\title{Tracking and Vertexing for the Heavy Photon Search Experiment}

\author{Sho Uemura\\SLAC National Accelerator Laboratory\\HPS Collaboration}

\date{January 9, 2015}

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\begin{abstract}
	The Heavy Photon Search (HPS) requires precision tracking and vertexing of $e^+e^-$ pairs against a high background in a difficult experimental environment.
	The silicon vertex tracker (SVT) for HPS uses actively cooled silicon microstrip sensors with fast readout electronics.
	To maximize acceptance and vertex resolution with a relatively small detector, the SVT operates directly downstream of the target, close to the beam line, and inside of a dipole magnet.
	This talk presents the design and performance of the HPS SVT.
	
	%The silicon vertex tracker (SVT) operates close to the target and beamline, in vacuum and in the bore of a dipole magnet.
	%To maximize acceptance and vertex resolution with a relatively small detector, the SVT 
	%the first layer of silicon sensors is placed only 10~cm downstream of the target and 500 $\mu$m away from the beam line.
	%Much of the SVT --- the sensors, frontend readout, and ADCs --- operates in vacuum and inside the bore of a dipole magnet.
	%The HPS silicon vertex tracker employs actively cooled silicon microstrip sensors with fast readout electronics, directly downstream of a target and inside of a dipole magnet
	%A simple, small-scale version of the HPS SVT was operated on beam at Jefferson Lab in 2012; 
	%the lessons learned from that detector have been incorporated in the current SVT.

	%The Heavy Photon Search (HPS) is a new experiment at Jefferson Lab that will search for 
	%massive U(1) vector bosons (also known as heavy photons, dark photons, or $A'$)
	%of mass 20--1000 MeV that couple to electric charge with relative coupling $\alpha'/\alpha$ of $10^{-5}$--$10^{-10}$.
	%The HPS experiment is designed to produce heavy photons by electron scattering off a fixed target, and 
	%detect decays to $e^+e^-$ pairs with two signatures (invariant mass resonance and displaced decay vertex).
	%The detector is a compact, large-acceptance forward spectrometer 
	%comprising a silicon microstrip tracker for momentum measurement and vertexing and an electromagnetic calorimeter for triggering on $e^+e^-$.
	%This talk will give an overview of the HPS experiment and its current status after test, commissioning, and engineering runs.
\end{abstract}

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