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

\title[Dark Photons at SeaQuest]{Direct Search for Dark Photons with the SeaQuest Spectrometer}

\author[Sho Uemura]{Sho Uemura, Kun Liu, Ming Liu\\Los Alamos National Laboratory\\SeaQuest Collaboration}
%\institute{bumming around}
\date[May 30, 2018]

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

\begin{document}

%\setcounter{framenumber}{2} 
\begin{frame}
    \titlepage
\end{frame}

%\begin{frame}{What is the dark photon?}
%\begin{columns}
%\column{0.6\textwidth}
%\begin{itemize}
%\item ``Dark sector'' emerging as a picture of dark matter that is compatible with light dark matter, and 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 The mixing can come from different mechanisms: natural scale for one-loop diagrams is $\epsilon\sim 10^{-2}-10^{-4}$, two-loop $\epsilon\sim 10^{-3}-10^{-6}$
%
%\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}{Parameter space}
%\begin{columns}
%\column{0.55\textwidth}
%\begin{itemize}
%\item Mass hierarchy: dark photon decays visibly if $m_{A'}<2m_\chi$, invisibly if $m_{A'}>2m_\chi$
%\begin{itemize}
%\item SeaQuest is sensitive to visible decays
%\end{itemize}
%\item Two relevant parameters: mass $m_{A'}$, coupling strength $\epsilon=\sqrt{\alpha'/\alpha}$
%\begin{itemize}
%\item Coupling strength governs production from, and decay to, Standard Model matter
%\item Favored region is $m_{A'}$ MeV---GeV, $\epsilon>10^{-6}$
%\end{itemize}
%\end{itemize}
%%\begin{center}
%%\includegraphics[width=0.6\textwidth]{st2_done_1000}
%%\end{center}
%\column{0.45\textwidth}
%\includegraphics[width=\textwidth]{seaquest_reach}
%\end{columns}
%\end{frame}

\begin{frame}{The SeaQuest facility}
    \begin{columns}
        \column{0.4\textwidth}
        \begin{itemize}
            \item Fixed-target muon spectrometer, Fermilab 120 GeV proton beam
            \item Primary program: Drell-Yan measurements of sea quark distributions
                \begin{itemize}
                    \item E906 (unpolarized targets, 2012--2017), E1039 (polarized targets, 2019--2020)
                \end{itemize}
                %\item Measurement of the nucleon sea quark distribution using Drell-Yan% ($q\bar{q}\to \mu^+\mu^-$)
            \item Parasitic searches for dark photons approved 2015 (E1067)
                %\item Thin ($\sim$10\%$\lambda_I$) rotating targets: LH2, LD2, C, Fe, W
                %\item Iron-filled dipole magnet serves as beam dump; second dipole magnet is used for momentum measurement
                %\item Drift chambers for tracking, scintillator hodoscopes for trigger
        \end{itemize}
        %\begin{center}
        %\end{center}
        \column{0.6\textwidth}
        \begin{flushright}
            \includegraphics[width=\textwidth]{seaquest_setup}
            \tiny{arXiv:1706.09990}
        \end{flushright}
    \end{columns}
\end{frame}

\begin{frame}{Production and signatures at SeaQuest}
    \begin{itemize}
        \item Three dominant production mechanisms: meson decay, proton bremsstrahlung, Drell-Yan
            (yields from arXiv:1804.00661)
            %\begin{itemize}
        \item Prompt $A' \to \mu^+\mu^-$: bump-hunt
        \item Displaced $A' \to \mu^+\mu^-$: background suppressed by vertexing
        \item Displaced $A' \to e^+e^-$: background absorbed in dump
            %\end{itemize}
    \end{itemize}
    \begin{columns}
        %\column{0.35\textwidth}
        %\begin{center}
        %\includegraphics[width=\textwidth]{ProductionAprime}
        %\end{center}
        \column{0.3\textwidth}
        \includegraphics[width=\textwidth]{meson_decay}

        \includegraphics[width=\textwidth]{proton_bremsstrahlung}

        \includegraphics[width=\textwidth]{drell-yan}

        \column{0.55\textwidth}
        \begin{flushright}
            \includegraphics[width=\textwidth]{ProductionAprime}
        \end{flushright}

        %\includegraphics[width=\textwidth]{darkphoton-BR-1-3000-LOG}
    \end{columns}
\end{frame}

\begin{frame}{SeaQuest searches for dark photons}
    \begin{columns}
        \column{0.55\textwidth}
        \begin{itemize}
                %\item Prompt dark photons (large $\epsilon$, large $m_{A'}$): look for a mass bump above the smooth Drell-Yan background
            \item Dimuons in main SeaQuest dataset
                \begin{itemize}
                    \item Bump-hunt at high mass (ongoing effort)
                \end{itemize}
            \item Dimuon displaced-vertex trigger
                \begin{itemize}
                    \item Commissioned 2017
                \end{itemize}
            \item Dielectron trigger
                \begin{itemize}
                    \item EMCal for electron PID (proposals in preparation)
                \end{itemize}
                %\item Non-prompt dark photons (small $\epsilon$): look for dilepton vertices deep inside or after the beam dump
                %\item Non-prompt search requires a new trigger for low-mass displaced vertices, which was commissioned this year
        \end{itemize}
        %\begin{center}
        %\includegraphics[width=\textwidth]{dimuon_mass}
        %\includegraphics[width=0.6\textwidth]{dimuon_z}
        %\includegraphics[width=\textwidth]{prompt}

        %\includegraphics[width=\textwidth]{displaced}
        %\end{center}
        %\column{0.35\textwidth}
        %\includegraphics[width=\textwidth]{prompt}

        %\includegraphics[width=\textwidth]{displaced}

        \column{0.45\textwidth}
        \begin{flushright}
            \includegraphics[width=\textwidth]{dimuon_mass}
            \tiny{E906 preliminary}
        \end{flushright}

        %\includegraphics[width=\textwidth]{prompt}

        %\includegraphics[width=\textwidth]{displaced}
        %\includegraphics[width=\textwidth]{dimuon_z}
    \end{columns}
    \begin{center}
        %\includegraphics[width=0.48\textwidth]{prompt}
        \includegraphics[width=0.7\textwidth]{displaced}
    \end{center}
\end{frame}

\begin{frame}{Displaced vertex trigger}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            \item Two new fine-grained scintillator hodoscopes measure track Y
            \item Existing station 4 paddles are used for muon ID
            \item FPGA trigger extrapolates tracks to the beam plane and fires on pairs of tracks with large Z
                % acceptance: z=400 to 650 cm
                %\item Extruded scintillator bars detect charged particles, wavelength-shifting fibers collect light and transport it to the SiPMs
                %\item Station 1: four boxes, 80 1-cm bars each
                %\item Station 2: four boxes, 50 2-cm bars each
        \end{itemize}
        \begin{center}
            %\includegraphics[width=0.7\textwidth]{trigger_sketch}
            \includegraphics[width=0.8\textwidth]{trigger_schematic}
            %\includegraphics[width=0.7\textwidth]{st2_done_1000}
        \end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth]{1mhodo_safety}
    \end{columns}
\end{frame}

\begin{frame}{Trigger hodoscopes}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            \item Extruded scintillator bars detect charged particles, wavelength-shifting fibers collect light and transport it to SiPMs
            \item Each station is split into quadrants; active area has a beam gap of $|y|>7.5$ cm but minimal gap in $x$
            \item Station 1: $z=8$ m, 1 cm segmentation, 80 bars/quadrant
                %80 cm long
            \item Station 2: $z=15$ m, 2 cm segmentation, 50 bars/quadrant
                %100 cm long
                %\item Station 1: four boxes, 80 1$\times$1 cm bars each
                %\item Station 2: four boxes, 50 2$\times$2 cm bars each
        \end{itemize}
        \begin{center}
            %\includegraphics[width=0.7\textwidth]{st2_done_1000}
            \includegraphics[width=0.55\textwidth]{IMG_4732}
            \includegraphics[width=0.4\textwidth]{IMG_4793_1000}

        \end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth]{st1_done_1000}

    \end{columns}
\end{frame}

\begin{frame}{Readout and services}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            \item Power supplies provide independent control of every SiPM bias voltage
            \item Postage-stamp preamps read out the SiPMs and send signals to discriminators
            \item Discriminators fan out to TDCs (readout) and CAEN V1495 FPGA boards (trigger)
        \end{itemize}
        \begin{center}
            \includegraphics[width=0.45\textwidth]{IMG_4794_half}
            \hspace{0.05\textwidth}
            \includegraphics[width=0.45\textwidth]{IMG_4795_half}
        \end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth]{cal_fibers_1000}
    \end{columns}
\end{frame}

%trigger requirements and acceptance
\begin{frame}{Trigger logic}
    \begin{columns}
        \column{0.6\textwidth}
        \begin{itemize}
            \item Two levels: identify displaced tracks, trigger on pairs
            \item L1: three-way coincidence within each quadrant
                \begin{itemize}
                    \item Identify displaced tracks ($z_0 \in [400,650]$ cm) in each quadrant using hit patterns (``roads'')
                \end{itemize}
            \item L2: two-out-of-four coincidence between opposite-sign quadrants
                %\begin{itemize}
                    %\item Require pairs of displaced tracks, opposite sign
                        %\item $z_0$ matching possible
                %\end{itemize}
                % acceptance: z=400 to 650 cm
                %\item Extruded scintillator bars detect charged particles, wavelength-shifting fibers collect light and transport it to the SiPMs
                %\item Station 1: four boxes, 80 1-cm bars each
                %\item Station 2: four boxes, 50 2-cm bars each
        \end{itemize}
        \begin{center}
            %\includegraphics[width=0.7\textwidth]{trigger_sketch}
            \includegraphics[width=0.8\textwidth]{trigger_schematic}
            %\includegraphics[width=0.7\textwidth]{st2_done_1000}
        \end{center}
        \column{0.4\textwidth}
        \includegraphics[width=\textwidth]{trigger_roads}
    \end{columns}
\end{frame}


\begin{frame}{Installation and commissioning}
    \begin{columns}
        \column{0.5\textwidth}
        \begin{itemize}
            \item Trigger hodoscopes installed on the SeaQuest beamline spring 2017
                %\item Detectors and trigger electronics tested and timed in
            \item Displaced vertex trigger rate is $\sim$5\% of the SeaQuest Drell-Yan trigger, acceptable for parasitic running
            \item 5 days of good data taken with the displaced vertex trigger before accelerator shutdown: $8\times 10^{15}$ live protons on target
            \item Expect O($10^{18}$) POT over the next two years, parasitic with new SeaQuest polarized target run
                % 8e15 protons on target
        \end{itemize}
        %\begin{center}
        %    \includegraphics[width=0.4\textwidth]{coincidence_2017-06-16}
        %    \hspace{0.1\textwidth}
        %    \includegraphics[width=0.4\textwidth]{triggerrate_ratio}
        %\end{center}
        \column{0.25\textwidth}
        \includegraphics[width=\textwidth]{IMG_2459_1000}

        \column{0.25\textwidth}
        \includegraphics[width=\textwidth]{IMG_2539_1000}
    \end{columns}
\end{frame}

%\begin{frame}{Analysis status and plans}
    %\begin{columns}
        %\column{\textwidth}
        %\begin{itemize}
            %\item Alignment and reconstruction: done
            %\item Detector efficiency: done
            %\item Trigger performance: in progress
            %\item Next steps:
                %\begin{itemize}
                    %\item Look for signal
                    %\item Understand our expected signal: update signal yields using as-built trigger geometry
                %\end{itemize}
        %\end{itemize}
        %\begin{center}
            %\hspace{0.1\textwidth}
        %\end{center}
    %\end{columns}
%\end{frame}

\begin{frame}{Detector performance}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            \item Efficiencies $\sim$95\% excepting $\sim$10\% bad channels
            \item Inefficiency: bar gaps
            \item Bad channels: inconsistent optical coupling (will fix)
        \end{itemize}
        \begin{center}
            \includegraphics[width=0.75\textwidth,page=30]{efficiency}
        \end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth,page=4]{efficiency}

        \includegraphics[width=\textwidth,page=31]{efficiency}

        %\column{0.30\textwidth}
        %\includegraphics[width=\textwidth,page=30]{efficiency}
        %\includegraphics[width=\textwidth]{IMG_2539_1000}
    \end{columns}
\end{frame}

%trigger performance: road checking
\begin{frame}{Trigger performance in 2017 data}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            %\item Check all trigger inputs arrive in time: OK
                %\begin{itemize}
                    %\item Top: hit times after delay adjustment (green: St1, blue: St2, red: H4)
                %\end{itemize}
            \item Displaced-vertex trigger is 150 ns late relative to the event (cabling mistake during commissioning)
            \item Damage report: lost all hits in station 1 drift chamber (120 ns drift time) and $\sim$50\% of hits in other drift chambers
            \item We can make straight tracks in stations 2--4 and try to assess backgrounds in the non-bend view
                \begin{itemize}
                    \item Problem: very bad (and angle-dependent) tracking efficiency
                \end{itemize}
            \item We can look at hodoscope hit information (not in time relative to events that fired the displaced-vertex trigger) to understand trigger backgrounds
                \begin{itemize}
                    \item May allow us to optimize the trigger criteria
                \end{itemize}
                %\item Input delays must be adjusted to compensate for time-of-flight and cable delays
                %\item All quadrant triggers must fire in time with each other, and the final dark photon trigger must have the same latency as the E906 DY trigger
                %\item Middle: time distribution of one quadrant's trigger signal
        \end{itemize}
        %\begin{center}
        %\end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth]{roadcheck}

        %\includegraphics[width=\textwidth]{TLquad_crop}

        %\includegraphics[width=\textwidth]{h1_aft_inh_nim_02}
    \end{columns}
\end{frame}

\begin{frame}{Schedule and prospects}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            \item Updated reach estimates soon
                \begin{itemize}
                    \item Realistic trigger geometry and acceptance
                \end{itemize}
            \item SeaQuest will run with polarized target (E1039) for two years: displaced-vertex dark photon search will run parasitically
                \begin{itemize}
                    \item Displaced-vertex trigger will be ready to go when beam is available
                \end{itemize}
            \item Possible PID upgrade (using recycled PHENIX EMCal) will add sensitivity to dielectron decay channel and other new physics (SIMPs, iDM)
        \end{itemize}
        %\begin{center}
        %\includegraphics[width=0.6\textwidth]{st2_done_1000}
        %\end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth]{e1039_target}

        \includegraphics[width=\textwidth]{Visible_Aprime_Future}
        \tiny{arXiv:1804.00661}
    \end{columns}
\end{frame}

\begin{frame}{EMCal upgrade}
    \begin{columns}
        \column{0.65\textwidth}
        \begin{itemize}
            \item One PHENIX EMCal sector: $2\times4$ m$^2$ wall of Pb-scintillator shashlyks
            \item Refurbish the readout: replace PMTs with SiPMs, new readout electronics
            \item Simple energy threshold can trigger on non-MIP particles
            \item Track matching enables electron ID
                %\begin{itemize}
                %\item P
                %\end{itemize}
        \end{itemize}
        \begin{center}
            \includegraphics[width=\textwidth]{emcal_location}
        \end{center}
        \column{0.35\textwidth}
        \includegraphics[width=\textwidth]{phenix_emcal}

        %\column{0.35\textwidth}
        %\includegraphics[width=\textwidth]{Visible_Aprime_Future}
    \end{columns}
\end{frame}


% Detector efficiency
% Trigger efficiency?
% EMCal


%\begin{frame}{Fix vertex fit}
%\begin{columns}
%\column{0.6\textwidth}
%\begin{itemize}
%\item The resolution of the reconstructed mass should be independent of Z but is worse for displaced vertices.
%\end{itemize}
%\begin{center}
%\includegraphics[width=\textwidth]{mass_shift_40}
%\end{center}
%\column{0.4\textwidth}
%\includegraphics[width=\textwidth,page=4]{acceptance_40}
%\end{columns}
%\end{frame}

\end{document}
