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\section{The Silicon Strip Tracker Layout}
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\label{sec:Layout}
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The CMS SST
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instruments the radial range between 20~cm and 116~cm and $|\eta| < 2.5$ around the
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LHC interaction point.
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The central region ($|z| < 118$ cm
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\footnote{A CMS coordinate system, used through this note, is defined in such a way that
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$z$ is the coordinate along the LHC beam axis, $y$ is the vertical direction and $x$
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complete the system; the origin being the nominal beam interaction point.})
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is split into an Inner Barrel (TIB), made of four detector layers, and an
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Outer Barrel (TOB), made of six detector layers. The TIB is shorter than the TOB, and is
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complemented
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by three Inner Disks per side (TID), each Disk being in turn composed of three
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Rings. The forward and backward regions
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(124~cm $ < |z| < $282~cm) are covered by nine Endcap (TEC) disks per side, each one made of
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up to seven rings.
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The two innermost layers of both TIB and TOB as well as rings number one, two and five
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of TEC and one and two of TID are instrumented with double-sided detector modules.
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A complete description of the Silicon Tracker layout (Fig.\ref{fig:layout})
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can be found elsewhere~\cite{ref:layout}.\\
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\begin{figure}[!htb]
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\begin{center}
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\includegraphics[width=0.85\textwidth]{Figs/rz.pdf}
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\end{center}
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\caption{Longitudinal cross section of one quarter of the CMS SST.
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Thicker (blue) segments indicate double-sided silicon microstrip modules.
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The nominal beam interaction point is located in (0,0), dimensions are in mm.
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The pseudorapidity ($\eta$) coverage is also shown.}
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\label{fig:layout} % Give a unique label
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\end{figure}
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The whole tracker region is embedded into the CMS 4~Tesla solenoidal magnetic field.
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Charged particle transverse momentum resolution of about 1.5\% for centrally-produced
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muon of 100~GeV/$c$ is expected~\cite{ref:ptdr}. \\
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From the detector construction point of view it is important to note that the TIB/TID
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system is divided into two physically separated structures: TIB/TID+, which is located in the
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$|z| > 0$ region and TIB/TID-, located in the $|z| < 0$.\\
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The entire tracker is inserted in a carbon fiber Support Tube which is attached to
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the Electromagnetic Calorimeter and insulated by the rest of the experiment by a
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'Thermal Shield'.
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