Session S15: Mini-symposium on New Forces at the GeV Scale and Dark Matter II

Accelerator-Produced sub-GeV Dark Matter Search Using MiniBooNE

Cosmological observations indicate that our universe contains dark matter (DM), yet we have no measurements of its microscopic properties. Whereas the gravitational interaction of DM is well understood, its interaction with the Standard Model is not. Direct detection experiments, the current standard, search for a nuclear recoil interaction and have a low-mass sensitivity edge of order 1 GeV. To detect DM with mass below 1 GeV, either the sensitivity of the experiments needs to be improved or use of accelerators producing boosted low-mass DM are needed. Using neutrino detectors to search for low-mass DM is logical due to the similarity of the DM and $\nu$ signatures in the detector. The MiniBooNE experiment, located at Fermilab on the Booster Neutrino Beamline, has produced the world's largest collection of $\nu$ and $\bar{\nu}$ samples and is already well understood, making it desirable to search for accelerator-produced boosted low-mass DM. A search for DM produced by 8.9 GeV/c protons hitting a steel beam-dump has finished, collecting $1.86\times10^{20}~\mathrm{POT}$. Analysis techniques, predicted sensitivity, and preliminary results on the partial data set will be presented.   

Hidden Sector Searches at the NOvA Near Detector

We search for Axions, Dark Matter candidates and Hidden Sector particles from New Physics, possibly produced in the NuMI fixed-target complex. The main signatures of such particles interacting in the NOvA Near Detector may be either single showers from scattering interactions or di-lepton tracks from the particle decays within the detector. The upgraded neutrino source, delivering nearly 1E15 POT per sec, surpasses the most stringent dark matter production upper limits of current models in the under-10GeV mass range. We take advantage of the sophisticated electron shower identification algorithms of NOvA to interrogate the data from the first production runs with the near detector. Initially, we search for interactions on atomic electrons at large energy transfer. We focus on indications of any excess events above the predicted neutrino neutral-current rates at these ranges. These studies will influence the development of further data analysis channels and the designs of the next generations of neutrino near detectors as well as dedicated detectors for hidden sector searches worldwide.   

A search at Super-Kamiokande for low mass dark matter candidates in the T2K neutrino beam

The T2K neutrino beam is produced by colliding 30 GeV protons with a graphite target, and some dark sector models predict that a dark matter candidate could be created in the collision. This massive and neutral particle could scatter off a nucleon in Super-Kamiokande, a 50 kilotonne water Cherenkov detector. Similar to the neutral-current quasielastic neutrino-oxygen interaction, the dark matter candidate could interact with the oxygen nucleus, kicking out a nucleon and leaving the nucleus in an excited state. As the nucleus deexcites, 6 MeV gamma-rays are emitted which can be efficiently detected by Super-Kamiokande. The longer time of flight for a dark matter candidate, compared to a neutrino, allows separation between the dark matter induced signal and the neutrino induced background. In the intense global effort to measure dark matter, this complementary search investigates the sub-GeV mass range where other experiments have reduced sensitivity.   

Projections for Dark Photon Searches at Mu3e

We show that dark photons (A') with masses ~10-80 MeV can be probed in the decay $\mu^+\to e^+ \nu_e \bar{\nu}_\mu A'$, $A' \to e^+e^-$, with the upcoming Mu3e experiment at the Paul Scherrer Institute (PSI) in Switzerland. With an expected $10^{15}$ ($5.5\times 10^{16}$) muon decays in 2015-2016 (2018 and beyond), Mu3e has the exciting opportunity to probe a substantial fraction of currently unexplored dark photon parameter space, probing kinetic-mixing parameter, $\epsilon$, as low as $\epsilon^2 \sim 10^{-7}~(10^{-8})$. No modifications of the existing Mu3e setup are required.   

The Heavy Photon Search Experiment at Jefferson Lab

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.   

Tracking and Vertexing for the Heavy Photon Search Experiment

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.