Bulletin of the American Physical Society
2006 Division of Nuclear Physics Annual Meeting
Wednesday–Saturday, October 25–28, 2006; Nashville, Tennessee
Session DG: Mini-symposium on Identifying Dark Matter II: Axionic and Sterile Neutrino Dark Matter |
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Sponsoring Units: DNP Chair: George Fuller, University of California, San Diego Room: Gaylord Opryland Hermitage D |
Friday, October 27, 2006 2:00PM - 2:36PM |
DG.00001: Axion Astrophysics and Cosmology Invited Speaker: Experimental evidence suggests that the strong interactions conserve the discrete CP symmetry. Standard Model QCD, however, predicts that CP should be violated unless the angular parameter $\Theta$ is exceedingly small ($<$ 10$^{-10}$). The most elegant and compelling solution to this so-called Strong-CP problem was proposed by Peccei and Quinn and involves the spontaneous breaking of a new U(1)$_{PQ}$ global symmetry. The axion arises as the pseudo-Goldstone Boson associated with this SSB. Astrophysics has played an important role in constraining the allowed axion mass. I will review the arguments from stellar evolution and supernovae that lead to an upper bound of 1-10 meV for the mass. Axions with $\mu$eV mass have not been ruled out and would have sufficient relic density to be a very plausible candidate for cold dark matter. I will describe different scenarios for axion production in the early universe and comment on their compatibility with current measurements of cosmological parameters. Finally, I will summarize the current experimental and theoretical bounds of the axion-to-photon coupling constant. [Preview Abstract] |
Friday, October 27, 2006 2:36PM - 2:48PM |
DG.00002: Microwave Cavity Searches for Axions D.B. Tanner, L.D. Duffy, P. Sikivie, S.J. Asztalos, G. Carosi, D. Carter, C. Hagmann, D. Kinion, L.J. Rosenberg, K. van Bibber, D.B. Yu, R.F. Bradley The axion is a hypothetical elementary particle proposed as a solution to the ``strong CP'' problem. The mass of the axion is constrained by experimental and astrophysical considerations to a range where the axion is a very plausible cold dark matter candidate. This weakly interacting dark matter makes up the halo of our galaxy. In the ADMX experiment, halo axions flow through a microwave resonant cavity permeated by a static magnetic field where some convert into microwave photons. These photons are detected by an ultra-low-noise receiver. The ADMX Collaboration has set limits on the axion-to-photon coupling and /or local axion halo mass density for axion mass between 1.9 and 3.3 $\mu$eV. [Preview Abstract] |
Friday, October 27, 2006 2:48PM - 3:00PM |
DG.00003: The High Resolution Search for Axions in Galactic Halo Substructure Leanne Duffy The Axion Dark Matter eXperiment uses a Sikivie microwave cavity detector to search for dark matter axions. The new, high resolution channel is designed to search for discrete flows of axions passing through the detector. Such flows are expected to be present in our galactic halo from tidal stripping of dwarf galaxies and from late infall of dark matter on our galactic halo. A discrete flow of axions with small velocity dispersion will appear as a narrow peak in the output of a microwave cavity detector. Such a peak can be searched for with high signal-to-noise ratio using the high resolution channel. This new channel increases the sensitivity of ADMX by a factor of 3, compared to using ADMX's medium resolution channel only. [Preview Abstract] |
Friday, October 27, 2006 3:00PM - 3:12PM |
DG.00004: Technology for Next Generation Dark-Matter Axion Searches Darin Kinion, S.J. Asztalos, G. Carosi, C. Hagmann, L.J. Rosenberg, K. van Bibber, L.D. Duffy, P. Sikivie, D.B. Tanner, R. Bradley The ADMX Collaboration has set limits on the axion-to-photon coupling for axion mass between 1.9 and 3.3 $\mu$eV, assuming both that axions dominate the local halo density and are `hadronic' or KSVZ axions. A definitive search should relax both constraints, i.e. be sensitive to DFSZ model axions comprising a fraction of the local halo density. We will show that such a search could be realized using near-quantum-limited microwave amplifiers based on dc SQUIDs. The first phase of this upgrade is currently underway. [Preview Abstract] |
Friday, October 27, 2006 3:12PM - 3:24PM |
DG.00005: A Search for KK Axions with DRIFT detectors using Johanna Turk Theoretical models with Kaluza-Klein (KK) axions predict that they will be produced in the solar core, with some fraction becoming trapped in gravitational orbits around the Sun. The mass range of gravitationally trapped KK axions is typically between 2 and 12 keV and they are unstable with long lifetimes, in principle allowing them to be directly detected by decay to 2 photons. We explore the potential for observation of KK axions by gaseous detectors using data collected with the Directional Recoil Identification From Tracks (DRIFT) negative ion TPC operating in the Boulby Mine. [Preview Abstract] |
Friday, October 27, 2006 3:24PM - 3:36PM |
DG.00006: Searching for the dark matter U boson with a positron beam Bogdan Wojtsekhowski A fixed-target experiment with a 300 MeV positron beam at high luminosity is proposed that would provide a unique sensitivity search for the dark matter boson U in the reaction e+e- $\rightarrow$ U gamma in the relevant mass range. A detailed plan of the experiment will be presented. [Preview Abstract] |
Friday, October 27, 2006 3:36PM - 3:48PM |
DG.00007: Coherent Sterile Neutrino Production in the Early Universe Chad Kishimoto, George Fuller, Christel Smith We calculate the resonant production of sterile neutrinos from active neutrinos in the early universe when there is a significant net lepton number residing in active neutrino seas. We study feedback on this process from the expansion rate of the universe, and we find interesting implications for primordial nucleosynthesis and models of sterile neutrino dark matter. [Preview Abstract] |
Friday, October 27, 2006 3:48PM - 4:00PM |
DG.00008: Sterile Neutrinos and Supernova Nucleosynthesis Joshua Beun, Gail McLaughlin, Rebecca Surman, Raph Hix Neutrinos play an important role in the core-collapse supernova environment, from facilitating the explosion mechanism to influencing the outflow's elemental composition. Traditional heavy element nucleosynthesis, the r-process, are stifled by electron neutrinos during the alpha particle formation epoch. Introduction of a sterile neutrino species can temper this alpha effect as well as generate an environment sufficiently neutron-rich for fission cycling to occur. Fission cycling in the r-process produces abundance patterns similar to the halo star data. Here we examine reductions in the neutrino flux necessary to achieve fission cycling; sterile neutrinos or other new physics may realize these reductions. [Preview Abstract] |
Friday, October 27, 2006 4:00PM - 4:12PM |
DG.00009: Sterile Neutrinos and Big Bang Nucleosynthesis Christel Smith, George Fuller, Chad Kishimoto We calculate primordial element abundances in the presence of neutrino spectral distortion resulting from active-sterile transformation. We find that the effects of adding a significant lepton number to the big bang nucleosynthesis calculation are reversed when we include nonthermal distorted spectra. Our results show that this can be true for a variety of $\nu_e$ and $\bar\nu_e$ spectral distortions arising from various active-sterile transformation processes. [Preview Abstract] |
Friday, October 27, 2006 4:12PM - 4:24PM |
DG.00010: Primordial Element Synthesis Calculations with the bigbangonline.org Software Suite M.S. Smith, E.J. Lingerfelt, J.P. Scott, W.R. Hix, C.D. Nesaraja, G.M. Fuller, D. Tytler, L.F. Roberts Predictions of the abundances of $^2$H, $^4$He, and $^7$Li synthesized three minutes after the Big Bang can be compared with abundances inferred from observations to constrain the total amount of baryonic matter in the Universe, the number of $\nu$ species, and other cosmological parameters. These constraints can be compared to those derived from measurements of the cosmic microwave background. A new online suite of computer codes has been developed at {\bf bigbangonline.org} to facilitate custom big bang nucleosynthesis (BBN) calculations. Users of this freely available system can specify the latest set of input thermonuclear reaction rates and cosmological parameters to set up their simulation, and the latest primordial abundance observations to determine their constraints. Monte Carlo BBN simulations [1] are also enabled, where uncertainties of the input reaction rates are propagated into uncertainties of the cosmology constraints. The suite features excellent visualization tools and enables sharing of simulation results between Users. Features of the suite and its utilization in a new set of BBN calculations will be presented. \newline [1] M.S. Smith et al., Ap. J. Suppl. 85 (1993) 219.\newline *Managed by UT-Battelle, LLC, for the US D.O.E. under contract DE-AC05-00OR22725. [Preview Abstract] |
Friday, October 27, 2006 4:24PM - 4:36PM |
DG.00011: Searching for an X-Ray Emission Line from Sterile Neutrino Dark Matter John Tomsick If keV-mass sterile neutrinos exist and if they are the Dark Matter, Abazajian \& Fuller have argued that decays of these particles could lead to an X-ray emission line that could be detected by current satellites such as XMM-Newton and the Chandra X-ray Observatory. In this presentation, I discuss the work that has been done to search for this line in the X-ray background, from clusters of galaxies, and from nearby galaxies. I also discuss prospects for further searches that could lead to discovering the signature emission line or ruling out sterile neutrinos as a significant contributor to the Dark Matter. [Preview Abstract] |
Friday, October 27, 2006 4:36PM - 4:48PM |
DG.00012: Measuring Active-Sterile Neutrino Oscillations with a Stopped Pion Neutrino Source Richard Van de Water, Gerry Garvey, Andrew Green, William Louis, Geoff Mills, Heather Ray, Richard Schirato, Hywel White The possible existence of light sterile neutrinos is of great interest in many areas of particle physics, astrophysics, and cosmology. Furthermore, should the MiniBooNE experiment at Fermilab confirm the LSND oscillation signal, then new measurements are required to identify the mechanism responsible for these oscillations. Possibilities include sterile neutrinos, CP or CPT violation, variable mass neutrinos, Lorentz violation, and extra dimensions. In this paper, we consider an experiment at a stopped pion neutrino source to determine if active-sterile neutrino oscillations with $\Delta \mbox{m}^2$ greater than 0.1 ev can account for the signal. By exploiting stopped $\pi^+$ decay to produce a monoenergetic $\nu_\mu$ source, and measuring the rate of the neutral current reaction $\nu_{x} \hspace{0.05in} ^{12}\mbox{C}\rightarrow \nu_{x} \hspace{0.05in} ^{12}\mbox{C}^{*}(15.11)$ as a function of distance from the source, we show that a convincing test for active-sterile neutrino oscillations can be performed. [Preview Abstract] |
Friday, October 27, 2006 4:48PM - 5:00PM |
DG.00013: Sterile Neutrinos in a 6x6 Matrix T. Goldman, B.H.J. McKellar, G.J. Stephenson, Jr. An early study of neutrino mixing within the see-saw framework considered random mass matrices in what is now known as the sterile sector[1]. The mixing angles in the lepton sector were found to be closely distributed about the CKM angles that were assumed. In that work, rank 3 was assumed for the weak isospin zero Majorana mass matrix in the sterile neutrino sector. We report here on the character of new results using a reduced rank (``singular'') sterile matrix. We find that an additional flavor misalignment in the sterile sector can produce several interesting effects, including: 1) mass eigenstates that lead to very large flavor mixing among active neutrinos, and 2) small values for the 1-3 mixing angle parameter[2]. We also discuss the limits that current observations place on the mass scale of light sterile neutrinos in this model. [1]T.\ Goldman and G.\ J.\ Stephenson, Jr., ``How Large Are the Neutrino Mixing Angles?'' {\it Phys.\ Rev.\ D} {\bf 24}, 236 (1981). [2]G.\ J.\ Stephenson, Jr.\ , T.\ Goldman, B.\ H.\ J.\ McKellar and M.\ Garbutt, ``Large Mixing from Small: Pseudo-Dirac Neutrinos and the Singular Seesaw,'' {\it Int.\ J.Mod.Phys.}{\bf A20} (2005) 6373; [hep-ph/0404015]. [Preview Abstract] |
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