Direct Search for Dark Matter WIMPS Complementary experimental - - PowerPoint PPT Presentation

Direct Search for Dark Matter WIMPS

Complementary experimental approaches: Direct and indirect searches, LHC

Simplified direct detection overview

(R. Lang, APS physics 6,136 (213))

Two paradigms

• Generic WIMPs ~100 GeV
• Low mass WIMPs (e.g. Asymmetric Dark Matter scenario ~5 GeV,...)

High Mass Frontier

Strategy: Increase exposure no background

• “Natural” weak scale WIMPS 10-9 -10-10 pb /nucleon
• Irreducible neutrino background at 10-12 pb from coherent scattering of

atmospheric neutrinos Which detector technology ?

• Noble liquids probably most natural choice for ton scale detectors

(Xe requires background improvement of a few 1000 to reach 10-12 pb)

• Cryogenic detectors may also play a useful role for weak scale WIMPs

Need a few 100 kg to reach 10-10 pb/nucleon Complementary: Very different backgrounds and detection mechanism Different nuclei and experiments needed for confirmation of signal

• Several target materials are needed (isospin violating coupling)

Direct detection limits

Snowmass Summary Report 2013

• WIMP-nucleon cross section, assuming σ ~ A2 to allow comparison of experiments
• Xe is dominating the high mass range (LUX ~10-9 pb)

Low Mass Frontier

expected recoil spectrum: Xe, 5 GeV WIMP

Need excellent signal to noise

– recoils mostly below 1 keV – threshold much more important than mass – kg scale detectors sufficient

Which detector technology ?

cryogenic detectors: – excellent S/N makes them most natural choice for low threshold CDMSlight: use Neganov-Luke and give up discrimination 0.176 keVee / 0.84 keVnr threshold

CRESST: 600 eV recoil threshold – detectors with light nuclei most useful

CMDS Si CaWO4, Al2O3 ??

Noble liquids:

– Large uncertainty of recoil energy scale (Leff , energy and field dependence of electric field quenching)

– S2 only might be useful, no fiducialization, no convincing idea for calibration of recoil energy scale

Low Mass region

Confusing situation:

– Several hints and one claim (DAMA), excluded by others

– Unsuspected backgrounds, systematic uncertainties in nuclear recoil energy scale ? – Isospin violating coupling may considerably relax tension

(rate on nucleus depends on fn/fp, drastic reduction possible)

CRESST Present Run

α and 210Pb recoil background completely suppressed in all new types of detector modules (strongly reduced in conventional)

181W 179Ta 179Ta 181W

CRESST Present Run

• New self grown crystals (TUM) ~10 times lower β/γ background
• Energy resolution and accuracy of calibration at sub keV level
• Some detectors run at 0.6 keV threshold (lowest of all DM searches)

CRESST and Future

• Run for ~ 2 years and collect 2000 kg days of data
• Grow new set of radiopure crystals in Munich and prepare detectors modules of

the new type and replace conventional ones as soon as possible

• R&D for detector modules with M>1kg.
• Upgrade CRESST set-up at Gran Sasso to house ~50 kg detectors
• Develop common tower structure for integrating CRESST type detectors in

EURECA/SuperCDMS

Conclusion

Detector technology pioneered at MPI with excellent potential for making a useful contribution in DM search, especially for low mass WIMPs Excellent energy resolution and perfect discrimination of alpha backgrounds at high energies makes this detector technology an excellent choice for a next generation of neutrinoless double beta decay searches (Federica's talk) Other attractive (high risk/high gain) applications in neutrino physics: Calorimetric measurement of electron capture in 163Ho for next generation of direct neutrino mass experiments with sensitivity mν< 0.1 eV