Showing papers by "Vyacheslav Klyukhin published in 1998"

Measurement of the top quark mass using dilepton events

Abstract: The D0 Collaboration has performed a measurement of the top quark mass m{sub t} based on six candidate events for the process t{ovr t}{r_arrow}bW{sup +}{ovr b}W{sup {minus}} , where the W bosons decay to e{nu} or {mu}{nu} . This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb{sup {minus}1} of {radical}(s)=1.8 TeV p{ovr p} collisions. We obtain m{sub t}=168.4{plus_minus}12.3(stat){plus_minus} 3.6(syst) GeV/c{sup 2} , consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields m{sub t}=172.0{plus_minus}7.5 GeV/c{sup 2} . {copyright} {ital 1998} {ital The American Physical Society}

Direct measurement of the top quark mass by the DO Collaboration

Abstract: We determine the top quark mass m{sub t} using t{bar t} pairs produced in the DO/ detector by {radical} (s) =1.8thinspTeV p{bar p} collisions in a 125thinsppb{sup {minus}1} exposure at the Fermilab Tevatron. We make a two constraint fit to m{sub t} in t{bar t}{r_arrow}bW{sup +}{bar b}W{sup {minus}} final states with one {ital W} boson decaying to q{bar q} and the other to e{nu} or {mu}{nu}. Likelihood fits to the data yield m{sub t}(l+jets)=173.3{plus_minus}5.6thinsp(stat)thinsp{plus_minus}thinsp5.5thinsp(s st) GeV/c{sup 2}. When this result is combined with an analysis of events in which both {ital W} bosons decay into leptons, we obtain m{sub t}=172.1{plus_minus}5.2thinsp(stat)thinsp{plus_minus}thinsp4.9thinsp(syst) GeV/c{sup 2}. An alternate analysis, using three constraint fits to fixed top quark masses, gives m{sub t}(l+jets)=176.0{plus_minus}7.9thinsp(stat){plus_minus}thinsp4.8thinsp(syst) GeV/c{sup 2}, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented. {copyright} {ital 1998} {ital The American Physical Society}

Search for first generation scalar leptoquark pairs in pp̅ collisions at √s = 1.8 TeV

Abstract: We have searched for first generation scalar leptoquark (LQ) pairs in the enu+jets channel using ppbar collider data (integrated luminosity= 115 pb^-1) collected by the DZero experiment at the Fermilab Tevatron during 1992-96. The analysis yields no candidate events. We combine the results with those from the ee+jets and nunu+jets channels to obtain 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of beta, the branching fraction to a charged lepton. Comparing with the next-to-leading order theory, we set 95% CL lower limits on the LQ mass of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively.

Measurement of Dijet Angular Distributions and Search for Quark Compositeness

Abstract: We have measured the dijet angular distribution in {radical}(s)=1.8 TeV p {bar p} collisions using the D0 detector. Order {alpha}{sup 3}{sub s} QCD predictions are in good agreement with the data. At 95{percent} confidence limit the data exclude models of quark compositeness in which the contact interaction scale is below 2TeV. {copyright} {ital 1998} {ital The American Physical Society}

Experimental Search for Chargino and Neutralino Production in Supersymmetry Models with a Light Gravitino

Abstract: We search for inclusive high $E_T$ diphoton events with large missing transverse energy in $p\bar{p}$ collisions at $\sqrt{s}$=1.8 TeV. Such events are expected from pair production of charginos and neutralinos within the framework of the minimal supersymmetric standard model with a light gravitino. No excess of events is observed. In that model, and assuming gaugino mass unification at the GUT scale, we obtain a 95% CL exclusion region in the supersymmetry parameter space and lower mass bounds of 150 GeV/c$^2$ for the lightest chargino and 75 GeV/c$^2$ for the lightest neutralino.

A Measurement of the W Boson Mass at the Fermilab pp̄ Collider

Abstract: We report a measurement of the W boson mass based on an integrated luminosity of 82 pb −1 from pp collisions at √s = 1.8 TeV recorded in 1994-1995 by the D0 detector at the Fermilab Tevatron. We identify W bosons by their decays to e∨ V and extract the mass by fitting the transverse mass spectrum from 28 323 W boson candidates. A sample of 3563 dielectron events, mostly due to Z→ee decays, constrains models of W boson production and the detector. We measure M W = 80.44±0.10(stat)±0.07(syst) GeV. By combining this measurement with our result form the 1992-1993 data set, we obtain M W = 80.43±0.11 GeV.

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

Abstract: A measurement of the mass of the W boson is presented which is based on a sample of 5982 W → eνv decays observed in pp 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/c 2 . Detailed discussions of the determination of the absolute energy scale, the measured efficiencies, and all systematic uncertainties are presented.