The search closes in

By Cindy Weiss, CLAS Today

Rob Roser Photo courtesy of Fermilab

Rob Roser, CLAS ’84, for the past ten years has led the Collider Detector at Fermilab (CDF), the Fermi National Accelerator Laboratory in Batavia, Ill. The CDF is a collaboration of scientists searching for the elusive Higgs boson, a predicted, but not yet seen, sub-atomic particle that could confirm theories in physics about how mass originates.

Recently, scientists at Fermilab found a “bump” in data from the lab’s Tevatron particle collider that could be caused by the Higgs boson. The finding is particularly exciting since the more powerful Large Hadron Collider (LHC) at the CERN laboratory in Switzerland, has also found hints, but not clear evidence, of the Higgs. The Tevatron was shut down in 2011 due to federal budget cuts, but data from the collisions it produced are still being analyzed. Scientists use these powerful colliders to accelerate sub-atomic particles and produce collisions that can reveal information about their structure.

Roser, who became head of the Scientific Computing Division of Fermilab in January, is a 1984 physics graduate in CLAS who credits UConn with giving him a strong physics background.

Did you enter UConn as a physics major? How did you become interested in the field?

No – I entered as a liberal arts major. I knew I was interested in math and science but had certainly not settled on physics when I started.  It took at least a year before I made a choice.  Physics was by far the hardest class I had and that intrigued me…

Were any faculty or peers at UConn particularly influential?

Quentin Kessel  (professor of physics) had more influence on my career than anyone – ever.  I spent 3.5 years working in his laboratory and he taught me how to be a physicist.  I refined my skills in graduate school but UConn and QK get most of the credit.

Describe what you do at Fermilab and your involvement in the Higgs boson project.

For the last decade, I have led the CDF collaboration.  This is an experiment on the Tevatron. It comprises 600 physicists from 60 universities and 15 countries.  One of our overarching goals is to search for the Higgs Boson.

As a scientist with management responsibilities, how do you organize researchers to work as a team?

Organizing physicists is a lot like herding cats.  It is very hard to do.  Most of the scientists on my experiment work for universities all over the world.  I don’t sign their paychecks and so my control over them is minimal.  My job is to gather consensus and to convince people it is in their best interest as well as the experiments to take on a certain project or responsibility.   It’s a constant negotiation.

With the Tevatron no longer running and the data in, is there a lot of analysis still to be done?

The Tevatron has collected an amazing data sample.  It would be of interest for the next decade if the next machine at CERN were not working so well.  However, given we are not the only game in time –our job is to complete our core analyses within the year.  Analyses which do not compete with the Large Hadron Collider can take longer and will.

What would it take to confirm a finding of the Higgs boson? Why is the particle so hard to identify?

Higgs boson’s predicted place in physics. Drawing from Fermilab

Higgs boson’s predicted place in physics.
Drawing from Fermilab

The Higgs boson is challenging because it is difficult to produce.  At the Tevatron, we produce about 500 per year out of literally hundreds of billion collisions.  The challenge is to find those few hundred.  Discoveries are made based on a statistical analysis of the data. One cannot claim a discovery based on a single collision.  What makes the Higgs so challenging is that its characteristic signature is not so different than many mundane physics processes.  Thus it takes a reasonable statistical sample to separate the signal events from background.  The Tevatron has the tools to make a discovery – however, to do so requires a larger data sample than we currently have access too.  We tried to run longer but budget realities prevented that.  The best we can do is to claim strong evidence.  We are not there yet but hope to be this summer.  These are exciting times.

How would finding the Higgs boson change the field of physics?

In our current understanding of physics, we do not know why the fundamental particles have the masses that they have.  Finding the Higgs would take a big step in that direction.   However, finding it is not the end of the story.  It is rather the beginning of the next chapter of characterizing it and making sure its properties agree with our theoretical bias.

And not finding it?

Perhaps even more interesting – it means there is another explanation.

When you were an undergraduate physics major, did you ever think you would be working on a project like this?  What advice would you give to current physics majors?

Find a topic in physics that you feel passionate about and pour your heart and soul into it.  If you love what you do – the rest is easy.

Learn more about the recent discovery and the Higgs boson.

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