Benn Tannenbaum

Who am I?

With hairPhoto of me with hair Photo of me without hair a little Photo of me with no hair none!

I'm a Postdoctoral Fellow in the Department of Physics and Astronomy at the University of California at Los Angeles, working in the collider physics arena. Presently, I'm working on the end cap muon trigger code for the CMS experiment, a large device to be built and used at CERN in Geneva, Switzerland. Data-taking is scheduled to start in the latter half of the first decade of the next century. Since I also want to actually do some physics, I'm also a member of the CDF collaboration, a large experiment at the Fermi National Accelerator Laboratory. I also did my Ph.D. on CDF, while at the University of New Mexico.

Where am I?

These days, I'm in Los Angeles. Sometimes I get sent to Chicago to work at FNAL, and occasionally CERN in Geneva, or perhaps UC Davis or Univ. Florida. Gotta get those frequent flier miles!

What do I do?

UCLA is responsible for the design of some of the trigger hardware used in the endcap muon chambers for the CMS collaboration. Some explanation: CMS (Compact Muon Solenoid) is one of two large experiments being built at CERN, a multi-purpose laboratory just outside Geneva Switzerland. These experiments will use colliding proton beams provided by the LHC (Large Hadron Collider). CMS consists of many different detectors working in concert. These include devices to measure the energy and position of charged particles as they pass through the detector. These detectors are positioned in a cylinder around the point where the two proton beams collider and in disks at either end of the cylinder (to measure particles that travel with angles less than ~45 degrees away from the direction of the beam).

Muons, heavier cousins of electrons, tend to pass completely through detectors without stopping. That means we cannot measure their energy particularly accurately. However, since we know the mass of the muon quite well, a measurement of their momentum is taken instead. All charged particles follow an arc as they pass through a magnetic field. By measuring this arc we can determine the momentum of the muon (since we already know the magnetic field and the mass of the muon). Thus, we build special muon chambers to measure the position of the muon in several places along its path. In CMS, there are 3 (or 4...) stations of chambers at each end of the central cylinder. These stations consist of chamber segmented in either 10 or 20 degrees, each with six layers of readout.

The proton beams at the LHC will collide every 25 nanoseconds--40,000,000 times per second! We do not have the ability to record every single collision, nor would we want to. The vast majority of the collisions are uninteresting. We select certain events using electronics called a trigger. It looks at the various detectors to see if they have potentially interesting information for that event. The UCLA trigger hardware examines the six layers of each of the endcap muon chambers and tries to construct a local charged track (LCT) using the hits on the layers. If an LCT is found, that information is passed on to the next part of the trigger.

CMS, and all modern particle physics experiments, do Monte Carlo studies to determine how their detectors will work. We build software models of the detectors and run simulations of events. We then build prototype devices and subject them to conditions similar to what is expected in the actual experiment (a test beam). We then take what we've learned from the test beam and incorporate that information into the simulation. Iterate, and eventually you get to the real device! My responsibility is to incorporate a simulation of UCLA's LCT cards into CMSIM, the CMS simulation package. I have some web pages about all that...

I've also written a short page on how to use QFL, the CDF detector simulator. You can also read what I did for my dissertation.

I used to have an amazing amount of time to spend surfing the web, finding amazingly cool things that boggle the mind. To save you all that drudgery, here's my hotlist.

What I used to do

All kinds of things!

Return to the CDF Home Page, the people of CDF, or the UCLA-collider home page.

Contact information

Benn Tannenbaum	     University of California at Los Angeles 
Office: 4-162 Knudsen Hall, [310] 206-5022 
Snail:  405 Hilgard St., UCLA, Department of Physics and Astronomy, 
        Los Angeles, CA  90095-9000
FAX:    [310] 206-1091
Benn Tannenbaum (
last updated 15 October 1999