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%\title[GEANT4/EGS5]{GEANT4/EGS5}

\title[The Heavy Photon Search]{The Heavy Photon Search Experiment at Jefferson Laboratory}

\author{Sho Uemura}
\institute{SLAC\\\vspace{0.2 cm} on behalf of the HPS Collaboration\\\includegraphics[width=0.35\textwidth]{HPS_logo}}
\date[April 14, 2013]

\titlegraphic{
		\includegraphics[height=0.1\textheight]{SLAC_Logo}\hspace*{4.75cm}~
		\includegraphics[height=0.1\textheight]{partner_logo_v2}
}

\begin{document}

\begin{frame}
	\titlepage
\end{frame}

\begin{frame}{What is the heavy photon?}
	\begin{columns}
	\column{0.6\textwidth}
		\begin{itemize}
			\item A new massive $U(1)$ boson with no (direct) coupling to SM
			\begin{itemize}
				\item Kinetic mixing with the photon $\to$ weak coupling to electric charge [Holdom 1986]
			\end{itemize}
			\item If it couples to dark matter, could serve as ``portal'' to the dark sector
			\item Two relevant parameters: mass $m_{A'}$, relative coupling strength $\alpha'/\alpha$
		\end{itemize}
	\column{0.4\textwidth}
	\begin{center}
		\includegraphics[width=\textwidth]{sm_dark}

		\includegraphics[width=\textwidth]{kinetic_mixing}
	\end{center}
	\end{columns}

\end{frame}

\begin{frame}{Why do we care?}
	\begin{columns}
	\column{0.6\textwidth}
	\begin{columns}
	\column{0.6\textwidth}
		\begin{itemize}
			\item PAMELA, Fermi, AMS find cosmic ray $e^+$ excess
			\begin{itemize}
				\item DM annihilation? Can't be direct (no $\bar{p}$ excess), but consistent with sub-GeV $m_{A'}$
			\end{itemize}
			% \begin{itemize}
			% 	\item Sub-GeV $m_{A'}$ is easy to obtain theoretically
			% \end{itemize}
		\end{itemize}
	\column{0.4\textwidth}
		\begin{center}
			\includegraphics[width=\textwidth]{ams_galprop}

			\includegraphics[width=\textwidth]{dm_aprime}
		\end{center}
	\end{columns}
	\begin{columns}
	\column{0.8\textwidth}
		\begin{itemize}
			\item Muon g-2 deviates from SM predictions
			\begin{itemize}
				\item Can be explained by $A'$
			\end{itemize}
			% \begin{itemize}
			% 	\item Sub-GeV $m_{A'}$ is easy to obtain theoretically
			% \end{itemize}
		\end{itemize}
	\column{0.2\textwidth}
		\begin{center}
			\includegraphics[width=\textwidth]{gm2c}
		\end{center}
	\end{columns}
	\begin{itemize}
		\item Many current searches! See Tuesday talk by John Jaros
	\end{itemize}
	\column{0.4\textwidth}
			\includegraphics[width=\textwidth]{limits.png}
	\end{columns}

\end{frame}

\begin{frame}{Producing heavy photons}
	\begin{columns}
	\column{0.65\textwidth}
	\begin{itemize}
		\item Similar to bremsstrahlung: $e^-$ (1.1, 2.2 and 6.6 GeV) on high-Z fixed target
	\end{itemize}
	\column{0.35\textwidth}
	\includegraphics[width=0.8\textwidth]{prod_diagram}
	\end{columns}
	\begin{center}
		\includegraphics[width=0.65\textwidth]{production}
	\end{center}
	\begin{itemize}
		\item $A'$ carries most of incident $e^-$ energy (unlike $\gamma$ bremsstrahlung)
		\item Pairs from $A'$ decay are produced along beam with some decay length and small opening angle
		% \begin{itemize}
		% 	\item Track pairs, find vertex and invariant mass
		% \end{itemize}
	\end{itemize}
\end{frame}

\begin{frame}{Search channels}
	\begin{columns}
	\column{0.5\textwidth}
	\begin{itemize}
		\item Bump hunt: look for a peak in pair invariant mass
			\begin{itemize}
				\item $A'$ decays compete with QED tridents; mass resolution ($\sim$MeV) is key
			\end{itemize}
		\item Vertexing: look for pairs originating downstream of the target
			\begin{itemize}
				\item Requires a tracker close to the target for $\sim$mm vertex resolution
			\end{itemize}
		\item HPS probes a large unexplored region of the parameter space
	\end{itemize}
	\column{0.5\textwidth}
		\includegraphics[width=\textwidth]{reach.pdf}
	\end{columns}
\end{frame}

\begin{frame}{The HPS detector}
	\begin{center}
		\includegraphics[width=0.8\textwidth]{svt.pdf}
	\end{center}
	\begin{columns}
	\column{0.5\textwidth}
		\begin{itemize}
			\item Thin (0.125\% or 0.25\% $X_0$) tungsten target
			\item Silicon microstrip tracker in vertical B-field for measurement
			\item PbWO$_4$ calorimeter and scintillator hodoscopes for trigger
		\end{itemize}
	\column{0.5\textwidth}
		\includegraphics[width=\textwidth]{hps_setup.pdf}
	\end{columns}
\end{frame}

\begin{frame}{Killing backgrounds \dots in space}
	\begin{center}
		\includegraphics[width=\textwidth]{hps_side}
	\end{center}
	\begin{columns}
	\column{0.6\textwidth}
		\begin{itemize}
			\item Main detector background is electrons scattered in the target and bent by the tracking field: ``sheet of flame''
			\item Vacuum transport for primary+scattered beam through entire detector
			\item All detectors split $\pm$15 mrad above and below beam plane
			\begin{itemize}
				\item Active region of tracker layer 1 is 1.5 mm from beam
			\end{itemize}
		\end{itemize}
	\column{0.4\textwidth}
		\includegraphics[width=\textwidth]{flame.pdf}

		\includegraphics[width=\textwidth]{occupancy.png}
	\end{columns}
\end{frame}

\begin{frame}{Killing backgrounds \dots in time}
	\begin{columns}
	\column{0.5\textwidth}
	\begin{itemize}
		\item CEBAF at JLab: continuous beam (499 MHz rep rate and 100\% duty cycle)
		\item Use time resolution to reject out-of-time hits
		\begin{itemize}
			\item Tracker readout: APV25 (CMS) with 24 ns sampling period (2 ns resolution after time reconstruction)
			\item ECal and muon system readout: FADC250 (JLab) with 4 ns sampling period
		\end{itemize}
	\end{itemize}
	\column{0.5\textwidth}
		\includegraphics[width=\textwidth]{t0}
	\end{columns}
\end{frame}

\begin{frame}{2012 test run and beyond}
	\begin{columns}
	\column{0.45\textwidth}
	\begin{itemize}
		\item Built and ran a test version of the tracker and the full ECal in a parasitic run with a photon beam
		\item Demonstrated key challenges:
		\begin{itemize}
			\item verified MC treatment of multiple Coulomb scattering
			\item multi-kHz trigger and readout
			\item tracker hit time reconstruction
		\end{itemize}
		\item On track for full run when CEBAF resumes operation after 12 GeV upgrade --- late 2014
	\end{itemize}
	\column{0.55\textwidth}
		\includegraphics[width=\textwidth]{tracker3}

		\includegraphics[width=\textwidth]{track.pdf}
	\end{columns}
\end{frame}
\end{document}
