LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of CP Violation in B-0 -> J/psi K-S(0) Decays. Phys. Rev. Lett., 115(3), 031601–9pp.
Abstract: Measurements are presented of the CP violation observables S and C in the decays of B-0 and (B) over bar (0) mesons to the J/psi K-S(0) final state. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, and contains a total of 41 560 selected B-0 and (B) over bar (0) decays. The analysis of the time evolution of these decays yields S = 0.731 +/- 0.035(stat) +/- 0.020(syst) and C = -0.038 +/- 0.032(stat) +/- 0.005(syst). In the standard model, S equals sin(2 beta) to a good level of precision. The values are consistent with the current world averages and with the standard model expectations.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Measurement of partial branching fractions of inclusive charmless B meson decays to K+, K-0, and pi(+). Phys. Rev. D, 83(3), 031103–8pp.
Abstract: We present measurements of partial branching fractions of B -> K+ X, B -> (KX)-X-0, and B -> pi(+) X, where X denotes any accessible final state above the endpoint for B decays to charmed mesons, specifically for momenta of the candidate hadron greater than 2.34 (2.36) GeV for kaons (pions) in the B rest frame. These measurements are sensitive to potential new-physics particles which could enter the b -> s(d) loop transitions. The analysis is performed on a data sample consisting of 383 X 10(6)B (B) over bar pairs collected with the BABAR detector at the PEP-II e(+)e(-) asymmetric energy collider. We observe the inclusive B -> pi(+) X process, and we set upper limits for B -> K+ X and B -> (KX)-X-0. Our results for these inclusive branching fractions are consistent with those of known exclusive modes, and exclude large enhancements due to sources of new physics.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2011). Search for CP violation using T-odd correlations in D(+) -> K(+)K(S)(0) pi(+)pi(-) and D(s)(+) -> K(+)K(S)(0) pi(+)pi(-) decays. Phys. Rev. D, 84(3), 031103–9pp.
Abstract: We search for CP violation in a sample of 20 000 Cabibbo-suppressed decays, D(+) -> K(+)K(S)(0)pi(+)pi(-), and 30 000 Cabibbo-favored decays, D(+) -> K(+)K(S)(0)pi(+)pi(-). We use 520 fb(-1) of data recorded by the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider operating at center of mass energies near 10.6 GeV. We search for CP violation in the difference between the T-odd asymmetries obtained using triple product correlations of the D(+)(D(s)(+)) and D(-)(D(s)(-)) decays, respectively. The T violation parameter values obtained are A(T)(D(+)) = (-12.0 +/- 10.0(stat) +/- 4.6(syst)) x 10(-3) and A(T)(D(s)(+)) = (-13.6 +/- 7.7(stat) +/- 3.4(syst)) x 10(-3), which are consistent with the standard model expectations.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Multidifferential study of identified charged hadron distributions in Z-tagged jets in proton-proton collisions at vs=13 TeV. Phys. Rev. D, 108(3), L031103–13pp.
Abstract: Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a Z boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 < pT < 100 GeV and in the pseudorapidity range 2.5 < ? < 4. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb(-1). Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Observation of the decay (B)over-bar(0) -> Lambda(+)(c)(p)over-bar pi(0). Phys. Rev. D, 82(3), 031102–8pp.
Abstract: In a sample of 467 x 10(6) B (B) over bar pairs collected with the BABAR detector at the PEP- II collider at SLAC we have observed the decay (B) over bar (0) -> Lambda(+)(c)(p) over bar pi(0) and measured the branching fraction to be (1.94 +/- 0.17 +/- 0.14 +/- 0.50 x 10(-4), where the uncertainties are statistical, systematic, and the uncertainty on the Lambda(+)(c) -> pK(-)pi(+) branching fraction, respectively. We determine an upper limit of 1.5 x 10(-6) at 90% C.L. for the product branching fraction B((B) over bar (0) -> Sigma(+)(c) (2455)(p) over bar) x B(Lambda(+)(c) -> pK(-) pi(+)). Furthermore, we observe an enhancement at the threshold of the invariant mass of the baryon- antibaryon pair.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Search for CP violation in the decay tau(-) -> pi K-(s)0 (>= 0 pi(0))v(tau). Phys. Rev. D, 85(3), 031102–8pp.
Abstract: We report a search for CP violation in the decay tau(-) -> pi K--(s)0 (>= 0 pi(0))v(tau) using a data set of 437 x 10(6) tau-lepton pairs, corresponding to an integrated luminosity of 476 fb(-1), collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) storage rings. The CP-violating decay-rate asymmetry is determined to be (-0.36 +/- 0.23 +/- 0.11)% approximately 2.8 standard deviations from the standard model prediction of (0.36 +/- 0.01)%.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Search for di-muon decays of a low-mass Higgs boson in radiative decays of the Gamma(1S). Phys. Rev. D, 87(3), 031102–8pp.
Abstract: We search for di-muon decays of a low-mass Higgs boson (A(0)) produced in radiative Gamma(1S) decays. The Gamma(1S) sample is selected by tagging the pion pair in the Gamma(2S, 3S) -> pi(+)pi(-) Gamma(1S) transitions, using a data sample of 92.8 x 10(6) Gamma(2S) and 116.8 x 10(6) Gamma(3S) events collected by the BABAR detector. We find no evidence for A(0) production and set 90% confidence level upper limits on the product branching fraction B(Gamma(1S) -> gamma Lambda(0)) x B(Lambda(0)->mu(+)mu(-)) in the range of (0.28 – 9.7) x 10(-6) for 0.212 <= m(A0) <= 9.20 GeV/c(2). The results are combined with our previous measurements of Gamma(2S,3S) -> gamma Lambda(0), Lambda(0) -> mu(+)mu(-) to set limits on the effective coupling of the b quark to the Lambda(0).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2013). Evidence of B+ -> tau(+)nu decays with hadronic B tags. Phys. Rev. D, 88(3), 031102–9pp.
Abstract: We present a search for the decay B+ -> tau(+)nu using 467.8 x 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with one completely reconstructed B- in the hadronic decay mode (B- -> D-(*X-)0(-) and B- -> J/psi X-). We examine the rest of the event to search for a B+ -> tau(+)nu decay. We identify the tau(+) lepton in the following modes: tau(+) -> e(+)nu(nu) over bar, tau(+) -> mu(+)nu(nu) over bar, tau(+) -> pi(+)(nu) over bar and tau(+) -> rho(+)(nu) over bar. We find an excess of events with respect to the expected background, which excludes the null signal hypothesis at the level of 3.8 sigma (including systematic uncertainties) and corresponds to a branching fraction value of B(B+ -> tau(+)nu) = (1.83(-0.49)(+0.53)(stat) +/- 0.24(syst)) x 10(-4).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2015). Observation of the baryonic decay (B)over-bar(0) -> Lambda(+)(c)(p)over-barK(-)K(+). Phys. Rev. D, 91(3), 031102–7pp.
Abstract: We report the observation of the baryonic decay (B) over bar (0) -> Lambda(+)(c)(p) over barK(-)K(+) using a data sample of 471 x 10(6) B (B) over bar pairs produced in e(+)e(-) annihilations at root s = 10.58 GeV. This data sample was recorded with the BABAR detector at the PEP- II storage ring at SLAC. We find B((B) over bar (0) -> Lambda(+)(c)(p) over barK(-)K(+)) = (2.5 +/- 0.4((stat)) +/- 0.2((syst)) +/- 0.6(B(Lambda c+)) ) x 10(-5) where the uncertainties are statistical, systematic, and due to the uncertainty of the Lambda(+)(c) -> (p) over barK(-)pi(+) branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay (B) over bar (0) -> Lambda(+)(c)(p) over bar phi, we determine the upper limit B((B) over bar (0) -> Lambda(+)(c)(p) over bar phi) < 1.2 x 10(-5) at 90% confidence level.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Measurement of b hadron fractions in 13 TeV pp collisions. Phys. Rev. D, 100(3), 031102–11pp.
Abstract: The production fractions of (B) over bar (0)(s) and Lambda(0)(b) hadrons, normalized to the sum of B- and (B) over bar (0) fractions, arc measured in 13 TeV pp collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of 1.67 fb(-1). These ratios, averaged over the b hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are 0.122 +/- 0.006 for (B) over bar (0)(s) and 0.259 +/- 0.018 for Lambda(0)(b) where the uncertainties arise from both statistical and systematic sources. The Lambda(0)(b) ratio depends strongly on transverse momentum, while the (B) over bar (0)(s) ratio shows a mild dependence. Neither ratio shows variations with pseudorapidity. The measurements are made using semileptonic decays to minimize theoretical uncertainties. In addition, the ratio of D+ to D-0 mesons produced in the sum of (B) over bar (0) and B- semileptonic decays is determined as 0.359 +/- 0.006 +/- 0.009, where the uncertainties are statistical and systematic.
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