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Penn Stater Returns from CERN: 10 Questions with Dan Abercrombie

Penn State senior Dan Abercrombie spent this past summer at CERN, the world’s largest particle physics laboratory and home of the Large Hadron Collider.

You may recall CERN as the lab responsible for creating a particle consistent with the theorized Higgs boson, sometimes referred to as the “God particle”. (Or, you might recognize CERN from these pop culture references in “The Big Bang Theory” and “Angels and Demons.”) Though Abercrombie didn’t discover any fundamental physics particles during his time at CERN, he still managed to work on some pretty cool stuff at the Geneva, Switzerland-based laboratory.

Abercrombie, a Williamsport, PA native, is a Schreyer Scholar majoring in physics and nuclear engineering. Prior to interning at CERN, he had worked with both the Intense Laser and the Advanced Multi-Phase Flow laboratories at Penn State. He was also the subject of a Penn State News story after he won a scholarship from the Astronaut Scholar Foundation.

We sat down with Abercrombie to discuss his experience working alongside the world’s best high-energy physicists and his personal work with quarks, bosons, and dark matter:

Onward State: How did you become so interested in high-energy physics?

Dan Abercrombie: In general, I really enjoy physics because things you see every day can be explained in terms of more fundamental ideas. For example, if you are familiar with the history of science, you may have heard that Kepler had three laws that describe the orbit of planets around the sun. Decades later, Newton proposed his law of gravitation which explained why all of Kepler’s observations were true.

Kepler’s observations were instrumental in allowing Newton to find his gravitational law, but I am more excited by the flexibility of Newton’s fundamental equation. In particular, I am excited by high-energy physics because it is the pursuit of answering the most fundamental questions we can think of, such as why objects have mass.

OS: Tell us how you got this internship at CERN.

DA: I participated in an REU program that is run by the University of Michigan and funded by the National Science Foundation. Professor Homer Neal of the University of Michigan told us the following story of the program’s origin:

[Neal] had asked the Director General of CERN if American students would be able to participate in the CERN Summer Student Programme. The response was that the DG would be fine with that, if CERN only had the money to sponsor the American students. Professor Neal’s response was to ask the NSF for funding, which was happy to help.

(Editor’s note: The United States is not a member of CERN, a European organization. The University of Michigan program allows American students to participate in CERN’s Summer Student Programme as if they were citizens of a CERN member state.)

OS: In layman’s terms, can you explain your research at CERN this summer?

DA: It depends on if ‘quark’ is included in the set of layman’s terms. Basically, quarks are what make up protons and neutrons, but they cannot really be separated. Every particle we observe has to be made up of multiple quarks. Of course, in collisions at CERN, quarks kind of bounce off each other so hard that they fly out of the protons being collided. The amount of energy it takes to separate quarks is enough to allow new quarks to basically pop out of the vacuum. (This is Einstein’s E=MC2.)

This way quarks are not isolated, but the result is a spray of particles called a jet. My research this summer focused on comparing different methods of identifying which particles came from the same jet.

OS: Now, in highly technical terms, can you explain your research at CERN?

DA: I don’t want to be too technical, so maybe some of your readers will still understand this:

I compared different grooming algorithms and cone sizes for reconstructing jets from a hadronic W boson, or a W that decays into quarks. I wanted to compare the dijet mass spectrum to get the optimal mass peak of the W. I defined optimal as having the narrowest peak width as well as a constant peak center as a function of the W’s transverse momentum and the event’s number of primary vertices, which is close to the number of simultaneous collisions.

The improved mass resolution will allow [particle physics detectors] CMS and ATLAS to agree on jet reconstruction algorithms for the next run. It will also be useful in future searches for dark matter, which the Higgs is expected to decay into.

OS: What is workplace atmosphere like at CERN?

DC: Aside from the usual adviser-student relationship, there is very little hierarchy at CERN. At least among the researchers, no one has the authority to boss others around. Everyone who is working there is highly motivated and genuinely excited about what they are doing, so they are willing to help each other when the plan of action seems reasonable. There is also a pretty fierce rivalry between CMS and ATLAS, which is a large driving force for those two groups. I worked on CMS, so I saw a lot of this.

(Editor’s note: CMS and ATLAS are competing particle physics detectors.)

Another thing people ask me is, “wasn’t the LHC not running?” This is true, but CERN was still a very busy place. There is a lot of data from the past runs that still needs to be looked at and understood.

OS: CERN is based in Geneva, Switzerland. Had you been to Europe before this summer, and if not, tell us about your experience there.

DA: I had never been outside the US at all before. I went hiking a couple of times, and the mountains were truly surreal. I grew up in Pennsylvania, so I am very accustomed to what we call “mountains” here, which are tiny in comparison.

I also spent time in Geneva and some French towns, and the amount of history was staggering. Many of the cathedrals I visited were far older than the United States. I also visited the Louvre and Musée d’Orsay while in Paris, and it was amazing to see so many of the famous art pieces all gathered together.

OS: Tell us a little about your hobbies or interests, outside of high-energy physics work.

DA: I play bass guitar with some friends back home. We started out in high school covering a bunch of blink-182 songs as well as writing originals that encapsulated our teen angst. We like to think that we’ve matured since then and write stuff influenced by bands such as Coheed and Cambria, The Fall of Troy, and Protest the Hero. We haven’t had time to record any of that yet though, so if you look us up (we’re on Facebook as Under Changing Skies), you’ll mostly find teen angst.

While at Penn State, I also like to play tennis and go jogging.

OS: What resources at Penn State have helped you along the way?

DA: Research experience definitely helped. I started off working in the Nuclear Engineering department, and while they are not focused on the same physics as the experiments using the LHC, a lot of the techniques are similar. There were also other Penn State students who went to CERN through the same program who I was able to talk to about their experience. One of them, John Groh, still goes here too.

OS: What are your career aspirations?

DA: I would like to eventually be a professor in physics at some research institution. Hopefully there will still be high energy experiments at that time. All I can say with certainty now though is that I want to go to pursue a Ph.D. in high energy physics. The LHC is scheduled to run again while I am in graduate school, so there should be plenty to do then.

OS: If you were a dinosaur, which would you be and why?

DA: Long neck (or Apatosaurus) because Littlefoot was too cool.

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About the Author

Bobby Chen

Writer and photographer, helping tell the many stories of the Penn State community.

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