Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session J13: Mini-Symposium: New Approaches to Search for non-WIMP Dark MatterFocus
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Sponsoring Units: DNP DPF Chair: Reyco Henning, University of North Carolina Room: Roosevelt 5 |
Sunday, January 29, 2017 10:45AM - 11:21AM |
J13.00001: New Frontiers in Dark Matter Detection Invited Speaker: Jesse Thaler Dark matter, detected thus far only through its couplings to gravity, remains an enigma. It is therefore essential to pursue a broad portfolio of search strategies to test for non-gravitational interactions between dark matter and visible matter. In this talk, I give an overview of recent progress in detecting dark matter and related particles, ranging from ultralight axion-like particles to hidden sector dark forces. [Preview Abstract] |
Sunday, January 29, 2017 11:21AM - 11:33AM |
J13.00002: The low-energy program of the \sc {Majorana Demonstrator} Ralph Massarczyk The {\sc Majorana} Collaboration constructed an ultra-low background, modular high-purity Ge detector array to search for neutrinoless double-beta decay in $^\mathrm{76}$Ge. Located at the 4850-ft level of the Sanford Underground Research Facility, the {\sc Demonstrator} detector assembly has the goal to show that it is possible to achieve background rates necessary for future ton-scale experiments. \\ The ultra-clean assembly in combination with low-noise p-type point contact detectors allows measurements with thresholds in the keV range. The talk will give an overview of the low-energy physics and recent achievements made since the completed {\sc Demonstrator} array started data taking in mid 2016. Recent results from campaign will be presented, including new limits on bosonic dark matter interaction rates. \\ This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics Program of the National Science Foundation, and the Sanford Underground Research Facility. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program. [Preview Abstract] |
Sunday, January 29, 2017 11:33AM - 11:45AM |
J13.00003: Can nuclear physics explain the anomaly observed in the internal pair creation in Beryllium-8 nucleus? Xilin Zhang, Gerald A. Miller Recently, the experimentalists in [Phys.Rev.Lett.116.042501(2016)] claimed seeing unexpected enhancement of the internal electron-positron pair ($e^+$-$e^-$) production in the large $e^+$-$e^-$ relative angle region in the EM transition from the Beryllium-8 nucleus’s second lowest $1^+$ state to its ground state. According to the experimentalists, the signal can be explained by a new neutral boson weighted around 17 MeV. This has stipulated significant interests in the particle physics community [e.g. Phys.Rev.Lett.117.071803(2016)]. In this talk, I will present our latest study of the underlying nuclear physics, and emphasize several pieces of physics that haven’t been well studied theoretically and not been included in the current experimental analysis, including the interferences between the dominant E1 and M1 transitions, two extra angular dependences, possible impact of E2 transition and its interferences with E1 and M1, and nuclear form factor. I will also point out that the previously measured on-shell photon production constrains the ratio between E1 and M1 contributions in the pair production, which however haven’t been checked in the current experimental analysis. In the end, I will discuss the possibility of nuclear physics being the origin of the observed anomaly. [Preview Abstract] |
Sunday, January 29, 2017 11:45AM - 11:57AM |
J13.00004: ${ }^{8}Be$ Anomalous Internal Pair Production: Possible E2 Transitions . Thomas Ward, David Koltick, Haoyu Wang Significant enhancement of ${ }^{8}Be$ internal pair production at 16.7 MeV with large angle correlations from the 18.150 MeV ($J^{\pi }=1^{+})$ level have been interpreted as a possible dark matter candidate, a light ($J^{\pi }=1^{+})$ neutral boson [PRL \underline {116}\textbf{(}2016)042501] or a fifth-force vector gauge boson [PRL \underline {117}(2016)071803]. We present a conventional alternative interpretation, unseen E2 transitions from the $J^{\pi }=2^{+}$levels at 16.626 MeV and 16.922 MeV populated in the decay of the 18.150 MeV ($J^{\pi }=1^{+})$ level. The calculated E2 transition probabilities agree well with the measured pair production intensity in the back angle correlation where one expects the E2 gamma-ray correlation to peak. . [Preview Abstract] |
Sunday, January 29, 2017 11:57AM - 12:09PM |
J13.00005: Sub-GeV Dark Matter Search with MiniBooNE Rex Tayloe Cosmological observations indicate that our universe contains dark matter (DM), however, we have yet to conclusively detect DM directly or measure its microscopic properties. Direct detection experiments search for a nuclear recoil interaction produced by a DM relic particle and have a sensitivity to DM particle mass down to order 1~GeV. To explore below this limit, searches for boosted dark matter in particle beams may be employed. The MiniBooNE experiment, which ran for a decade at Fermilab to measure $\nu$, $\bar{\nu}$ oscillations and interactions, conducted a dedicated run in 2014 with the Fermilab Booster 8~GeV proton beam incident on a steel beam stop. Using this beam configuration and the existing and well-understood MiniBooNE detector, the MiniBooNE-darkmatter collaboration searched for low-mass DM in nucleon recoil events. Results from this search as well as future prospects will be presented. [Preview Abstract] |
Sunday, January 29, 2017 12:09PM - 12:21PM |
J13.00006: Searching for heavy photons at Jefferson Lab using detached vertices Lawrence Weinstein, Holly Szumila-Vance The Heavy Photon Search (HPS) experiment in Jefferson Lab Hall B will look for a new U(1) vector boson (called a "heavy photon", "dark photon", or A') in the mass range from 20 to 600 MeV/c$^{\mathrm{2}}$. This A' could potentially couple to the ordinary photon through kinetic mixing, which would create a coupling to electric charge of ${\alpha }'/\alpha =\epsilon ^{2}$. If so, then the A' can be produced through electron interactions with a heavy target through a process analogous to bremsstrahlung. The A' could then decay to $e^{+}e^{-}$. If the coupling $\epsilon $ is large, we can directly detect a peak in the $e^{+}e^{-}$ mass spectrum above the dominant QED background. If $\epsilon $is small, then we can look for $e^{+}e^{-}$ events with a detached vertex resulting from A' decays downstream of the production target. In 2015 and 2016 we measured a few beam days each of 1.1 and 2.2 GeV electron scattering from tungsten using a large acceptance forward spectrometer consisting of a silicon vertex tracker located inside a dipole magnet and a lead tungstate electromagnetic calorimeter for triggering. This talk will present the detached vertex A' search, including preliminary results at 1.1 GeV if available. [Preview Abstract] |
Sunday, January 29, 2017 12:21PM - 12:33PM |
J13.00007: Resonance Search for a Heavy Photon in the 2015 Engineering Run Data of the Heavy Photon Search Experiment Omar Moreno The Heavy Photon Search (HPS) experiment at Jefferson Lab is searching for a new $U(1)$ vector boson (``heavy photon'',``dark photon'' or $A'$) in the mass range of 20-500 MeV/c$^{2}$. An $A'$ in this mass range is theoretically favorable and may also mediate dark matter interactions. The $A'$ couples to the ordinary photon through kinetic mixing, which induces their coupling to electric charge. Since heavy photons couple to electrons, they can be produced through a process analogous to bremsstrahlung, subsequently decaying to an $e^{+}e^{-}$, which can be observed as a narrow resonance above the dominant QED trident background. For suitably small couplings, heavy photons travel detectable distances before decaying, providing a second signature. Using the CEBAF electron beam at Jefferson Lab incident on a thin tungsten target, along with a compact, large acceptance forward spectrometer consisting of a silicon vertex tracker and lead tungstate electromagnetic calorimeter, HPS is accessing unexplored regions in the mass-coupling phase space. The HPS engineering run took place in spring of 2015 using a 1.056 GeV, 50 nA beam and collected 1165 nb$^{-1}$ (7.29 mC) of data. This talk will present the results of a resonance search for a heavy photon using the engineering run data. [Preview Abstract] |
Sunday, January 29, 2017 12:33PM - 12:45PM |
J13.00008: The Light Dark Matter eXperiment Owen Colegrove The Light Dark Matter eXperiment (LDMX) proposes a high-statistics search for low-mass dark matter at a new experimental facility, Dark Sector Experiments at LCLS-II (DASEL), at SLAC. LDMX employs the missing momentum technique, where electrons scattering in a thin target can produce dark matter via ``dark bremsstrahlung'' that are not observed in the detector. To identify these rare signal events, LDMX individually tags incoming beam-energy electrons, unambiguously associates them with low energy, moderate transverse-momentum recoils of the incoming electron, and establishes the absence of any additional forward-recoiling charged particles or neutral hadrons. LDMX will employ low mass tracking to tag incoming beam-energy electrons with high purity and cleanly reconstruct recoils. A high-speed, granular calorimeter with MIP sensitivity is used to reject the high rate of bremsstrahlung background at trigger level while working in tandem with a hadronic calorimeter to veto rare photo nuclear reactions. Ultimately, LDMX aims to probe thermal dark matter over most of the viable sub-GeV mass range to a decisive level of sensitivity. This talk will summarize the current status of the LDMX design and performance studies and progress in developing the DASEL beamline. [Preview Abstract] |
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