|
|
LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Determination of the X(3872) Meson Quantum Numbers. Phys. Rev. Lett., 110(22), 222001–8pp.
Abstract: The quantum numbers of the X(3872) meson are determined to be J(PC) = 1(++) based on angular correlations in B+ -> X(3872)K+ decays, where X(3872) -> pi(+) pi(-) j/psi and J/psi -> pi(+) mu(-). The data correspond to 1.0 fb(-1) of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements J(PC) = 2(-+) is rejected with a confidence level equivalent to more than 8 Gaussian standard deviations using a likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). First Measurement of the CP-Violating Phase in B-s(0) -> phi phi Decays. Phys. Rev. Lett., 110(24), 241802–8pp.
Abstract: A first flavor-tagged measurement of the time-dependent CP-violating asymmetry in B-s(0) -> phi phi decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between B-s(0)-(B) over bar (0)(s) mixing and the b -> s (s) over bars gluonic penguin decay amplitude. Using a sample of pp collision data corresponding to an integrated luminosity of 1.0 fb(-1) and collected at a center-of-mass energy of 7 TeV with the LHCb detector, 880 B-s(0) -> phi phi signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46, -0.76] rad at a 68% confidence level. The p value of the standard model prediction is 16%.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of forward Z -> e(+)e(-) production at root s=8 TeV. J. High Energy Phys., 05(5), 109–21pp.
Abstract: A measurement of the cross-section for Z-boson production in the forward region of pp collisions at 8 TeV centre-of-mass energy is presented. The measurement is based on a sample of Z -> e(+)e(-) decays reconstructed using the LHCb detector, corresponding to an integrated luminosity of 2.0 fb(-1). The acceptance is defined by the requirements 2.0 < eta < 4.5 and p(T) > 20 GeV for the pseudorapidities and transverse momenta of the leptons. Their invariant mass is required to lie in the range 60-120 GeV. The cross-section is determined to be sigma(pp -> Z -> e(+)e(-)) = 93.81 +/- 0.41(stat) +/- 1.48(syst) +/- 1.14(lumi) pb, where the first uncertainty is statistical and the second reflects all systematic effects apart from that arising from the luminosity, which is given as the third uncertainty. Differential cross-sections are presented as functions of the Z-boson rapidity and of the angular variable phi*, which is related to the Z-boson transverse momentum.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Observation of the suppressed ADS modes B-+/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)K-+/- and B-+/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)pi(+/-). Phys. Lett. B, 723(1-3), 44–53.
Abstract: An analysis of and B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays is presented where the D meson is reconstructed in the four-body final state K-+/-pi(-/+)pi(+)pi(-). Using LHCb data corresponding to an integrated luminosity of 1.0 fb(-1), first observations are made of the suppressed ADS modes B-+/- ->[pi K-+/-(-/+)pi(+)pi(-)](D)K-+/- and B +/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)pi(+/-) with a significance of 5.1 sigma and greater than 10 sigma, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B-+/- -> DK +/- amplitudes is determined to be r(B)(K) = 0.097 +/- 0.011.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Observation of the decay B-c(+) -> psi(2S)pi(+). Phys. Rev. D, 87(7), 071103–7pp.
Abstract: The decay B-c(+) -> psi(2S)pi(+) with psi(2S) -> mu(+)mu(-) is observed with a significance of 5.2 sigma using pp collision data corresponding to an integrated luminosity of 1.0 fb(-1) collected by the LHCb experiment. The branching fraction of B-c(+) -> psi(2S)pi(+) decays relative to that of the B-c(+) -> J/psi pi(+) mode is measured to be B(B-c(+) -> psi(2S)pi(+))/B(B-c(+) -> J/psi pi(+)) = 0.250 +/- 0.068(stat) +/- 0.014(syst) +/- 0.006(B). The last term is the uncertainty on the ratio B(psi(2S) -> mu(+)mu(-))/B(J/psi -> mu(+)mu(-)).
|
|
