Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session U15: Mini-symposium on New Forces at the GeV Scale and Dark Matter III |
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Sponsoring Units: DNP Chair: Stepan Stepanyan, Jefferson Lab Room: Key 11 |
Monday, April 13, 2015 3:30PM - 3:42PM |
U15.00001: Heavy Photon Search Commissioning Run and Performance of the Electromagnetic Calorimeter Holly Szumila-Vance The Heavy Photon Search (HPS) experiment at Jefferson Lab will search for a possible new heavy vector boson that couples weakly to electric charge and can decay to $e^+e^-$ pairs. HPS utilizes an Electromagnetic Calorimeter (ECal) for fast triggering and complementary energy information in the reconstruction of the $e^+e^-$ invariant mass. The ECal is composed of 442 PbWO$_4$ crystals readout through large area avalanche photo-diodes and digitized using flash ADCs. The initial testing and calibration of the ECal began in the fall of 2014 using a light monitoring system, cosmic muons, and 2 GeV beam electrons. Proper performance of the ECal is crucial for optimizing the trigger selection for potential Heavy Photon events and eliminating background from accidentals. This talk covers the design, calibration, and performance of the HPS ECal during the commissioning run. [Preview Abstract] |
Monday, April 13, 2015 3:42PM - 3:54PM |
U15.00002: Results from the HPS Commissioning Run Nathan Baltzell The overwhelming evidence for the existence of dark matter is yet to be confirmed by direct detection. A dark photon could resolve existing puzzles in particle physics and provide a coupling with ordinary matter, but the parameter space of MeV-GeV masses and small couplings remains largely unexplored by experiments. The Heavy Photon Search in Hall-B at Jefferson Lab was designed to search for such a photon, radiated by few-GeV electrons, via its mass and vertex signatures in its decay to $e^{+}e^{-}$. The detector consists of a compact silicon tracker in a dipole field for momentum and vertex resolution, combined with a calorimeter for triggering and energy measurements. At the end of 2014, we commissioned the calorimeter, data acquisition, and triggering systems at the design luminosity. Preliminary results on expected and measured inclusive electron rates, as well as reconstruction of $e^{+}e^{-}$ invariant mass, will be presented. [Preview Abstract] |
Monday, April 13, 2015 3:54PM - 4:06PM |
U15.00003: Status of the DarkLight Experiment Charles Epstein The DarkLight experiment aims to search for a dark photon in the low mass region 10-100 MeV/c$^2$. The process $e^-p\rightarrow e^-pe^+e^-$ will be studied by using the Jefferson Lab energy-recovering linac's high-intensity 100 MeV, 1 MW electron beam incident on a gaseous hydrogen target. Full track reconstruction of the four-particle final state will be performed in order to search for a resonance on the e$^+$-e$^-$ invariant mass spectrum. A Phase 1 DarkLight experiment is in preparation in which we will additionally address new Standard Model measurements at low energy and high intensity. The design of the complete (Phase 2) DarkLight experiment is currently in progress. The status of the Phase 1 experiment will be described and the plan for the Phase 2 experiment presented. [Preview Abstract] |
Monday, April 13, 2015 4:06PM - 4:18PM |
U15.00004: DarkLight Invisibles Effort Narbe Kalantarians The DarkLight (Detecting A Resonance Kinematically with eLectrons Incident on a Gaseous Hydrogen Target) experiment at Jefferson Lab intends to study the process $e^{-}p\to e^{-}p{A}'$, with ${A}'$ being a hidden gauge boson decaying to $e^{-}e^{+}$. DarkLight will explore the A' mass region 10-100 MeV with sensitivity to couplings as low as ${\alpha }'/\alpha_{EM} \propto $ 10$^{\mathrm{-7\thinspace }}$with 1 ab$^{\mathrm{-1}}$ of data. The complete kinematic information provided by the DarkLight detector also permits a search for an invisibly decaying ${A}'$. In contrast to the numerous visible decay searches, both attempted and planned, there is considerably less data for the invisible decay. Furthermore, the limited data for invisibles' searches is from beam-dump and indirect decays, making this a unique measurement. This talk will focus on the invisibles effort for DarkLight, covering both the related physics and necessary instrumentation. [Preview Abstract] |
Monday, April 13, 2015 4:18PM - 4:30PM |
U15.00005: Search for a new gauge boson in a fixed-target experiment at CERN SPS Mikhail Kirsanov A fixed-target experiment at the CERN SPS utilizing the active beam dump and missing energy approach for the searches of a new gauge boson (A') with sub-GeV mass and mixing with ordinary photon is discussed. Electrons impinging on a high-Z target produce bremsstrahlung A's, decaying either to an e$^+$e$^-$ pair or invisibly to dark sector particles. The status of the experiment and the expected sensitivity in the test run in 2015 are presented. [Preview Abstract] |
Monday, April 13, 2015 4:30PM - 4:42PM |
U15.00006: Cornell Dark Photon Search James Alexander, Yuichi Kubota, Maxim Perelstein, David Rubin, Peter Wittich, Bogdan Wojtsekhowski We report on the concept and preliminary design of a search for dark photons. The A$'$ gauge boson of a nonstandard U(1) gauge symmetry (dark photon) may be produced in association with a normal photon in e+e- annihilation via $e^+e^-\to \gamma A'$. In the proposed experiment, the 5 GeV $e^+$ beam produced in Cornell's synchrotron is incident on a fixed target; following detection of the real photon, the A$'$ is reconstructed as a missing mass. This search strategy is wholly independent of the A$'$ decay channels. The sensitivity in A$'$ mass and kinetic coupling constant will be discussed. [Preview Abstract] |
Monday, April 13, 2015 4:42PM - 4:54PM |
U15.00007: ABSTRACT WITHDRAWN |
Monday, April 13, 2015 4:54PM - 5:06PM |
U15.00008: Light Meson Decays at Jefferson Lab Ilya Larin Decays of the eta and eta' mesons provide a unique possibility to probe physics beyond the Standard Model including searches for dark matter. The CLAS 6 GeV program in Hall B acquired large data-sets of light meson decays which are under analysis. The Jlab Eta Factory (JEF) Experiment has been proposed in Hall D to measure eta decays emphasizing rare neutral modes. Upgrading the central region of the GlueX forward calorimeter from lead glass to lead tungstate would provide 2 orders of magnitude background reduction compared to other facilities. Progress in CLAS 6 GeV light meson spectroscopy studies and details of the proposed JEF experiment will be presented. [Preview Abstract] |
Monday, April 13, 2015 5:06PM - 5:18PM |
U15.00009: Status of the APEX experiment Gregg Franklin, Rouven Essig, Philip Schuster, Natalia Toro, Bogdan Wojtsekhowski The A' EXperiment (APEX) will search for a new vector boson, $A'$, with weak coupling $\alpha' \agt 6\times 10^{-8} \alpha$ to electrons ($\alpha=e^2/4\pi$) in the mass range 65 MeV $< m_{A'} < $ 550 MeV. New vector bosons with such small couplings arise naturally from a small kinetic mixing of the ``dark photon'' $A'$ with the photon --- one of the very few ways in which new forces can couple to the Standard Model --- and have received considerable attention as an explanation of various dark matter related anomalies. $A'$ bosons are produced by radiation off an electron beam, and could appear as narrow resonances with small production cross-section in the trident $e^+e^-$ spectrum. We plan to search for the $A'$ by using the CEBAF electron beam at energies of $\approx$ 1--4 GeV incident on $0.5-10\%$ radiation length multi-foil Tungsten targets, and measure the resulting $e^+e^-$ pairs using the High Resolution Spectrometers and a septum magnet in Hall A at Jefferson Lab. With a 33-day run, the experiment will achieve very good sensitivity because the statistics of $e^+e^-$ pairs will be $\sim 10,000$ times larger in the explored mass range than any previous search for the $A'$ boson. This talk will discuss the experiment and present the results of a pilot run. [Preview Abstract] |
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