1. Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011 Simulating CDMS Detector Physics A condensed matter energy transport framework for Geant4 D. Brandt, M. Asai, E. Do Couto e Silva, B. Cabrera

2. Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011 The Cryogenic Dark Matter Search The Cryogenic Dark Matter Search (CDMS) is looking the direct interaction of dark matter with conventional matter The sensitive detector mass comprises a set of large high purity Germanium crystals Dark matter particles are expected to create free charge carriers and lattice vibrations

4. Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011 Phonons in the CDMS detector Phonon propagation is complicated by two facts: 1. Phonons spontaneously downconvert to low energy pairs with radically longer mean free paths 2. Phonon propagation is highly anisotropic due to anisotropic speed of sound in the crystal Above: Phonon propagation in Ge, simulated using Geant4

5. Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011 Charge propagation in the CDMS detector Charge propagation is complicated by the Germanium band structure. Electrons behave as though they have an anisotropic mass. Charge propagation in Geant4 in perspective (left) and from the side (right). Green = electrons, red = holes

6. Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011 Full physical model of energy transport The full model of energy transport in the detector is implemented using Geant4 Consequently, the implementation is flexible and highly re-usable Fast progress was made possible by the combination of CDMS experts and the core Geant4 development team on site at SLAC Above: Signal propagation in Ge. Red=hole, green = electron, blue = phonon

7. Validating the transport codes The intensity pattern recorded by the detector of a phonon point source at the crystal center is in good agreement with experimental results reported in the literature. A MatLab version of the simulation yields good agreement of carrier transport properties with experiment. We hope to begin validation of carrier transport in Geant4 in the next few weeks. Image from Cabrera et al., 2010, arxiv 1004.1233v1 Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011

8. The entire project is implemented using the Geant4 toolkit Daniel Brandt dbrandt@slac.stanford.edu Scientific Computing Workshop KIPAC, SLAC, 20 June 2011 Project implementation & applications Our efforts constitute the first condensed matter framework for Geant4 The Geant4 toolkit is freely available under a public license, making our efforts available to the scientific community We hope our work will find application in the cryogenic calorimeter community, other rare event search experiments and possibly nano-scale device physics This project has been made possible by the unique synergy of having the physics expertise and the Geant4 core development team on the same campus

9. California Institute of Technology Z. Ahmed, J. Filippini, S.R. Golwala, D. Moore Fermi National Accelerator Laboratory D. A. Bauer, F. DeJongh, J. Hall, D. Holmgren, L. Hsu, E. Ramberg, R.L. Schmitt, J. Yoo Massachusetts Institute of Technology E. Figueroa-Feliciano, S. Hertel, S.W. Leman, K.A. McCarthy, P. Wikus NIST K. Irwin Queen’s University C. Crewdon*, P. Di Stefano *, J. Fox *, S. Liu *, C. Martinez*, P. Nadeau *, W. Rau Saint Olaf College A. Reisetter Santa Clara University B. A. Young SLAC National Accelerator Laboratory/KIPAC * M. Asai, A. Borgland, P. Brink, D. Brandt, W. Craddock, E. do Couto e Silva,.G. Godfrey, J. Hasi, M. Kelsey, C. J. Kenney, P. C. Kim, R. Partridge, R. Resch, A. Tomada, D. Wright Southern Methodist University J. Cooley, B. Karabuga, H. Qiu Stanford University B. Cabrera, M. Cherry, L. Novak, R.W. Ogburn, M. Pyle, M. Razeti *, B. Shank*, S. Yellin, J. Yen* Syracuse University M. Kos, M. Kiveni, R. W. Schnee Texas A&M K. Koch*, R. Mahapatra, M. Platt *, K. Prasad *, J. Sander University of California, Berkeley M. Daal,T. Doughty, N. Mirabolfathi, A. Phipps, B. Sadoulet, D. Seitz, B. Serfass, D. Speller, K.M. Sundqvist University of California, Santa Barbara R. Bunker, D.O. Caldwell, H. Nelson University of Colorado Denver B.A. Hines, M.E. Huber University of Florida T. Saab, D. Balakishiyeva, B. Welliver * University of Minnesota H. Chagani*, J. Beaty, P. Cushman, S. Fallows, M. Fritts, T Hoffer*, O. Kamaev, V. Mandic, X. Qiu, R. Radpour*, A. Villano*, J. Zhang * new collaborators or new institutions in SuperCDMS NSF DOE about 100 collaborators