Studies of Gauge Boson Pair Production and Trilinear Couplings

The gauge boson pair production processes Wg, WW, WZ, and Zg were studied using pbarp collisions corresponding to an integrated luminosity of ~14 pb-1 at a center-of-mass energy of sqrt(s) = 1.8 TeV. Analysis of Wg prod with subsequent W boson decay to lv (l=e,mu) is reported, including a fit to the pT spectrum of the photons which leads to limits on anomalous WWg couplings. A search for WW prod with subsequent decay to l-lbar-v-vbar (l=e,mu) is presented leading to an upper limit on the WW prod cross section and limits on anomalous WWg and WWZ couplings. A search for high pT W bosons in WW and WZ prod is described, where one W boson decays to an ev and the second W boson or the Z boson decays to two jets. A maximum likelihood fit to the pT spectrum of W bosons resulted in limits on anomalous WWg and WWZ couplings. A combined fit to the three data sets which provided the tightest limits on anomalous WWg and WWZ couplings is also described. Limits on anomalous ZZg and Zgg couplings are presented from an analysis of the photon ET spectrum in Zg events in the decay channels (ee, mu-mu, and v-vbar) of the Z boson.Comment: 77 Pages including 40 Figures. Submitted to PR

Study of the ZZ\gamma and Z\gamma\gamma Couplings in Z(\nu\nu)\gamma Production

We have measured the ZZ-gamma and Z-gamma-gamma couplings by studying p-bar p -> (missing ET) gamma + X events at sqrt(s)=1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. This first study of hadronic Z-gamma production in the neutrino decay channel gives the most stringent limits on anomalous couplings available. A fit to the transverse energy spectrum of the photon in the candidate event sample, based on a data set corresponding to an integrated luminosity of 13.1 pb^(-1), yields 95% CL limits on the anomalous CP-conserving ZZ-gamma couplings of |h^Z_(30)|<0.9, |h^Z_(40)|<0.21, for a form-factor scale Lambda = 500 GeV. Combining these results with our previous measurement using Z -> ee and mu-mu yields the limits:|h^Z_(30)|<0.8, |h^Z_(40)|<0.19 (Lambda = 500 GeV) and |h^Z_(30)|<0.4, |h^Z_(40)|<0.06 (Lambda = 750 GeV).Comment: 10 pages, 2 figures, 2 table

Manejo del paciente en shock séptico

El shock séptico es la manifestación más grave de una infección. Esta se produce como consecuencia de una respuesta inflamatoria sistémica severa que lleva a un colapso cardiovascular y/o microcirculatorio, y a hipoperfusión tisular. La hipoperfusión constituye el elemento central que define la condición de shock y esta debe ser detectada y revertida en forma urgente desde la atención inicial. La evaluación de la perfusión periférica, la diuresis, y la medición del lactato y de la saturación venosa central, son las principales herramientas para evaluar la perfusión sistémica. La reanimación debe comenzar en forma inmediata con la administración agresiva de fluidos, la cual puede ser guiada por parámetros dinámicos de respuesta a fluidos, y continuada hasta normalizar u optimizar las metas de perfusión. En forma paralela se debe iniciar vasopresores en caso de hipotensión marcada, siendo el agente de elección noradrenalina, y conectar precozmente al paciente a ventilación mecánica frente a hipoperfusión severa que no responde a fluidos, o frente a un aumento del trabajo respiratorio. Adicionalmente, el foco infeccioso debe ser tratado agresivamente iniciando antibióticos lo antes posible

Limits on WWγ and WWZ couplings from W boson pair production

The results of a search for W boson pair production in pp̄ collisions at √s = 1.8 TeV with subsequent decay to eμ, ee, and μμ channels are presented. Five candidate events are observed with an expected background of 3.1 ± 0.4 events for an integrated luminosity of approximately 97 pb-1. Limits on the anomalous couplings are obtained from a maximum likelihood fit of the ET spectra of the leptons in the candidate events. Assuming identical WWγ and WWZ couplings, the 95% C.L. limits are -0.62&lt;Δκ&lt;0.77 (λ = 0) and -0.53&lt;λ &lt;0.56 (Δκ = 0) for a form factor scale Λ= 1.5 TeV

Zγ production in pp̄ collisions at √s=1.8 TeV and limits on anomalous ZZγ and Zγγ couplings

We present a study of Zγ+X production in pp̄ collisions at √s=1.8 TeV from 97 (87) pb-1 of data collected in the eeγ (μμγ) decay channel with the D0 detector at Fermilab. The event yield and kinematic characteristics are consistent with the standard model predictions. We obtain limits on anomalous ZZγ and Zγγ couplings for form factor scales Λ=500 GeV and Λ=750 GeV. Combining this analysis with our previous results yields 95% C.L. limits |hZ30|&lt;0.36, |hZ40|&lt;0.05, |hγ30|&lt;0.37, and |hγ40|&lt;0.05 for a form factor scale Λ=750 GeV

Determination of the mass of the W boson using the D∅ detector at the Fermilab Tevatron

A measurement of the mass of the W boson is presented which is based on a sample of 5982 W → eν decays observed in pp̄ collisions at √s = 1.8 TeV with the D∅ detector during the 1992-1993 run. From a fit to the transverse mass spectrum, combined with measurements of the Z boson mass, the W boson mass is measured to be MW = 80.350±0.140(stat)±0.165(syst)±0.160(scale) GeV/c2. Detailed discussions of the determination of the absolute energy scale, the measured efficiencies, and all systematic uncertainties are presented

Search for scalar leptoquark pairs decaying to electrons and jets in p̄ p collisions

We have searched for the pair production of first generation scalar leptoquarks in the eejj channel using the full data set (123 pb-1) collected with the DO detector at the Fermilab Tevatron during 1992-1996. We observe no candidates with an expected background of approximately 0.4 events. Comparing the experimental 95% confidence level upper limit to theoretical calculations of the cross section with the assumption of a 100% branching fraction of eq, we set a lower limit on the mass of a first generation scalar leptoquark of 225 GeV/c2. The results of this analysis rule out the interpretation of the excess of high Q2 events at DESY HERA as leptoquarks which decay exclusively to eq

Limits on WWγ and WWZ couplings from IV boson pair production

The results of a search for W boson pair production in pp collisions at √s= 1.8 TeV with subsequent decay to eμ, ee, and μμ channels are presented. Five candidate events are observed with an expected background of 3.1 ±0.4 events for an integrated luminosity of approximately 97 pb-1. Limits on the anomalous couplings are obtained from a maximum likelihood fit of the ET spectra of the leptons in the candidate events. Assuming identical WWγ and WWZ couplings, the 95% C.L. limits are -0.62&lt;Δκ&lt;0.77 (X. = 0) and -0.53&lt;λ &lt;0.56 (Δκ=0) for a form factor scale Λ= 1.5 TeV. © 1998 The American Physical Society

Color coherent radiation in multijet events from pp- collisions at √s = 1.8 TeV

We report on a study of color coherence effects in pp- collisions at a center of mass energy √s = 1.8 TeV. The data were collected with the DØ detector during the 1992-1993 run of the Fermilab Tevatron Collider. We observe the presence of initial-to-final state color interference with the spatial correlations between soft and hard jets in multijet events in the central and in forward pseudorapidity regions. The results are compared to Monte Carlo simulations with different color coherence implementations and to the predictions of script O sign(α3s) QCD calculations. © 1997 Elsevier Science B.V