Blas Cabrera - Stanford UniversitySLAC Experimental SeminarPage 3 Dark Matter WIMPs The Science –Scientific case compelling for dark matter WIMPs both from particle physics side and astrophysics side Galaxy formed in dark matter gravitational potential –Our solar system rotates through swarm of WIMPs 10 9 /cm 2 /s –These would only interact with nuclei not electrons ~ (m N /m e ) 2 –Nearly all backgrounds interact with e’s produced by gammas CDMS II detectors and program –Tower 1 (4 Ge and 2 Si detectors) at SUF (neutron limited) –Same Tower 1 at Soudan - PRL 93, (2004) best by x4 –Towers 1& 2 (2004) and Towers 1-5 (2005) - x20 (n limited) SuperCDMS detectors and program –Development Project - 5 kg Ge new detectors run at Soudan –Phase A (25 kg Ge) & Phase B (150 kg Ge) run at SNOLab –Can run 1000 kg Ge at SNOLab before neutron limited Conclusions: to succeed need SLAC technical and management experience
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Blas Cabrera - Stanford University SLAC Experimental Seminar Page 1 The Search for Dark Matter in the form of WIMPs: CDMS (Cryogenic Dark Matter Search) Extending the search for dark matter WIMPs beyond CDMS-II with SuperCDMS SLAC Experimental Seminar November 17, 2004 Blas Cabrera CDMS Collaboration At Stanford: Paul Brink, Laura Baudis (now at U Florida), Jodi Cooley, Clarence Chang, Walter Ogburn, Matt Pyle, Daniel Soto, Betty Young (SCU),
UC Berkeley, Stanford, LBNL, UC Santa Barbara,Case Western Reserve U, FNAL, Santa Clara U, NIST, U Colorado Denver, Brown U, U Minnesota,U Florida, Princeton
– Scientific case compelling for dark matter WIMPs both from particle physics side and astrophysics side
• Galaxy formed in dark matter gravitational potential– Our solar system rotates through swarm of WIMPs 109/cm2/s– These would only interact with nuclei not electrons ~ (mN/me)2
– Nearly all backgrounds interact with e’s produced by gammas• CDMS II detectors and program
– Tower 1 (4 Ge and 2 Si detectors) at SUF (neutron limited)– Same Tower 1 at Soudan - PRL 93, 211301 (2004) best by x4– Towers 1& 2 (2004) and Towers 1-5 (2005) - x20 (n limited)
• SuperCDMS detectors and program– Development Project - 5 kg Ge new detectors run at Soudan– Phase A (25 kg Ge) & Phase B (150 kg Ge) run at SNOLab– Can run 1000 kg Ge at SNOLab before neutron limited
• Conclusions: to succeed need SLAC technical and management experience
Possible SLAC roles• At Stanford we know how to fabricate detectors for 25 kg experiment, but for 150 kg and 1000 kg we need to mass produce the fabrication/mounting
• SLAC could take central responsibility for fabrication with a combination of in house facilities (radon suppression) and commercial production.
• Other major areas include electronics (custom boards), DAQ (with digitizers for 10k channels readout at a 50 Hz for calibrations), computing (first pass data reduction, data analysis and Monte Carlo simulations).
• With Spokesperson for SuperCDMS at Stanford, SLAC could & should take the lead role in project management
• Alternative method to identify near-surface events– Phonon sensors on both sides are virtual ground reference.– Bias rails at +3 V connected to one Qamp– Bias rails at -3 V connected to other Qamp– Signals coincident in both Qamps correspond to events drifted out of the bulk.
– Events only seen by one Qamp are < 1.0 mm of the surface.
New Read-out schemes• Two-stage SQUIDs for reading out new phonon sensors
– Allows lower Rn, more TESs, better phonon sensor surface area coverage.• Will improve effectiveness of present phonon risetime cut even further.
– Allows move to Al-Mn TESs to overcome W Tc variability• Resitivity of Al-Mn < W, hence risk /design constraint of electro-thermal oscillation if change-over to two-stage SQUIDs not implemented.
– Commensurate with NIST-style time-domain multiplexing.• ZIP detector phonon pulses are probably sufficiently slow to utilize this scheme effectively to reduce the readout wiring to room temperature that would otherwise be required.
• “…We need to study dark matter directly by detecting relic dark matter particles in an underground detector and by creating dark matter particles at accelerators, where we can measure their properties and understand how they fit into the cosmic picture.”
• “… The particle nature of dark matter can be verified by finding the rare events they would produce in a sensitive underground dark matter detector such as CDMS. …”
• “However, to understand the true nature of dark matter particles, particle physics experiments must produce them at accelerators and study their quantum properties. Physicists need to discover how they fit into a coherent picture of the universe. Suppose experimenters detect WIMPs streaming through an underground detector. What are they? Are they the lightest supersymmetric particle? The lightest particle moving in extra dimensions? Or are they something else?”
• Did not go the final step of saying that if supersymmetry discovered at an accelerator then we must see if it is the dark matter with direct detection experiments.
