S. Abachi

Measurement of the Top Quark Pair Production Cross Section in p-pbar Collisions

We present a measurement of the ttbar production cross section in ppbar collisions at root(s) = 1.8TeV by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately 125 pb^-1 accumulated during the 1992-1996 collider run. We observe 39 ttbar candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7+-2.2 events. For a top quark mass of 173.3GeV/c^2, we measure the ttbar production cross section to be 5.5+-1.8 pb.

Second Generation Leptoquark Search in p-pbar Collisions at square root s =1.8 TeV

We report on a search for second generation scalar leptoquarks with the D0 detector at the Fermilab Tevatron {ital pp}{ovr bar} collider at {radical}{ital s}=1.8TeV. This search is based on 12.7pb{sup {minus}1} of data. Second generation leptoquarks are assumed to be produced in pairs and to decay into a muon and quark with branching ratio {beta} or into a neutrino and quark with branching ratio 1{minus}{beta}. We obtain cross section times branching ratio limits as a function of leptoquark mass and set lower limits on the leptoquark mass at the 95% confidence level. {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.

Search for S quarks and Gluinos in p-pbar Collisions at square root s =1.8 TeV

We present a search for events consistent with the production and decay of the squarks and gluinos of the minimal supersymmetric standard model (MSSM) in the D0 detector at the Fermilab Tevatron {ital p{bar p}} collider. We examined data for events containing large missing transverse energy and three or more jets. We observed no excess of events above the expected yield from standard model processes. For a choice of MSSM parameter values, we set a lower limit at the 95% confidence level on the mass of the gluino of 144 GeV/{ital c}{sup 2} for all squark masses and a lower limit of 212 GeV/{ital c}{sup 2} for equal squark and gluino masses.

Measurement of the WW{gamma} Gauge Boson Couplings in p-pbar Collisions at square root s =1.8 TeV

The {ital WW}{gamma} gauge boson couplings were measured using {ital p{bar p}}{r_arrow}l{nu}{gamma}+{ital X} (l={ital e},{mu}) events at {radical}{ital s}=1.8 TeV observed with the D0 detector at the Fermilab Tevatron Collider. The signal, obtained from the data corresponding to an integrated luminosity of 13.8pb{sup {minus}1}, agrees well with the standard model prediction. A fit to the photon transverse energy spectrum yields limits at the 95% confidence level on the {ital CP}-conserving anomalous coupling parameters of {minus}1.6{lt}{Delta}{kappa}{lt}1.8 ({lambda}=0) and {minus}0.6{lt}{lambda}{lt}0.6 ({Delta}{kappa}=0). Similar limits are obtained for the {ital CP}-violating coupling parameters.

Search for W Boson Pair Production in p-pbar Collisions at square root s = 1.8 TeV

The results of a search for W boson pair production in p{bar p} collisions at {radical}s = 1.8 TeV with subsequent decay to dilepton (e{mu}, ee, and {mu}{mu}) channels are presented. One event is observed with an expected background of 0.56 {plus_minus} 0.13 events with an integrated luminosity of approximately 14 pb{sup {minus}1}. Assuming equal strengths for the WWZ and WW{gamma} gauge boson coupling parameters {kappa} and {lambda}, limits on the CP-conserving anomalous coupling constants are {minus}2.6 < {delta}{kappa} < 2.8 and {minus}2.1 {lambda} < 2.1 at the 95% confidence level.

W and Z Boson Production in p-pbar Collisions at square root s =1.8 TeV

The inclusive cross sections times leptonic branching ratios for W and Z boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the D0 detector at the Fermilab Tevatron collider: Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb, Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb, Sigma_Z*B(Z->e, e) = 0.218 +/- 0.011 +/- 0.012 nb, Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb. The first error is the combined statistical and systematic uncertainty, and the second reflects the uncertainty in the luminosity. For the combined electron and muon analyses we find: [Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49. Assuming Standard Model couplings, this result is used to determine the width of the W boson: Gamma(W) = 2.044 +/- 0.093 GeV.