Bob Jacobsen

Office: 425 Physics South
Main: (510) 708-5988
Other: (510) 486-7355

Job title: 
Professor Emeritus

Bob obtained a B.S.E.E. from MIT in 1978. He spent 1976 through 1986 working in the computer and data communications industry for a small company that was successively bought out by larger and larger companies. He left in 1986 to return to graduate school in physics, obtaining his Ph.D. in experimental high energy physics from Stanford in 1991. From 1991 through 1994, he was a Scientific Associate and Scientific Staff Member at CERN, the European Laboratory for Nuclear Physics, in Geneva Switzerland. While there, he was a member of the ALEPH collaboration concentrating on B physics and on the energy calibration of the LEP collider. He joined the faculty at Berkeley in 1995.

Research Interests

Fundamental particle physics, particularly from the experimental perspective, is my primary research interest. Over the past 20 years the “Standard Model” of high energy physics has triumphed in precise tests of predictions of various quantities. The next step is to learn more about the unknown parameters, particularly in the neutrino sector, and to search for hints to the remaining phenomenological mysteries: Dark Energy and Dark Matter.

The LHC collider and experiments provide one powerful approach to these next steps.  But it’s also possible to make progress with smaller projects that address specific questions.  For example, a number of different techniques are being used, and new ones are being proposed, for experimental searches for dark matter.  My interest lies with using very quiet targets, for example heavily-shielded and high pure targets of liquid Xenon, and watching them with high-sensitivity phototube arrays to detect possible interactions with dark matter particles as they transit through the Earth. Much like the initial solar neutrino experiments of decades ago, this is an exercise in careful understanding of backgrounds and observation of very small, low-rate signals with high confidence levels.  Experimentally, it’s hard, but also a lot of fun.  From a physics perspective, confirmed observations of dark matter particles would open up an entirely new window on fundamental physics.

Current Projects

The LUX detector is located 4850 feet underground at the Homestake Mine in Lead, South Dakota. In 2013 it published the best-yet limits on WIMP-type dark matter.  In 2014 and 2015 we’ll have a longer run to gather more data, along with new calibration methods to improve our ability to understand that data.  After that, the next step is a larger detector, called “LZ”.  This 6+ tonne liquid Xenon detector will replace LUX in the cavern, and provide a large improvement in sensitivity.  It’s being designed now (2014) and will be constructed at LBL and other sites over the next few years. We expect “first dark”, the initial operation, some time in 2018.


R. Assmann, et al. (The LEP Energy Group), “The energy calibration of LEP in the 1993 scan,” Z. Phys. C 66, 567 (1995).

“LEP data confirm train timetables,” CERN Bulletin 48, 95 (27 November 1995).

The BaBar collaboration, The BaBar Physics Book: Physics at Asymmetric B Factory, SLAC-R-0504.

Research interests: