1. Search for Solar Axions with the CAST experiment J. Galán on behalf of the CAST Collaboration University of Zaragoza (Spain) 8/Oct/2009J.Galán11th ICATPP Como, Italy

2. The CAST Collaboration Canada Universiy of British Columbia, Department of Physics, Vancouver M. Hasinoff Croatia Rudjer Boskovic Institute, Zagreb Rudjer Boskovic, M. Krcmar, B. Lakic, A. Ljubicic France DAPNIA, CEA-Saclay, Gif-sur-Yvette S. Aune, E. Ferrer-Ribas, I. Giomataris, T. Papaevangelou Germany TU Darmstadt, Institut für Kernphysik D. H. H. Hoffmann, M.Kuster, A. Nordt GSI Darmstadt D. H. H. Hoffman Universität Frankfurt, Institut für Angewandte Physik, Frankfurt J. Jacoby Universität Freiburg H. Fischer, J. Franz, F.H. Heinsus, D. Kang, K. Königsmann, J. Vogel MPE Garching H.Bräuninger, M. Kuster, A. Nordt WHI München R. Kotthaus, G. Lutz, G. Raffelt, P. Serpico Greece University of Patras A. Gardikiotis,Y. Semertzidis, M.Tsagri, K. Zioutas National Center for Scientific Research “Demokritos”, Athens T. Karageorgoplou, G. Fanourakis, T. Geralis, K. Kousouris Aristotle University of Thessaloniki C. Eleftheriadis, A. Liolios, I. Savvidis, T. Vafeiadis Hellenic Open University, Patras C. Bourlis, S. Tzamarias Russia Russian Academy of Science, Institute for Nuclear Research (INR), Moscow A.Belov, S. Gninenko Spain University of Zaragoza B. Beltrán, J. Carmona, S. Cebrián, T. Dafni, J. Galán, H. Gómez, I.G. Irastorza, G.Luzón, A. Morales, J. Morales, A. Ortiz, A. Rodríguez, J.Ruz, A. Tomás, J. Villar Turkey Dogus University, Istambul E. Arik, S.Boydag, S.A. Cetin, O.B. Dogan, I. Hikmet, C. Yildiz USA Lawrence Livermore National laboratory, Livermore, CA M. Pivovaroff, R. Soufli, K. van Bibber University of Chicago, Enrico Fermi Institute and KICP J. Collar, D. Miller Switzerland European Organization for Nuclear Research (CERN), Genève D.Autiero, K. Barth, S. Borgui, M. Davenport, L. Di Lella, N. Elias, C. Lasseur, T. Ninikowski, A. Palacci, H.Riege, L. Stewart, L. Walkiers 8/Oct/2009J.Galán11th ICATPP Como, Italy

3. Outline Introducing the Axion and Solar Axion Model. Review the Axion detection techniques. The CAST Helioscope Description. CAST Status (results from 4He Phase and progress in 3He Phase). The new He3 System and detector performances Future of Helioscope Axion Searches. 8/Oct/2009J.Galán11th ICATPP Como, Italy

4. Why do we need Axions? All you need is Axions! Bad agreement between theoretical and experimental values for the electric dipole moment of neutron QCD predicts violation of CP in strong interactions 8/Oct/2009J.Galán11th ICATPP Como, Italy 4 Peccei-Quinn introduced the axion field to solve this problem

5. What are the Axion properties? Neutral pseudoscalar Practically stable Very low mass Very low cross-section Coupling to photons 8/Oct/2009J.Galán11th ICATPP Como, Italy The theory predicts one unique parameter (scale factor) to describe the axion. If the axion mass is small enough could contribute to the content of Cold Dark Matter of the Universe. 5 Mass depends on this parameter and it needs to be determined experimentally.

6. Direct Axion Detection Techniques (I) Bragg Difraction Microwave Cavity Searches e.g. Asztalos et al., Phys. Rev. D 69, 011101(2004) [astro-ph/0310042] Geomagnetic Axion Conversion Axions can convert to photons in Earth’s magnetic field Davoudiasl & Huber, hep-ph/0509293 Idea is to observe the Sun through the Earth 8/Oct/2009J.Galán11th ICATPP Como, Italy 6

7. Direct Axion Detection Techniques (II) Laser experiments Light Shining Through Wall Vacuum properties e.g. Grin et al. 2006 astro-ph/0611502v1 Telescope Searches Helioscope Searches Inoue et al. 2002 astro-ph/0204388v1 Lazarus et al. Phys. Rev. Lett. 69 2333 (1992) 8/Oct/2009J.Galán11th ICATPP Como, Italy 7

8. Production: The Solar Axion Spectrum Axions should be produced in the core of the Sun. The well known Solar Model is used to calculate the expected axion flux in Earth 8/Oct/2009J.Galán11th ICATPP Como, Italy 8

9. Detection: The Probability Conversion L = magnet lenght, Γ = absorption coefficient events/day Assuming : Expected Number of counts 8/Oct/2009J.Galán11th ICATPP Como, Italy 9

10. The Experimental Axion Signature On resonance Off Resonance ∆m = 7 meVOff Resonance ∆m = 11 meV Off Resonance ∆m = 2 meV 8/Oct/2009J.Galán11th ICATPP Como, Italy 10

11. The Experimental Axion Signature On resonance Off Resonance ∆m = 7 meVOff Resonance ∆m = 11 meV Off Resonance ∆m = 2 meV Signature to identify an axion signal. And a way to determine the axion mass in a vacuum phase. 8/Oct/2009J.Galán11th ICATPP Como, Italy 11

12. CAST Location 8/Oct/2009J.Galán11th ICATPP Como, Italy

13. The CAST Helioscope LHC dipole: L = 9.3m, B = 9T Solar Tracking : 3.5 h/day, background data rest of the day 4 x-ray detectors Signal : excess of x-rays while pointing the Sun 8/Oct/2009J.Galán11th ICATPP Como, Italy 13

14. Tracking System Precision GRID Measurements Horizontal and Vertical encoders define the magnet orientation Correlation between H/V encoders has been established for a number of points (GRID points) Periodically checked with geometer measurements CAST magnet is tracking the Sun with the required precision. Sun Filming Twice a year (March – September) Direct optical check. Corrected for optical refraction Verify that the dynamic Magnet Pointing precision (~ 1 arcmin) is with our aceptance 8/Oct/2009J.Galán11th ICATPP Como, Italy 14

15. CAST Status and progress ma<0.02eV Completed(2003-2004) PRL94(2005)121301 JCAP04(2007)020 P< 13.4mbar, 160steps 0.02<ma<0.39eV Completed(2005-2006) JCAP02(2009)008 P< 120 mbar 0.39<ma<1.16eV Started in Nov 2007 Will continue to Dec2010 2 weeks data in 2008 (2-4eV) few eVup to 1keV range CAST Phase I (Vacuum) CAST Phase II (4He) CAST Phase II (3He) Low Energy Solar Axions 8/Oct/2009J.Galán11th ICATPP Como, Italy 15

16. CAST Status and progress ma<0.02eV Completed(2003-2004) PRL94(2005)121301 JCAP04(2007)020 P< 13.4mbar, 160steps 0.02<ma<0.39eV Completed(2005-2006) JCAP02(2009)008 P< 120 mbar 0.39<ma<1.16eV Started in Nov 2007 Will continue to Dec2010 2 weeks data in 2008 (2-4eV) few eVup to 1keV range CAST Phase I (Vacuum) CAST Phase II (4He) CAST Phase II (3He) Low Energy Solar Axions CAST continues taking data and measuring with sensitivity for axion masses above 0.75eV Today -> Pstep : 564 8/Oct/2009J.Galán11th ICATPP Como, Italy 16

17. The 3He System Upgrade: The metering volumes 4He gas saturates at ~16 mbar for T=1.8 K, for higher pressures only 3He remains gas Controlled injection of He in the bores. Order of 1000 pressure steps required Precise measurement of gas quantity Precise monitoring of gas pressure and temperature High reproducibility precision (back and forward) Extra safety for 3He loss 8/Oct/2009J.Galán11th ICATPP Como, Italy 17

18. The 3He System : Expansion volume The new 3He System is prepared to protect the thin Cold windows in case of Magnet Quench. 8/Oct/2009J.Galán11th ICATPP Como, Italy 18

19. The 3He System : Expansion volume The new 3He System is prepared to protect the thin Cold windows in case of Magnet Quench. Refilling must be done as fast as posible to dont loss data taking efficiency. 8/Oct/2009J.Galán11th ICATPP Como, Italy 19

20. 3He Control, Monitoring and Recovery System 8/Oct/2009J.Galán11th ICATPP Como, Italy 20

21. Daily Data Taking Protocol 8/Oct/2009J.Galán11th ICATPP Como, Italy Detectors data is analysed daily and sent by mail to the CAST collaboration. A protocol takes into account the background level of the detectors. All the information from the 4 detectors taking data in CAST is taken into account The protocol allows us to decide if we should continue measuring in the same pressure step. In such way, we avoid to skip a signal that is close to the sensitivity limit of the experiment. 21

22. Detectors Systems (4He Phase) 8/Oct/2009J.Galán11th ICATPP Como, Italy 2) X-ray Telescope coupled to pnCCD pn CCD chip Pixels 150μm x 150μm Excellent Energy resol. X-ray finger automated calibration ABRIXAS space X-ray telescope 27 nested mirror cells. Magnet bore size (42.5 mm) pnCCD Focus from d=43mm to d=3mm Improved signal/noise by a factor of up ~200 Background in Signal Region: 0.18cts/h (1-7keV) 22

23. Detectors Systems (4He Phase) 8/Oct/2009J.Galán11th ICATPP Como, Italy 2) Micromegas X-ray detector (sunrise) 3) TPC detector (sunset both bores) 2) Micromegas X-ray detector (sunrise side) Position sensitive (x-y) Precision ~ 70μm Low background Very stable Background: 25cts/h(2-10keV) (for the full magnet bore) 3) TPC detector (sunset both bores) Position sensitive Proper hielding Background: 85cts/h(2-12keV) (for the both magnet bores) 23

24. Detectors Data (4He Phase) 8/Oct/2009J.Galán11th ICATPP Como, Italy TPC Mean background versus Tracking Spectrum CCD Hitmap Integrated background and Tracking + 1 day tracking Micromegas Mean Background Rate + Trackings 24

25. Detector Systems (2008) New Sunrise Micromegas Detection Line New vacuum detection line holding space for focussing device installed in 2007. Implemented frontal calibration system. Implemented new shielding (Cupper, Lead, Cadmium, Plexiglass and Polyethylene. Improved control and monitoring of detector gas system and improved vacuum. Clean Nitrogen flux surrounding the detector inside the inner shielding. 8/Oct/2009J.Galán11th ICATPP Como, Italy 25

26. Detector Systems (2008) 8/Oct/2009J.Galán11th ICATPP Como, Italy New Sunset Micromegas Detectors 2 new Micromegas detectors installed in Sunset side replacing the previous TPC. Background level reduced by more than a factor 20 due to discrimination capabilities from micromegas detectors versus TPC detector. System redesigned and vacuum improvements achieved. Calibration is taken daily from the detectors back. Some work already schedulled for implementing frontal calibrators. 26

27. CAST Frame Store CCD (fall 2009) Better low energy response: 0.2 keV < E < 1 keV Lower background (built of radio pure materials) Better energy resolution (<160eV(FWHM) @ 6keV) Mechanical design, cooling system (CERN: engineers, Cryolab) Imaging area 256 x 256 Pixels 75 x 75 μm2 1.92 x 1.92 cm2 8/Oct/2009J.Galán11th ICATPP Como, Italy 27

28. Prospects for the post-CAST era 8/Oct/2009J.Galán11th ICATPP Como, Italy Experience gathered during last years running with the improved detectors systems and the latests and expected new technology in the coming years could push the limits in axion searches even lower. Sensitivity Estimator 29

29. CAST has published (JCAP02(2009)008, arXiv:0810.4482v2 [hep-ex])the best laboratory limit for the mass range 0.02eV-0.39eV, with 4He as buffer gas inside the magnet bores. Since 2008 CAST has been collecting data with 3He in the magnet bores. 2010: CAST should be able to fulfil its program In parallel, we are developing the low energy (visible) axion program High sensitivity detectors may lead to great improvements in mass region up to 0.02 eV (Vaccuum) Conclusions 8/Oct/2009J.Galán11th ICATPP Como, Italy 30

30. Backup Slides

31. MICROMEGAS Ultralow Background Periods 8/Oct/2009J.Galán11th ICATPP Como, Italy Observed periods of very low background in micromegas detectors. Several improvements: New designed shielding. New micromegas detectors made of low radiactivity materials. More sofisticated statistical analysis. Still not well understood nature background could be dominated by: Radon Compton scattering (not signal like in 85-90% of the cases) Ectons ( explosive electron emission ) Work in progress for understanding the low background nature. Full simulation process chain. Underground Laboratory controlled measurements. 28