The CRESST Dark Matter Search Status Report Cryogenic Rare Event Search with Superconducting Thermometers CRESST is a collaboration of: Max-Planck-Institut für Physik Technische Universität München University of Oxford Universität Tübingen Laboratori Nazionali del Gran Sasso

Federica Petricca - MPI Project Review 2010 Outline The CRESST Detector Status of the experiment MPI activities Ongoing run Analysis Next run Light Detectors Holding of target crystals Alternative target crystals 20.12.2010 Federica Petricca - MPI Project Review 2010

CRESST Cryogenic Detectors Scintillating target crystals Modular structure Multi-target possible CaWO4 h=40mm ∅=40mm m=300g W-SPT Light absorber CaWO4 target crystal reflecting scintillating housing 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Outline The CRESST Detector Status of the experiment MPI activities Ongoing run Analysis Next run Light Detectors Holding of target crystals Alternative target crystals 20.12.2010 Federica Petricca - MPI Project Review 2010

Status of the experiment CRESST running since spring 2009 9 fully functioning CaWO4 modules 1 fully functioning ZnWO4 module 6 modules with not operational light detector (Tc too low) 1 module with not operational crystal (?) ~750 kg/day of net exposure Gamma calibration Neutron calibration Various test of the shielding 20.12.2010 Federica Petricca - MPI Project Review 2010

Status of the experiment CRESST running since spring 2009 (Preliminary) results presented Module 5 a O W MPI colloquium – 23.06.2010 Visit of the Fachbeirat – 27.10.2010 Publication in preparation Unexpected events in oxygen recoil band 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Outline The CRESST Detector Status of the experiment MPI activities Ongoing run Analysis Next run Light Detectors Holding of target crystals Alternative target crystals 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Analysis of Compound Target Materials The CRESST Dark Matter Search – New Analysis Methods and Recent Results J. Schmaler, PhD thesis, TUM (2010) WIMPs should mainly scatter off tungsten nuclei for light WIMPs: W recoils below energy threshold  O and Ca relevant! new analysis method: takes into account contributions of all nuclei simultaneously need to work in full 2-D parameter space (energy/light yield) includes new methods for calculating exclusion limits based on 2-D data density of expected signal for a 15 GeV WIMP 20.12.2010 Federica Petricca - MPI Project Review 2010 8

Analysis of Compound Target Materials The CRESST Dark Matter Search – New Analysis Methods and Recent Results J. Schmaler, PhD thesis, TUM (2010) exclusion limits for elastic WIMP scattering benefits of new analysis method: strongly enhanced sensitivity for light WIMPs two-dimensional: exploits full information of CRESST data to obtain limits robust against unknown backgrounds 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Analysis of Detectors’ Characteristics Optimization of CRESSTII detector modules M. Kiefer, PhD thesis, TUM (in preparation) Large number of running detector modules Study characteristics at low temperature Light emitted Light detected Model: distribution of energy in a module 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Analysis of Detectors’ Characteristics Optimization of CRESSTII detector modules M. Kiefer, PhD thesis, TUM (in preparation) CaWO4 better than ZnWO4 Composite better than conventional composite conventional No large variation in light detection efficiency within the modules 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Outline The CRESST Detector Status of the experiment MPI activities Ongoing run Analysis Next run Light Detectors Holding of target crystals Alternative target crystals 20.12.2010 Federica Petricca - MPI Project Review 2010

Light Detectors - Production More detectors running Production of new LD Reproducibility of transition WII-146 WII-132 WII-106 20.12.2010 Federica Petricca - MPI Project Review 2010

Light Detectors - Production More detectors running Production of new LD Reproducibility of transition ESD problem 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Light Detectors – Optimization The detectors Parameters Determining the sensitivity of the CRESST-II Experiment P. Huff, PhD thesis, TUM (2010) Improve event-by-event discrimination Understanding of the factors determining the width of the bands  possibility for improvement Thermometer with separated heater Two implemented in run32 All newly produced heaters Black Silicon light absorber Tested in Munich Modified thermometer size 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Outline The CRESST Detector Status of the experiment MPI activities Ongoing run Analysis Next run Light Detectors Holding of target crystals Alternative target crystals 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 20.12.2010 Federica Petricca - MPI Project Review 2010

Holding of target crystals most likely origin of no-light events: stress relaxation events at contact surface between clamps and crystal clamps mostly covered with plastic layer more no-light events than with pure metal clamps consequence of 2008 run: new clamps for all crystals no plastic coverage 20.12.2010 Federica Petricca - MPI Project Review 2010

Holding of target crystals Module 5 non scintillating clamp a 210Po 206Pb a High 210Pb content in the clamp material 20.12.2010 Federica Petricca - MPI Project Review 2010

Holding of target crystals Reduction of background Alternative spring material New reflecting coating (Al) New scintillating coating (Epo-tek +PPO) Need testing: Radiopurity Production and handling Low temperature performance 20.12.2010 Federica Petricca - MPI Project Review 2010

Holding of target crystals Reduction of background Alternative spring material New reflecting coating (Al) New scintillating coating (Epo-tek +PPO) CaWO4 balls Improved holder design Test facility at GS for studying prototypes 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Outline The CRESST Detector Status of the experiment MPI activities Ongoing run Analysis Next run Light Detectors Holding of target crystals Alternative target crystals 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Al2O3:Ti 20.12.2010 Federica Petricca - MPI Project Review 2010

Alternative target crystals Light Yield Measurements of CdWO4 and Al2O3:Ti for the CRESST Dark Matter Search R. Kleindienst, Diploma Thesis, TUM (2010) Cryogenic measurement with small target crystal CdWO4 Light Yield ~ 2 CaWO4 comparable with LY CaWO4 for large crystals (measured in test cryostat at Gran Sasso)  Further improvement of crystal quality Al2O3:Ti (50 to 500 ppm) Light Yield ~1/2 CaWO4  Low light yield W-SPT Light absorber Target crystal 20mm x 10mm x 5mm reflecting housing 20.12.2010 Federica Petricca - MPI Project Review 2010

Alternative target crystals Cryogenic measurement with small target crystal CsI Light Yield ~ 7 CaWO4 Aspects under investigation: performance as cryogenic calorimeter possible surface effects position dependence intrinsic radioactivity W-SPT Light absorber Target crystal 20mm x 10mm x 5mm reflecting housing  Needs to be measured in the test facility at Gran Sasso 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Future Study reproducibility of transitions in light detectors Investigation of new light absorbers Black Silicon Optimization of thermometer size Characterization of new scintillators CsI CdWO4 20.12.2010 Federica Petricca - MPI Project Review 2010

Federica Petricca - MPI Project Review 2010 Future Detectors ready New holders in production Solution for target crystal holding to be finalized Conclusion of ongoing run early 2011 approaching 1T/day Installation of new detectors and maintenance Start of new run mid 2011 study excess of events in the oxygen band with lower background and higher mass We want to thank the MPI staff that is involved with the preparation of the new CRESST Run 20.12.2010 Federica Petricca - MPI Project Review 2010