51�������

Abstract:

We measure the relative rate of production of orbitally excited (L=1) states of B mesons (B**) by observing their decays into Bπ^±. We reconstruct B mesons through semileptonic decay channels using data collected pp̄ collisions at √s= 1.8 TeV. The fraction of light B mesons that are produced as L= 1B** states is measured to be 0.28±0.06(stat)±0.03(syst). We also measure the collective mass of the B** states, and quantify the result by quoting the (model-dependent) mass of the lowest B** state to be m(B1) = 5.71 ±0.02GeV/c². ©2001 The American Physical Society.

Abstract:

We apply a quasi-model-independent strategy (“SLEUTH”) to search for new high [Formula Presented] physics in ≈100 [Formula Presented] of [Formula Presented] collisions at [Formula Presented] collected by the DØ experiment during 1992–1996 at the Fermilab Tevatron. Over 32 [Formula Presented] [Formula Presented] [Formula Presented] and [Formula Presented] exclusive final states are systematically analyzed for hints of physics beyond the standard model. Simultaneous sensitivity to a variety of models predicting new phenomena at the electroweak scale is demonstrated by testing the method on a particular signature in each set of final states. No evidence of new high [Formula Presented] physics is observed in the course of this search, and we find that 89% of an ensemble of hypothetical similar experimental runs would have produced a final state with a candidate signal more interesting than the most interesting observed in these data. © 2001 The American Physical Society.

Abstract:

We report on a search for supersymmetry using the DØ detector. The 1994-1996 data sample of √s = 1.8 TeV pp̄ collisions was analyzed for events containing two leptons (e or μ), two or more jets, and missing transverse energy. Assuming the minimal supergravity model, with A0 = 0 and μ < 0, various thresholds were employed to optimize the search. No events were found beyond expectation from the background. We set a lower limit at the 95% C.L. of 255 GeV/c2 for equal mass squarks and gluinos for tan β = 2, and present exclusion contours in the (m0, m1/2) plane for tan β = 2-6.

Abstract:

We describe a search for the pair production of first-generation scalar and vector leptoquarks in the [Formula Presented] and [Formula Presented] channels by the DØ Collaboration. The data are from the 1992–1996 [Formula Presented] run at [Formula Presented] at the Fermilab Tevatron collider. We find no evidence for leptoquark production; in addition, no kinematically interesting events are observed using relaxed selection criteria. The results from the [Formula Presented] and [Formula Presented] channels are combined with those from a previous DØ analysis of the [Formula Presented] channel to obtain 95% confidence level (C.L.) upper limits on the leptoquark pair-production cross section as a function of mass and of [Formula Presented] the branching fraction to a charged lepton. These limits are compared to next-to-leading-order theory to set 95% C.L. lower limits on the mass of a first-generation scalar leptoquark of 225, 204, and 79 [Formula Presented] for [Formula Presented] [Formula Presented] and 0, respectively. For vector leptoquarks with gauge (Yang-Mills) couplings, 95% C.L. lower limits of 345, 337, and 206 [Formula Presented] are set on the mass for [Formula Presented] [Formula Presented] and 0, respectively. Mass limits for vector leptoquarks are also set for anomalous vector couplings. © 2001 The American Physical Society.