Accelerator Neutrinos

Abstract:

The mean charged-particle multiplicity of jets in dijet events with dijet masses were analyzed using collider detectors. The jet energy and direction were measured in the central lead-scintillator electromagnetic (CEM) and iron-scintillator hadronic (CHA) calorimeters. It is shown that the fraction of gluon jets decreases to 23%-26% at 630 GeV/c² from 61%-63% of all jets at 80 GeV/c².

Abstract:

We present results of searches for diphoton resonances produced both inclusively and also in association with a vector boson (W or Z) using 100 pb-1 of pp̄ collisions using the CDF detector. We set upper limits on the product of cross section times branching ratio for both pp̄→γγ+X and pp̄→γγ+ W/Z. Comparing the inclusive production to the expectations from heavy sgoldstinos we derive limits on the supersymmetry-breaking scale √F in the TeV range, depending on the sgoldstino mass and the choice of other parameters. Also, using a NLO prediction for the associated production of a Higgs boson with a W or Z boson, we set an upper limit on the branching ratio for H → γγ. Finally, we set a lower limit on the mass of a "bosophilic" Higgs boson (e.g., one which couples only to γ, W, and Z bosons with standard model couplings) of 82 GeV/c2 at 95% confidence level. ©2001 The American Physical Society.

Abstract:

We report on a measurement of the ratio of the differential cross sections for W and Z boson production as a function of transverse momentum in proton-antiproton collisions at √s = 1.8 TeV. This measurement uses data recorded by the DØ detector at the Fermilab Tevatron in 1994-1995. It represents the first investigation of a proposal that ratios between W and Z observables can be calculated reliably using perturbative QCD, even when the individual observables are not. Using the ratio of differential cross sections reduces both experimental and theoretical uncertainties, and can therefore provide smaller overall uncertainties in the measured mass and width of the W boson than current methods used at hadron colliders. © 2001 Elsevier Science B.V. All rights reserved.

Abstract:

We present a search for electroweak production of single top quarks in ≈90 pb-1 of data collected with the DØ detector at the Fermilab Tevatron collider. Using arrays of neural networks to separate signals from backgrounds, we set upper limits on the cross sections of 17 pb for the s-channel process pp̄ → tb + X, and 22 pb for the t-channel process pp̄ → tqb + X, both at the 95% confidence level. © 2001 Elsevier Science B.V. All rights reserved.

Abstract:

Double diffraction differential cross sections in pp collisions at √s = 1800 and 630 GeV were measured. Results were compared with data at √s = 200 and 900 GeV and with predictions based on Regge theory and factorization. A factorization breakdown comparable in magnitude to that observed in single diffraction dissociation was found. The data are in agreement with the renormalized gap probability model.