C. Cretsinger

Search for the decay b→Xsμ+μ−

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.

tt̄ production cross section in pp̄ collisions at √s = 1.8 TeV

Results are presented on a measurement of the t (t) over bar pair production cross section in p (p) over bar collisions at roots=1.8 TeV from nine independent decay channels. The data were collected by the D empty set experiment during the 1992-1996 run of the Fermilab Tevatron Collider. A total of 80 candidate events is observed with an expected background of 38.8+/-3.3 events. For a top quark mass of 172.1 GeV/c(2), the measured cross section is 5.69+/-1.21(stat)+/-1.04(syst) pb.Results are presented on a measurement of the ttbar pair production cross section in ppbar collisions at sqrt{s} = 1.8 TeV from nine independent decay channels. The data were collected by the Dzero experiment during the 1992-1996 run of the Fermilab Tevatron Collider. A total of 80 candidate events are observed with an expected background of 38.8 +- 3.3 events. For a top quark mass of 172.1 GeV/c^2, the measured cross section is 5.69 +- 1.21 (stat) +- 1.04 (sys) pb.

Rapidity gaps between jets in pp-bar collisions at sqrt s =1.8 TeV.

First experimental results are presented from a search for events with a rapidity gap between jets. The D0 detector was used to examine events produced by the Fermilab Tevatron [ital p[bar p]] collider at [radical][ital s] =1.8 TeV. The fraction of events with an observed rapidity gap between the two highest transverse energy ([ital E][sub [ital T]]) jets is measured as a function of the pseudorapidity separation between the jet edges ([Delta][eta][sub [ital c]]). An upper limit at the 95% confidence level of 1.1[times]10[sup [minus]2] is obtained on the fraction of events with non particles between the jets, for events with [Delta][eta][sub [ital c]][gt]3 and jet [ital E][sub [ital T]] greater than 30 GeV.

Rapidity gaps between jets in [ital p[bar p]] collisions at [radical][ital s] =1. 8 TeV

First experimental results are presented from a search for events with a rapidity gap between jets. The D0 detector was used to examine events produced by the Fermilab Tevatron [ital p[bar p]] collider at [radical][ital s] =1.8 TeV. The fraction of events with an observed rapidity gap between the two highest transverse energy ([ital E][sub [ital T]]) jets is measured as a function of the pseudorapidity separation between the jet edges ([Delta][eta][sub [ital c]]). An upper limit at the 95% confidence level of 1.1[times]10[sup [minus]2] is obtained on the fraction of events with non particles between the jets, for events with [Delta][eta][sub [ital c]][gt]3 and jet [ital E][sub [ital T]] greater than 30 GeV.