\section{CALORIMETERS}
\label{sec-cals}

   Because of the Tevatron's physics program dependence
on lepton identification and jet energy measurement,
calorimetry is a critical aspect of Run II experiments.
As an example, Fig.~\ref{fig-d0-top-end} shows a candidate
top quark event from the D\O \ experiment.  The calorimeters
are used for identification and measurement of the
electron, neutrino and jets from the decays of the top
quarks in these events.

   Calorimetry is divided into two parts, electromagnetic
and hadronic.  Nearest the vertex is the electromagnetic
calorimeter which measures the energy of electrons and photons
(including those from $\pi^0$ and $\eta$ decay) and has
improved position measurement at the point of maximum 
shower development.  Farther back is the hadronic 
calorimeter which measures the energy of hadrons as
they interact with the material of the calorimeter.  
Muons deposit a small ammount of energy (due to ionization)
in both sections, and the lack of a large energy deposit
can be used to identify a particle as a muon.  Neutrinos
deposit no energy at all in these calorimeters, but
the absense of energy deposition appears as a momentum
imbalance in the transverse plane, also called ``missing
$E_T$".

\begin{figure}[hb]
\begin{center}
\epsfxsize=4.5in
\epsfbox{d0_top_evt.eps}
\caption{An end view of a 
$t\overline{t} \rightarrow e + {\rm jets}$ 
event from D\O.  The electron is at 5:00, the neutrino
at 8:00, and several jets are visible at the top half
of the detector.}
\end{center}
\label{fig-d0-top-end}
\end{figure}

\subsection{CDF's Central and Endplug Calorimeters}

   The CDF central calorimeter is largely unchanged.  Towers
are $15^\circ$ in $\phi$ and 0.1~units of $\eta$ and are 
composed of alternating layers of scintillator and
absorber - lead in the case of the electromagnetic 
calorimeter and iron in the case of the hadronic 
calorimeter.  A set of wire chambers with additional
cathode strip readout is located at the depth of
maximum shower development: these chambers provide 
detailed profiles of the transverse shower development,
and are used to identify electrons vs. hadrons and
$\pi^0 \rightarrow \gamma + \gamma$ decays vs. single
photons.  In front of the calorimeter, behind a single
radiation length of absorber from the magnet coil is an
additional set of chambers.  This preconverter is used
primarily to separate photons from $\pi^0$'s on a
statistical basis.  The probability $P$ a photon will 
deposit energy in the preconverter is given by 
$P=e^{-1}$ (about 60\%) and the probabiity a $\pi^0$ will 
deposit energy is instead 
$P=(2e^{-1}-e^{-2})$ (about 80\%).

   The scintillator has a very fast response time
(a few 10's of nanoseconds), so is well suited for the
faster crossing time of Run 2.  The gas-based shower 
maximum and preconverter detectors are slower, taking a
few hundred nanoseconds to completely collect all the
signal.  However, because the occupancies are quite
low in these devices, it's reasonable to collect the
charge in multiple crossings, and then have the front
end electronics deconvolve the pulse shape by summing
the data from the previous crossings.

   Forward of $30^\circ$ ($\eta=1.3$), however, the
calorimeters have been completely replaced.  Originally,
CDF used two gas-sampling calorimeters, one between
$30^\circ$ and $10^\circ$ and the other forward of
$10^\circ$.  The relatively slow signal formation
time of these calorimeters compared to scintillator
made their replacement for Run II desirable.  
Additionally, there were two operational difficulties
that this technology change also addressed: controlling
the gas gain in the face of temperature and pressure 
changes in the experimental hall is no longer necessary,
and the large calorimeter signals from slow neutrons
(so-called ``Texas Towers") will no longer be present.

   The new endplug calorimeter (Fig.~\ref{fig-cdfendplug})
covers from $30^o$
($\eta=1.3$ for the hadronic section, and $\eta=1.1$
for the electromagnetic section, which fits inside the
magnet bore) down to $3^o$ ($\eta=3.6$)  The electromagnetic
section is made of alternating lead plates and scintillator sheets
and the hadronic section is made of alternating steel plates and
scintillator sheets.  In this ``megatile" design, grooves are cut 
in the scintillator to optically isolate one $\eta-\phi$
section from another (calorimeter segmentation is shown
in Fig.~\ref{fig-cdfendtile})
, and additional grooves are cut to route
wavelength shifting fiber.  Light that is produced by the
scintillator is absorbed in the fiber where it excites
a green fluorescent dye.  This green light is emitted inside
the fiber where it is totally internally reflected and
transported to photomultiplier tubes mounted outside the
calorimeter, on the east and west faces of the detector.

\begin{figure}
\begin{center}
\epsfxsize=4.5 in
\epsfbox{plug_schem.eps}
\end{center}
\caption{The new CDF endplug calorimeter.}
\label{fig-cdfendplug}
\end{figure}

\begin{figure}
\begin{center}
\epsfxsize=4.5 in
\epsfbox{plug_seg.eps}
\end{center}
\caption{The $\eta-\phi$ segmentation of the new CDF 
endplug calorimeter.  The coarser segmentation at 
high rapidity is determined by the minimum fiber
bend radius - smaller tiles cannot be constructed
with reliable optical readout.}
\label{fig-cdfendtile}
\end{figure}

   At the maximum point of electromagnetic shower
development a position and energy sensitive shower
maximum detector is installed.  Unlike in the central
case, where the corresponding subdetector is gas-based, 
in the plug region it is constructed of strips of 
scintillator with an embedded wavelength shifting fiber,
and read out by multi-anode photomultiplier tubes.  This
allows for a faster signal formation time, so that no
electronic deconvolution is necessary, and for the first
time provides information on shower shape (used for
electron-hadron and $\pi^0$-$\gamma$ separation) in the
forward region.

  CDF has proposed a ``miniplug" detector to cover the
far forward region, similar to D\O\'s Forward Proton Detector
(described below).  At the time of this writing, this was
still in the proposal phase.

\subsection{D\O's Calorimeters and Preshower Detectors}
D\O's hermetic, radiation-hard uranium and liquid-argon 
calorimeter~\cite{d0runI} consists of three separate cryostats: the Central 
Calorimeter (CC), and the two Endcap Calorimeters (EC's). Each is segmented
into an electromagnetic section, a hadronic section, and a coarse hadronic 
section (inside to outside), with many layers of sampling. Each is 
divided into pseudoprojective towers covering $\eta \times \phi = 0.1 
\times 0.1$.  The readout of the electromagnetic section has four layers of 
longitudinal segmentation.  The third electromagnetic layer,
at EM shower maximum, has segmentation $\eta \times \phi = 0.05 \times 0.05$.
The readout of the hadronic sections have 4 (5) longitudinal layers in the 
CC (EC's). There are no projective cracks.  
The calorimeter  provides hermetic coverage to $|\eta|<4$.
The energy resolution is $\sigma_E/E=15\%/\sqrt{E({\rm GeV})} \oplus 0.4\%$
for electrons and photons.  For charged pions and 
jets the resolutions were approximately $50\%/\sqrt{E({\rm GeV})}$ and
$80\%/\sqrt{E({\rm GeV})}$, respectively.  Figure~\ref{fig-d0det} shows 
the three cryostats within the D\O \ detector.

The calorimeters and cryostats remain unchanged from Run~I but new 
readout electronics are required in order to cope with the Run~II bunch 
spacing. To minimize the effects of pileup, the pulse-shaping and readout 
time was reduced. Analog buffering is used to store the data while 
waiting out the trigger decision. These tasks are performed without a 
degredation of the resolution relative to the Run~I detector.

The Inter Cryostat Detectors (ICD's) augment the D\O \ liquid argon 
calorimeters by providing a measurement of the energy in between the 
central and endcap cryostats. This improves the energy measurement for 
jets which straddle the intercryostat region and improves the resolution 
of the missing transverse energy measurement. New ICD's are required for 
Run~II because the old ones wouldn't be able to operate in the magnetic 
field of the solenoid magnet. Sixteen new ICD detector segments 
form an annular ring of 1/2" thick scintillator covering 
$1.1\le |\eta| \le 1.4$ on the hadronic section of the inner end of each 
EC cryostat. The sixteen segments are further segmented into sections of size 
$\Delta \eta \times \Delta \phi =0.1 \times 0.1$. 
Each section has an embedded wavelength shifting fiber
to collect light. These are in turn connected to long clear fibers which carry
the light to photomultiplier tubes located underneath the cryostats, in a 
region with reduced magnetic field from the solenoid. 

The Central and Forward Preshower Detectors (CPS and FPS) are new 
additions to D\O.   The primary purpose is to exploit the difference 
between energy loss mechanisms of electrons and photons with that of the 
backgrounds, principally hadronic jets with leading $\pi^0$'s, to improve 
the trigger and offline purity.  Secondly, they provide a precision 
measurement of the starting point of the electromagnetic showers.
The CPS is cylindrically shaped, mounted on the outside of the solenoid 
magnet, and covers the region $|\eta|\le 1.3$. The FPS are shaped like 
annular rings, mounted on the inside of the EC's, and cover the region
$1.5\le|\eta|\le 2.5$. The FPS and CPS are shown in Fig.~\ref{fig-d0-fps3}.

The CPS has three layers of triangular-shaped scintillating strips with 
embedded wavelength shifting fibers~\cite{adams1,adams2}.
The strips are arrayed in axial, and 
$\pm 22.5 ^\circ$ stereo orientations behind a 7/32" thick lead converter. 
The effect of the solenoid plus the lead totals two radiation 
lengths at $\eta=0$ and increases to four radiation lengths at the ends.  
The CPS works in combination with the fiber tracker to identify photons 
from electrons from hadronic tracks. Simply put, photons produce no track
in the fiber tracker, but interacting in the lead, leave a cluster of 
energy in the CPS. Electrons have a track and a similar cluster of energy 
in the CPS. Muons and charged pions have tracks but, 
not interacting in lead, leave only a 
minimum-ionizing hit in the CPS.  Only the axial layers are used in the 
Level~1 trigger.

The FPS has two pairs of layers of the triangular-shaped scintillating strips,
one pair in-front-of and another pair behind a two radiation length lead 
converter. Each pair of layers consists of two arrays of the triangular-shaped
scintillating strips, with wavelength shifing fiber, offset by $22.5 ^\circ$ 
from each other. Particle identification works the same way in the FPS 
as in the CPS except that the first two layers of the FPS provide hits from 
electrons (and other charged particles) but not from photons. Those
hits are in addition to the track-stubs from the inner trackers.

\begin{figure}
\begin{center}
\epsfxsize=4.5 in
\epsfbox{d0-fps3.eps}
\end{center}
\caption{One quarter $r-z$ view of the end of the D\O \ trackers 
and the start of the EC, indicating the Central Preshower, the Level~0 
detector, the solenoid magnet and calorimeter cryostats, and the Forward 
Preshower detector.  The Forward Preshower detector is shown in detail 
in the inset. }
\label{fig-d0-fps3}
\end{figure}

The D\O \ Run~II luminosity monitor (Level~0) consists of two  
arrays of plastic scintillation counters located on the inside faces 
of the EC's and arranged symmetrically around the beampipe. 
The pseudorapity coverage is $2.7 \le |\eta| \le 4.4$. Because the 
solenoid field is $\sim 1$~Tesla in that region, short magnetic field 
resistant photomultiplier tubes are used to read the light. A coincidence
of hits in the counters on both sides of the interaction point 
provides the simplest indication that an inelastic collision occurred.

A new near beam detector called the ``Forward Proton Detector" is planned 
for Run~II. It is a series of small, retractable scintillating fiber 
detectors placed a few millimeters from the beamline in the region 20-60 
meters from both sides of the interaction point. They are triggered by 
small scintillation counters and readout by multi-anode PMT's. Their 
purpose is to identify scattered protons and anti-protons in diffractive 
events. 

\begin{table}[ht]
 \begin{tabular}{ l  r  r } \hline \hline 
%  \multicolumn{3}{|c|} {Electromagnetic Calorimetry} \\ \hline
 Electromagnetic Calorimetry   
                          & CDF Experiment   & D\O \ Experiment \\ \hline
  Absorber Material       & Lead             & Uranium          \\
  Readout technology      & Scintillator     & Liquid Argon     \\    
  Resolution ($\sigma(E)/E$)             
                          & $13.5\%/\sqrt{E} \oplus 2\%$
                                             & $15\%/\sqrt{E}\oplus 0.4\%$
                                                                \\
  Longit. Readout Segm.        
                          &      -           &   4  layers     \\
  Granularity  ($\eta-\phi$)     
                          & $0.1 \times 0.3$ & $0.1 \times 0.1$ \\
  Granularity @ shower maxmimum 
                          & $0.005\times 0.005$
                                             & $0.05 \times 0.05$  
                                                                \\ \hline
% \multicolumn{3}{|c|} {Hadronic Calorimetry} \\ \hline
 Hadronic Calorimetry     & CDF Experiment   & D\O \ Experiment \\ \hline
  Absorber Material       & Iron             & Uranium          \\
  Readout technology      & Scintillator     & Liquid Argon     \\
  Resolution  ($\sigma(E)/E$)  
                          & $80\%/\sqrt{E}$  & $50\%/\sqrt{E}$  \\
  Longit. Readout Segm.  
                          &      -           & 4 (CC)  5 (EC) layers   \\ 
  Granularity  ($\eta-\phi$)     
                          & $0.1 \times 0.3$ & $0.1 \times 0.1$ \\
                                                                \hline \hline
 \end{tabular}
 \caption{Electromagnetic (EM) and hadronic calorimetry performance for
  the CDF and D\O\ detectors.  Because performance depends on 
  many details (geometry, beam conditions, etc.) these values
  should be regarded as approximate.}
\end{table}








