LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Production of associated Y and open charm hadrons in pp collisions at root s=7 and 8 TeV via double parton scattering. J. High Energy Phys., 07(7), 052–36pp.
Abstract: Associated production of bottomonia and open charm hadrons in pp collisions at root s = 7 and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb(-1) accumulated with the LHCb detector. The observation of five combinations, Y(1S)D-0, Y(2S)D-0, Y(1S)D+, Y(2S)D+ and Y(1S)D (s) (+) , is reported. Production crosssections are measured for Y(1S)D-0 and Y(1S)D+ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism.
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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). Measurement of the CP Violation Parameter A(r) in D-0 -> K+K- and D-0 -> pi(+)pi(-) Decays. Phys. Rev. Lett., 118(26), 261803–9pp.
Abstract: Asymmetries in the time-dependent rates of D-0 -> K+K- and D-0 -> pi(+)pi(-)decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3 fb(-1). The asymmetries in effective decay widths between D-0 and (D) over bar (0) decays, sensitive to indirect CP violation, are measured to be A(r)(K+K-) = (-0.30 +/- 0.32 0.10) x 10(-3) and A(r) pi(+)pi(-)) = (0.46 +/- 0.58 +/- 0.12) x 10(-3), where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2022). Search for an Axionlike Particle in B Meson Decays. Phys. Rev. Lett., 128(13), 131802–8pp.
Abstract: Axionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing B meson decays. We report herein a search for an ALP, a, in the reaction B-+/- -> K(+/-)a, a -> gamma gamma using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range 0.175 GeV < m(a) < 4.78 GeV.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Observation of the Y(1(3)D(J)) bottomonium state through decays to pi(+)pi Y-(1S). Phys. Rev. D, 82(11), 111102–7pp.
Abstract: Based on 122 X 10(6)Y(3S) events collected with the BABAR detector, we have observed the Y(1(3)D(J)) bottomonium state through the Y(3S) -> gamma gamma Y(1(3)D(J)) -> gamma gamma pi(+)pi Y-(1S) decay chain. The significance for the J = 2 member of the Y(1(3)D(J)) triplet is 5.8 standard deviations including systematic uncertainties. The mass of the J = 2 state is determined to be 10 164.5 +/- 0.8(stat) +/- 0.5(syst) MeV/c(2). We use the pi(+)pi(-) invariant mass distribution to confirm the consistency of the observed state with the orbital angular momentum assignment of the Y(1(3)D(J)).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2015). Measurement of the D-0 -> pi(-)e(+)nu(e) differential decay branching fraction as a function of q(2) and study of form factor parametrizations. Phys. Rev. D, 91(5), 052022–25pp.
Abstract: Based on a sample of 500 million e(+)e(-) -> c (c) over bar events recorded by the BABAR detector at c. m. energies of close to 10.6 GeV, we report on a study of the decay D0 ->pi(-)e(+)nu(e). We measure the ratio of branching fractions, R-D = B(D-0 -> pi(-)e(+)nu(e))/beta(D-0 -> K-pi(+)) = 0.0713 +/- 0.0017(stat) +/- 0.0024(syst), and use the present world average for B(D-0 -> K-pi(+)) to obtain B(D-0 -> pi(-)e(+)nu e) = (2.770 +/- 0.068(stat) +/- 0.092(syst) +/- 0.037(ext)) x 10(-3) where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on q(2), the four-momentum transfer squared between the D and the pi meson, is compared to various theoretical predictions for the hadronic form factor, f(+,D)(pi)(q(2)), and the normalization vertical bar V-cd vertical bar x f(+,D)(pi)(q(2) = 0) = 0.1374 +/- 0.0038(stat) +/- 0.0022(sys)t +/- 0.0009(ext). is extracted from a fit to data. Using the most recent LQCD prediction of f(+,D)(pi)(q(2) = 0) = 0.666 +/- 0.029, we obtain vertical bar V-cd vertical bar = 0.206 +/- 0.007(exp) +/- 0.009(LQCD). Assuming, instead, vertical bar V-cd vertical bar = vertical bar V-us vertical bar = 0.2252 +/- 0.0009, we obtain f(+,D)(pi)(q(2) = 0) = 0.610 +/- 0.020(exp) +/- 0.005(ext). The q(2) dependence of f(+,D)(pi)(q(2)) is compared to a variety of multipole parametrizations. This information is applied to B-0 -> pi(-)e(+)nu(e) decays and, combined with an earlier B-0 -> pi(-)e(+)nu(e) measurement by BABAR, is used to derive estimates of vertical bar V-ub vertical bar.
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