Professor Chris Hays

Abstract:

A new measurement of the pseudorapidity (η) and transverse-energy (ET) dependence of the inclusive jet production cross section was carried out. The differential cross section d²σ/(dETdη) was considered as a function of jet ET in five intervals of up to |η| = 3. Results were compared with next-to-leading order predictions from QCD.

Abstract:

The search for large extra spatial dimensions at hadron colliders was performed by looking for effects of virtual Kaluza-Klein gravitons in the production of dielectrons and diphotons at high energies. No evidence was found for large extra dimension (ED). A model-independent 95% C.L. upper limit of 0.46 TeV^-4 was set on the parameter nG.

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.