Dr Elizabeth Gallas

Abstract:

We report a measurement of the top quark mass using six candidate events for the process (Formula presented), observed in the D0 experiment at the Fermilab (Formula presented) collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of (Formula presented). We combine this result with our previous measurement in the (Formula presented) channel to obtain (Formula presented) as the best value of the mass of the top quark measured by D0. © 1999 The American Physical Society.

Abstract:

We present a search for charged Higgs bosons in decays of pair-produced top quarks using 109.2 ± 5.8pb-1 of data recorded from pp collisions at √ s = 1.8 TeV by the D0 detector during 1992-1996 at the Fermilab Tevatron. No evidence is found for charged Higgs production, and most parts of the [MH+, tan β] parameter space where the decay t → H+ b has a branching fraction close to or larger than that for t → W+ b are excluded at 95% confidence level. Assuming mt = 175 GeV and σ(pp → tt) = 5.5 pb, for MH+ = 60 GeV, we exclude tan β < 0.97 and tan β > 40.9. © 1999 The American Physical Society.

Abstract:

We report on a search for second generation leptoquarks (LQ) produced in pp collisions at √ = 1.8TeV using the D0 detector at Fermilab. Second generation leptoquarks are assumed to be produced in pairs and to decay to either μ or v and either a strange or a charm quark (q). Limits are placed on σ (pp → LQLQ → μ v + jets) as a function of the mass of the leptoquark. For equal branching ratios to μq and vq second generation scalar leptoquarks with a mass below 160 GeV/c2 vector leptoquarks with anomalous minimal vector couplings with a mass below 240 GeV/c2 and vector leptoquarks with Yang-Mills couplings with a mass below 290 GeV/c2 are excluded at the 95% confidence level. © 1999 The American Physical Society.

Abstract:

We search for new physics using events with one high transverse energy photon, two or more jets, and an apparent imbalance in transverse energy, in pp¯ collisions at the Fermilab Tevatron at √ s=1.8TeV. Such events are predicted for production of supersymmetric particles in some models. No excess is observed beyond expected background. For the parameter space of the minimal supersymmetric standard model with branching fraction B(∼ Χ02→ = γ ∼ Χ01) = 1 and mΧ02- mΧ01> 20 GeV, we obtain a 95% confidence level lower mass limit of 310 GeV for equal mass squarks and gluinos. The results are also interpreted in models with low energy gauge mediated supersymmetry breaking. © 1999 The American Physical Society.

Abstract:

Using data corresponding to an integrated luminosity of 79pb⁻¹, D0 has searched for events containing multiple jets and large missing transverse energy in pp¯ collisions at √s = 1.8TeV at the Fermilab Tevatron collider. Observing no significant excess beyond what is expected from the standard model, we set limits on the masses of squarks and gluinos and on the model parameters m0 and m1/2, in the framework of the minimal low-energy supergravity models of supersymmetry. For tanβ=2 and A0 = 0, with μ < 0, we exclude all models with m˜q<250 GeV/c². For models with equal squark and gluino masses, we exclude m < 260 GeV/c². © 1999 The American Physical Society.