1. The CAST Experiment A search for Solar Axions Jaime Ruz Armendáriz, LFNAE, Zaragoza University On behalf of the CAST Collaboration CASTCAST

2.  The CAST Experiment Motivation Motivation Description Description  CAST First Phase Description Description Results Results  CAST Second Phase Description Description Results Results  STATUS OUTLINE The CAST Experiment CASTCAST Jaime Ruz Armendáriz. HEP 2007, Manchester

3. MOTIVATION QCD predicts the breaking of CP symmetry in strong interactions, but so far this has never been observed by any experiment. CP violation implies then an electric dipole moment for the neutron… Experiments find Two different contributions here: QCD vacuum and EW quark mixing The Strong CP-Problem: Why is so small? CASTCAST Theoretically The CAST Experiment Jaime Ruz Armendáriz. HEP 2007, Manchester

4. Axion axion – gluon vertex θ absorbed in the definition of a Pseudo Scalar Goldstone boson resulting from the spontaneously broken symmetry introduced by Peccei-Quinn global chiral symmetry U PQ (1) to enforce strong CP conservation. Mass (from a-π 0 mixing): (Astrophysical Argument, HB) Coupling to photons:, where Mean life time for i.e. MOTIVATION CASTCAST The CAST Experiment Jaime Ruz Armendáriz. HEP 2007, Manchester

5. MOTIVATION CASTCAST The CAST Experiment Jaime Ruz Armendáriz. HEP 2007, Manchester

6. MOTIVATION CASTCAST The CAST Experiment SOLAR BLACK BODY RADIATION DIFFERENTIAL AXION FLUX AT THE EARTH SURFACE Jaime Ruz Armendáriz. HEP 2007, Manchester

7. DESCRIPTION CASTCAST The CAST Experiment Jaime Ruz Armendáriz. HEP 2007, Manchester

8. CAST aims to reconvert solar axions back into photons  DECOMMISSIONED LHC MAGNET. L=9.26 m B=9 T  3 X-ray DETECTORS (2003 - …)  1 X-ray telescope (2003 - …)  2 x 1.5 hours/day of exposure time TPC μMμM TELESCOPE Jaime Ruz Armendáriz. HEP 2007, Manchester CCD CASTCAST The CAST Experiment DESCRIPTION [2003 - 2004] Vacuum [2005 - 2006] 4 He [2007 - … ] 3 He m a < 0.02 eV m a < 0.34 eV m a < 1.16 eV

9. Jaime Ruz Armendáriz. HEP 2007, Manchester CASTCAST The CAST Experiment DESCRIPTION CAST-Magnet is crosscheck visually to be aligned with the Sun Center within 0.02°! MFB Tube 5.0 m2.6 m PointerCrosshairsCamera Magnet Optical Axis

10. SIGNAL Excess of X-ray in TRACKING over BACKGROUND Jaime Ruz Armendáriz. HEP 2007, Manchester CASTCAST The CAST Experiment CAST First Phase. DESCRIPTION Vacuum inside the cold bore (magnet region)Vacuum inside the cold bore (magnet region) The photon acquires an effective mass m γ = 0 (Coherence condition qL<1 )

11. 95% Upper Limit Best Fit g a  µM 95% Upper Limit CCD Best Fit g a  95% Upper Limit TPC Best Fit g a  95% Upper Limit Best Fit g a  95% Upper Limit Background 95% Upper LimitTracking 2003 DATA Background 2004 DATA Jaime Ruz Armendáriz. HEP 2007, Manchester CASTCAST The CAST Experiment CAST First Phase. RESULTS

12. Jaime Ruz Armendáriz. HEP 2007, Manchester CASTCAST The CAST Experiment CAST First Phase. RESULTS

13. CAST First Phase. Description Jaime Ruz Armendáriz. HEP 2007, Manchester CAST First Phase. RESULTS CASTCAST

14. CAST Second Phase. DESCRIPTION Extending coherence for higher axion masses … Extending coherence for higher axion masses … The photon acquires an effective mass m γ > 0 FILL MAGNET BORE WITH HELIUM Jaime Ruz Armendáriz. HEP 2007, Manchester The CAST Experiment CASTCAST

15. Coherence condition (qL << 1) restored for a narrow mass range around m γ m γ can be adjusted by changing the gas pressure Jaime Ruz Armendáriz. HEP 2007, Manchester Coherence restored for a narrow mass range around m γ Coherence restored for a narrow mass range around m γ CAST Second Phase. DESCRIPTION The CAST Experiment CASTCAST [2005 - 2006] 4 He [2007 - … ] 3 He m a < 0.34 eV m a < 1.16 eV

16. Jaime Ruz Armendáriz. HEP 2007, Manchester CAST Second Phase. RESULTS CASTCAST The CAST Experiment Preliminary Result 4 He Phase

17. STATUS No axions yet, CONTINUE DATA TAKING Jaime Ruz Armendáriz. HEP 2007, Manchester CASTCAST The CAST Experiment

18. Jaime Ruz Armendáriz. HEP 2007, Manchester STATUS No axions yet, CONTINUE DATA TAKING CASTCAST The CAST Experiment