp.
Abstract: The Υ(1 S) invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two b quarks, X bbbb. The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies s = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb. No signi fi cant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the X bbbb state. The limits are set in the fi ducial volume where all muons have pseudorapidity in the range [2 : 0; 5 : 0], and the X bbbb state has rapidity in the range [2 : 0; 4 : 5] and transverse momentum less than 15 GeV/c.
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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). Observation of the decay Lambda(0)(b) -> psi(2S)p pi(-). J. High Energy Phys., 08(8), 131–18pp.
Abstract: The Cabibbo-suppressed decay Lambda(0)(b) -> psi(2S)p pi(-) is observed for the fi rst time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb(-1) of integrated luminosity at centre-of-mass energies of 7, 8 and 13TeV, respectively. The psi(2S) mesons are reconstructed in the mu(+)mu(-) fi nal state. The branching fraction with respect to that of the Lambda(0)(b) -> psi(2S)pK(-) decay mode is measured to be B (Lambda(0)(b) -> psi(2S)p pi(-))/B (Lambda(0)(b) -> psi(2S)pK(-)) = (11.44 +/- 1.3 +/- 0.2)%, where the fi rst uncertainty is statistical and the second is systematic. The psi(2S) p and psi(2S)pi(-) mass spectra are investigated and no evidence for exotic resonances is found.
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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). Measurement of Z -> tau(+)tau(-) production in proton-proton collisions at root s=8 TeV. J. High Energy Phys., 09(9), 159–19pp.
Abstract: A measurement of Z -> tau(+)tau(-) production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb(-1), from pp collisions at root s = 8 TeV collected by the LHCb experiment. The tau(+)tau(-)candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for Z bosons with invariant mass between 60 and 120 GeV/c(2), which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5. The cross-section is determined to be sigma(pp -> Z -> tau+tau-)= 95.8 +/- 2.1 +/- 4.6 +/- 0.2 +/- 1.1 pb, where the first uncertainty is statistical, the second is systematic, the third is due to the LHC beam energy uncertainty, and the fourth to the integrated luminosity uncertainty. This result is compatible with NNLO Standard model predictions. The ratio of the cross-sections for Z -> tau(+)tau(- )to Z -> mu(+)mu(-) (Z -> e(+)e(-)), determined to be 1.01 +/- 0.05 (1.02 +/- 0.06), is consistent with the lepton-universality hypothesis in Z decays.
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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). Central exclusive production of J/psi and (2S) mesons in pp collisions at root s=13 TeV. J. High Energy Phys., 10(10), 167–27pp.
Abstract: Measurements are reported of the central exclusive production of J= and ( 2 S) mesons in pp collisions at a centre- of- mass energy of 13 TeV. Backgrounds are signi fi cantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross- sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2 : 0 < < 4 : 5, are measured to be The fi rst uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross- sections are also measured di ff erentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross- sections are derived and compared to previous experiments, and a deviation from a pure power- law extrapolation of lower energy data is observed.
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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). Measurement of the Lifetime of the Doubly Charmed Baryon Xi(++)(cc). Phys. Rev. Lett., 121(5), 052002–10pp.
Abstract: The first measurement of the lifetime of the doubly charmed baryon Xi(++)(cc) is presented, with the signal reconstructed in the final state Lambda K-+(c)-pi(+)pi(+). The data sample used corresponds to an integrated luminosity of 1.7 fb(-1), collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The Xi(++)(cc) lifetime is measured to be 0.256(-0.022)(+0.024) (stat) +/- 0.014(syst) ps.
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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). Measurement of the time-integrated CP asymmetry in D (0) -> K (S) (0) K (S) (0) decays. J. High Energy Phys., 11(11), 048–19pp.
Abstract: A measurement of the time-integrated CP asymmetry in D (0) -> K (S) (0) K (S) (0) decays is reported. The data correspond to an integrated luminosity of about 2 fb(-1) collected in 2015-2016 by the LHCb collaboration in pp collisions at a centre-of-mass energy of 13 TeV. The D (0) candidate is required to originate from a D (*+) -> D (0) pi (+) decay, allowing the determination of the flavour of the D (0) meson using the pion charge. The D (0) -> K (+) K (-) decay, which has a well measured CP asymmetry, is used as a calibration channel. The CP asymmetryfor D (0) -> K (S) (0) K (S) (0) is measured to be where the first uncertainty is statistical and the second is systematic. This result is combined with the previous LHCb measurement at lower centre-of-mass energies to obtain A(CP) (D-0 -> K-S(0) K-S(0)) = (2.3 +/- 2.8 +/- 0.9)%.
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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). Measurement of the CKM angle gamma using B-+/- -> DK +/- with D -> K-S(0)pi(+)pi(-), (KSK+K-)-K-0 decays. J. High Energy Phys., 08(8), 176–36pp.
Abstract: A binned Dalitz plot analysis of B-+/- -> DK +/- decays, with D -> K-S(0)pi(+)pi(-) and D -> (KSK+K-)-K-0, is used to perform a measurement of the CP-violating observables x(+/-) and y(+/-), which are sensitive to the Cabibbo-Kobayashi-Maskawa angle gamma. The analysis is performed without assuming any D decay model, through the use of information on the strong-phase variation over the Dalitz plot from the CLEO collaboration. Using a sample of proton-proton collision data collected with the LHCb experiment in 2015 and 2016, and corresponding to an integrated luminosity of 2.0 fb(-1), the values of the CP violation parameters are found to be x = (9.0 +/- 1.7 +/- 0.7 +/- 0.4) x 10(-2), y = (2.1 +/- 2.2 +/- 0.5 +/- 1.1) x 10(-2), x(+) = (-7.7 +/- 1.9 +/- 0.7 +/- 0.4) x 10(-2), and y(+) = (-1.0 +/- 1.9 +/- 0.4 +/- 0.9) x10(-2). The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the strong-phase measurements. These values are used to obtain gamma = (87(+)(12)(+11))degrees, r(B) = 0.086(-)(0.1)(43)(+0.013), and delta(B) = (101 +/- 11), where r(B) is the ratio between the suppressed and favoured B-decay amplitudes and delta(B) is the corresponding strong-interaction phase difference. This measurement is combined with the result obtained using 2011 and 2012 data collected with the LHCb experiment, to give gamma = (80(-9)(+10))degrees, r(B) = 0.080 +/- 0.011, and delta(B) = (110 +/- 10)degrees.
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