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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Study of eta-eta ' mixing from measurement of B-(s)(0) -> J/psi eta((')) decay rates. J. High Energy Phys., 01(1), 024–24pp.
Abstract: A study of B and B-s(0) meson decays into J/psi eta and J/psi eta' final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, collected by the LCHb experiment and corresponding to 3.0 fb(-1) of integrated luminosity. The decay B-0 -> J/psi eta' is observed for the first time. The following ratios of branching fractions are measured: B(B-0 -> J psi eta')/B(B-s(0) -> J psi eta') = (2.28 +/- 0.65 (stat) +/- 0.010 (syst) +/- 0.13 (f(s)/f(d)) x 10(-2) , B(B-0 -> J psi eta')/B(B-s(0) -> J psi eta') = (1.85 +/- 0.65 (stat) +/- 0.09 (syst) +/- 0.11 (f(s)/f(d)) x 10(-2) where the third uncertainty is related to the present knowledge of f(s)/f(d), the ratio between the probabilities for a b quark to form a B-s(0) or a B-0 meson. The branching fraction ratios are used to determine the parameters of eta-eta' meson mixing. In addition, the first evidence for the decay B-s(0) -> psi(2S)' is reported, and the relative branching fraction is measured, B(B-s(0) -> psi(2S)eta')/B(B-s(0) -> J psi eta') = (38.7 +/- 9.0 (stat) +/- 1.3 (syst) +/- 0.9(B)) x 10(-2), where the third uncertainty is due to the limited knowledge of the branching fractions of J/psi and psi(2S) mesons.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Precise measurements of the properties of the B-1(5721)(0,+) and B-2*(5747)(0,+) states and observation of B-+,B-0 pi(-,+) mass structures. J. High Energy Phys., 04(4), 024–27pp.
Abstract: Invariant mass distributions of B (+) pi (-) and B (0) pi (+) combinations are investigated in order to study excited B mesons. The analysis is based on a data sample corresponding to 3.0 fb(-1) of pp collision data, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Precise measurements of the masses and widths of the B (1)(5721)(0,+) and B (2)(5747)(0,+) states are reported. Clear enhancements, particularly prominent at high pion transverse momentum, are seen over background in the mass range 5850-6000 MeV in both B (+) pi (-) and B (0) pi (+) combinations. The structures are consistent with the presence of four excited B mesons, labelled B (J) (5840)(0,+) and B (J) (5960)(0,+), whose masses and widths are obtained under different hypotheses for their quantum numbers.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Evidence for the H -> b(b)over-bar decay with the ATLAS detector. J. High Energy Phys., 12(12), 024–71pp.
Abstract: A search for the decay of the Standard Model Higgs boson into a b (b) over bar pair when produced in association with a W or Z boson is performed with the ATLAS detector. The analysed data, corresponding to an integrated luminosity of 36.1 fb(-1), were collected in proton-proton collisions in Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV. Final states containing zero, one and two charged leptons (electrons or muons) are considered, targeting the decays Z -> vv, W -> lv and Z -> ll. For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed significance of 3.5 standard deviations, compared to an expectation of 3.0 standard deviations. This excess provides evidence for the Higgs boson decay into b-quarks and for its production in association with a vector boson. The combination of this result with that of the Run 1 analysis yields a ratio of the measured signal events to the Standard Model expectation equal to 0.90 +/- 0.18(stat.)(-0.19)(+0.21)(syst.). Assuming the Standard Model production cross-section, the results are consistent with the value of the Yukawa coupling to b-quarks in the Standard Model.
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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). Study of B-s(0) -> J/psi pi(+)pi-K+K- decays. J. High Energy Phys., 02(2), 024–34pp.
Abstract: The decays B-s(0) -> J/psi pi(+)pi-K+K- are studied using a data set corresponding to an integrated luminosity of 9 fb(-1), collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13TeV. The decays B-s(0) -> J/psi K*(K) over bar *0 and B-s(0) -> chi(c1)(3872)K+K-, where the K+K- pair does not originate from a phi meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate chi(c1)(3872)phi, J/psi K*0 (K) over bar *0, psi(2S)phi and chi(c1)(3872)K+K- states are reported. A structure, denoted as X(4740), is observed in the J/psi phi mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be m(X(4740)) = 4741 +/- 6 +/- 6 MeV/c(2), Gamma(X(4740)) = 53 +/- 15 +/- 11MeV, where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the B-s(0) meson is performed and gives a value of m(Bs)(0) = 5366.98 +/- 0.07 +/- 0.13MeV/c(2).
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Search for CP violation in D (+/-) -> (KSK +/-)-K-0 and D-s(+/-) -> K-S(0)pi(+/-) decays. J. High Energy Phys., 10(10), 025–19pp.
Abstract: A search for CP violation in Cabibbo-suppressed D (+/-) -> aEuro parts per thousand K (S) (0) K (+/-) and D (s) (+/-) -> aEuro parts per thousand K (S) (0) pi (+/-) decays is performed using pp collision data, corresponding to an integrated luminosity of 3 fb, recorded by the LHCb experiment. The individual CP-violating asymmetries are measured to be <Equation ID=“Equa”> <MediaObject> </MediaObject> </Equation> assuming that CP violation in the Cabibbo-favoured decays is negligible. A combination of the measured asymmetries for the four decay modes D ((s)) (+/-) -> aEuro parts per thousand K (S) (0) K (+/-) and D ((s)) (+/-) -> aEuro parts per thousand K (S) (0) pi (+/-) gives the sum <Equation ID=“Equb”> <MediaObject> </MediaObject> </Equation> In all cases, the first uncertainties are statistical and the second systematic. The results represent the most precise measurements of these asymmetries to date and show no evidence for CP violation.
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