Paul D. Grannis

Hadron and electron response in a uranium liquid argon calorimeter from 10 to 150 GeV

Abstract A uranium liquid argon calorimeter, with a total depth of nine absorption lengths, has been exposed to electrons and hadrons in the energy range of 10–150 GeV. Two configurations with different uranium plate thicknesses were successfully operated. In both cases the response was found to be linear over the entire energy regime. We present measurements of various contributions to energy resolution, differences in electron/hadronm/muon response, longitudinal and transverse shower profiles and electron position resolution.

The DO central track trigger

An overview of the system architecture and algorithms used for the DO Central Track Trigger (CTT) in the Run 2 of the Fermilab Tevatron Proton-Antiproton Collider is presented. This system uses information from the newly commissioned Central Fiber Tracker and Preshower Detectors to generate Level 1 trigger decisions. It also generates lists of seed tracks and preshower clusters that are sent to the Level 1 Muon Trigger, L2 Silicon Track Trigger, and Central and Forward Preshower Level 2 preprocessors. The system consists of modular boards which utilize field-programmable gate arrays (FPGAs) to implement trigger algorithms. The system delivers trigger decisions every 132 ns, based on input data flowing at a maximum sustained rate of 475 gigabits per second. The first results of trigger efficiency studies are presented.

A measurement of the electromagnetic form factor of the eta meson and of the branching ratio for the eta Dalitz decay

Abstract In an optical spark chamber experiment we have obtained a sample of 80 eta Dalitz decays ( η → e + e − γ ) and have measured the eta electromagnetic form factor to be F ( X ) = 1.0−(0.22 ±0.45) X , where X = M ee 2 / M η 2 , and the branching ratio ( η → e + e − γ /( η → π + π − π 0 )= (0.0082 ± 0.0020).

A measurement of the charge asymmetry in the decay η → π+π−γ

Abstract An experiment has been carried out at the Rutherford Laboratory to look for a possible asymmetry in the eta decay to three pions. Eta mesons were produced in the process π − p → η n. The experiment produced 165311 decays η → π + π − π o from which we determined a value for the charge asymmetry A = (0.0028 ± 0.0026). We see no evidence for C -violation in this decay.

A new upper limit for the branching ratio for the decay η → π0e+e−

Abstract We have looked for the decay η → π0e+e− in an optical spark chamber experiment at the Rutherford Laboratory. Our observations are consistent with no events being seen and give an upper limit rate (η → π0e+e−)/ rate (η → all)

Radiation damage studies of cerium-doped radiation-resistant lead glass detectors☆

Optical absorption measurements have been made on unirradiated and irradiated samples of cerium oxide doped lead silicate particle detector glasses. The addition of CeO2 introduces one prominent and one weak absorption band near the ultraviolet transmission limit. However the CeO2 greatly reduces the rate of formation of the radiation induced absorption. Detector size blocks of lead glass with 0.0, 0.25, and 1.2 weight percent CeO2 were used to determine the energy resolution for 5 GeV electrons. The resolution deteriorates from 12 to 33% as the CeO2 changes from 0.0 to 1.2%. At these CeO2 levels, calculations indicate the yield of doped glass becomes superior to that of undoped glass for doses greater than 500 rad.

The top quark (20 years after its discovery)

On the twentieth anniversary of the observation of the top quark, we trace our understanding of this heaviest of all known particles from the prediction of its existence, through the searches and discovery, to the current knowledge of its production mechanisms and properties. We also discuss the central role of the top quark in the Standard Model and the windows that it opens for seeking new physics beyond the Standard Model.

Total and elastic cross‐sections and global event characteristics in p̄p and pp collisions at √s=53 GeV

We have measured the total pp and pp cross sections at √s=52.8 GeV in the same experiment using the total rate method. The pp cross section is significantly above that for pp collisions. We also present measurements of the differential elastic cross‐sections for pp scattering. Preliminary results on the inclusive distributions for pp and pp collisions indicate that the annihilation component is primarily central and results in multiplicities above the average.

The evolution of hadron-collider experiments

High-energy accelerator beams colliding head-on have now completed the discovery of all the fundamental particles required by particle theory’s standard model. The search is on for new ones.

First results from the central tracking trigger of the DO experiment

An overview of the DO Central Track Trigger (CTT) for the Tevatron Run 2 program is presented. This newly commissioned system uses information from the DO Central Fiber Tracker and Preshower Detectors to generate trigger information for the first level of the three-tiered DO Trigger. The system delivers tracking detector trigger decisions every 132 ns, based on input data flowing at a rate of 475 Gbit per second. Initial results indicate excellent performance of the CTT. First studies of efficiency and trigger performance of the CTT are presented.