Professor Daniela Bortoletto

Abstract:

We present a study of events with W bosons and hadronic jets produced in p̄p collisions at a center of mass energy of 1.8 TeV. The data consist of 51 400 W± → e± decay candidates from 108 pb-1 of integrated luminosity collected using the CDF detector at the Fermilab Tevatron Collider. Cross sections and jet production properties have been measured for W + ≥1 to ≥4 jet events. The data are compared to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.

Abstract:

We describe the properties of six-jet events, with the six-jet mass exceeding [Formula presented] produced at the Fermilab proton-antiproton collider operating at a center-of-mass energy of 1.8 TeV. Observed distributions for a set of 20 multijet variables are compared with predictions from the HERWIG QCD parton shower Monte Carlo program, the NJETS leading order QCD matrix element Monte Carlo program, and a phase-space model in which six-jet events are distributed uniformly over the kinematically allowed region of the six-body phase space. In general the QCD predictions provide a good description of the observed six-jet distributions. © 1997 The American Physical Society.

Abstract:

This Letter describes a direct search for charged Higgs boson production in proton-antiproton collisions at sqrt(s)=1.8 TeV recorded by the Collider Detector at Fermilab. Two-Higgs-doublet extensions to the standard model predict the existence of charged Higgs bosons. In such models, the branching fraction for top quarks B(t → H b → tau nu b) can be large. This search uses the hadronic decays of the tau lepton in this channel to significantly extend previous limits on charged Higgs production. © 1997 The American Physical Society.

Abstract:

We present the results of a search for first generation scalar leptoquarks pairs (S1S®1) in 110 ± 7 pb⁻¹ of data collected by the Collider Detector at Fermilab. We assume both leptoquarks decay to an electron and a quark. Three candidate events, with masses below 140 GeV/c² and consistent with background expectations, are observed. We obtain a 95% confidence level upper limit on the production cross section as a function of the leptoquark mass. Using a next-to-leading order calculation of S1S®1 production, we exclude scalar leptoquarks with mass less than 213GeV/c² at 95% C.L. for a branching ratio into eq equal to 1. © 1997 American Physical Society.

Abstract:

We report on a search for supersymmetric squark and gluino particles in a data sample of 19 [Formula presented] of [Formula presented] collisions at [Formula presented] TeV recorded by the Collider Detector at Fermilab. We searched for events containing jets plus appreciable missing transverse energy [Formula presented] This signature is indicative of pair production and subsequent decay of squarks and/or gluinos. After all cuts, there are [Formula presented] events with [Formula presented] GeV and three jets, and [Formula presented] events with [Formula presented] GeV and four jets. These numbers of events are consistent with estimates of standard model processes plus detector-induced background sources. The analysis yields lower limits on gluino and squark masses, based on the predictions from the mnimal supersymmetric extension of the standard model. At the [Formula presented] confidence level, we find gluino and squark mass limits up to 216 [Formula presented] assuming equal gluino and squark masses, and gluino mass limits up to [Formula presented] [Formula presented] independent of squark mass. © 1997 The American Physical Society.