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Extended figure caption for two figures of results from the
STAR Small Prototype EMC 1995 Test Run.
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Contact person for these figures and this caption: 
W.J. Llope
llope@physics.rice.edu
713-527-4741
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The Small Prototype ElectroMagnetic Calorimeter (SPEMC) for STAR was tested at
the BNL B2 test beam line in two runs during June, 1994 and May, 1995. The
device is a six tower prototype of STAR's barrel EMC, which is a
lead-scintillator sampling calorimeter with a depth of $\sim$20$X_0$ that
covers rapidities between plus and minus one and the full azimuth, totalling
$\sim$50 m$^2$ in area. A  Shower Maximum Detector (SMD), which is a wire/strip
chamber, is situated at a depth of $\sim$5$X_0$ inside the stack to provide a
position resolution of less than one centimeter and to allow several different
methods for the discrimination of hits from hadronic and electromagnetic
particles. More detailed information on the SPEMC and the two test runs can be
obtained from the World Wide Web at the address http://bonner-mac8.rice.edu/.

Some results obtained from the in-beam tests of the prototypical SPEMC+SMD
system are shown in the accompanying figures. During these runs, beams of
positive and negative electrons, pions, and muons over a wide range of momenta
were directed at the device, which was configured in a number of different ways
including three different SMDs, several angles of incidence of the beam, and
several different depth-segmentations of the calorimeter. The first figure
depicts the summed pulse height spectra for 5 GeV/c $\pi^-$ and $e^-$. The
insets show the linearity and resolution for electrons over a range of momenta
from 0.3 to 8 GeV/c, where $\mu$ and $\sigma$ are the mean value and width of
Gaussian fits to the electron total pulse height spectra. The resolution that
was achieved is significantly better than the design goal. The second figure
shows typical results obtained from the wire/strip chamber SMD for the 5 GeV/c
beams. The significant differences in the total SMD signals for pions and
electrons that are apparent are just one of the means of discriminating between
electromagnetic and hadronic particles using the present EMC+SMD system. The
insets show the correlations between the X and Y positions of electron hits as
measured by the SMD versus the same positions of the incident beams, which
indicate that the SMD indeed provides position resolutions of less than a
centimeter.