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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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

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

\author{Sho Uemura}
\institute{SLAC\\\vspace{0.2 cm} on behalf of the HPS Collaboration\\\includegraphics[width=0.35\textwidth]{HPS_logo}}
\date[March 8, 2016]

\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}{Dark forces and the heavy photon}
	\begin{columns}
	\column{0.6\textwidth}
		\begin{itemize}
%			\item Motivations: direct detection and SUSY searches aren't finding anything
			\item ``Dark sector'' emerging as a picture of dark matter that allows for self-scattering, collisional excitation, annihilation
			\begin{itemize}
				\item Standard Model forces don't couple to the dark sector, dark forces don't couple to Standard Model matter
				\item ``Portals'' create weak effective couplings between the sectors
			\end{itemize}
			\item Vector portal: dark mediator is a massive $U(1)$ boson (heavy photon)
			\begin{itemize}
				\item Kinetic mixing with the photon $\to$ weak coupling to electric charge
			\end{itemize}
			\item A different motivation: muon $g$-2 anomaly

%			\item A new massive $U(1)$ boson with no (direct) coupling to SM
%			\item One possible ``portal'' between SM and a dark sector
%			\item Useful in explaining PAMELA/Fermi/AMS positron excess, muon g-2 anomaly
		\end{itemize}
	\column{0.4\textwidth}
	\begin{center}
		\includegraphics[width=\textwidth]{sm_dark}

		\includegraphics[width=\textwidth]{kinetic_mixing}

		\includegraphics[width=0.4\textwidth]{gm2c}

	\end{center}
	\end{columns}
\end{frame}

\begin{frame}{Parameter space}
	\begin{itemize}
		\item Two relevant parameters: mass $m_{A'}$, relative coupling strength $\epsilon^2=\alpha'/\alpha$
		\item Let's assume $A'\to$ dark is kinematically forbidden, and $A'\to e^+e^-$ is allowed
		\begin{itemize}
			\item If $A'\to$ dark is allowed, decays compete: generically, coupling to DM $\alpha_D$ is much larger than coupling to SM
%			\item Searches for $A'\to$dark: invisible decay searches, DM production experiments
		\end{itemize}
		\item $\epsilon^2$ controls both production from, and decay to, SM (the harder it is to make an $A'$, the longer the lifetime)
		\item Branching fractions depend on $m_{A'}$
	\end{itemize}
	\begin{center}
		\includegraphics[width=0.4\textwidth]{branchingfraction}
	\end{center}
\end{frame}

%\begin{frame}{Searching for the heavy photon}
%	\begin{columns}
%	\column{0.6\textwidth}
%		\begin{itemize}
%			\item Produce the heavy photon, 
%			\begin{itemize}
%				\item Can heavy photon decay to the dark sector?
%			\end{itemize}
%		\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}{Past and current searches}
	\begin{columns}
	\column{0.5\textwidth}
		\begin{itemize}
			\item Production: anything that makes virtual photons (bremsstrahlung, Drell-Yan, $e^+e^-$ colliders, meson decays)
%			\item HPS and most current experiments look for SM decay products
%			\begin{itemize}
%				\item If decay to DM is kinematically allowed, life is harder!
%			\end{itemize}
%			\item Production: Bremsstrahlung, Drell-Yan, meson decays
			\item Searches: thick fixed targets (beam dumps), thin fixed targets, colliders, meson factories
			\item Signatures: mass bumps, displaced vertices, missing energy
%			\item Beam dumps (thick fixed targets)
%			\item Thin fixed targets
%			\item Colliders
%			\item Rare decays ($\pi\to \gamma A'$, $h\to ZA'$)
		\end{itemize}
	\column{0.5\textwidth}
	\begin{center}
		\includegraphics[width=\textwidth]{reach-otherexps}
	\end{center}
	\end{columns}
\end{frame}

\begin{frame}{Producing heavy photons}
	\begin{itemize}
		\item Similar to bremsstrahlung: $e^-$ on high-Z fixed target
		\item $A'$ carries most of incident $e^-$ energy% (unlike $\gamma$ bremsstrahlung)
		\item Pairs from $A'$ decay are produced along beam with small opening angle
		\item Decay length depends on coupling, can be measurable
		\item Measure momentum and direction of decay products to get the invariant mass
		\item The recoil electron can improve the measurement precision, if detected
	\end{itemize}
	\begin{center}
		\includegraphics[width=0.4\textwidth]{branchingfraction}
		\includegraphics[width=0.6\textwidth]{production}
	\end{center}
\end{frame}

\begin{frame}{HPS search channels}
	\begin{columns}
	\column{0.6\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 is key
			\end{itemize}
		\item Vertexing: look for pairs originating downstream of the target (zero-background, cut and count)
			\begin{itemize}
				\item Requires a tracker close to the target for $\sim$mm vertex resolution
			\end{itemize}
			\item Main background for both searches is QED tridents
	\end{itemize}
	\begin{center}
		\includegraphics[width=\textwidth]{rad-bh-diagrams}
	\end{center}
	\column{0.4\textwidth}
		\includegraphics[width=\textwidth]{ctau}

		\includegraphics[width=\textwidth]{vertexing_demo}
	\end{columns}
\end{frame}

\begin{frame}{The HPS detector}
	\begin{center}
		\includegraphics[width=0.7\textwidth]{HPS-pic}
%		\includegraphics[width=0.8\textwidth]{svt.png}
	\end{center}
	\begin{columns}
	\column{0.6\textwidth}
		\begin{itemize}
			\item Chicane downstream of CLAS detector in JLab Hall B
			\item 50-450 nA electron beam at 1.1-6.6 GeV
			\item Thin (4 or 8 $\mu$m) tungsten target
			\item Silicon microstrip tracker in dipole magnet for measurement
			\item PbWO$_4$ calorimeter for trigger
		\end{itemize}
	\column{0.4\textwidth}
		\begin{center}
			\includegraphics[width=\textwidth]{svt.png}
		
			\includegraphics[width=0.8\textwidth]{hallb}
		\end{center}
	\end{columns}
\end{frame}

\begin{frame}{HPS reach}
	\begin{columns}
	\column{0.5\textwidth}
	\begin{itemize}
		\item HPS probes a large unexplored region of the parameter space
%			\begin{itemize}
%				\item Bump-hunt region is under pressure; vertexing is our strength
%			\end{itemize}
%		\item Extra: at 6.6 GeV, HPS is sensitive to true muonium
		\item Mass range is limited on the left by detector acceptance, on the right by production cross-section
		\item Bump hunt reach is limited on the bottom by statistics ($S/\sqrt{B}$ in a mass window)
		\item Vertexing reach is limited on the upper right by the resolvable decay length (tails of the trident vertex distribution)
		\end{itemize}
	\column{0.5\textwidth}
		\includegraphics[width=\textwidth]{A-visible-HPS-official-6-2015}
	\end{columns}
\end{frame}

\begin{frame}{Requirements}
	\begin{itemize}
		\item big boosts, small opening angles (15 mrad): far forward
		\item vertexing -> close in (10 cm)
		\item degraded beam goes through detector: elastic scatters, hard brems
		\begin{itemize}
			\item avoid backgrounds: space, time, trigger
		\end{itemize}
		\item multiple scattering dominates: minimize mass
	\end{itemize}
\end{frame}

\begin{frame}{Killing backgrounds \dots in space}
	\begin{columns}
	\column{0.6\textwidth}
	\begin{center}
		\includegraphics[width=\textwidth]{hps_side}
	\end{center}
		\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 (inactive silicon extends to 0.5 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 ($\sigma_t\approx$ 2 ns)
			\item ECal readout: FADC250 (JLab) with 4 ns sampling period ($\sigma_t\approx$ 400 ps, can resolve beam bunches)
		\end{itemize}
	\end{itemize}
	\column{0.5\textwidth}
		\includegraphics[width=\textwidth]{t0}

		\includegraphics[width=\textwidth]{clustertime}
	\end{columns}
\end{frame}

\begin{frame}{Killing backgrounds \dots with trigger}
	\begin{itemize}
		\item Trigger requires two clusters in time coincidence, $E_{sum}<E_{beam}$, opposite sides of the beam axis
		\begin{itemize}
			\item Elastic-scattered electrons: $E\approx E_{beam}$, bent to the electron side
			\item Pairs: $E_{sum}<E_{beam}$, split top-bottom and left-right
		\end{itemize}
		\item Trigger can be highly selective: captures essentially all $A'$ events where the $e^+e^-$ pair hits the ECal, with trigger rate on backgrounds of 5-20 kHz
	\end{itemize}
	\begin{center}
		\includegraphics[width=0.5\textwidth]{trigger_ratevsacceptance}
	\end{center}
\end{frame}

\begin{frame}{Measurement}
	\begin{columns}
		\column{0.6\textwidth}
		\begin{itemize}
			\item Track momentum: limited by MS in silicon
			\item Opening angle: limited by layer 1 $\sigma_y$ and vertex $\sigma_z$
			\item Bump-hunt: vertex is fixed at $z=0$
			\item Vertexing: vertex Z is limited by MS in layer 1
%				\begin{itemize}
%					\item Large layer-1 scatters can be identified because vertex momentum does not point back to beamspot
%				\end{itemize}
		\end{itemize}
		\column{0.4\textwidth}

			\includegraphics[width=\textwidth]{constraints}

	\end{columns}
	\begin{center}
		\includegraphics[width=0.5\textwidth]{mass-resolution}
		\includegraphics[width=0.5\textwidth]{vertexRes-1pt1-2pt2-6pt6}
	\end{center}
\end{frame}

\begin{frame}{Beamline}
%	\begin{columns}
%		\column{0.6\textwidth}
		\begin{itemize}
			\item Asymmetric ``pancake'' beamspot
			\begin{itemize}
				\item Narrow $\sigma_y$: stronger beamspot constraint for vertexing
				\item Wide $\sigma_x$: spread out the beam to limit target heating
			\end{itemize}
			\item Beam tails at $10^{-6}$ level
			\item Special precautions to protect the SVT
			\begin{itemize}
				\item Orbit locks for beam stability
				\item Protection collimator in front of SVT
				\item Halo counter FSD to trip beam if it scrapes the collimator
				\item Scan wires mounted directly on the SVT
			\end{itemize}
		\end{itemize}
%		\includegraphics[width=0.7\textwidth]{beamsize}
%		\column{0.4\textwidth}
%	\end{columns}
	\begin{center}
		\includegraphics[width=0.43\textwidth]{beamsize}
		\includegraphics[width=0.33\textwidth]{beam-tails}
	\end{center}
\end{frame}

\begin{frame}{ECal}
	\begin{columns}
		\column{0.55\textwidth}
		\begin{itemize}
			\item PbWO$_4$ crystals with APD readout, based on CLAS Inner Calorimeter
			\item 250 MHz digitization and pulse fitting, great time resolution
			\item Energy resolution can improve on SVT momentum resolution, but limited by edge effects
		\end{itemize}
		\column{0.45\textwidth}
		\includegraphics[width=\textwidth]{ECal}

		\includegraphics[width=\textwidth]{ecal_module}
%		\includegraphics[width=\textwidth]{ecal-eres}
	\end{columns}
	\begin{center}
		\includegraphics[width=0.4\textwidth]{fee-eres}
		\includegraphics[width=0.4\textwidth]{ecal-tres}
	\end{center}
\end{frame}

\begin{frame}{The HPS SVT}
	\begin{center}
		\includegraphics[width=0.8\textwidth]{svt_cutaway}
	\end{center}
	\begin{itemize}
		\item The silicon vertex tracker (SVT) provides the basic HPS measurements: charge, momentum and vertex
		\item Dipole B-field (0.5 T at 2.2 GeV) from target to end of tracker
		\item Six layers: pairs of silicon microstrip sensors in small-angle stereo
			\begin{itemize}
				\item Layers 1--3 (single-ended) are mounted on hinges and can move away from the beam
				\item Layers 4--6 (double-ended) are fixed at 15 mrad
			\end{itemize}
	\end{itemize}
\end{frame}

\begin{frame}{Design performance and resolutions}
%	\begin{columns}
%		\column{0.6\textwidth}
		\begin{itemize}
			\item Hit resolutions: $\sigma_x<125 \mu$m, $\sigma_y<10 \mu$m
			\begin{itemize}
				\item Small-angle stereo trades off $\sigma_x$ for hit confusion
			\end{itemize}
			\item Single-hit efficiency better than 99\%, track efficiency better than 95\%
			\item Momentum resolution $\sigma_p/p \approx 6.5\%$ with 1.05 GeV beam (scales as 1/$B$)
			\item All resolutions (momentum, mass, vertex) dominated by multiple scattering
		\end{itemize}
%		\column{0.4\textwidth}
		\begin{center}
		\includegraphics[width=0.75\textwidth]{svt-design}
		\end{center}
%		\includegraphics[width=\textwidth]{trkeff}
%		\includegraphics[width=0.5\textwidth]{fee-pres}

%		\includegraphics[width=\textwidth]{pz2pt2GeV-MomRes-Tracks}

%		\includegraphics[width=\textwidth]{vertexRes-1pt1-2pt2-6pt6}
%		\includegraphics[width=\textwidth]{massRes-2pt2}

%	\end{columns}
\end{frame}

\begin{frame}{SVT design constraints}
	\begin{itemize}
		\item Thin ($<1\% X_0$ per layer): minimize multiple scattering
		\item Fast ($\sigma_t\approx 2$ ns): cut backgrounds (4 MHz/mm$^2$) with hit time measurement
		\item Cold: silicon at $-10^\circ$C to mitigate radiation damage
		\item Mobile: fine adjustment of distance from beam
		\item In vacuum: avoid beam-gas backgrounds
		\item Near target, near beam (10 cm downstream of target, 0.5 mm from beam): maximize vertex resolution and acceptance
		\item Compact: fits in existing magnet (16'' W $\times$ 7'' H)
	\end{itemize}
	\begin{center}
		\includegraphics[width=0.4\textwidth]{svt_drawing}
		\includegraphics[width=0.3\textwidth]{svt_box_downstream}
		\includegraphics[width=0.3\textwidth]{scatterplot}
	\end{center}
\end{frame}

\begin{frame}{Mechanical design}
	\begin{columns}
		\column{0.5\textwidth}
		\begin{itemize}
			\item Sensors from D0 run IIb
			\item Support structure is thinner than the silicon; total average thickness 0.7$X_0$ per module
			\item Spring pivot pulls the silicon flat, module structure cools silicon from both ends
			\item ``U-channels'' support and cool modules in sets of 3
			\item Aligned to 100 $\mu$m, surveyed to 50 $\mu$m
		\end{itemize}
		\column{0.5\textwidth}
		\includegraphics[width=\textwidth]{l123}

		\vspace{0.2cm}

		\includegraphics[width=\textwidth]{l456}
	\end{columns}
	\begin{center}
		\includegraphics[width=0.8\textwidth]{l456_hm}
	\end{center}
\end{frame}

\begin{frame}{SVT data acquisition}
	\begin{columns}
		\column{0.6\textwidth}
		\begin{itemize}
			\item APV25-based hybrid readout board: triggered 40 MHz analog readout
			\item Frontend boards: control and trigger, low voltage distribution, ADC
			\item Flange boards: vacuum penetration and copper-to-fiber transceivers
			\item RCE DAQ: data reduction, event building, integration with JLab DAQ
			\item Trigger rate up to 50 kHz, data rate to tape up to 100 MB/s
		\end{itemize}

		%\includegraphics[width=0.3\textwidth]{flangeboards}
		\column{0.4\textwidth}
		\includegraphics[width=\textwidth]{svt_febs}

		\includegraphics[angle=90,width=\textwidth]{flangeboard}

		\includegraphics[width=\textwidth]{rce}
	\end{columns}
\end{frame}

\begin{frame}{Hit time reconstruction}
	\begin{columns}
		\column{0.55\textwidth}
		\begin{itemize}
			\item Beam backgrounds make $\sim$100 junk hits per event
			\item Hottest strips see hit rates over 1 MHz; lots of pileup
			\item Read out six samples at 24 ns intervals, fit preamp pulse shape including pileup for $\sigma_t\approx 2$ ns
			\item Use hit times in track finder to reject junk hits
		\end{itemize}
		\column{0.45\textwidth}
		\includegraphics[width=\textwidth]{t0}

		\includegraphics[width=\textwidth]{linfit}
	\end{columns}
\end{frame}

\begin{frame}{Assembly and installation}
	\begin{center}
		\includegraphics[width=0.6\textwidth]{svt_box}
		\includegraphics[width=0.4\textwidth]{svt_box_with_si}
	\end{center}
	%\begin{columns}
	%\column{0.4\textwidth}
	%\includegraphics[width=\textwidth]{svt_box}
	%
	%\includegraphics[width=\textwidth]{svt_box_with_si}
	%
	%\column{0.35\textwidth}
	%\includegraphics[width=\textwidth]{svt_box_with_febs}
	%
	%\includegraphics[width=\textwidth]{svt_box_with_cables}
	%\end{columns}
	\begin{center}
		\includegraphics[width=0.8\textwidth]{svt_done_open}
	\end{center}
\end{frame}

\begin{frame}{HPS status and run plan}
	\begin{itemize}
		\item HPS schedule is constrained by other Hall B experiments (CLAS, PRad)
		\item Test run (bare-bones SVT, photon beam): May 2012
		\item ECal-only commissioning run: December 2014
		\item Engineering run: March-May 2015
			\begin{itemize}
				\item 1 week (nights and weekends) of physics data at 1.05 GeV and nominal SVT position: about 2 days of beam
			\end{itemize}
		\item 2.3 GeV physics run February-March 2016
			\begin{itemize}
				\item 4 weekends of physics data: about 1.5 days of beam so far
			\end{itemize}
	\end{itemize}
	\begin{center}
		\includegraphics[width=0.4\textwidth]{engrun-beamtime}
		\includegraphics[width=0.6\textwidth]{physrun-beamtime}
	\end{center}
\end{frame}

\begin{frame}{Elastic and Moller scatters}
	\begin{columns}
		\column{0.55\textwidth}
		\begin{itemize}
			\item Elastic scatters ($E\approx E_{beam}$) are a basic normalization and calibration signal
			\begin{itemize}
				\item Scale and resolution for momentum and energy, time resolution, alignment
				\item Rates within 5\% of MC
			\end{itemize}
			\item Moller scatters: $E_{sum}=E_{beam}$, $m=\sqrt{2E_{beam}m_e}$, exact correlation between the two detected particles
			\begin{itemize}
				\item Mass resolution as expected
				\item Tag-and-probe measurement of tracking efficiency: roughly 95\%
			\end{itemize}
		\end{itemize}
%	\begin{center}
%		\includegraphics[width=\textwidth]{fee-rates}
%	\end{center}
		\column{0.45\textwidth}
		\includegraphics[width=\textwidth]{fee-eres}

		\includegraphics[width=\textwidth]{fee-pres}

	\end{columns}
\end{frame}

%\begin{frame}{Moller scatters}
%	\begin{columns}
%		\column{0.55\textwidth}
%		\begin{itemize}
%			\item Moller scatters: $E_{sum}=E_{beam}$, $m=\sqrt{2E_{beam}m_e}$, exact correlation between the two detected particles
%			\begin{itemize}
%				\item Mass resolution as expected
%				\item Tag-and-probe measurement of tracking efficiency: roughly 95\%
%			\end{itemize}
%		\end{itemize}
%		\column{0.45\textwidth}
%		\includegraphics[width=\textwidth]{mollerres}
%
%	\end{columns}
%\end{frame}

%\begin{frame}{Tridents}
%	\begin{columns}
%		\column{0.55\textwidth}
%		\begin{itemize}
%			\item Radiative ($E_{sum}\approx E_{beam}$) and Bethe-Heitler tridents ($E_{sum}<< E_{beam}$)
%			\item $A'$ cross-section is normalized to radiative trident cross section
%		\end{itemize}
%		\begin{center}
%			\includegraphics[width=\textwidth]{rad-bh-diagrams}
%		\end{center}
%		\column{0.45\textwidth}
%		\includegraphics[width=\textwidth]{trident-pevspp}
%
%		\includegraphics[width=\textwidth]{trident-mass}
%
%	\end{columns}
%\end{frame}

\begin{frame}{Vertexing tridents}
	\begin{columns}
		\column{0.55\textwidth}
		\begin{itemize}
			\item Multiple scattering distribution leads to Gaussian core and non-Gaussian tail
			\item Large scatters in L1 can fake a displaced vertex; large scatters in later layers can cause misassociated hits
%			\item Tails of the vertex distribution agree between data (black) and MC (red)
			\item Work continues on using both data and MC to characterize tails
		\end{itemize}
		\column{0.45\textwidth}
		\includegraphics[width=\textwidth]{golden-mgraham-norm-36}

		\includegraphics[width=\textwidth]{tails}
%		\includegraphics[width=\textwidth]{overlay-slice-36}
	\end{columns}
\end{frame}

\begin{frame}{Progress and plans for analysis}
%	\begin{columns}
%		\column{0.55\textwidth}
		\begin{itemize}
%			\item Detector performance papers in progress
			\item Finishing detector performance studies, calibrations, alignment
			\item Preparing bump-hunt and vertexing analyses
			\item Blinded analysis: only using 10\% of the data right now
%			\item Physics processes we can observe:
		\end{itemize}
		\begin{center}
		\includegraphics[width=0.5\textwidth]{trident-pevspp}
		\includegraphics[width=0.5\textwidth]{trident-mass}
		\end{center}

%		\column{0.45\textwidth}
%%		\includegraphics[width=\textwidth]{fee-eres}
%%
%%		\includegraphics[width=\textwidth]{fee-pres}
%
%	\end{columns}
%	\begin{center}
%		\includegraphics[width=0.7\textwidth]{fee-rates}
%	\end{center}
\end{frame}

\appendix
\backupbegin
\begin{frame}{Vertex resolution}
	\begin{columns}
		\column{0.6\textwidth}
		\begin{itemize}
			\item Vertexing search achieves $10^{-7}$ rejection of the trident background
			\item Misassociated layer 1 hits are the main source of vertex tails
		\end{itemize}
		\column{0.4\textwidth}
		\includegraphics[width=\textwidth]{vtx2pt2-80mev}

		\includegraphics[width=\textwidth]{tails}
	\end{columns}
\end{frame}

\begin{frame}{Reach}
	\begin{columns}
		\column{0.4\textwidth}
		\begin{itemize}
			\item Vertex cut (10--30 mm) set for $<0.5$ events/mass bin
		\end{itemize}
		\begin{center}
			\includegraphics[width=0.5\textwidth]{decay-lengths-2pt2}
			\includegraphics[width=0.5\textwidth]{decay-lengths-6pt6}
		\end{center}
		\column{0.6\textwidth}
		\includegraphics[width=\textwidth]{reach}
	\end{columns}
\end{frame}

\begin{frame}{Test run}
	\begin{columns}
		\column{0.6\textwidth}
		\begin{itemize}
			\item 2012 test run with first-attempt design on a very tight schedule
			\item Developed all the basic elements of our design, and found areas for improvement
			\item Proved detector performance (timing, S/N, efficiencies)
		\end{itemize}
		\begin{center}
			\includegraphics[width=0.7\textwidth]{testrun_svt_jlab}
		\end{center}
		\column{0.35\textwidth}
		\includegraphics[width=\textwidth]{time_res}

		\includegraphics[width=\textwidth]{sn_landau}
	\end{columns}
\end{frame}

\begin{frame}{Potential upgrades}
	\begin{columns}
		\column{0.6\textwidth}
		\begin{itemize}
			\item Layer 0: add thin silicon at 5 cm to improve vertex resolution and recoil electron acceptance
			\item Possible increases in rate and current 
			\item SuperHPS: two-armed spectrometer with much higher luminosity
		\end{itemize}
		\column{0.35\textwidth}
		\includegraphics[width=\textwidth]{time_res}

		\includegraphics[width=\textwidth]{sn_landau}
	\end{columns}
\end{frame}

\begin{frame}{Detailed reach}
	\begin{columns}
	\column{0.55\textwidth}
	\begin{itemize}
		\item purple, dashed: 1 week of 50nA, 1.1 GeV beam on a 0.125\% target
		\item blue, dashed: 1 week of 200nA, 2.2 GeV beam on a 0.125\% target
		\item blue, solid: 3 weeks of 200nA, 2.2 GeV beam on a 0.125\% target
		\item dark green: 2 weeks of 450nA, 6.6 GeV beam on a 0.25\% target, detecting $A'\to e^+e^-$
		\item light green: 2 weeks of 450nA, 6.6 GeV beam on a 0.25\% target, detecting $A'\to \mu^+\mu^-$
		\item red:  the statistical combination of all of the above
		\item green shaded:  3 months each of 2.2 GeV and 6.6 GeV
	\end{itemize}
	\column{0.45\textwidth}
		\includegraphics[width=\textwidth]{HPS-Proposal2014-DetailedReach}
	\end{columns}
\end{frame}

\backupend
\end{document}