ICHEP / 24 Status Report of CERN Axion Solar Telescope (CAST) Experiment Dieter H.H. Hoffmann (Tech. University Darmstadt & GSI – Darmstadt) on behalf of the CAST collaboration ICHEP, Moscow July 27 th 2006

ICHEP / 24 Summary of presentation Brief CAST overview Analysis of 2004 data (phase I) CAST phase II Schedule for next months Conclusions CAST Collaboration

ICHEP / 24 CERN and CAST CAST

ICHEP / 24 CAST working principle  Sikivie [1983] Axion source Axion detection

ICHEP / 24 CAST history CAST construction CAST phase ICAST phase II First commissioning runs First Physics runs Physics runs – Enhanced operation Work to upgrade for phase II First physics runs – phase II 4 He Phase II (4He) operation

ICHEP / 24 C ern A xion S olar T elescope Thomas Sahner

ICHEP / 24 CAST setup overview LHC test magnet TPC Micromegas & CCD/Telescope

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ICHEP / 24 Tracking System : Calibrated and correlated with celestial coordinates Tracking System : Calibrated and correlated with celestial coordinates Twice a year (September&March) we can film the Sun through the window Looking at sunrise Magnet, sun tracking

ICHEP / 24 TPC

ICHEP / 24 HEC μMμM XRT CCD HEC

ICHEP / 24 Solar axion spectrum P a  γ  1.7  

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ICHEP / 24 ~33% → On-Axis Effective Areas at PANTER and at CAST Energy [keV] Calculated effective area in PANTER (48 mm diameter aperture) Measured Effective area in PANTER (48 mm diameter aperture) Expected effective area at CAST (42 mm diameter aperture) The effective area of the X-ray telescope f (E γ ). ↓ 4.5 keV

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ICHEP / data analysis CCD/Telescope Spot position well determined Full sensitivity of telescope exploited Counts inside the spot compatible with background level Tracking dataSignal simulation No axion signal detected

ICHEP / data analysis TPC 2004 subtracted spectrum Micromegas 2004 subtracted spectrum ~200 h of tracking data for each detector Almost non-interrupted operation. High quality data No axion signal detected

ICHEP / result for New exclusion plot, improving 2003 result Factor of 7 improvement beyond previous experimental searches. It goes beyond astrophysical limit of globular clusters for coherence masses Publication now under preparation

ICHEP / 24 CAST phase II – principle of detection Extending the coherence to higher axion masses... Coherence condition (qL << 1) is recovered for a narrow mass range around m  N e : number of electrons/cm 3  : gas density (g/cm 3 )

ICHEP / 24 CAST phase II CAST phase II approved by CERN Research Board on Dec 2004 CAST phase II approved by CERN Research Board on Dec 2004 Data taking with 4 He started last November Data taking with 4 He started last November 3 He phase will start mid 2007 (LLNL will provide the 3 He) 3 He phase will start mid 2007 (LLNL will provide the 3 He) CAST phase II sensitivity Cosmological limit (Hannestad et al, JCAP 0507 (05) 002) Present progress

ICHEP / 24 Schedule 2006 JulyAugSepOctNovDec Data taking with 4 He 1 step per day tests for ramping? 3 He system road map Complete TDR Complete Add. MoU TD Review Start construction components New detection line MM+optic PANTER tests Installation in CAST P ~ 9 mbar m a ~ 0.31eV P ~ 12 mbar m a ~ 0.37eV

ICHEP / 24 Schedule 2007 JFMAMJJASOND 3 He System Installation in CAST Commissionin g Data taking Start 3 He physics runs Double step Possibility of ramping mode? Data taking Time needed to fully exploit new setup P ~ 45 mbar m a ~ 0.71 eV P ~ 120 mbar m a ~ 1.16 eV

ICHEP / 24 Conclusions CAST has successfully performed its transition into phase II: Phase I data analysis finished. Publication under preparation Upgrades to start phase II done during 2005: 4 He system, cold windows Phase II 4 He data taking ongoing Started in Nov 2005 Up to 4 mbar scanned already. 4 He runs planned until the end of the year Installation of new detector line with a second X-ray optics planned before the end of the year Phase II 3 He operation scheduled for mid next year 3 He system designed. Technical report in preparation Schedule for next months has been presented CAST will reach 60 mbar (0.8 eV) during He allows extension to even higher masses (1.16 eV)