CDF Collaboration(Aaltonen, T. et al), Cabrera, S., & Cuenca Almenar, C. (2010). Measurements of the top-quark mass using charged particle tracking. Phys. Rev. D, 81(3), 032002–21pp.
Abstract: We present three measurements of the top-quark mass in the lepton plus jets channel with approximately 1.9 fb(-1) of integrated luminosity collected with the CDF II detector using quantities with minimal dependence on the jet energy scale. One measurement exploits the transverse decay length of b-tagged jets to determine a top-quark mass of 166.9(-8.5)(+9.5)(stat) +/- 2.9(syst) GeV/c(2), and another the transverse momentum of electrons and muons from W-boson decays to determine a top-quark mass of 173.5(-8.9)(+8.8)(stat) +/- 3.8(syst) GeV/c(2). These quantities are combined in a third, simultaneous mass measurement to determine a top-quark mass of 170.7 +/- 6.3(stat) +/- 2.6(syst) GeV/c(2) .
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2011). Studies of tau(-) -> eta K- nu(tau) and tau(-) -> eta pi(-) nu(tau) at BABAR and a search for a second-class current. Phys. Rev. D, 83(3), 032002–10pp.
Abstract: We report on analyses of tau lepton decays tau(-) -> eta K- nu(tau) and tau(-) -> eta pi(-) nu(tau), with eta -> pi(+) pi(-) pi(0), using 470 fb(-1) of data from the BABAR experiment at PEP-II, collected at center-of-mass energies at and near the Y(4S) resonance. We measure the branching fraction for the tau(-) -> eta K- nu(tau) decay mode, B(tau(-) -> eta K- nu(tau)) = (1.42 +/- 0.11(stat) +/- 0.07(syst)) x 10(-4), and report a 95% confidence level upper limit for the second-class current process tau(-) -> eta pi(-) nu(tau), B(tau(-) -> eta pi(-) nu(tau)) < 9.9 x 10(-5).
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2013). Measurement of the Lambda(0)(b) lifetime and mass in the ATLAS experiment. Phys. Rev. D, 87(3), 032002–19pp.
Abstract: A measurement of the Lambda(0)(b) lifetime and mass in the decay channel Lambda(0)(b) -> J/psi (mu(+) mu(-))Lambda(0)(p pi(-)) is presented. The analysis uses a signal sample of about 2200 Lambda(0)(b) and (Lambda) over bar (0)(b) decays that are reconstructed in 4.9 fb(-1) of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Lambda(0)(b) lifetime and mass. They are measured to be tau(Lambda b) = 1.449 +/- 0.036(stat) +/- 0.017(syst) ps and m(Lambda b) = 5619.7 +/- 0.7(stat) +/- 1.1(syst) MeV.
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T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Escudero, L., Gomez-Cadenas, J. J., Izmaylov, A., Monfregola, L., et al. (2013). Evidence of electron neutrino appearance in a muon neutrino beam. Phys. Rev. D, 88(3), 032002–41pp.
Abstract: The T2K Collaboration reports evidence for electron neutrino appearance at the atmospheric mass splitting, vertical bar Delta m(32)(2)vertical bar approximate to 2.4 X 10(-3) eV(2). An excess of electron neutrino interactions over background is observed from a muon neutrino beam with a peak energy of 0.6 GeV at the Super-Kamiokande (SK) detector 295 km from the beam's origin. Signal and background predictions are constrained by data from near detectors located 280 m from the neutrino production target. We observe 11 electron neutrino candidate events at the SK detector when a background of 3.3 +/- 0.4(syst) events is expected. The background-only hypothesis is rejected with a p value of 0.0009 (3.1 sigma), and a fit assuming nu(mu) -> nu(e) oscillations with sin (2)2 theta(23) = 1, delta(CP) = 0 and vertical bar Delta m(32)(2)vertical bar = 2.4 X 10(-3) eV(2) yields sin (2)2 theta(13) = 0.088(-0.039)(+0.049)(stat + syst).
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2014). Search for a multi-Higgs-boson cascade in W(+)W(-)b(b)over-bar events with the ATLAS detector in pp collisions at root s=8 TeV. Phys. Rev. D, 89(3), 032002–23pp.
Abstract: A search is presented for new particles in an extension to the Standard Model that includes a heavy Higgs boson (H-0), an intermediate charged Higgs-boson pair (H-+/-), and a light Higgs boson (h(0)). The analysis searches for events involving the production of a single heavy neutral Higgs boson which decays to the charged Higgs boson and a W boson, where the charged Higgs boson subsequently decays into a W boson and the lightest neutral Higgs boson decaying to a bottom-antibottom-quark pair. Such a cascade results in a W-boson pair and a bottom-antibottom-quark pair in the final state. Events with exactly one lepton, missing transverse momentum, and at least four jets are selected from a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in proton-proton collisions at root s = 8 TeV at the LHC. The data are found to be consistent with Standard Model predictions, and 95% confidence-level upper limits are set on the product of cross section and branching ratio. These limits range from 0.065 to 43 pb as a function of H-0 and H-+/- masses, with m(h)o fixed at 125 GeV.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Dalitz plot analysis of B-0 -> (D)over-bar(0)pi(+)pi(-) decays. Phys. Rev. D, 92(3), 032002–40pp.
Abstract: The resonant substructures of B-0 --> (D) over bar (0)pi(+)pi(-) decays are studied with the Dalitz plot technique. In this study a data sample corresponding to an integrated luminosity of 3.0 fb(-1) of pp collisions collected by the LHCb detector is used. The branching fraction of the B-0 --> (D) over bar (0)pi(+)pi(-) decay in the region m((D) over bar (0)pi(+/-)) > 2.1 GeV/c(2) is measured to be (8.46 +/- 0.14 +/- 0.29 +/- 0.40) x 10(-4), where the first uncertainty is statistical, the second is systematic and the last arises from the normalization channel B-0 --> D*(2010)(-)pi(+). The pi(+)pi(-) S-wave components are modeled with the isobar and K-matrix formalisms. Results of the Dalitz plot analyses using both models are presented. A resonant structure at m((D) over bar (0)pi(-)) approximate to 2.8 GeV/c(2) is confirmed and its spin-parity is determined for the first time as J(P) = 3(-). The branching fraction, mass and width of this structure are determined together with those of the D-0*(2400)(-) and D-2*(2460)(-) resonances. The branching fractions of other B-0 --> (D) over bar (0)h(0) decay components with h(0) --> pi(+)pi(-) also reported. Many of these branching fraction measurements are the most precise to date. The first observation of the decays B0 --> (D) over bar (0)f(0)(500), B-0 --> (D) over bar (0)f(0)(980), B-0 --> (D) over bar (0)rho(1450), B-0 --> D-3(*)(2760)(-)pi(+) and the first evidence of B-0 --> (D) over bar (0)f(0)(2020) are presented.
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T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Izmaylov, A., Novella, P., Sorel, M., & Stamoulis, P. (2018). Measurement of the single pi(0) production rate in neutral current neutrino interactions on water. Phys. Rev. D, 97(3), 032002–13pp.
Abstract: The single pi(0) production rate in neutral current neutrino interactions on water in a neutrino beam with a peak neutrino energy of 0.6 GeV has been measured using the empty set, one of the subdetectors of the T2K near detector. The production rate was measured for data taking periods when the Pempty setD contained water (2.64 x 10(20) protons-on-target) and also periods without water (3.49 x 10(20) protons-on-target). A measurement of the neutral current single pi(0) production rate on water is made using appropriate subtraction of the production rate with water in from the rate with water out of the target region. The subtraction analysis yields 106 +/- 41 +/- 69 signal events where the uncertainties are statistical (stat.) and systematic (sys.) respectively. This is consistent with the prediction of 157 events from the nominal simulation. The measured to expected ratio is 0.68 +/- 0.26(stat) +/- 0.44(sys) +/- 0.12(flux). The nominal simulation uses a flux integrated cross section of 7.63 x 10(-39) cm(2) per nucleon with an average neutrino interaction energy of 1.3 GeV.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo, F. L., et al. (2018). Search for flavor-changing neutral currents in top quark decays t -> Hc and t -> Hu in multilepton final states in proton-proton collisions at root s=13 TeV with the ATLAS detector. Phys. Rev. D, 98(3), 032002–25pp.
Abstract: Flavor-changing neutral currents are not present in the Standard Model at tree level and are suppressed in loop processes by the unitarity of the Cabibbo-Kobayashi-Maskawa matrix; the corresponding rates for top quark decay processes are experimentally unobservable. Extensions of the Standard Model can generate new flavor-changing neutral current processes, leading to signals which, if observed, would be unambiguous evidence of new interactions. A data set conesponding to an integrated luminosity of 36.1 fb(-1) of pp collisions at a center-of-mass energy of root s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider is used to search for top quarks decaying to up or charm quarks with the emission of a Higgs boson, with subsequent Higgs boson decay to final states with at least one electron or muon. No signal is observed and limits on the branching fractions B(t -> Hc) < 0.16% and B(t -> Hu) < 0.19% at 95% confidence level are obtained (with expected limits of 0.15% in both cases).
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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). Measurement of lepton universality parameters in B+ -> K+ l+ l- and B0 -> K0 l+ l- decays. Phys. Rev. D, 108(3), 032002–46pp.
Abstract: A simultaneous analysis of the B thorn & RARR; K thorn e thorn e- and B0 & RARR; K & DBLBOND;0e thorn e- decays is performed to test muonelectron universality in two ranges of the square of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Measurement and interpretation of moments in inclusive semileptonic decays (B)over-bar -> Xcl(nu)over-bar. Phys. Rev. D, 81(3), 032003–25pp.
Abstract: We present results for the moments of observed spectra in inclusive semileptonic B-meson decays to charm hadrons (B) over bar -> X(c)l(-)(nu) over bar. Moments of the hadronic-mass and the combined mass-and-energy spectra for different minimum electron or muon momenta between 0.8 and 1: 9 GeV/c are obtained from a sample of 232 X 10(6) Gamma(4S) -> B (B) over bar events, collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We also present a reevaluation of the moments of electron-energy spectra and partial decay fractions B((B) over bar -> X(c)e(-)(nu) over bar) for minimum electron momenta between 0.6 and 1: 5 GeV/c based on a sample of 51 X 10(6) Gamma(4S) -> B (B) over bar events. The measurements are used for the extraction of the total decay fraction, the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V-cb vertical bar, the quark masses m(b) and m(c), and four heavy-quark QCD parameters in the framework of a Heavy-Quark Expansion (HQE). We find B((B) over bar -> X(c)l(-)(nu) over bar = (10.64 +/- 0.17 +/- 0.06)% and vertical bar V-cb vertical bar = (42.05 +/- 0.45 +/- 0.70) X 10(-3).
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