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A Search for Axions from the Sky

A Search for Axions from the Sky. Kay Königsmann Seminar at CERN 8 September 2004. Why do we need an axion ?. the QCD Lagrangian may contain a term. with  being an arbitrary parameter O(1) and G  being the gluon field tensor (a la F  in QED)

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A Search for Axions from the Sky

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  1. A Search for Axions from the Sky Kay Königsmann Seminar at CERN 8 September 2004

  2. Why do we need an axion ? the QCD Lagrangian may contain a term with  being an arbitrary parameterO(1)and Gbeing the gluon field tensor(a la F in QED) BUT: this term violates CP ! Why? Seminar at CERN

  3. Lagrangian density with CP-violation of this term can only be seen by investigating the properties under Lorentz-transformations with help from Andreas Schäfer (but too complicated for this talk) Seminar at CERN

  4. CP-Violation ~ but easy to understand when calculating G G whereas CP conserving ! is CP violating ! thus : Seminar at CERN

  5. But there is no P-violation in the strong interaction sector ! How do we know ? the electric dipole moment of the neutron is measured to be dn< 10-25 e cm : the predicted value of dn'£10-15 e cm implies a value of  < 10-10 this means that  would need to be fine tuned to such a small value: something physicists don’t like Seminar at CERN

  6. How to circumvent P-violation ? The original proposal by Peccei & Quinn in 1974 : a U(1) symmetry • existence of a new, massless pseudoscalar field a , the axion field (J PC = 0-+), interacting with the gluon field • this adds two other terms to the Lagrangian : Kinetic term Peccei-Quinn scale thus: if  = <a> / fa no P-violating term remains ! Seminar at CERN

  7. The PQ - Axion • Solid predictions for • its mass: ma = 75 keV (x + 1/x) > 150 keV • where x is the ratio of the two vacuum expectation values (giving mass to up and down quarks) • and for the branching ratios J/ ! a  and Y! a  • this Axion was quickly ruled out (although some beam dump experiments kept on claiming a signal) Seminar at CERN

  8. Crystal Ball and the axion both measurements by a young post doc yielded the result (Königsmann) thus ruling out the standard PQ-axion Seminar at CERN

  9. Therefore: the invisible axion here the PQ-mechanism is decoupled from the electroweak scale: the normal Higgs field and a new field awith a very(!) high VEV fa thus no dependence on the ratio of VEVs anymore, just on fa , the axion decay const (fa in analogy to f) Seminar at CERN

  10. Axion coupling tophotons Axions can decay to photons because of a  qq transitions  a-0 mixing (0-+) albeit with a reduced coupling strength w.r.t. the 0 by ' f / fa its lifetime is given by a/ fa2 ma-3 > 1017 y for ma = 1 eV exceeding the lifetime of the universe by 107 ! Seminar at CERN

  11. Axion coupling to photons CP-conserving ! with and Seminar at CERN

  12. Astrophysical constraints Astrophysical arguments from energy loss of HB- stars in globular cluster, Raffelt 1996 ga < 10-10 GeV-1 which implies Seminar at CERN

  13. Other axion properties i.e. the range we are interested in is ma < 1eV ( with fa > 107 GeV ) Note:generally, CAST is a search for any kind of light neutral bosons coupling to two photons, Axions being the most popular example Seminar at CERN

  14. Axions as Cold Dark Matter • an Axion with mass 10-5 < ma < 10-1 eV is an excellent candidate for cold dark matter • thus a proof of its existence would have major consequences for our understanding of the universe ! It’s energy density would be about 0.5 GeV/cm3 in our galaxy! compare to crit = 5*10-6 GeV/cm3for our universe Seminar at CERN

  15. Principle of Detection Transverse magnetic field (B) X ray X ray detector Solar axions axions axions axion-to-photon conversion in the magnet L photon-to-axion Conversion in the sun

  16. Energy spectrum of axion flux Average energy '4.2 keV • ' 4*1012 axions/cm2 s * (ga/10-10 GeV)2 Planck’s law

  17. Conversion probability in the magnet where M = 1 for full coherence over magnet ( Lma2 / 2Ea < 1) this results in signal counts/day of Na~ 6 Axions / day with g = 10-10 GeV-1, B = 9T, L = 9.3m, Area = 13cm2 Seminar at CERN

  18. The CAST experiment: CERN Axion Solar Telescopewith L=9.3m and B=9T : 100*better sensitivity than previous expts

  19. Using adecommissioned LHC magnet on a rotating platform Sunrise axions Sunset axions 2 X-ray gas detectors + 1 CCD with a X-ray focussing device

  20. The magnet at -8 degrees Seminar at CERN

  21. at CERN CAST SPS LHC Seminar at CERN

  22. The CAST Collaboration (1) Croatia, ZagrebRuder Boskovic Institute  M. KRCMAR, A. LJUBICIC, B. LAKIC (2) France, Gif-Sur-YvetteCentre d'Etudes de Saclay (CEA-Saclay), DAPNIA S. ANDRIAMONJE, St. AUNE, A. DELBART, E. FERRER RIBAS, I. GIOMATARIS, I.G. IRASTORZA, (3) Germany, DarmstadtTechnische Universitat Darmstadt, Institut für KernphysikT. DAFNI , D. HOFFMANN, K. Kanapathipillai, M. MUTTERER, H. RIEGE, Y. SEMERTZIDIS (4) Germany, FrankfurtApplied Physics V. ARSOV,J. JACOBY (5) Germany, FreiburgAlbert-Ludwigs-Universität Freiburg H. FISCHER, J. FRANZ , F.-H. HEINSIUS, D. KANG, K. KÖNIGSMANN (6) Germany, GarchingMax-Planck-Gesellschaft (MPG), Max-Planck-Institut für Extraterrestrische Physik H. BRÄUNINGER, J. ENGLHAUSER , P. Friedrich, R. Hartmann, M. Kuster (7) Germany, MuenchenMax-Planck-Institut für Physik, Werner-Heisenberg-InstitutR. KOTTHAUS, G. LUTZ, G. RAFFELT (8) Greece, AthensNational Center for Scientific Research "Demokritos" (NRCPS) G. FANOURAKIS, Th. GERALIS, K. Kousouris, K. ZACHARIADOU (9) Geece, ThessalonikiAristotle University of Thessaloníki Ch. ELEFTHERIADIS, A. LIOLIOS, A. NIKOLAIDIS, I. SAVVIDIS, K. ZIOUTAS (10) Italy, PisaScuola Normale Superiore (SNS)L. DiLella (11) Russia, MoskvaRussian Academy of Sciences, Institute for Nuclear Research (INR) S. GNINENKO, N. GOLOUBEV (12) Spain, ZaragozaUniversidad de Zaragoza, Facultad de Ciencias, Instituto de Física Nuclear y Altas Energías B. BELTRAN, J. CARMONA, S. CEBRIAN, Gl. LUZON, A. MORALES, J. MORALES, A. ORTIZ DE SOLORZANO, J. Ruz, M. SARSA, J. VILLAR (13) Switzerland, GeneveEuropean Organization for Nuclear Research (CERN) K. BARTH, M. DAVENPORT, R. DE OLIVEIRA, M. DIMARCO, F. FORMENTI, A. MCDONALD, Th. PAPAEVANGELOU, A. PLACCI, L. STEWART, B. VULLIERME, L. WALCKIERS (14) United States of America, Chicago, IlUniversity of Chicago, Enrico Fermi Institute J. COLLAR , D. MILLER, J. VIEIRA (15) United States of America, Columbia, ScUniversity of South Carolina, Department of Physics and Astronomy F. AVIGNONE, R. CRESWICK, H. FARACH

  23. Magnet, sun tracking Looking at sunrise twice a year (September & March) we can film the sun through a window Seminar at CERN

  24. Optical sun tracking Sun partly hidden by trees and leaves Seminar at CERN

  25. Tracking accuracy Comparison between 2002 and 2004 grid • checked by geometers twice a year • comparison of 2002 and 2004 tracking reproducibility better than 1 mm • tracking system calibrated and correlated to celestial coordinates Seminar at CERN

  26. Magnet quenching 8 events in 2003 6 events in 2004 only one real quench Seminar at CERN

  27. With several innovative detectors • TPC : time projection chamber • Micromega : drift chamber with micro-strips • CCD : charged coupled Si-detector attached to a focusing X-ray telescope (used on the ABRIXAS space mission) Seminar at CERN

  28. TPC Sun tracking time: 63 h Background time : 720 h Seminar at CERN

  29. The TPC layout • a conventional Time Projection Chamber (TPC) built with low radioactivity materials (mainly Plexiglas) • drift space 10 cm • charge collected by a MWPC at the end of the drift space: • 48 anode wires, 96 cathode wires • signal measurement by 10 MHz Flash- ADC’s Seminar at CERN

  30. TPC Spectrum from 2003 Dataimprovement in 2004: 3 times less background Seminar at CERN

  31. Subtracted TPC spectrum with signal at 95% CL solar axion signal limit (95% CL ) ga < 1.46 * 10-10 GeV-1 ( 95% CL ) Seminar at CERN

  32. MicroMega Sun tracking time: 77 h Background time : 809 h Seminar at CERN

  33. The MicroMega detector 192 charge collection strips for x and for y Seminar at CERN

  34. The MicroMega detector 350 m X-Y strip pitch low threshold ~ 0.6 keV gas : 95%Ar + 5%Isobutan low background good spatial resolution Seminar at CERN

  35. MicroMega Spectrum from 2003improvement in 2004: 3 times less background from Cu K line gagg < 1.44 * 10-10 GeV-1 ( 95% CL )

  36. CCD +X-ray telescope Sun tracking time: 121 h Background time : 1233 h Seminar at CERN

  37. CCD detector for the X-ray telescope: 1 x 3 cm2 CCD with energy resolution of < 500 eV is used with in combination with a X-ray telescope ceramic substrate glue coating tin solder socket cooling mask PCB board CCD can work in vacuum : no window needed Seminar at CERN

  38. X-ray telescope 43 mm ∅ G focal point of ' 7 mm2 G G G g 27 nested pairs of mirrors from 43 mm LHC magnet aperture to < 3 mm  i.e. measure signal and background simultaneously signal-to-noise improvement Seminar at CERN

  39. X-ray telescope Seminar at CERN

  40. Focus of a X-ray source x-y image of a 6.4 keV X-ray beam in MicroMega chamber (note: log scale for density) the spot of 7mm2 will yield a much better signal to noise ratio Seminar at CERN

  41. X-ray telescope alignment with Laser and 56Fe source Seminar at CERN

  42. Spot of a Laser Beam on the CCD 1 cm 3 cm Seminar at CERN

  43. Image of a X-Ray Source through the CAST Magnet 1 cm 3 cm Seminar at CERN

  44. Background spectrum of the CCD Counts /(cm2 sec keV) Improvement in 2004 by a factor of 1.5 10 2 Energy / keV ga < 1.21 * 10-10 GeV-1 (95% CL) Seminar at CERN

  45. Exclusion limits from all 3 Detectors • TPC: g a < 1.46 £ 10-10 GeV-1 • MM: g a < 1.44 £ 10-10 GeV-1 • CCD: g a < 1.21 £ 10-10 GeV-1 • Combined : g a < ? £ 10-10 GeV-1 Seminar at CERN

  46. Combined exclusion Plot Seminar at CERN

  47. CAST vs. PVLAS Seminar at CERN

  48. laser light magnetic dipole (photon-axion conversion) magnetic dipole (axion-photon conversion) wall PVLAS is a LASER experiment to search for the invisible axion polarised LASER light propagating through a magnetic dipole magnet produces axions (using mirrors at the end of each dipole for multiple traversals) Seminar at CERN

  49. CAST: 2nd phase The coherence condition is :L ma2 / Ea < 1 which holds for ma < 0.02 eV/c2 for a photon energy of 4.2 keV in vacuum Coherence can be restored for ma by filling the magnetic conversion region with 4He or 3He gas to give photons an effective mass: then coherence for L (ma2 - m2) / Ea < 1 implies many steps in  necessary since Seminar at CERN

  50. CAST : 2nd phase <6 mbar 4He <60 mbar 3He Seminar at CERN

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