\documentclass[prd,twocolumn,amsmath,amssymb]{revtex4}
\pagestyle{empty}
% use this for PRL/PRD %\documentclass[prd,twocolumn,showpcs,amsmath,amssymb]{revtex4}
%*****Date of recertification: April 4, 2004***** 
\begin{document} 

\title{A Brief Description of the D\O\ Detector in Run II} 

\author{T. Ferbel} 
\date{\today}

\begin{abstract}
The text below provides a description of the main elements of the 
D\O\ Detector in Run II of the Tevatron. It is intended as a rough 
template for insertion into our papers on data analysis. Clearly, 
different analyses will emphasize different aspects of the hardware, 
and you should therefore feel free to modify the wording and any 
technical details. In fact, you are encouraged to modify the text 
somewhat to avoid issues of plagiarism.
\end{abstract}

\maketitle

The D\O\ detector is comprised of the following main elements. 
A magnetic central-tracking system, which consists of a silicon 
microstrip tracker (SMT) and a central fiber tracker (CFT), 
both located within a 2~T superconducting solenoidal 
magnet~\cite{run2det}. The SMT has $\approx 800,000$ individual 
strips, with typical pitch of $50-80$ $\mu$m, and a design 
optimized for tracking and vertexing capability at $|\eta|<3$. 
The system has a six-barrel longitudinal structure, each with 
a set of four layers arranged axially around the beam pipe, 
and interspersed with 16 radial disks. The CFT has eight thin 
coaxial barrels, each supporting two doublets of overlapping 
scintillating fibers of 0.835~mm diameter, one doublet being 
parallel to the collision axis, and the other alternating by 
$\pm 3^{\circ}$ relative to the axis. Light signals are transferred 
via clear light fibers to solid-state photon counters (VLPC) that 
have $\approx 80\%$ quantum efficiency.

Central and forward preshower detectors located just outside 
of the superconducting coil (in front of the calorimetry) are 
constructed of several layers of extruded triangular scintillator 
strips that are read out using wavelength-shifting fibers and 
VLPCs. The next layer of detection involves three 
liquid-argon/uranium calorimeters: a central section (CC) covering 
$|\eta|$ up to $\approx 1$, and two end calorimeters (EC) 
extending coverage to $|\eta|\approx 4$, all housed in separate 
cryostats~\cite{run1det}. In addition to the preshower detectors, 
scintillators between the CC and EC cryostats provide sampling 
of developing showers at $1.1<|\eta|<1.4$.

A muon system resides beyond the calorimetry, and consists of 
a layer of tracking detectors and scintillation trigger counters 
before 1.8~T toroids, followed by two more similar layers after 
the toroids. Tracking at $|\eta|<1$ relies on 10~cm wide drift 
tubes~\cite{run1det}, while 1~cm mini-drift tubes are used at 
$1<|\eta|<2$.

Luminosity is measured using plastic scintillator arrays located 
in front of the EC cryostats, covering $2.7 < |\eta| < 4.4$. 
A forward-proton detector, situated in the Tevatron tunnel on 
either side of the interaction region, consists of a total of 
18 Roman pots used for measuring high-momentum charged-particle 
trajectories close to the incident beam directions.

The trigger and data acquisition systems are designed to accommodate 
the large luminosity of Run II. Based on preliminary information 
from tracking, calorimetry, and muon systems, the output of the first 
level of the trigger is used to limit the rate for accepted events 
to $\approx$ 1.5~kHz. At the next trigger stage, with more refined 
information, the rate is reduced further to $\approx$ 800~Hz. 
These first two levels of triggering rely purely on hardware and firmware. 
The third and final level of the trigger, with access to all the 
event information, uses software algorithms and a computing farm, 
and reduces the output rate to $\approx$ 50~Hz, which is written to tape.

{\em Special add-on for work based largely on the Muon Spectrometer; 
this can be inserted at the end of the above paragraph on the Muon 
System: Coverage for muons is partially compromised in the region of 
$|\eta|<1$  and  $|\phi| < 0.2$ rad, where the calorimeter is supported 
mechanically from the ground (see H. T. Diehl, D\O\ Note 4088, January, 2003). }


\begin{thebibliography}{99}
  \bibitem{run2det} V. Abazov, et al., in preparation for submission 
to Nucl. Instrum. Methods Phys. Res. A, and T. LeCompte and H.T. Diehl, 
``The CDF and D\O\ Upgrades for Run II'',  Ann. Rev. Nucl. Part. Sci. 
{\bf 50}, 71 (2000).

  \bibitem{run1det} S. Abachi, {\it et al}., Nucl. Instrum. Methods 
Phys. Res. A {\bf 338}, 185 (1994). 
\end{thebibliography}

\end{document}



