Professor Chris Hays

Abstract:

The R-parity violating decay of the neutralino X̃10 into a moun and two jets in 77.5 pb-1 of data was searched. For tanβ=2, squark masses below 240 GeV/c2 and gluino masses below 224 GeV/c2 were exluded. For equal masses of squarks and gluinos, the mass limit was 265 GeV/c2. These limits were found to be comparable to those achieved previously in complementary channels.

Abstract:

We have measured the W boson mass using the DØ detector and a data sample of 82 pb-1 from the Fermilab Tevatron collider. This measurement uses W→eν decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such "edge" electrons have not been used in any previous DØ analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous DØ W boson mass measurements, we obtain MW=80.483±0.084 GeV. The 8% improvement from the previous DØ measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.

Abstract:

The results of a search for leptoquark (LQ) pairs in (85.2 ±3.7) pb-1 of pp̄ collider data collected by the DO experiments were presented. Scalar leptoquarks for the masses less than 98 GeV/c2, vector leptoquarks for masses less than 200 GeV/c2 and coupling which produced the minimum cross-section were excluded. Results showed absence of an evidence for leptoquark production and a limit was set on νν + jets as a function of the mass of leptoquark.