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Search for Solar Axions: the CAST experiment at CERN cast.web.cern.ch/CAST/

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Search for Solar Axions: the CAST experiment at CERN http://cast.web.cern.ch/CAST/. Berta Beltrán (University of Zaragoza, Spain) XXXXth Rencontres de Moriond La Thuile, March 2005. Outline. The physics behind CAST : Axions. Principle of detection The CAST experiment : Description :

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  1. Search for Solar Axions:the CAST experiment at CERNhttp://cast.web.cern.ch/CAST/ Berta Beltrán (University of Zaragoza, Spain) XXXXth Rencontres de Moriond La Thuile, March 2005

  2. Outline The physics behind CAST: Axions. Principle of detection The CAST experiment: Description: Magnet, tracking, … X-ray detectors. Data Analysis and 2003 results. Berta Beltrán

  3. The Axion is a light pseudoscalar resulting from the Peccei-Quinn mechanism to enforce strong-CP conservation [Peccei-Quinn(1977),Wilczek (1978), Weinberg(1978)] • Axions may exist as primordial cosmic relics copiously produced in the very early universe, and these axions are one of the most interesting non-baryonic cold dark matter candidates. [See the PDG for an interesting review on axions] Axions : Motivation Berta Beltrán

  4. The Sun as an axion source Thermal photons Axions Fluctuating electric fields of the charged particles in the hot plasma Solar physics + Primakoff effect γ a Differential solar axion flux at Earth. -e [K. van Bibber et al. PRD 39,(1989)] Ze Berta Beltrán

  5. CAST: Principle of detection Transverse magnetic field (B) Axion X-ray (same energy and momentum) X-ray detector L [Sikivie PRL 51 (1983)] • Expected number of photons in the x-ray detector: Differential axion flux at the Earth (cm-2 s -1 keV -1 ) Conversion probability of an axion into photon ( (B×L)2) For gaγγ =1×1O-10 GeV-1 t=100 h , S=15 cm2 N γ ≈ 30 events S Magnet bore area (cm2) t Measurement time (s) Berta Beltrán

  6. But this is a coherent process only when the axion andphoton fields remain in phase over L Coherence condition states thatqL < 1 (axion-photon momentum transfer) with • Vacuum inside the magnet: mγ =0 We are sensitive to axion masses ≤ 2.3×10 -2 eV (CAST phase I) • Buffer gas (He) inside the magnet:mγ,eff >0 Different gas pressures P will make us sensitive to different axion masses up to 1 eV(CAST phase II) Berta Beltrán

  7. CAST Collaboration Aristotle University of Thessaloníki, Thessaloniki, Greece Christos ELEFTHERIADIS, Anastasios LIOLIOS, Argyrios NIKOLAIDIS, Konstantin ZIOUTAS, Ilias SAVVIDIS. Scuola Normale Superiore (SNS), Pisa, Italy Luigi DI LELLA Russian Academy of Sciences, Institute for Nuclear Research (INR), Moskva, Russia Alexandre BELOV, Sergei GNINENKO, Nikolai GOLUBEV Instituto de Física Nuclear y Altas Energías, Universidad de Zaragoza, Zaragoza, Spain Berta BELTRAN, Jose Manuel CARMONA, Susana CEBRIAN, Gloria LUZON, Angel MORALES, Julio MORALES, Alfonso ORTIZ DE SOLORZANO, Jaime RUZ, Jose VILLAR, Maria Luisa SARSA. European Organization for Nuclear Research (CERN), Geneve, Switzerland Klaus BARTH, Enrico CHESI, Martyn DAVENPORT, Christian LASSEUR, Thomas PAPAEVANGELOU, Alfredo PLACCI, Louis WALCKIERS, Laura STEWART, Dario AUTIERO. Enrico Fermi Institute, University of Chicago, Chicago, Il, United States of America David MIlLER, Juan COLLAR, Joaquin VIEIRA University of South Carolina, Department of Physics and Astronomy, Columbia, Sc, United States of America Frank AVIGNONE, Richard CRESWICK, Horacio FARACH National Center for Scientific Research "Demokritos" (NRCPS), Athens, Greece George FANOURAKIS, Theodoros GERALIS, Konstantin KOUSOURIS, Katerina ZACHARIADOU. University of British Columbia, Department of Physics, Vancouver, Canada Michael HASINOFF Ruder Boskovic Institute, Zagreb, Croatia Milica KRCMAR, Biljana LAKIC, Ante LJUBICIC Centre d''Etudes de Saclay (CEA-Saclay), DAPNIA, Gif-Sur-Yvette, France Samuel ANDRIAMONJE, Stephan AUNE, Esther FERRER, Ioanis GIOMATARIS, Igor G. IRASTORZA Technische Universitat Darmstadt, Institut für Kernphysik, Darmstadt, Germany Theopisti DAFNI, Dieter HOFFMANN, Manfred MUTTERER, Yannis SEMERTZIDI, Hans RIEGE Johann-Wolfgang-Goethe Universität Frankfurt, Institut für Kernphysik, Frankfurt Am Main, Germany Vladimir ARSOV, Joachim JACOBY Albert-Ludwigs-Universität Freiburg, Freiburg, Germany Horst FISCHER, Jurgen FRANZ, Donghwa KANG, Kay KONIGSMANN, Fritz-Herber HEINSIUS Max-Planck-Gesellschaft (MPG) Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany Heinrich BRAEUNINGER, Jakob ENGLHAEUSER, Peter FRIEDRICH, Markus KUSTER Max-Planck-Institut fur Physik Muenchen, Germany Rainer KOTTHAUS, Gerhard LUTZ, Georg RAFFELT, William SERBER, Pasquale SERPICO. 68 participants from 15 institutions Berta Beltrán

  8. Genève CAST: Point 8 CERN (Meyrin site) CAST at CERN: Berta Beltrán

  9. CAST: Axion helioscope experimental setting Magnet feed box Sunsetdetector: TPC 10 m long LHC dipole prototype 14º Sunrise detectors: CCD, Calorimeter, µMegas 80º Berta Beltrán

  10. Description of the experiment: LHC Magnet • Superconducting LHC test dipole. • Use of superfluid 4He to cool the system down to 1.8 K • L= 9.26 m long and magnetic field up to 9 Tesla. • The magnetic filed is confined in twin pipes of ~14.5 cm2 area each. • The aperture of each of the bores fully covers the potentially axion-emitting solar core (~1/10th of the solar radius) • Mount on a moving platform allowing ± 8º V; ± 40º H Berta Beltrán

  11. Tracking system Snapshot of the tracking program • Software with astronomical calculations. • Communicates with the motors→ interface to move the magnet. • The overall CAST pointing precision in better than 0.01º • Both the hardware and the software of the tracking system have been precisely calibrated by means of geometric survey measurements. Berta Beltrán

  12. N2 FLUX 200 l/h 5 mm COPPER 1.85×10 counts/KeV/sec/cm2 2 mm CADMIUM Reduction by a factor ~4.5 25 mm LEAD 4.13×10-5 counts/KeV/sec/cm2 200 mm POLYETHYLENE X-ray detectors: TPC (CERN) • Position sensitive • Conventional technology: robustness and stability guaranteed • Use of a passive shielding to reduce the level of the background. Berta Beltrán

  13. 2003 2004 X-ray detectors: μMegas (Saclay/Athens/CERN) • Very good spatial resolution (350 μm X-Y strip pitch) • Low threshold (0.8 keV) • CAST prototype: two dimensional strip read out Berta Beltrán

  14. 3 mm  1.6 m X-ray focusing device + CCD (MPI/HLL) • Focusing device; • Space technology (prototype for the ABRIXAS satellite) • From 48 mm Ø (LHC magnet aperture) →~3 mm Ø • Big signal to noise ratio improvement • About 35% efficiency due to reflections • The CCD camera: • Very good energy resolution (<0.5 keV) • Low threshold • Windowless operation in vacuum: efficiency close to 100% in the full energy range. 43 mm  Berta Beltrán

  15. X-ray detectors: Calorimeter (Chicago) • In the experiment only during the 2004 data taking. • The goal is to extend sensitivity to axion induced γ’s from few keV to ~150 Mev • First time that this kind of search is performed. Berta Beltrán

  16. CAST experiment: status • 2003 data taking • Running for about six months. • Data already analyzed → First CAST results (K.Zioutas et. al. 2005 PRL, in press). • 2004 data taking • Improved conditions in the three detectors (shiledings,….). • Add of a fourth detector (calorimeter) for High Energy axions. • Improvements in the tracking system and in the magnet: more reliability and longer periods of data tacking. • Running from May to November without problems. • 2005 • Updating the experiment setup for the second phase of CAST • Analyzing 2004 data… Berta Beltrán

  17. TPC subtracted spectrum and “expected” axion-photons spectrum c/keV/cm2/s Solar-axion-photons spectrum for g ~ 6 x 10-10 GeV-1 (Tokyo Helioscope sensitivity) Comparison of sensitivities of CAST and Tokyo Helioscope CAST TPC Subtracted spectrum Energy [keV] Berta Beltrán

  18. CAST 2003 result Tracking (dots) and background (dashed line) spectra of the CCD. Subtracted spectrum TPC , μMegas • No signal over background in any of the three detectors. Berta Beltrán

  19. CAST 2003 result Axion exclusion plot • Combined upper limit obtained (95% C.L.): gaγγ<1.16×10-10 GeV-1 Berta Beltrán

  20. Backup slides Berta Beltrán

  21. Axions: Motivation • Strong CP problem: QCD lagragian has a non-perturbative term: field strength tensor and its dual where g gauge coupling and Θ→ QCD vacuum; M = quark mass matrix This is an arbitrary parameter that violates CP if ≠ 0 ; but it is constrained by t he neutron dipole moment to be ≤ 10-10 .Why so small? Peccei-Quinn solution: is a dynamical variable with classical potential that is minimized by =0. The prize for this is the introduction of an additional spontaneously broken global symmetry and its associated pseudo-Goldstone boson, the axion. Berta Beltrán

  22. Axions : Phenomenology • The AXION is: • pseudoscalar • neutral • practically stable • phenomenology driven by the breaking scale fa and the specific axion model • Axion mass: Axion-photon coupling present in almost every axion model This gives rise to the Primakoff effect:axion-photon conversion(and vice versa) in the presence of electromagnetic fields. That is the only axion phenomenology on which CAST relies… Berta Beltrán