Hard single diffractive jet production at D0

Preliminary results from the D{null} experiment on jet production with forward rapidity gaps in {ital p{anti p}} collisions are presented. A class of dijet events with a forward rapidity gap is observed at center-of-mass energies {radical}s = 1800 GeV and 630 GeV. The number of events with rapidity gaps at both center-of-mass energies is significantly greater than the expectation from multiplicity fluctuations and is consistent with a hard single diffractive process. A small class of events with two forward gaps and central dijets is also observed at 1800 GeV. This topology is consistent with hard double pomeron exchange

Heavy Flavours at Colliders

I review some topics in the production and decays of heavy flavours that are relevant for collider physics. In particular, I discuss the present status and some recent progress related to masses, parton densities and fragmentation functions of heavy quarks, as well as threshold resummation, polarized onium production at high transverse momentum, and a factorization theorem for $B \to\pi\pi$ decays.Comment: 12 pages. Plenary talk given at UK Phenomenology Workshop on Collider Physics, Durham, England, 19-24 Sep 1999 Comments and references adde

Transverse energy distributions within jets in p{anti p} collisions at {radical}s = 1.8 TeV

The distribution of the transverse energy in jets has been measured in p{anti p} collisions at {radical}s = 1.8 TeV using the D0 detector at Fermilab. This measurement of the jet shape is made as a function of jet transverse energy in both the central and forward rapidity regions. Jets are observed to narrow both with increasing transverse energy and with increasing rapidity. Next-to-leading order partonic QCD calculations are compared to the data. Although the calculations qualitatively describe the data, they are shown to be very dependent on renormalization scale, parton clustering algorithm and jet direction definition and fail to consistently describe the data in all regions

Rapidity dependence of the inclusive J/{Psi} production in p{bar p} collisions at {radical}s = 1.8 TeV

We have studied J/{psi} production in p{bar p} collisions at {radical}s = 1.8 TeV with the D0 detector at Fermilab, using a {mu}{sup +}{mu}{sup {minus}} data sample collected during the 1994--1995 collider run. We have measured the inclusive J/{psi} production cross section as a function of the J/{psi} transverse momentum, p{sub T}{sup J/{psi}}, in the central and forward rapidity regions. The cross section d{sigma}/dp{sub T}{sup J/{psi}} for {vert_bar}{eta}{sup J/{psi}}{vert_bar} 8 GeV/c. The data are compared with the next-to-leading (NLO) QCD calculations, which take into account different J/{psi} production mechanisms

Measurement of inclusive triple differential dijet cross section, d{sup 3}{sigma}/dE{sub T}d{eta}{sub 1}d{eta}{sub 2} in p{bar p} collisions at {radical}s = 1.8 TeV

Measurement of the inclusive triple differential dijet cross section, d{sup 3}{sigma}/dE{sub T}d{sub {eta}1}d{sub {eta}2}, at a center of mass energy {radical}s = 1.8 TeV with the D0 detector during the 1992--1993 run. The sensitivity of this measurement to different parton distribution functions is explored. A comparison of the data to NLO theory using different parton distributions functions indicates the need for a smaller gluon content in the x range accessible at the Tevatron than is predicted by current parton distribution sets

New phenomena results presented at the 1996 A.P.S. Division of Particles and Fields meeting

This paper is a compendium of the D0 papers submitted to the 1996 Division of Particles and Fields meeting in Minneapolis/St. Paul, Minnesota. Each paper is reproduced here in full. The papers are: (1) a search for squarks and gluinos in the dielectron channel; (2) search for excited quarks decaying to two-jets with the D0 detector; (3) search for di-jet resonances produced in association with W bosons at D0; (4) search for first generation scalar leptoquarks at D0 detector; (5) search for SUSY gaugino production through the trilepton signature; (6) search for heavy neutral gauge bosons at D0

Measurement of B{sup 0} {minus} {bar B}{sup 0} mixing using dimuons at D0

The D0 experiment at Fermilab has determined the B{sup 0} {minus} B{sup 0} mixing probability x using dimuon events produced in p{bar p} collisions at {radical}s = 1.8 TeV. Using a sample of 172 dimuon events, we have determined the time and flavor averaged mixing probability x to be 0.09 {plus_minus} 0.04(stat){plus_minus}0.03(sys) [preliminary] in agreement with the present world average

Rapidity gaps between jets at D0

Results are presented from an analysis of the particle multiplicity distribution between high transverse energy jets produced at the Fermilab Tevatron p{bar p} Collider at {radical}s = 1.8 Tev. Using the D0 detector, we examine the particle multiplicity distribution between the two highest transverse energy jets. For events with large rapidity separation, we observed a significant excess of events at low tagged-particle multiplicity which is consistent with a strongly interacting color-singlet exchange process

Search for W boson pair production in p{bar p} collisions at {radical}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