Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session J11: Minisymposium: Dark Forces below the Proton Mass Scale |
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Sponsoring Units: DNP Chair: O. Keith Baker, Yale University Room: Embassy F |
Sunday, April 1, 2012 1:30PM - 2:06PM |
J11.00001: Theory and Status of New Sub-GeV Forces Invited Speaker: Natalia Toro The search for new forces mediated by sub-GeV particles with very weak coupling to matter (``dark forces'') is an emerging frontier in physics beyond the standard model. These forces remain quite weakly constrained, but will be explored by several experiments in the coming years. We will outline the theoretical motivations for such forces, and their possible connection to the physics of dark matter and the anomalous magnetic moment of the muon. We will also discuss their phenomenology and the prospects for upcoming searches at high-energy colliders, flavor factories, and dedicated fixed-target experiments. Though the talk will focus on searches for MeV-to-GeV-mass force carriers, we will also briefly discuss a related class of searches for even lower-mass particles mixing with the photon, known as ``paraphotons.'' [Preview Abstract] |
Sunday, April 1, 2012 2:06PM - 2:18PM |
J11.00002: Dark Photon Searches at MAMI Achim Denig The A1 high resolution spectrometer setup at the Mainz Microtron MAMI is ideally suited for Dark Photon searches in the mass range below 1 GeV. We present recent results from a pilot run as well as perspectives for future measurements. The electron beam is scattered on a high $Z$ nuclear target and two A1 spectrometers are measuring $e^+e^-$ pairs which are expected to be emitted from a $\gamma^\prime$ decay. QED background from Bethe-Heitler processes are giving the major background to the potential Dark Photon signal. We also report on future measurements with the MESA accelerator, which is supposed to cover the Dark Photon mass range below 50 MeV. Together with the MAMI program this will allow to cover the entire Dark Photon parameter range, which may explain the presently observed deviation between Standard Model theory and the direct measurement of the anomalous magnetic moment of the muon. [Preview Abstract] |
Sunday, April 1, 2012 2:18PM - 2:30PM |
J11.00003: New experimental results for a vector boson A Bogdan Wojtsekhowski, Rouven Essig, Philip Schuster, Natalia Toro The search for a new vector boson, $A'$, in the test run of A' EXperiment (APEX) results in a limit for a weak coupling $\alpha' \ga 10^{-6} \alpha$ to electrons ($\alpha=e^2/4\pi$) in the mass range 175 MeV $< m_{A'} <$ 250 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 in any previous search for the $A'$ boson. This talk will discuss the experiment and present the [Preview Abstract] |
Sunday, April 1, 2012 2:30PM - 2:42PM |
J11.00004: The Heavy Photon Search Experiment at Jefferson Lab Francois-Xavier Girod New heavy vector bosons, also known as ``heavy photons'', ``dark photons'', or ``hidden sector photons'', are expected on very general theoretical grounds. Recent astrophysical evidence motivates the direct search for a heavy photon $A'$ in the mass range $m_{A'} \sim 20$ to 1000 MeV/c$^{2}$, with coupling to ordinary photons {\it via} a kinetic mixing term $\propto\epsilon$, expected around $10^{-5}$ to $10^{-2}$. Such a new dark force gauge boson below the GeV range would naturally mediate TeV range dark matter annihilation, and interaction with ordinary matter. Existing constraints from collider searches and beam dump experiments leave much of this preferred $(m_{A'},\epsilon)$ phase space unexplored. The detection of electroproduced $A'$ on a heavy target from their decay into $e^{+}e^{-}$ pairs comes with a copious QED trident background. Using the high luminosity and precision beam available from Jlab, and combining a silicon microstrip vertex tracker with a lead-tungstate calorimeter for triggering, the HPS experiment will hunt for the $A'$ in a large $\epsilon$ range, with unique sensitivity in the lower coupling range using vertexing to suppress the trident background. In this talk, the experimental setup and goals of the HPS experiment will be presented. [Preview Abstract] |
Sunday, April 1, 2012 2:42PM - 2:54PM |
J11.00005: A Torsion-Balance Search for Axion-Like Particles Frank Fleischer, Seth Hoedl, Eric Adelberger, Blayne Heckel, C.D. Hoyle, David Shook, Erik Swanson Axion-like particles can mediate macroscopic parity and time-reversal symmetry violating forces. We will present a search for such a force between polarized electrons and unpolarized atoms using a novel torsion pendulum operating in the unshielded magnetic field of an electromagnet. Laboratory bounds on this force were improved by more than 10 orders of magnitude for pseudoscalars heavier than $1\,\mathrm{meV}$, and constraints on this force were established over a broad range of astrophysically interesting masses from $10\,\mu\mathrm{eV}$ to $10\,\mathrm{meV}$. Plans for a next generation of this experiment will be discussed. [Preview Abstract] |
Sunday, April 1, 2012 2:54PM - 3:06PM |
J11.00006: Searching for hidden Sector Photons and Chameleons with ADMX A. Wagner, C. Boutan, M. Hotz, D. Lyapustin, L.J. Rosenberg, G. Rybka, S.J. Asztalos, G. Carosi, C. Hagmann, D. Kinion, K. van Bibber, J. Hoskins, J. Hwang, C. Martin, P. Sikivie, I. Stern, N.S. Sullivan, D.B. Tanner, R. Bradley, J. Clarke The Axion Dark Matter eXperiment (ADMX) is a microwave cavity detector designed to search for the standard axion that may exist as a solution to the stong-CP problem. In addition this experiment is also sensitive to other light bosons such as hidden sector photons, chameleons, etc. Here we describe proof-of-concept experiments run with the ADMX Phase I system to search for these new particles as well as describe sensitivity expected from ADMX Phase II, currently under construction. [Preview Abstract] |
Sunday, April 1, 2012 3:06PM - 3:18PM |
J11.00007: LIPSS status and LIPSS-2 future experiments James R. Boyce, A. Afanasev, O.K. Baker, K.B. Beard, G. Biallas, M. Minarni, T.R. Robinson, M. Shinn The LIght Pseudoscalar and Scalar Search (LIPSS) experiment was the first dark matter experiment to use a photon beam from a high average power free-electron laser (FEL). LIPSS employed the ``Light Shining through a Wall'' (LSW) technique. Results from these laboratory dark matter searches established new boundaries for six possible dark matter particles. In addition, the experimental set-up can be modified for dark energy particle searches using the ``Particles in a Jar'' technique. The LIPSS set-up will be summarized and a brief description of other DM/DE search possibilities (LIPSS-2) with the FEL facility will be discussed. [Preview Abstract] |
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