Geant4 Joins the Hunt for Dark Matter

Much as sunlight shining through a glass of water makes light patterns on a tabletop, phonons travel through a germanium crystal in preferred directions, creating patterns like the one seen above. (Simulated image courtesy Daniel Brandt.)

by Kelen Tuttle

Deep underground, the Cryogenic Dark Matter Search experiment hunts for the brief—and rare—flash of a dark-matter particle zipping through detectors. Yet what would such a flash look like? And how can the CDMS collaboration carefully distinguish it from background particles like those originating from the cosmic rays that zing through the detector with far greater frequency than dark-matter particles?

Using the Geant4 software toolkit, originally designed to simulate high-energy particle physics experiments, a small team of SLAC researchers is working with the CDMS collaboration to answer just these questions for the future experiments.

CDMS began its search for dark matter at Stanford in the mid-1990s, and in the intervening years has evolved and improved in sensitivity. The next experiment, SuperCDMS at Soudan, is now under construction in Minnesota's Soudan Mine. There, protected from most cosmic rays and other pesky background noise by miles of dirt and rock, 15 kilograms of 1-inch thick germanium crystals will be cooled to nearly absolute zero as they wait for dark matter particles to pass through.

Detecting elusive dark matter particles with a germanium detector is possible because the interior of every crystal, be it the Hope Diamond or a grain of table salt, is constantly vibrating as the atoms transfer vibrations from one to the next. These waves, or "phonons," travel through the crystal, each carrying a discrete unit of vibrational energy.

Welcome, New SLACers!

by Maria Mastrokyriakos

SLAC welcomed 30 recently hired employees at the October New Employee Orientation, which took place on October 8. Please welcome our new staff as they embark on their new career paths here at SLAC.

Front row (from left): Poonam Pandey, Gregorio Curiel, Jing Yin, James Morales, Dehong Zhang, Catherine Meyers, Robert Woods, Ki Hwan Lee, Despina Milathianaki, Rajan, Mumtaz Pierre-Davis Winn, Mikhail Dubrovin.

Back Row (from left): Victoria Schwerin, Evan Rodriguez, Satyajit Patwardhan , Richard Atkinson, Dentell Reed, Mary Lee, Ryan Ford, Joel Barragan, Grace Tsai, Paul Brink, Alan Fry, Norman Bobczynski, Octavian Matei.

Not Pictured: Benjamin Tu, Michael Fonda, Yong Kim, Ling Teng and Richard Wittman.

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Geant4 Joins the Hunt for Dark Matter Much as sunlight shining through a glass of water makes light patterns on a tabletop, phonons travel through a germanium crystal in preferred directions, creating patterns like the one seen above. (Simulated image courtesy Daniel Brandt.) by Kelen Tuttle Deep underground, the Cryogenic Dark Matter Search experiment hunts for the brief—and rare—flash of a dark-matter particle zipping through detectors. Yet what would such a flash look like? And how can the CDMS collaboration carefully distinguish it from background particles like those originating from the cosmic rays that zing through the detector with far greater frequency than dark-matter particles? Using the Geant4 software toolkit, originally designed to simulate high-energy particle physics experiments, a small team of SLAC researchers is working with the CDMS collaboration to answer just these questions for the future experiments. CDMS began its search for dark matter at Stanford in the mid-1990s, and in the intervening years has evolved and improved in sensitivity. The next experiment, SuperCDMS at Soudan, is now under construction in Minnesota's Soudan Mine. There, protected from most cosmic rays and other pesky background noise by miles of dirt and rock, 15 kilograms of 1-inch thick germanium crystals will be cooled to nearly absolute zero as they wait for dark matter particles to pass through. Detecting elusive dark matter particles with a germanium detector is possible because the interior of every crystal, be it the Hope Diamond or a grain of table salt, is constantly vibrating as the atoms transfer vibrations from one to the next. These waves, or "phonons," travel through the crystal, each carrying a discrete unit of vibrational energy. Read more... (Photo by Barbara Hemstad.) Welcome, New SLACers! by Maria Mastrokyriakos SLAC welcomed 30 recently hired employees at the October New Employee Orientation, which took place on October 8. Please welcome our new staff as they embark on their new career paths here at SLAC. Front row (from left): Poonam Pandey, Gregorio Curiel, Jing Yin, James Morales, Dehong Zhang, Catherine Meyers, Robert Woods, Ki Hwan Lee, Despina Milathianaki, Rajan, Mumtaz Pierre-Davis Winn, Mikhail Dubrovin. Back Row (from left): Victoria Schwerin, Evan Rodriguez, Satyajit Patwardhan , Richard Atkinson, Dentell Reed, Mary Lee, Ryan Ford, Joel Barragan, Grace Tsai, Paul Brink, Alan Fry, Norman Bobczynski, Octavian Matei. Not Pictured: Benjamin Tu, Michael Fonda, Yong Kim, Ling Teng and Richard Wittman.	Events Today (10:00 a.m.) CBIS Seminar: Phase Contrast X-ray Imaging Access (see all) Parking Lot A Closures RSB Project Info and Updates Announcements (see all \| submit) Lab Announcements Updated Retirement Plan Summaries Available Online Opportunity to Support Small Business Research Proposals Community Bulletin Board LCLS/SSRL Users' Meeting Registration Training (see all \| register) Lab Training Calendar Registration Today (9:00 a.m.) Haz Waste Management Refresher Today (10:00 a.m.) Rad Worker Practical Today (2:00 p.m.) Laser Safety Basics News (submit) Silicon Strategy Shows Promise for Batteries Rice U. news release on Eurekalert Key Component Contract for Iter Fusion Reactor BBC News Science Shot: Young Galaxies Made Stars from Scratch ScienceNOW
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