CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Observation of single top quark production and measurement of vertical bar V-tb vertical bar with CDF. Phys. Rev. D, 82(11), 112005–59pp.
Abstract: We report the observation of electroweak single top quark production in 3: 2 fb(-1) of p (p) over bar collision data collected by the Collider Detector at Fermilab at root s = 1.96 TeV. Candidate events in the W + jets topology with a leptonically decaying W boson are classified as signal-like by four parallel analyses based on likelihood functions, matrix elements, neural networks, and boosted decision trees. These results are combined using a super discriminant analysis based on genetically evolved neural networks in order to improve the sensitivity. This combined result is further combined with that of a search for a single top quark signal in an orthogonal sample of events with missing transverse energy plus jets and no charged lepton. We observe a signal consistent with the standard model prediction but inconsistent with the background-only model by 5.0 standard deviations, with a median expected sensitivity in excess of 5.9 standard deviations. We measure a production cross section of 2.3-(+0.6)(0.5) (stat + sys) pb, extract the value of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-tb vertical bar = 0.91(-0.11)(+0.11) (stat + sys) +/- 0.07 (theory), and set a lower limit vertical bar V-tb vertical bar > 0.71 at the 95% C. L., assuming m(t) = 175 GeV/c(2).
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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Measurement of the WW plus WZ production cross section using a matrix element technique in lepton plus jets events. Phys. Rev. D, 82(11), 112001–15pp.
Abstract: We present a measurement of the WW + WZ production cross section observed in a final state consisting of an identified electron or muon, two jets, and missing transverse energy. The measurement is carried out in a data sample corresponding to up to 4.6 fb(-1) of integrated luminosity at root s = 1.96 TeV collected by the CDF II detector. Matrix element calculations are used to separate the diboson signal from the large backgrounds. The WW + WZ cross section is measured to be 17.4 +/- 3.3 pb in agreement with standard model predictions. A fit to the dijet invariant mass spectrum yields a compatible cross section measurement.
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CDF Collaboration(Aaltonen, T. et al), Cabrera, S., & Cuenca Almenar, C. (2010). Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV using soft electron b-tagging. Phys. Rev. D, 81(9), 092002–18pp.
Abstract: We present a measurement of the top-quark pair-production cross section in p (p) over bar collisions at root s = 1.96 TeV using a data sample corresponding to 1.7 fb(-1) of integrated luminosity collected with the Collider Detector at Fermilab. We reconstruct t (t) over bar events in the lepton + jets channel, consisting of e nu + jets and μnu + jets final states. The dominant background is the production of W bosons in association with multiple jets. To suppress this background, we identify electrons from the semileptonic decay of heavy-flavor jets ("soft electron tags''). From a sample of 2196 candidate events, we obtain 120 tagged events with a background expectation of 51 +/- 3 events, corresponding to a cross section of sigma(t (t) over bar) = 7.8 +/- 2.4(stat) +/- 1.6(syst) +/- 0.5(lumi) pb. We assume a top-quark mass of 175 GeV/c(2). This is the first measurement of the t (t) over bar cross section with soft electron tags in run II of the Tevatron.
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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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Ceccopieri, F. A., Rinaldi, M., & Scopetta, S. (2017). Parton correlations in same-sign W pair production via double parton scattering at the LHC. Phys. Rev. D, 95(11), 114030–6pp.
Abstract: Same-sign W boson pair production is a promising channel to look for signatures of double parton interactions at the LHC. The corresponding cross section has been calculated by using double parton distribution functions, encoding two parton correlations, evaluated in a light-front quark model. The obtained result is in line with previous estimates which make use of an external parameter, the so-called effective cross section, not necessary in our approach. The possibility to observe for the first time two-parton correlations, in the next LHC runs, has been established.
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Celestino-Ramirez, J. M., Escrihuela, F. J., Flores, L. J., & Miranda, O. G. (2024). Testing the nonunitarity of the leptonic mixing matrix at FASERv and FASERv2. Phys. Rev. D, 109(1), L011705–6pp.
Abstract: The FASERv experiment has detected the first neutrino events coming from LHC. Near future highstatistic neutrino samples will allow us to search for new physics within the neutrino sector. Motivated by the forthcoming promising FASERv neutrino data, and its successor, FASERv2, we study its potential for testing the unitarity of the neutrino lepton mixing matrix. Although it would be challenging for FASERv and FASERv2 to have strong constraints on this kind of new physics, we discuss its role in contributing to a future improved global analysis.
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Celis, A., Cirigliano, V., & Passemar, E. (2014). Lepton flavor violation in the Higgs sector and the role of hadronic tau-lepton decays. Phys. Rev. D, 89(1), 013008–19pp.
Abstract: It has been pointed out recently that current low-energy constraints still allow for sizable flavor-changing decay rates of the 125 GeV boson into leptons, h -> tau l (l = e, mu). In this work we discuss the role of hadronic tau-lepton decays in probing lepton flavor violating couplings in the Higgs sector. At low energy, the effective Higgs coupling to gluons induced by heavy quarks contributes to hadronic tau decays, establishing a direct connection with the relevant process at the LHC, pp(gg) -> h -> tau l. Semileptonic transitions like tau -> l pi pi are sensitive to flavor-changing scalar couplings, while decays such as tau -> l eta((l)) probe pseudoscalar couplings, thus providing a useful low-energy handle to disentangle possible Higgs flavor violating signals at the LHC. As part of our analysis, we provide an appropriate description of all the relevant hadronic matrix elements needed to describe Higgs mediated tau -> pi pi transitions, improving over previous treatments in the literature.
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Celis, A., Cirigliano, V., & Passemar, E. (2014). Model-discriminating power of lepton flavor violating tau decays. Phys. Rev. D, 89(9), 095014–14pp.
Abstract: Within an effective field theory framework, we discuss the possibility to discriminate among different operators that contribute to lepton flavor violating (LFV) tau decays. Correlations among decay rates in different channels are shown to provide a basic handle to unravel the origin of LFV in these processes. More information about the underlying dynamics responsible for LFV can be gathered from differential distributions in three-body decays like tau -> μpi pi or tau -> 3 mu: these are considered in some detail. We incorporate in our analysis recent developments in the determination of the hadronic form factors for tau -> μpi pi. Future prospects for the observation of LFV tau decays and its interpretation are also discussed.
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Celis, A., Fuentes-Martin, J., Jung, M., & Serodio, H. (2015). Family nonuniversal Z ' models with protected flavor-changing interactions. Phys. Rev. D, 92(1), 015007–17pp.
Abstract: We define a new class of Z' models with neutral flavor-changing interactions at tree level in the down-quark sector. They are related in an exact way to elements of the quark mixing matrix due to an underlying flavored U(1)' gauge symmetry, rendering these models particularly predictive. The same symmetry implies lepton-flavor nonuniversal couplings, fully determined by the gauge structure of the model. Our models allow us to address presently observed deviations from the standard model and specific correlations among the new physics contributions to the Wilson coefficients C-9, 10((')l) can be tested in b -> sl(+)l(-) transitions. We furthermore predict lepton-universality violations in Z' decays, testable at the LHC.
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Celis, A., Fuentes-Martin, J., Vicente, A., & Virto, J. (2017). Gauge-invariant implications of the LHCb measurements on lepton-flavor nonuniversality. Phys. Rev. D, 96(3), 035026–8pp.
Abstract: We study the implications of the recent measurements of R-K and R-K* by the LHCb Collaboration. We do that by adopting a model-independent approach based on the Standard Model effective field theory (SMEFT), with the dominant new physics (NP) effects encoded in the coefficients of dimension-6 operators respecting the full Standard Model (SM) gauge symmetry. After providing simplified expressions for R-K and R-K*, we determine the implications of the recent LHCb results for these observables on the coefficients of the SMEFT operators at low and high energies. We also take into account all b -> sll data, which combined lead to effective NP scenarios with SM pulls in excess of 5 sigma. Thus, the operators discussed in this paper would be the first dimension-6 terms in the SM Lagrangian to be detected experimentally. Indirect constraints on these operators are also discussed. The results of this paper transcend the singularity of the present situation and set a standard for future analyses in b -> s transitions when the NP is assumed to lie above the electroweak scale.
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