P. Grudberg

Search for the decay b->x(s)+mu+mu

Abstract We have searched for the flavor-changing neutral current decay b → X s μ + μ − in p p collisions at s = 1.8 TeV with the DO detector at Fermilab. We determine the 90% confidence level limit for the branching fraction to be B ( b → X s μ + μ − ) −4 . We argue that this limit is more stringent than the best published limit on this decay rate.We have searched for the flavor-changing neutral current decay b ->s mu+ mu- in p pbar collisions at sqrt(s) = 1.8 TeV with the DO detector at Fermilab. We determine the 90% confidence level limit for the branching fraction to be B(b ->X_s mu+ mu-)<3.2 x 10^{-4}. We argue that this limit is more stringent than the best published limit on this decay rate.

Limits on anomalous WW(gamma) and WWZ couplings

Limits on the anomalous WWγ and WWZ couplings are presented from a simultaneous fit to the data samples of three gauge boson pair final states in pp collisions at √s=1.8TeV: Wγ production with the W boson decaying to eν or μν, W boson pair production with both of the W bosons decaying to eν or μν, and WW or WZ production with one W boson decaying to eν and the other W boson or the Z boson decaying to two jets. Assuming identical WWγ and WWZ couplings, 95% C.L. limits on the anomalous couplings of -0.30<Δκ<0.43 (λ=0) and -0.20<λ<0.20 (Δκ=0) are obtained using a form factor scale Λ=2.0TeV. Limits found under other assumptions on the relationship between the WWγ and WWZ couplings are also presented.

Limits on WWZ and WW{gamma} Couplings from p-pbar right arrow e{nu}jjX events at square root s =1.8 TeV

We present limits on anomalous WWZ and WW-gamma couplings from a search for WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p -> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron Collider during the 1992-1995 run. The data sample corresponds to an integrated luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling parameters, the 95% CL limits on the CP-conserving couplings are -0.33<lambda<0.36 (Delta-kappa=0) and -0.43<Delta-kappa<0.59 (lambda=0), for a form factor scale Lambda = 2.0 TeV. Limits based on other assumptions are also presented.

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.